Samacheer
GOVERNMENT OF TAMILNADU
STANDARD NINE
TERM I VOLUME 3
SCIENCE SOCIAL SCIENCE
NOT FOR SALE
Untouchability is Inhuman and a Crime
A Publication Under Free Textbook Programme of Government of Tamilnadu
Department of School Education
© Government of Tamilnadu
First Edition - 2013
(Published under Uniform System of School Education Scheme in Trimester Pattern)
Textbook Prepared and Compiled by
State Council of Educational Research and Training
College Road, Chennai - 600 006.
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Tamilnadu Textbook Corporation
College Road, Chennai - 600 006.
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ii
CONTENTS
UNIT TOPIC PAGE NO. (1 - 122)
SCIENCE
BIOLOGY 1. 2. Animal kingdom Cells CHEMISTRY 3. 4. Is matter around us pure? Atomic structure PHYSICS 5. 6. 7. Measuring instruments Motion Liquids Practicals
3 24
39 54
69 81 101 114
iii
CONTENTS
UNIT TOPIC SOCIAL SCIENCE HISTORY 1. 2. 3. Ancient Civilizations Intellectual Awakening in 6th Century B.C. Medieval Age GEOGRAPHY 1. 2. 3. 4. 5. Tamil Nadu Physiography of Tamil Nadu Climate of Tamil Nadu Resources of Tamil Nadu Tamil Nadu - Agriculture CIVICS 1. The Union Government ECONOMICS 1. Demand and Supply 233 220 162 169 177 189 205 124 142 151 PAGE NO. (123 - 236)
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SCIENCE
STANDARD NINE
TERM I
SCIENCE
1
Note to the teacher… As we present this revised edition of the Science Textbook, we would like to express our deepest gratitude to the learners and the teaching community for their enthusiastic responses. In science some concepts could be subjected to change from time to time as new theories and principles are constantly being evolved. We have tried to present facts and concepts of science (both concrete and abstract) in a visually appealing manner without detracting from the content. Activity based learning is now accepted as the basis of science education. These activities should be regarded as a means for open-ended investigation rather than for verification of principles/content given in the textbook has been designed to facilitate low cost activities and experiments using locally available materials. With a view to streamlining the activities, we have now segregated them into three groups: y I Do y We Do - activities to be done by an individual learner. - activities to be done by a group of learners and
y We Observe - activities to be demonstrated by the teacher. The third group of activities have a higher degree of difficulty or require careful handling as it may involve dealing with chemicals, electricity etc., The “More to know” snippets in the text represents some unusual and interesting facts or information in which the students need not be examined. The evaluation section is nothing but another space for learning in a different manner. As the focus is on understanding, rote learning is to be discouraged thoroughly. Application of learnt ideas, problem solving skills and critical thinking is to be encouraged. There could be scope for more than one answer to a question, which should be acknowledged always. To facilitate further reference, books and websites have been suggested at the end of each lesson. Suggestions and constructive criticism are most welcome. Valuable suggestions will be duly incorporated. - Authors sciencetextbook@gmail.com
2
BIOLOGY
Introduction
CHAPTER - 1
There are millions and millions of different organisms living along with us and around us. Could we remember all by their names? Biologists have helped us achieve this by sorting all living things into meaningful groups. Animals originated approximately 600 million years ago. More than 2 million existing varieties of animals have been identified. Of these more than 12,72,000 are invertebrates and fewer than 62,000 species are vertebrates. The system of sorting living organisms into various groups based on similarities and differences is called classification. taxon is the kingdom and the smallest is the species.
Kingdom
Phylum
Class
TAXONOMY
The branch of biology dealing with identification, description, nomenclature and classification of living organisms is called taxonomy. Biological classification helps us to identify organisms and also recognize those already classified. Carolus Linnaeus classified organisms based on the similarities and differences into small groups called taxa.
Order
Family
Genus
Species
Units of Taxonomy
Levels of classification
According to the order of arrangement the different levels of taxa (singular taxon) are Kingdom, Phylum, Class, Order, Family, Genus and Species.The largest
Criteria for classification
1. Grade of organisation – animals are grouped into unicellular and multicellular based on the number of cells.
MORE TO KNOW Carolus Linnaeus, the Swedish Botanist is regarded as the father of modern taxonomy. (1707-1778) 4 Aristotle, the father of Zoology was the first to classify animals based on their similarities and differences. (384-322 BC)
ANIMAL KINGDOM
c. Eucoelomate – Animals with a true coelom (eg. Earth worm) Acoelomate ectoderm mesoderm endoderm
Pseudocoelomate ectoderm mesoderm endoderm coelom
2. Germ layers – Germ layers are collection of cells formed during development of an embryo. These layers give rise to different organs as the embryo become an adult. Based on the number of layers the multicellular animals are classified into diploblastic (two germ layers ectoderm,endoderm) and triploblastic (three germ layers - ectoderm, mesoderm and endoderm) animals. 3. Symmetry – it refers to the arrangement of body parts around a central axis. Based on symmetry, animals are classified into a. Asymmetrical. eg. Amoeba b. Radially symmetrical. eg. Hydra c. Bilaterally symmetrical. eg. Earth worm 4. Coelom – the fluid filled space between the body wall and digestive tract is called coelom. Based on the nature of coelom, animals are divided into a. Acoelomate – Animals without a coelom. eg. Tape worm b. Pseudocoelomate – Animals with a false coelom. eg. Round worm 5
Eucoelomate ectoderm mesentery endoderm mesoderm coelom
a. Poikilothermic animals – whose body temperature varies with that of environment. eg. Fish, frog b. Homeothermic animals – whose body temperature always remains constant and slightly higher than the environment. eg. Birds, man Animals are classified into two major groups, namely invertebrates and vertebrates based on the absence or presence of back bone (Vertebral column)
SCIENCE
5. Body temperature – animals are classified into two groups on the basis of their ability to regulate their body temperature into
BIOLOGY
CHAPTER - 1 actIvIty – 1.1 I DO
1.1. Invertebrates
Invertebrates are classified into nine phyla namely 1. Phylum Protozoa (eg. Amoeba) 2. Phylum Porifera (eg. Sponges) 3. Phylum Coelenterata (eg. Hydra) 4. Phylum Platyhelminthes (eg. Tape worm) 5. Phylum Aschelminthes (eg. Roundworm) 6. Phylum Annelida (eg. Earthworm) 7. Phylum Arthropoda (eg. Cockroach) 8. Phylum Mollusca (eg. Snail) and 9. Phylum Echinodermata (eg. Starfish)
I collect a sample of water from a fresh water pond and I prepare a micro slide. Afterwards adding a drop of methylene blue stain to the water. After I view the slide under a microscope, I try to find an amoeba.
2. Phylum Porifera
These are non-motile marine animals attached to some solid support such as rocks or shells. These are multicellular animals with perforated(having holes) bodies. The cells are loosely arranged without the formation of tissues.The pores lead to a canal system which helps in circulating water throughout the body to bring in food and oxygen. They possess an internal skeleton made up of calcareous or silicious spicules. Reproduction is both by asexual (budding or gemmule formation) or sexual method (fusion of male and female gametes). eg. Sycon, Sponges
1. Phylum Protozoa
These are generally unicellular microscopic animals. Locomotion takes place by cilia, flagella or pseudopodia. Mode of nutrition may be holozoic, saprozoic or parasitic. They reproduce asexually by binary or multiple fission and sexually by conjugation. eg. Amoeba, Paramoecium
Cilia Contractile vacuole
Micro nucleus Macro nucleus Food vacuole
Sponges
3. Phylum Coelenterata
Paramoecium
These animals are aquatic with radial symmetry. They may be sessile(Polyps) or free floating(medusa). There is a 6
ANIMAL KINGDOM distinct body cavity called coelenteron or gastro vascular cavity. The body bears slender, flexible tentacles around the mouth. The tentacles at their tip bears stinging cells called cnidoblasts which have poisonous barbs to sting their prey. They are used for protection and for attack. Reproduction takes place either by asexual (budding or fission) or by sexual method (by gametes). eg. Sea anemone, Hydra
4. Phylum Platyhelminthes (flat worms)
These are flat, leaf like, ribbon like organisms. They are triploblastic, bilaterally symmetrical and acoelomate animals. These are either free living (eg. Planaria) or parasitic (eg. Tape worm). Parasites have organs of attachment such as hooks and suckers. They are mostly hermaphrodites (i.e. male and female sex organs are present in the same individual). eg. Planaria, Liverfluke
Tape worm Planaria
Sea anemone
MORE TO KNOW
5. Phylum Aschelminthes (round or thread worms)
The body is cylindrical, unsegmented and protected by a resistant cuticle. The animals are bilaterally symmetrical, triploblastic and pseudocoelomate. Circulatory and respiratory systems are absent. Sexes are separate(male and female) and fertilization is internal(inside the body). These are familiar as parasitic worms causing elephantiasis (filarial worm) and ascariasis (ascaris).
The Australian sea wasp or box jelly fish (Chironex fleckeri) is the most venomous coelenterate in the world. It has enough poison to kill about sixty people. ACTIvITy – 1.2 I DO
I observe a permanent slide of hydra under a microscope. I observe the mouth, tentacles and basal disc of hydra and I draw a neat labelled diagram. 7
Ascaris
SCIENCE
BIOLOGY
6. Phylum Annelida
Do you know about vermicompost? Which animal plays a vital role in vermicomposting?
CHAPTER - 1
Earthworm
The body is elongated, cylindrical and segmented (i.e. the body is divided into compartments called segments). They move with the help of setae and parapodia. They exhibit cephalisation (formation of a distinct head) and metamerism (segmental repetition of identical organs). eg. Earthworm, leech
Butterfly
7. Phylum Arthropoda
Do you know which is the largest phylum? Do you know which is the most successful group of animals on earth? Arthropods are the largest group of organisms and insects are the most successful group of animals. It includes crustaceans (eg. crab, prawn), insects (eg. butterfly, cockroach), arachnids (eg. spider, scorpion) and myriapods
(centipedes and millipedes). These forms have jointed legs with a chitinous exoskeleton. The jointed limbs are used for locomotion, feeding and sensing. Their body is also segmented and grouped together to form head, thorax and abdomen. It is covered by a hard, firm external skeleton made up of a strong substance called chitin. Arthropods possess compound eyes. They have open type of circulation where blood vessels are absent and the body fluid circulates in the body cavity, bathing all the organs.
Scorpion
MORE TO KNOW EARThWORMS are referred to as “Farmer’s Friend”? Why? Earthworm plays a vital role in improving the fertility of the soil. It ploughs the land and assists in the recycling of organic matter for the efficient growth of the plants. The soil system is loosened, stirred up and aerated by the vertical migration of earthworms. hIRUDIN - is a naturally occurring protein in the salivary glands of Leeches that has a blood anticoagulant property. Hence blood fails to clot ensuring continuous flow of blood when the leech sucks the blood. This property is widely used in the field of medicine and used in the treatment of blood clotting disorders and in the development of anticoagulant pharmaceuticals . 8
ANIMAL KINGDOM
8. Phylum Mollusca
Molluscs form the second largest group of organisms. Body is soft, unsegmented and without appendages. It is surrounded by a thin, fleshy structure called mantle which secretes a hard calcareous shell. They move around with the help of a muscular foot. Respiration is usually by gills called ctenidia. eg. snail, mussel, oysters
9. Phylum Echinodermata
These are marine organisms. Their skin is covered by calcareous spines. Echinoderms are unique because they have a system of water-filled canals inside the body. These canals project out in the form of hundreds of tube feet on the underside of their body. A starfish moves with the help of tubefeet. Tube feet have suction cups at their ends and are powered by muscles and hydraulic force from the water-vascular system. The water-vascular system also helps in the exchange of gases, internal transport of nourishment, and excretion. eg.starfish, sea cucumber
Mussels
Starfish
Biodiversity of India
India has an immense variety of plants and animals. It is a home to 2000 species of fishes, 182 species of amphibians, 453 species of reptiles, 1200 species of birds and 350 species of mammals. India ranks within the top 10 countries in the world in the biodiversity of vertebrates. Complete the following paragraph :
MORE TO KNOW Insects form one of the most successful groups of animals. More than a million species of insects are known today. ACTIvITy – 1.3 I DO
I make a list of any five poisonous invertebrates.
All animals have one common characteristic ________. The invertebrates are animals that do not have ________.The largest invertebrate group is ________ . Animals with a soft body covered with one or two hard shells are ________. The spiny skinned organisms are ________.
9
SCIENCE
BIOLOGY
CHAPTER - 1
1.2. VERTEbRATES
The Vertebrates are the most advanced group of organisms on Earth. These animals are larger in size than the invertebrates. They are coelomate , triploblastic and bilaterally symmetrical. They have a strong and flexible vertebral column made of a chain of cylindrical bones. Vertebrates also show characteristics that include body segmentation, closed blood circulation and presence of a well developed internal skeleton. They also have well developed brain. How do vertebrates differ from invertebrates? Sl.No. 1. 2. 3. Invertebrates They do not have a back bone. They include both unicellular and multicellular organisms. Vertebrates They have a distinct back bone. They include only multicellular organisms.
They have different types of They have two pairs of limbs for locomotory organs such as locomotion. pseudopodia, flagella, cilia, etc., Organisms may be free living or parasitic. Systems are simple in organisation. Reproduction is by asexual or sexual methods. All organisms are free living. Systems are complex and highly organised. Reproduction is only by sexual method.
4 5. 6.
Vertebrates are classified into five classes as follows. 1. Pisces. 2. Amphibia 3. Reptilia 4. Aves 5. Mammalia
1. Pisces
These are aquatic animals and their skin is covered with over lapping scales which form the exoskeleton. The Endoskeleton is made up of either cartilage (tough, flexible tissue) eg. Shark or bone eg. Catla. The body is streamlined. Respiration is by gills which are covered by lid-like structure called an operculum on either side. Heart is two chambered (one auricle and one ventricle). These are poikilothermic animals. They are either oviparous or viviparous. 10
Lion fish
2. Amphibia
Amphibians are poikilothermic vertebrates which can live on land as well as in water (dual life). Body is divisible into head and trunk. Skin is moist and slimy and helps in exchange of gases for respiration. The heart is three chambered (two auricles and one
ANIMAL KINGDOM
MORE TO KNOW Unforgiving fish? The stone fish is a highly poisonous fish in the world. The poison is carried in its skin and in sacs attached to razor sharp spines along its back. When attacked or even accidentally stepped on, the stone fish pushes its spines into the predator and releases the poison into the wounds which usually results in paralysis or death. MORE TO KNOW Amphibians are good indicators of environmental changes. They breathe partially through their skin which makes them sensitive to radiation, pollution and habitat destruction. Scientists believe amphibians can show the first signs of environmental emergencies. In the last 20 years, the number of amphibian species have declined, with some species becoming extinct due to acid rain, ozone depletion and chemical pollution.
Salamander
ventricle). Respiration is by gills (tadpole), skin and lungs (adult). Fertilisation is external(outside the body). They are oviparous (egg laying) showing complete metamorphosis. eg. Frogs, Toads and Salamanders
How to distinguish frogs from toads?
S.No. 1 2 3 4 5 6 TOAD Short hind legs. Rough, warty skin. Spends little time in water. FROG Long hind legs. Moist, smooth skin. Spends more time in water.
Walks and makes short hops. Jumps. Toothless. Webless hind feet. Teeth in upper jaw. Webbed hind feet.
MORE TO KNOW The drug derived from the extract of Poison arrow frog (Epipedobates tricolor) works as a powerful painkiller. It has the same benefits of morphine but without any side effects.
11
SCIENCE
BIOLOGY
3. Reptilia
CHAPTER - 1
These are poikilothermic creeping or crawling terrestrial animals and their body is covered with dryskin or epidermal scales. A thin membrane called the tympanum represents the ear. Heart is three chambered. They breathe through lungs. They are oviparous. Development is direct and the young ones resemble their parents. eg. Snakes, Turtles, Lizards
Indian Cobra
MORE TO KNOW The slowest reptile The fastest reptile World’s fastest snake The world’s longest snake Largest poisonous snake Smallest reptile Largest reptile Giant tortoise of Galapagos islands. Spiny-tailed Iguana of Costa Rica. The black mamba of Africa A reticulated python King Cobra. mini meleon Komodo dragon.
4. Aves
Birds are characterized by the presence of feathers, modified forelimbs (wings), beak and air filled bones (pneumatic bones). These are homeothermic and oviparous which lay cledoic eggs (with shell) with large amount of yolk (reserve food). The hind limbs are modified for walking, swimming or clasping. The heart is four chambered. Fertilization is internal. Pigeon, Crow and Sparrow are examples of birds that we commonly see flying around us. Ostrich, penguin, emu and cassowary are examples of birds that do not fly.
Peacock
Owl
12
ANIMAL KINGDOM
Vedanthangal Birds Sanctuary
It is one of the spectacular breeding grounds in India. It is located in Kancheepuram District of Tamilnadu (about 75 km from Chennai). The bird life (residents and visitors) include Cormarants, Darters, Herons, Egrets, Open billed stork, Spoon bills, white ibis, Little grebe, Blackwinged suits, Grey pelican etc. November to February is the ideal season to visit the sanctuary. MORE TO KNOW f Woodpeckers not only peck the wood for insects but can also hear the sound of insects crawling inside the wood. f Penguins can survive freezing cold temperatures because of a thick layer of the fat below their skin which act as heat insulator. f Owls can easily hunt in darkness, since their eye balls are elastic and can be focused instantly at any distance. They can widely open their pupil to allow more light to enter.
Vedanthangal birds sanctuary
MORE TO KNOW
Echolocation in Bats
Echolocation is also called bio sonar which is used by several animals like bats. These animals emit ultrasound waves and listen to the echoes of those calls that return from various object in the surroundings. They use these echoes to locate, range and identify the objects. It is used for navigation and for hunting in total darkness.
5. Mammalia
Mammals are Homeothermic vertebrates characterised by presence of milk producing glands (mammary glands). Their skin has hair as well as sweat and oil glands. Heterodont dentition (different types of teeth), external ears or pinnae, diaphragm (muscle which separate thorax and abdomen), four chambered heart, pulmonary respiration (lungs), internal fertilization and viviparity are other salient features. Rat, Cat, Whale, Dolphin, Elephant, Monkey and Man are examples of mammals. Bat is an example of a flying mammal. 13
Dolphins
SCIENCE
BIOLOGY
ACTIVITY – 1.4
CHAPTER - 1
I DO
I visit the zoo and note down the different animals and their feeding habits. ACTIVITY – 1.5 1. A marine invertebrate that has a porous body: ___________________ 2. A marine invertebrate that has a soft body and a shell:___________________ 3. A homoeothermic vertebrate with modified fore limbs: ___________________ 4. A marine invertebrate that is covered with spines :___________________ 5. An invertebrate that has a segmented body and jointed limbs: ______________ 6. A vertebrate that has fur and feeds its young with milk : ___________________ 7. A vertebrate that has dry scaly skin : ___________________ 8. An invertebrate that has a long, segmented body without any limbs: ___________________ I DO
1.3. VARIOUS MODES OF REPRODUCTION IN ANIMALS
Lion with cub Hippopotamus with young one
Reproduction is the capacity of an organism to produce young ones of their own kind. Living things reproduce to ensure the continuation of their species. All animals have the ability to reproduce. The process of reproduction can be asexual or sexual. Sl.No. 1. Asexual Reproduction It involves a single parent. Sexual Reproduction It involves two parents (male and female) each capable of producing gametes. It involves the fusion of male and female gametes [(i.e.) Sperm and ovum] resulting in the formation of zygote.
2.
It does not involve the fusion of gametes.
14
ANIMAL KINGDOM
Asexual Reproduction
In asexual reproduction, new individuals are formed from a single parent. A single celled organism may simply divide and give rise to independent daughter cells. Some of the ways in which organisms reproduce asexually are multiple fission, binary fission, budding, gemmule formation and sporulation. Each daughter nucleus is surrounded by cytoplasm and plasma membrane and thus a number of daughter cells are formed. Each cell separates and leads an independent life.
Budding (eg. Hydra)
Binary fission (eg. Paramoecium)
Paramoecium is an unicellular organism which reproduces by binary fission. In this process a constriction appears at the centre which divides the nucleus and cytoplasm into two parts. Thus a single paramoecium is divided into two daughter cells.
Hydra with bud
Constriction
Nuclear Division
Gemmules (eg. Sponges)
Gemmules are internal buds found in sponges and are resistant to unfavourable condition. These buds have an outer thick layer with numerous air spaces and two inner chitinous layers. On the onset of favourable conditions, the cell mass comes out of the gemmule through an opening called the micropyle. Later the cell mass develops into a young sponge. ACtIvIty – 1.6 I DO
Daughter Paramoecia
Binary fission in Paramoecium
Multiple Fission (eg. Amoeba)
Many protozoans reproduce by multiple fission under unfavourable condition. In this process, the nucleus of the parent cell divides repeatedly to form a number of daughter nuclei.
I observe a micro slide of binary fission in amoeba. 15
SCIENCE
Hydra reproduces asexually by budding. During budding the body wall of hydra produces an outgrowth (bud) due to repeated cell division at one specific site. This bud gradually grows in size and develops a mouth and tentacles at the free end. Soon a constriction appears at the point of contact and the daughter hydra gets separated from the mother and leads an independent life.
BIOLOGY
CHAPTER - 1
Advantages of Asexual reproduction
1. It requires only one parent. 2. It does not involve gametes and fertilization. 3. The young ones have identical characteristics of their parents.
Disadvantages of Asexual reproduction
1. Offspring do not show much variation from parents. This reduces the chances of having a variety that could lead to formation of new species after hundreds of years. 2. Undesirable characters are transfered from parent to offspring without any change.
Gemmule
Spore and cyst formation (eg. Plasmodium)
This type of reproduction is common among protozoan parasites such as plasmodium (malarial parasite). This method is also called sporulation. During unfavourable conditions, the protoplasm is condensed and covered by a thick, protective covering called the cyst. When conditions are favourable, the cyst gets dissolved. The protoplasm regains its original nature and undergoes multiple fission giving rise to numerous independent daughter cells. This process is called sporulation. MORE TO KNOW
Sexual reproduction
Sexual reproduction involves the production of sex cells or gametes. The male organism gives rise to male gamete or sperm and the female organism gives rise to the female gamete or the ovum. In sexual reproduction the male and female gametes fuse together to form a single cell called the zygote. The zygote grows to be a new adult. Gametes are produced in organs that are generally referred to as the gonads. The male gonad is the testis and the female gonad is the ovary. If an organism carries any one type of gonad it is said to be a unisexual organism. In this case the sexes are said to be separate: male and female. Bisexual organisms, also referred to as hermaphrodites, are those that possess both testis and ovary in the same body. Hydra and Tapeworm are examples of bisexual organisms. Unicellular organisms like Paramoecium are also known to reproduce sexually. Two Paramoecia come together, establish a bridge-
Regeneration
Animals like Sponges, Hydra, Planaria and Starfish exhibit regeneration. It is a complex process which involves the repair of damaged cells or tissues or redevelopment of severed part or formation of whole body from a small fragment.
Autotomy
It refers to the power of self cutting of body parts for defence. Examples – Regeneration of arms in Starfish, regeneration of tail in House Lizard. 16
ANIMAL KINGDOM like connection and exchange genetic material. Each of them separate and divide independently to give rise to daughter cells . This method of sexual reproduction is called conjugation. reproductive organ is the ovary which produce the ova or eggs. A sperm and an egg fuse to form a zygote. The fusion of sperm and ovum is called fertilization. The zygote further develops into an embryo and later becomes an adult.
1 2 3 4 6
7
1.4. FERTILIZATION
Fertilization is a process of fusion of haploid male and female gamete to form a diploid zygote.
5
Types of fertilization
The two types of fertilization are, (a) External fertilization – The fusion of the gametes occurs outside the body of the animal. (eg. Frogs, Echinoderms) (b) Internal fertilization – The fusion of the gametes occur within the body of the female parent. (eg. Reptiles, Birds and Mammals)
Conjugation in Paramoecium
SExUAL REPRODUCTION Schematic representation of sexual reproduction
Male Female
1.5. VIVIPAROUS ANIMALS
Testis Ovary In Viviparous animals, example Mammals, a zygote develops into an embryo that grows inside the mother and receives nourishment directly from the mother. After a period of time the mother gives birth to young ones that resemble the adult.
Sperm (n)
Ovum (n)
Zygote (2n)
Embryo
Young individual In higher organisms, two individuals of a species (male and female) are involved in sexual reproduction. The male reproductive organ is the testis which produce the sperms. The female 17
SCIENCE
BIOLOGY
CHAPTER - 1
1.6. OVIPAROUS ANIMALS
Oviparous animals lay eggs laden with yolk. These eggs are laid outside after the process of internal fertilization (e.g. Reptiles and insects). The embryonic development takes place outside the body of the mother. Land dwelling animals lay eggs with shell (cledoic eggs). The shell gives protection and prevents desiccation. Aquatic animals lay eggs without a shell(noncledoic eggs) MORE TO KNOW Ovoviviparous animals In these animals the embryos develop inside the eggs that are retained within the mother’s body until they are ready to hatch. The young ones are nourished by the egg yolk and there is no placental connection. eg. Vipers
Cledoic eggs
Non cledoic eggs
changes which transform the young ones into adults are known as metamorphosis. MORE TO KNOW Moulting hormone Moulting hormone or ecdysone or juvenile hormones are secreted by the neuro secretory cells of the brain and controls moulting in insects. Types of metamorphosis
1.7. YOUNG ONES TO ADULT
The young ones which emerge from the egg either has resemblance or no resemblance with the adult. The young one has to pass through morphological, anatomical and physiological changes and get transformed into an adult. These Life cycle of Grasshopper
1. Incomplete metamorphosis
Among animals where the young ones resemble the adult, growth in size takes place. In arthropods the shell covering the body is shed periodically, to match the growth of the animal. Life cycle of Grasshopper: The newly hatched young ones resembles the adult except in size, wings and reproductive organs. The young ones which hatch out of the egg (nymphs) undergo several intermediary stages through successive moultings to become an adult. Egg Nymph Adult e.g Grasshopper, Mayfly
Nymphs Eggs Adult
18
ANIMAL KINGDOM
Eggs Larva
Pupa Adult
Complete metamorphosis
Life cycle of Butterfly size. Then the larva enters a resting stage the pupa and develops a pupal case (cocoon) around it. After a period of time, the adult or imago emerges out of the cocoon. Larva Pupa Adult Egg e.g. Butterfly, Silk moth.
2. Complete metamorphosis
Life cycle of Butterfly The young ones are strikingly different from the adults and the process of development starts with larva which hatches out of the egg. It is worm like and termed as caterpillar. The larva feeds voraciously on leaves and increase in
EVALUATION
Section – A Think and answer
1. The arrangement of body parts in an organism is known as symmetry. Classify organisms based on symmetry. 2. Reptilia → Pisces → Aves → Mammalia → Amphibia Arrange in correct sequence according to the evolutionary trend. 3. Coelenterates have a special mechanism to protect themselves from their enemies. Explain how? 4. Some Platyhelminthes are parasites. Mention any two adaptations. 5. Frogs can live on land and in water. Mention any two adaptations. 19
SCIENCE
BIOLOGY
Section – B
CHAPTER - 1
6. Millions of organisms inhabit the earth. They are classified and placed under different groups. Mention the need for classification. 7. a) Match the organisms with their locomotory organs. b) Correlate the locomotory organs with their mode of existence. Organisms Paramoecium Fishes Frogs Aves Mammals Locomotory organs Limbs Webbed feet Wings Fins Cilia
8. The eggs of birds are Cledoic (shell) and contains yolk. Mention the role of the shell and yolk in birds. 9. Most of the birds can fly. List the structural adaptations which enable them to fly. 10. Earthworms can increase soil fertility. Justify. 11. Both the Sperm and Ovum contains haploid set (n) of chromosomes. Give reason. 12. In insects during metamorphosis, the outer skin is cast off periodically. Name the process and mention its significance.
Section C
13. Match the following columns A, B and C to make meaningful sequences: One is done for you: Birds lay eggs that are cledoic a). Column A Platyhelminthes Frogs hydra birds grasshopper b). Column A Tapeworm Earthworm Starfish Paramoecium Mussels eggs nematocyst parasites amphibious nymph Column B Vermi compost Spiny Skin Locomotion Shell Hooks and suckers 20 Column B Column C protection molting cledoic Hooks and suckers gills and lungs Column C Calcareous spines Parasite Soft body Organic farming Cilia
ANIMAL KINGDOM
Section D Answer the following in not more than two sentences:
14. Mammals are homeotherms. List the vertebrate classes that are poikilotherms. 15. Fertilization is internal in mammals. Name a group that have external fertilization 16. Nymphs undergo a process to become an adult grasshopper. Define it. 17. Frogs and toads are different but they are in the same group - amphibians. Are spider and mosquito related? How? 18. Insects are the most successful group of animals. List the reasons.
Section E Answer in a paragraph
19. How do poikilotherms adapt to change in the environmental temperatures. Give an example. 20. Taxonomy is the science of classification. Imagine you are a biologist and make a list of criteria how you would classify a pearl oyster. 21. Young insects undergo changes to become adults. Define this change. Compare the life cycle of a grasshopper with that of a butterfly.
SUGGESTED ACTIVITIES Activity • Cut a paper into seven pieces. • Write seven units of taxonomy in the chart pieces. • Fix a double side tape at the back of each chart pieces. • Fix the units of Taxonomy in the correct order on a chart paper. • Submit it for assessment. Activity • Prepare the branches of evolutionary tree with paper. • Fix the pictures of animals according to their evolution. • Let the students make an evolutionary tree for vertebrates. 21 Learning by doing Learning by doing
• Collect the pictures of different classes of animals of vertebrates.
SCIENCE
BIOLOGY
Activity
CHAPTER - 1
Observation
• While you are visiting your native village, observe natural hatching phenomenon of hen. • Write a paragraph about natural hatching. Activity • Observe ten animals in your locality. • Write down the common names of above animals. • Find out the zoological names of the above animals with the help of Website, or senior students or parents. Assignment
Common Names
Zoological Names
Activity Observe any two animals in your locality and enlist its parental care.
Observation
Assessment activity Class Topic Activity :9 : Animal Kingdom : Individual
Method of Assessment : Preparation of worksheet Aim: To Identify and differentiate between Invertebrate and Vertebrate animals Materials required: Pictures, Photos and preserved animals of Invertebrates and Vertebrates. Procedure: • • • • Ask the students to observe the animal pictures carefully. Ask them about the locomotary organs of the animals. Ask them about their mode of nutrition. Teacher explains the mode of reproduction of animals.
Conclusion: The students learn to identify the invertebrates and Vertebrates. 22
ANIMAL KINGDOM
Sl. No. Name of the animal Housefly Earthworm Starfish Hen Fish Frog Invertebrates Verterbrates
Remedial Activities: 1. Show additional animals pictures of animals from books and websites. Ask students to identify Invertebrates and vertebrates. 2. By using the permanent charts of organ system of animals, the teacher explains the complexity of organ system. Life Skills Through this activity the life skill such as creative thinking, co-operation and interpersonal relationship are developed. Assignment Activity Prepare a table and write the classification for the following animals. (Cockroach, Cat, Dog, Lion, Tiger) Name of the animal Kingdom Phylum Class Order Family Genus Species
Further reFerence
Books: 1. Developmental Biology - Arumugam.N, Saras Publications. 2. A Manual of Zoology, VolumeI& II - Ekambaranatha Iyar, E.K. and T.N.Ananthakrishnan, Viswanathan &Co. 3. Invertebrates - Barnes, R.D.,W.B.Saunders Publications.
Websites : http://www.worldanimal.net http://www.animaltrial.com
23
SCIENCE
Cells 2.1. PROKARYOTIC AND eUKARYOTIC Cells
Cells are the smallest functional unit in a living organism. Based on the complexity of organization, especially nuclear organization, the cells are classified into two types. 1) Prokaryotic cells. 2) Eukaryotic cells.
Cell wall Ribosomes Flagella DNA Cell membrane
1. Prokaryotic cells
Cells which lack a well organized nucleus are called prokaryotic cells. eg. Bacteria and blue green algae (Cyano Bacteria). Their DNA (Deoxyribo nucleic Acid) is not enclosed by a nuclear membrane. They also lack membrane bound organelles. The organisms which possess prokaryotic cells are called Prokaryotic organisms or Prokaryotes. They are considered to be primitive organisms.
Capsule
2. Eukaryotic Cells
The cells of all plants (except a few Bacteria and Cyano Bacteria) and animals possess a well organized nucleus they are called Eukaryotic cells. Their genetic material is enclosed by a nuclear
A Prokaryotic cell (Bacteria)
membrane. They possess membrane bound organelles like Endoplasmic reticulum, golgi body, mitochondria, plastids and vacuoles. The organisms which possess eukaryotic cells are called Eukaryotic organisms or Eukaryotes.
Differences between Prokaryotic cell and Eukaryotic cell
Prokaryotic Cell It is generally smaller (1-10 microns) in size It lacks a well organized nucleus as its nuclear material is not surrounded by a nuclear membrane. It has a single chromosome Nucleolus is absent It lacks membrane bound cell organelles. Cell division occurs by fission or budding. Mitotic and meiotic divisions are absent Ribosomes are smaller 25 eukaryotic Cell It is comparatively larger (5-100 microns) in size. It contains a well organized nucleus as its nuclear material is surrounded by a nuclear membrane. It has more than one chromosome. Nucleolus is present It possesses membrane bound cell organelles. Cell division takes place by mitosis and meiosis. Ribosomes are larger
1.
2. 3. 4. 5. 6. 7.
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sl. No.
BIOLOGY
AcTiviTy – 2.1 f f f f
CHAPTER - 2 i DO
I take a drop of curd and put it on a slide and I stain it with saffranin. I heat the back of the slide for few minutes. I observe the slide under compound microscope. My observation : The bacteria seen in the microscope is a _________ (Prokaryotic cell/Eukaryotic cell) MORE TO KNOW
f The study of cell is not possible without a microscope. Robert Hooke in 1665 coined the term cell and discovered the cellular structure of cork. f Anton van Leeuwenhoek (1674), studied the structure of bacteria, protozoa, etc. under the simple microscope which he himself designed. f Robert Brown, a Scottish botanist, discovered that all cells contain nucleus.
Ultra structure of a Plant Cell
f Purkinje coined the term, ‘protoplasm’ for the living substance present inside the cell.
Compound Microscope
2.2 STRUCTURAL ORGANIZATION OF A CELL
Ribosome Cell wall Vacuole Plasma membrane Smooth endoplasmic reticulum Nucleus
Cytoplasm Chloroplast
Golgi apparatus
Nucleolus Rough endoplasmic reticulum
Mitochondrion
Amyloplast
Ultra structure of a Plant cell
26
Cells
Smooth endoplasmic reticulum
Golgi apparatus
Cytoplasm
Centrioles Ribosome
Nucleolus Nucleus
Rough endoplasmic reticulum Vacuole
Microvilli
Plasma Membrane Lysosome
Mitochondrion
Ultra structure of an Animal cell
A study of the diagrams of Plant cell and Animal cell shows the following differences:
Sl.No. 1. 2. 3. 4. 5. 6. 7.
Plant cell is larger than animal cell. Animal cell is comparatively smaller in size. Plant cell has large vacuoles which Animal cell usually lacks vacuoles. occupy more space in the cell. Even if they are present, they occur in minute sizes. Centrosome is present only in the All the animal cells of some lower plants. centrosomes. cells have
Lysosomes are found only in the Lysosomes are found in all animal eukaryotic plant cells. cells. Plant cell contains plastids. Plastids are absent Mostly, starch is the storage Glycogen is the storage material. material.
27
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Plant cell Animal cell Plant cell has an outer rigid cell Animal cell lacks a cell wall. wall which is made up of cellulose.
BIOLOGY
ACTIvITY – 2.2
CHAPTER - 2
I DO
I Imagine that a cell is like a large swimming pool….and I dive into it…How would I feel? What interesting things would I possibly find floating around me? I talk about it in my classroom or I write a story about it.
2.3. Cell MeMBRANe AND Cell WAll
Cell Membrane (Plasma membrane or Plasmalemma)
The contents of the cell are enclosed by a thin, delicate living membrane called cell membrane. It is the outer boundary of the cell. Cell membrane is flexible and is made up of a continuous bilayer of lipid molecules and protein molecules. All cell organelles are also bound by a similar membrane. The cell wall consists of three layers namely, middle lamella, primary wall and secondary wall. The middle lamella is a thin amorphous cement like layer between two adjacent cells. Primary wall is the first formed wall of the cell and is produced inner to the middle lamella. The secondary wall is a thick layer found inner to the primary wall.
Functions
1. ell wall gives a definite shape to the C plant cells. 2. t gives rigidity and provides I mechanical strength to the cell. I 3. t protects the protoplasm against injury. I 4. t also plays an important role in the transfer of materials between cells.
Functions f lasma membrane selectively P regulates the entry and exit of the substances into and out of the cell. Therefore, it is called a selectively permeable membrane or semipermeable membrane. f t provides an outer boundary to the I cell and protects the cell from injury. f t allows the flow of materials and I information between different organelles of the same cell, as well as between the adjacent cells. f t provides some organic connections I between the adjacent cells.
2.3.1. CYTOPlAsM
Cytoplasm is the jellylike, translucent, homogeneous substance that fills up a cell. It consists of vital molecules such as carbohydrates, lipids, proteins, amino acids, minerals and water. The cytoplasm moves around slowly carrying the organelles around in a process called cytoplasmic streaming. It helps to keep the cell organelles dynamic and in motion. The portion of cytoplasm immediately below the cell membrane is gel-like and is called ectoplasm. The
CELL WALL
Cell wall is present only in plant cells. It is a rigid protective covering outside the plasma membrane. Presence of cell wall in plant cells distinguishes them from animal cells. Most of the plant cell walls are made up of cellulose.
28
Cells
ACTIvITY – 2.3 I cut a small piece of onion and separate a peel. I place the peel on a glass slide in a drop of water and I put a drop of saffranin or methylene blue on the peel. I wash it in water to remove the excess stain and I put a drop of glycerine and cover it with a coverslip. I observe it under the microscope. My observation about the onion cell : ______________________ ___________________________________________________ ____________________________________________________ I DO
cytoplasm between the ectoplasm and nuclear membrane is liquefied and is called endoplasm. The cytoplasm together with the nucleus is referred to as the protoplasm. metabolism. The cell organelles are embedded within the cytoplasm. Each organelle performs specific functions in the cell.
a) ough endoplasmic reticulum : R
They are found in cells which synthesize proteins. This type of endoplasmic reticulum possesses rough walls because the ribosomes are attached to it. They are found in cells which synthesize lipid. The walls are smooth as ribosomes are not attached to its membrane.
Cytoplasm is the seat of cellular
b) mooth endoplasmic reticulum: S
2.3.2. Cell ORGANelles
A cell performs a variety of functions. To understand the functioning of the cell, it is necessary to know briefly about the structure of cell organelles.
Functions
1. ndoplasmic Reticulum (ER) provides E large surface area for the metabolic activities of the cell. R 2. ough endoplasmic reticulum plays an important role in protein synthesis. 3. mooth endoplasmic reticulum is S involved in the synthesis of steroids, hormones and lipids.
Endoplasmic Reticulum
Endoplasmic reticulum is a complex and interconnected system of membrane bound channels and tubules. It is spread throughout the cytoplasm and is continuous with the plasma membrane and nuclear membrane. There are two types of Endoplasmic Reticulum. a. ough Endoplasmic Reticulum. R (RER) b. mooth Endoplasmic Reticulum. S (SER)
Golgi Complex or Golgi apparatus The Golgi apparatus was first described by Camillo Golgi. Golgi complex consist of saucer-like cisternae, compartments called network of interconnecting tubules, vesicles and vacuoles at the peripheral regions. In plant cells, Golgi apparatus is referred to as dictyosomes.
29
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BIOLOGY
CHAPTER - 2
MORe TO KNOW Lysosomes are involved in the destruction of aged and wornout cellular organelles. Therefore they are also called demolition squads or scavangers or cellular housekeepers.
Cisterna
Ribosomes
Ribosomes are small granular structures made up of ribonucleic acids Vesicles (RNA) and proteins. They occur free in the cytoplasm as well as attached to the Golgi complex outer surface of the rough endoplasmic Functions reticulum. Each ribosome consists of 1. olgi apparatus is involved in the G two subunits – a small subunit and a formation of lysosomes. large subunit. At the time of protein I 2. t is also responsible for the synthesis synthesis many ribosomes get attached of cell wall and cell membrane. to messenger RNA and form a structure called polyribosome or polysome.
Lysosomes
Lysosomes are small membrane bound 40S Subunit vesicles which contain powerful digestive enzymes. These serve as intracellular digestive system, hence they are called digestive bags. They are produced by the joint activity of Endoplasmic reticulum 60S Subunit 50S Subunit and Golgi apparatus. If the membrane of 70S Ribosome 80S Ribosome Lysosome happens to get ruptured, the enzymes of Lysosome would digest the entire cellular structure causing death of There are two types of ribosomes the cell. So Lysosomes are called ‘suicide a. 0S – Ribosome. It is small and 7 bags’. consists of 30S and 50S subunits. It is seen in prokaryotic cells. Functions b. 0S – Ribosome. It is made up of 8 1. ysosomes are involved in the L 40S and 60S subunits. It is seen intracellular digestion of food in eukaryotic cells. particles ingested by the cell through endocytosis. Functions 2. he lysosomes of WBCs (White blood T Ribosomes play an important role in cells) destroy pathogens and other protein synthesis. So they are called, foreign particles and thus take part in ‘protein factories’ of the cell. natural defence of the body. 30
30S Subunit
Cells
Vacuoles
Vacuoles are fluid– filled sacs bound by a single membrane called tonoplast. They are found, more in plant cells than in animal cells. Mature plant cells are found to have one large vacuole that almost fills up the entire cell. They may play the part of a contractile vacuole where excess water and waste is excreted from a cell. They also function as food vacuoles where they engulf material. For example, in Amoeba, the food vacuole engulfs food items and digests it using digestive juices. Vacuoles of plants are filled with cell sap containing minerals, sugars, amino acids and dissolved waste products. also contains the DNA and ribosomes. This makes it a unique organelle
Function
( M itochondria synthesize energy rich compounds such as ATP.
Outer membrane Inner membrane
DNA Mitochondrion
Cristae
Functions
1. acuoles store and concentrate V mineral salts as well as nutrients. 2. hey maintain proper osmotic pressure T in the cell for its turgidity.
Plastids
Plastids are disc or oval shaped organelles which occur in plant cells only. Plastids are of three types. They are Leucoplasts, Chromoplasts and Chloroplasts. 1. leucoplasts: These are colourless plastids which store food in the form of starch, lipids and proteins 2. hromoplasts: These are yellow or C reddish in colour due to the presence of pigments other than chlorophyll. Chromoplasts provide colour to many flowers and fruits. 3. hloroplasts: These are green C coloured plastids which possess the photosynthetic pigment chlorophyll which is present in leaves.
Mitochondria
Mitochondria are globular or cylindrical organelles. Each mitochondrion is bound by two membranes – an outer continuous membrane and an inner membrane thrown into folds called cristae. These cristae divide the inner chamber incompletely. The inner chamber is filled with homogenous dense material called the matrix. The cristae have pin headed bodies called F1 particles or Oxysomes which play an important role in respiration. The matrix of mitochondria contains enzymes necessary for the oxidation of food during respiration and release of energy in the form of ATP(Adenosine Triphosphate) molecules. Therefore mitochondria are called power houses of the cell. The mitochondria contain proteins and lipids. The mitochondrial matrix
Structure of chloroplast
Each chloroplast consists of a double membraned envelope and a matrix. The inner membrane is arranged along the length of the plastids as lamellae. At certain regions, the lamellae are thickened and appear like pile of coins. 31
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BIOLOGY
Outer Membrane Granum Lumen
CHAPTER - 2
The nucleoplasm has two types of nuclear structures i) the nucleolus and, ii) chromatin. The nucleolus is a spherical body rich in protein and RNA. It is the site of ribosome formation. There may be one or more nucleoli in the nucleoplasm.
The chromatin is a network of fine threads composed of genetic material Inner Membrane DNA (Deoxyribonucleic acid) and Stroma Thylakoids proteins. During cell division chromatin is condensed into thick cord like Chloroplast structures called Chromosomes. The chromosomes contain genes and each These are called the grana. Each granum gene is responsible for one hereditary consists of disc shaped membranous character of the organism. Genes sacs called thylakoids. Inside these contain information for inheritance of grana, the chlorophyll is located. The traits or characters from parents to the non-thylakoid portion of the matrix is offsprings of the next generation. called stroma. It contains a number of enzymes involved in photosynthesis.
Centrosome
Centrosome is present in animal cells and in certain lower plants. It is absent in prokaryotic cells and in higher plant cells. It is located in the cytoplasm, just outside the nucleus. It contains a pair of small, hollow granules called centrioles.
Ribosomes
Chromatin Nucleolus Nucleoplasm Nuclear Envelope
Functions
Centrioles play an important role in the formation of spindle fibres during cell division.
2.4. NUCleUs
A nucleus is commonly seen as a spherical structure surrounded by a double membrane called the nuclear envelope. Nuclear envelope encloses a ground substance called nucleoplasm or karyolymph. The nuclear envelope has a large number of holes or ‘pores’ called nuclear pores. They allow the movement of molecules across the nuclear envelope in and out of the nucleus.
Functions:
Nucleus
1. ucleus controls all the metabolic N activities of the cell. 2. t controls the inheritance of characters I from parents to offsprings. 3. t controls cell division. I
2.4.1. ChROMOsOMes
Chromosomes are thread-like condensed chromatin fibres which contain hereditary information and are visible only during cell division.
32
Cells
Chromatid Centromere Arms Centromere Centromere
Arms Chromatid
Metacentric
Telomere
Submetacentric Acrocentric Telocentric
Structure of chromosome
Types of chromosomes
ACTIvITy – 2.4
WE DO
ACTIvITy – 2.5
WE DO
Each chromosome consists of two similar structures called chromatids. Both the chromatids are joined at a particular point called centromere.
Types of chromosomes
Based on the location of the centromere, the chromosomes are of four types. 1.Metacentric Chromosome: The centromere lies in the middle of the chromosome and the two arms are almost equal in length. It is a V-shaped chromosome.
f We prepare models of types of chromosomes, using Coloured paper / Coloured threads / China clay. f We display them in the classroom and discuss. f Also we display and explain them in the science club.
DNA Structure
Chromosomes are made of a long series of structures called genes. Genes are made of nucleic acids like DNA (Deoxyribonucleic acid) or RNA(Ribonucleic acid). DNA is the genetic material in most of the organisms 33
SCIENCE
f Let the students divide themselves into 5 groups. f etthefirstgroupdrawthestructure L of Endoplasmic Reticulum. Write a note on the structure and functions and display for other students. f Let the second group draw the structure of Golgi body. Write a note on the structure and functions and display for other students. f etthethird,fourthandfifthgroups L draw the structures of Ribosomes, Mitochondrion and Chloroplast respectively. Write a note on the structure and function of them, and display for other students. f Let all the students discuss and understand the structure and functions of cell organelles.
2.Submetacentric Chromosome: The centromere lies slightly away from the middle of the chromosome and hence, its one arm is slightly shorter than the other. It is a ‘J’ shaped chromosome. 3. Acrocentric chromosome: The centromere lies near the end and hence, one arm is very short and the other arm is very long. It is a rodshaped chromosome. Chromosome: The 4. Telocentric centromere lies at one end of the chromosome, and hence, there is only one arm on one side. It is also a rodshaped chromosome.
BIOLOGY and higher organisms. DNA is made up of millions of nucleotides. Each nucleotide is made up of a pentose sugar, a phosphate group and a nitrogenous base. The nitrogenous bases are of two kinds- Purines and Pyrimidines. Adenine and Guanine are the purines and Thymine and Cytosine are the pyrimidines. The helical(spiral) structure of DNA was proposed by Watson and Crick. DNA is a double stranded structure in which the two strands are coiled around each other forming a double helix. The backbone of the helix is formed of sugar and phosphate molecules. The nitrogenous bases are attached to sugar molecules. The two poly-nucleotide strands are held together by hydrogen bonds between specific pairs of purines and pyrimidines. aCTiviTy – 2.6
CHAPTER - 2
We Do
f We devide into groups and draw the diagram of the structure of DNA in a cardboard with the help of our textbook. f We fill the two strands of DNA with coloured threads. f We fix the coloured matchsticks between the two strands as seen in the diagram and label the parts with the help of textbook. f We display it in the classroom and discuss about the structure of DNA.
2.5. Cell Types
Division
anD
Adenine
Thymine
One of the most important characteristics of a living being is its ability to reproduce. The process of reproduction involves an increase in the number of cells by cell division. New cells can arise from pre-existing cells only through the process of cell division. Cell multiplication is needed for growth, development and repair of the body. Cells divide by three different methods. They are Amitosis, Mitosis and Meiosis. In each case, division of nucleus occurs before the division of cytoplasm.
Amitosis (Direct division)
Guanine
Cytosine
DNA Backbone
DNA structure
Amitosis is a simple method of cell division. It is also called direct cell division. The nucleus elongates and develops a constriction around its middle. The constriction gradually deepens and finally divides the nucleus into two daughter nucleus. This is followed by the constriction of the cytoplasm to form two daughter cells. This type of cell division is common in prokaryotes. (e.g. Bacteria, Amoeba) 34
Cells
Mitosis (or) Indirect cell division:
Mitosis takes place in somatic cells (body cells other than sperm and ovum). It is a division that produces two identical daughter cells, each containing the same number of chromosomes as in the parent cell. It is a continuous process and takes place in four phases. These are Prophase, Metaphase, Anaphase and Telophase.
Nuclear Membrane Centromere Cell wall
Interphase
Spindle fibres
Prophase
Interphase Before a cell undergoes mitotic division, it prepares itself for the division. This phase is called interphase. The chromatin material duplicates due to duplication of nucleic acids. This results in the formation of two chromatids.
Prophase f hromatin network begins to coil C and appears as long thread-like structures called chromosomes. f ach chromosome appears as two E chromatids that lie side by side and are joined at a point called centromere. f pindle fibres appear from the poles S and develop towards the centre. Nuclear membrane and nucleolus start disappearing.
Chromatid
Metaphase
Anaphase
Daughter cells Early Telophase Late Telophase
Chromosome
Nucleolus
Metaphase f he nuclear membrane totally T disappears. f hromatids become shorter and C thicker. f he chromatids move to the centre of T the cell along with their centromeres. f pindle fibres get attached to the S centromere.
Mitosis
Anaphase f The centromere of each chromosome divides into two and separates the chromatids. f he sister chromatids are pulled apart T towards the poles by the contraction of the spindle fibres. f ach chromatid gets a portion E of centromere, it becomes a chromosome. 35
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BIOLOGY
Telophase
f he daughter chromosomes reach T the poles. f he nucleolus and nuclear membrane T reappear and thus two daughter nuclei are formed at the two poles of the cell. f he spindle fibres disappear. T f hese stages bring about the T division of the nucleus and this is called karyokinesis. This is followed by the division of the cytoplasm.
CHAPTER - 2
In plant cells, the cytoplasmic division occurs by the formation of a cell plate at the centre of the cell between the two daughter nuclei. Thus at the end of mitosis, two identical daughter cells are formed.
Meiosis
Meiosis is a type of cell division which takes place in the reproductive cells of organisms. Unlike mitosis, meiosis results in four daughter cells each having half the number of chromosomes of the parent cell. These daughter cells become part of specialized reproductive cells called gametes (a sperm or an ovum). They are involved in sexual reproduction.
Cytokinesis
The division of cytoplasm is called cytokinesis.
evAlUATION
Section A Choose the correct answer
1. ower house of the cell P (chloroplast, nucleus, mitochondrion, lysosome). 2. he membrane of vacuole T (cell membrane, nuclear membrane, plasma lemma, tonoplast). 3. The organelle that destroys worn-out cells (centrosome, vacuole, lysosome, chromosome) 4. The cell division that form gametes (mitosis, amitosis, meiosis, both mitosis and meiosis).
Section B
5. Complete the table: Name of the chromosome 1. Metacentric 2. 3. Acrocentric 4. Telocentric Shape of the chromosome 1. 2. ‘J’ shaped chromosome 3. 4.
6. he mitochondria is referred to as the ‘powerhouse’ of a cell. What makes it a T unique organelle? 7. Vacuoles are fluid-filled sacs. How does it play a part in excretion and nutrition?
36
Cells
8. ook at the given picture. Identify the phase of cell division. What happens to the L cell immediately after this stage?
9. ook at the given picture. Describe the changes in the nuclear material from stage L A to stage B.
A
B
10. Meiosis gives rise to gametes. How is it different from mitosis? 11. enes are the physical basis of heredity. How are chromosomes, genes and G DNA connected? Explain. 12. Read the following statements and correct them. i) Golgi apparatus was first described by Watson and Crick.
Section C
13. A) Draw a mind-map of the parts of a cell. B) Fill in the blanks. i) Division of cytoplasm is known as ________. ii) Prokaryotic cells do not have well organized _______.
Further reFerence
Books: 1. Plant Physiology 2004 - Salisbury F.B and Ross C.W, Wadsworth publishers. 2. Cell Biology, Genetics, Molecular Biology, Evolution & Ecology - 2008 - Agarwal V.K and Verma P.S., S.Chand Publishers. 3. Life Science 1990 - Silver Burdett K Ginn Publications.
Websites : http://www.sciencecentral.com http://www.botany.org http://www.khanacademy.org
37
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ii) Cell wall is present in animal cells.
BIOLOGY sUGGesTeD ACTIvITIes (CCe)
CHAPTER - 2
I. Discussion • Draw the diagram of Plant cell in one part of the chart and Animal cell in the other part. • Observe them and discuss. • Differentiate the Plant cell from the Animal cell. • Fill up the following worksheet.
sl.No.
1. 2. 3.
Plant Cell
Cell wall is ________ _____________ are present. Vacuoles are __________ in size.
Animal Cell
Cell wall is ________ _____________ are absent. Vacuoles are __________ in size.
II. Activity based learning • • • • • • • • Let the students divide themselves into two groups A and B. Let the group A draw the structure of a plant cell on a cardboard. Let the group B draw the structure of an animal cell on a cardboard. From the cardboards, cut out portions showing the cell organelles. The cut out portions of the cell organelles are to be coloured with sketch pen. Let the group A fix the relevant organelles in the empty spaces of the animal cell. Let the group B fix the relevant cell organelles in the empty spaces of the plant cell. Discuss the structure of plant cell and animal cell after the cell organelles are fixed correctly.
III. Power point presentation • Prepare a power point presentation showing pictures of cell organelles and explain about any one organelle. Iv. Display • • • • • Draw the diagrams of different stages of Mitotic cell division in a chart. Fix a bead as the Nucleus. Use different coloured threads for chromosomes and spindle fibres. Observe the different stages and discuss. Write a note on every stage and display the chart.
v. Dictionary preparation • Collect scientific terms from the lesson. • With the help of Science Dictionary or Encyclopedia from your school library, find their meanings and write them down. • Arrange them in alphabetical order and submit. vI. You can do it • Take a suitable white PET bottle according to the diameter of the convex lens, cut top and bottom portion to a particular length. • Fix the lens at the top of the bottle. • Keep the object (e.g. pollen grain) in a horizontal surface and keep the bottle over it. • Observe the object through the lens. • Can you see the structure of pollen grain through the simple microscope you have prepared? • If so, let your friends also use it to observe the plant parts.
38
CHEMISTRY
Matter
The entire world around us that we can see, touch and feel is made up of matter. The sweet smelling fresh air that we breathe, the beautiful flowers and trees around us, the tasty fruits that we eat, the pets that we love, the roof and walls that make up our homes, the ground that we walk on, why even our own bodies are all made up of matter. Matter occupies space. In other words matter has volume. Some are large and some are small. The quantity of matter contained in any object is referred to as mass. Hence each matter is characterized by mass and volume. All matter exists in one of the three states - solid, liquid or gas. These are often referred to as the three physical states of matter. Classification of matter: 1. ccording to physical state as solid, A liquid and gas. 2. ccording to its composition as A element, compound and mixture.
CHAPTER - 3
Physical states of matter
Solid: Solids have a definite shape and a definite volume. They take a lot of energy to change the shape. They are rigid and not compressed appreciably even at high pressures. They usually have high densities and expand only very slightly when heated. In a solid, the molecules are held tightly together in definite arrangements. Liquid: Liquids have no definite shape and they take the shape of the container. They have a definite volume. They are not appreciably compressed by moderate pressures. They expand more than solids on heating and change into the gaseous state. They have lower densities than solids. Gas: Gases have no definite shape. They take the shape of the containing vessel. Gases have no definite volume. They have the property to fill the entire space available to them. They are easily compressed by even small pressures and also expand more than liquids on heating. They have low densities.
Solid
Liquid
Gas
40
IS MATTER AROUND US PURE?
Purity of Matter
Substances rarely exist in a pure form in nature. Often they are mixed with many other substances or materials. Their physical properties and chemical properties are either altered or are not clearly visible because of the presence of other substances. A pure substance is a distinct type of matter that has the same properties (physical and chemical) throughout the sample. elements in compounds are chemically bonded to each other. The physical and chemical properties of such compounds do not resemble the properties of any of the constituent elements. For example when hydrogen gas and oxygen gas are stored together in a container in the ratio 2:1, under certain conditions they would explosively combine to form water which is a liquid and has physical and chemical properties that are totally different from those of either hydrogen or oxygen. Water is a chemical compound. A molecule can be broken down chemically into atoms of the constituent elements. (figure (c)).
Elements, Compounds and Mixtures
According to its composition matter can be classified as element, compound and mixture.
Elements
An element is a type of substance that cannot be broken down chemically. When it is pure, the smallest unit of an element that displays all the properties of that element is an atom. Atoms of the same element may be visualized as similar looking tiny little objects (figure (a) below) each particle having the same physical and chemical properties as well. Many elements especially gases do not exist as single atoms. They exist in clusters (usually identical clusters of two or three atoms) as shown in figure (b) below. Examples of such elements are hydrogen, oxygen etc.
(c) Compound
3.1. MIxTurES
When two or more substances are mixed together and the substances retain their individual original identities, the combination is called a mixture. For example if you mix sand and water, sand retains its own properties and water retains its own properties. In a mixture, two or more substances are brought together and no chemical reaction takes MORE TO KNOW The purity of a substance is often determined by measuring its physical properties. For example, a colourless, odourless, tasteless liquid which at atmospheric pressure, boils at 100o C, freezes at 0o C and has a density of 1.0 g cm-3 is water. A pure substance can exist as element or compound. 41
(a) Atoms
(b) Molecules
Compounds
Compounds are substances resulting from the chemical combination of two or more elements in fixed proportions. The
SCIENCE
CHEMISTRY place. For example if hydrogen and oxygen, in any ratio are mixed together in a container gently at low temperatures in the absence of a spark, no chemical reaction would take place and the mixture would display the physical and chemical properties of hydrogen and oxygen. Types of mixtures Solid in solid Solid in liquid Solid in gas Liquid in solid
CHAPTER - 3
Examples Coins, alloys Sea water Smoke(carbon particles in air) Amalgam (metal + Mercury) Alcohol and water Cloud, fog Gas adsorbed by charcoal Soda drinks Air WE DO
3.2. HArACTErISTICS OF C MIxTurES
Mixtures may consist of substances in the same or different physical states. For example, bronze is an alloy consisting of the two solid metals, copper and tin; both are in the solid state. Most common solutions are mixtures of a solid in a liquid. For example salt dissolved in water. Mixtures are not pure substances since they are neither single type of distinct matter nor do they display single set of physical and chemical properties throughout the whole sample. As shown in figure (d) below, we can imagine mixtures to be different types of atoms or molecules held together but essentially retaining their individual physical and chemical properties. In mixtures, elements are physically mixed in any ratio and no new compound is formed. The substances making up a mixture are called constituents or components.
Liquid in liquid Liquid in gas Gas in solid Gas in liquid Gas in gas ACTIvITy –3.1
Left - Sulphur and Iron right - Iron sulphide
We mix iron powder and sulphur powder in a china dish. In another dish, we take the same substances and heat them strongly. We bring a magnet closely. Iron powder is attracted by the magnet and the compound iron sulphide is not. Now we distinguish a mixture and a compound. MORE TO KNOW The lead in your pencil is actually a form of carbon called graphite mixed with clay.
(d) Mixture 42
IS MATTER AROUND US PURE?
ACtIvIty –3.2 WE do sameproportionsinwhichtheyoccur at a place, and when this is done, no energychangesarenoticed. f The components of air can be separated by a physical method such as fractional distillation of liquid air. f iquid air does not have a definite L boiling point. It boils over a range of temperature between -196OC and -183OC. f If air is a compound, the composition of air expelled from humans should not be different from the composition of air around us. But it is known that during respiration, exhaled air has lower percentage of oxygen than ordinaryair. ACtIvIty –3.3 I do I classify the following into mixture or compound. (i) Alloys (ii) Smoke (iii) Juice (iv) Milk (v) Common salt (vi) Coffee (vii) Carbon dioxide (viii) Ice cream.
Is air around us pure? We discuss the reasons in groups.
Law of constant composition
A pure compound always contains the same elements combined together in the same definite proportions by weight irrespective of its method of preparation.
Is water a mixture or a compound?
Water is a compound because of the following reasons. f It is homogeneous. f t has definite physical constants I such as boiling point, freezing point, density,etc. f The properties of water are entirely different from those of its constituents, i.e, hydrogen and oxygen. f aterhasadefinitecompositionby W mass. TheratioofH:Obymassis1:8.
Composition of inhaled air and exhaled air during respiration.
Inhaled Air Contains78% nitrogen. Contains20% oxygen. Contains0.03% Carbon dioxide. Containsvery little moisture. Exhaled Air Contains78% nitrogen. Contains16% oxygen. Contains4%Carbon dioxide. Contains appreciable amount of moisture. in mass % 75.50% 23.20% 1.0% 0.046% Negligible Negligible
Is air a mixture or a compound?
Air is a mixture because of the following reasons. f irdoesnothaveafixedcomposition. A The composition of air varies from place to place. f rtificialaircanbemadebymixing A the various components of air in the
Composition of air
Gas Nitrogen Oxygen Argon Carbon dioxide Neon Helium 43
SCIENCE
CHEMISTRY
3.2.1. DIFFErENCES BETWEEN MIxTurE AND COMPOuND Mixture Elements are physically mixed in any ratio and no new compound is formed. They have no sharp or definite melting point, boiling point, density etc. A mixture exhibits the properties of its constituent or component elements. They are either homogeneous or heterogeneous in nature.
CHAPTER - 3
Compound Elements are chemically combined in a fixed ratio to form a new compound. They have definite melting point, boiling point, density etc. Property of a compound is different from its constituent or component elements. They are always homogeneous in nature.
Constituents of a mixture can be Constituents of a compound cannot be separated by physical methods like separated by physical methods. filtration, magnetic separation etc.
3.3. TyPES OF MIxTurES
There are two types of mixtures. They are, 1. Homogeneous mixture 2. Heterogeneous mixture H 3.3.1. OMOGENEOuS MIxTurES AND THEIr TyPES
There are three types of homogeneous mixtures. Solid homogeneous mixture - Alloys Liquid homogeneous mixture - lcohol in A water Gaseous homogeneous mixture - Air
Homogeneous Mixtures
Homogeneous mixtures consist of a uniform distribution of the substances throughout the mixture. Samples taken from any part of the mixture would have the same ratio of the ingredient substances and same physical and chemical properties although the properties of different samples may be different. Air is a homogeneous mixture of nitrogen,oxygen, argon and other traces of gases. All the ingredients of homogeneous mixtures necessarily have to be in the same state. Homogeneous mixtures are called solutions. ACTIvITy –3.4 I DO
Salt in water A cup of tea
ACTIvITy –3.5 f mix a drop of ink in water. I f observe whether I
I DO
the colour of the solution is uniform throughout.
Aspirin is a medicine for headache. It is composed of 60% carbon, 4.5% hydrogen and 35.5% oxygen by mass, regardless of its source. I observed that aspirin is a __________(mixture/compound) 44
f conclude that I it is a _______ (homogeneous mixture/ heterogeneous mixture)
IS MATTER AROUND US PURE?
3.3.2. HeTerogeneouS mIxTureS and THeIr TypeS Heterogeneous mixtures do not have a uniform composition. For example if you take dilute buttermilk in a vessel and keep it undisturbed at one place for some time then the particles settle to the bottom and the water comes to the top. The composition is not uniform. Ingredients of a heterogeneous mixture need not necessarily be in the same state, gas, liquid or solid. Solid - solid heterogeneous mixture mixture of sugar and salt Solid - liquid heterogeneous mixture ice cubes in water gas - gas heterogeneous mixture smoke in air. Liquid - liquid heterogeneous mixture kerosene in water. ACtIvIty –3.6 (i) Tea (ii) Ink (iii) Fruit salad (iv) Sugar solution ACtIvIty –3.7 I do
f I mix a spoonful of sand in water. f I try to see the particles of sand. f I observe whether the particles are evenly distributed in the mixture. f I write my conclusion about the nature of the mixture prepared.
I do
I classify each of the following as homogeneous or heterogeneous mixture
CLaSSIFICaTIon oF maTTer
Matter
Mixtures fVariable composition. f easily separated by physical methods. fNo definite physical constants.
Pure Substances fConstant composition. f not easily separated by physical methods. fHave definite physical constants.
Homogeneous Mixtures
Heterogeneous Mixtures
Elements f Contain atoms of the same kind.
Compounds f Contain two or more elements in a definite ratio by mass.
f Have the same f do not have the same composition composition throughout. throughout. f Components are f Components are distinguishable. indistinguishable.
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CHEMISTRY
3.4. EPArATION OF DIFFErENT S COMPONENTS OF A MIxTurE
Mixtures can be separated by simple physical procedures. To be able to separate the ingredients of a mixture we would need to know the physical properties of the individual ingredients. using the properties that are distinct and different, we can separate them. For example if both the ingredients of a mixture are soluble in water then we cannot separate the ingredients. However if we know that the melting point of two ingredients is different then we can use that knowledge to separate the ingredients. A good knowledge of physical properties is therefore very important.
CHAPTER - 3
S 3.4.1. EPArATION OF MIxTurES By SuBLIMATION Sublimation is defined as a process, in which a substance in solid state is directly converted into vapour state. At high temperature, the molecules of volatile solid move far away from each other making the solid substance into vapour.
1
2
1. Solid molecules evaporate 2. Iodine crystal vapourises
3. Sublimation of dry ice (carbon dioxide in ice form)
Separation of heterogeneous mixture
1. ecantation: used to separate a liquid D from a solid (present as large particles) that does not dissolve in it. 2. iltration: used to separate a liquid F from a solid (present as very small particles) which does not dissolve in the liquid. 3. ublimation: used to separate S a volatile solid substance from a mixture containing a non-volatile solid substance. 4. eparating funnel: used to separate S two completely immiscible liquids. ACTIvITy –3.8 I DO An equal quantity of fine salt and wheat flour are added into the beaker containing water and stirred well. The solubility of flour and salt in water are observed. The flour settles at the bottom of the beaker. I can now mention a suitable method of separation of flour from the salt. 46
3
Consider a mixture containing common salt and camphor. Both common salt and camphor are solid substances. Common salt is a non-volatile substance. It does not undergo sublimation. Camphor undergoes sublimation. Hence camphor can be separated from common salt by sublimation. ACTIvITy –3.9 WE ObSERvE
W e take a mixture containing common salt and camphor in a china dish placed over a stand and an inverted funnel is kept over it. The funnel stem is closed by means of cotton and the china dish is heated. The observations are recorded.
IS MATTER AROUND US PURE? cotton plug inverted funnel
immiscible liquids are usually separated by using a device named “separating funnel”. consider a mixture containing kerosene and water. both the liquids are immiscible with each other. by using a separating funnel, one liquid can be separated from the other. less denser liquid remains in the upper layer while high denser liquid remains in the lower layer. ACTIvITy –3.10 WE ObSERvE f take a mixture kerosene and water. containing
solidified camphor
vapours of camphor mixture of salt and camphor
f pour the mixture into a separating funnel. f close the mouth of the separating funnel. f Shake it for 10 minutes. MORE TO KNOW Solids that undergo sublimation are camphor, naphthalene, benzoic acid, iodine and ammonium chloride.
3.4.2. Separation of a mixture
f Hold the funnel in a stand for 15 minutes. f observe the changes. f note the lower and upper layers. f What is the principle behind it? Separation of HomogeneouS mixture
containing immiScible liquidS
1. distillation: used to separate a nonvolatile solid and a volatile liquid present together in a solution. 2. fractional distillation: used for separating funnel separating a mixture containing two or more liquids with an appreciable kerosene difference in their boiling points. 3. chromatography: Separation of two or water more dissolved solids can be carried out by chromatography. it can be used to separate samples as small as stop cock a picogram (10-12 g) and as large as several ions. it involves the distribution of solutes between a moving phase and a non-moving phase or stationary phase. 47
SCIENCE
CHEMISTRY
3.4.3. EPArATION OF A MIxTurE S CONTAINING MISCIBLE LIquIDS Fractional distillation is a suitable method for separation of a mixture containing miscible liquids. It works on the principle that the two liquids should vary in their boiling points by 25 K. f onsider a mixture containing two C liquids namely benzene and toluene.
CHAPTER - 3 f oth the liquids are miscible with B one another. f hey can be separated by fractional T distillation. f Boiling point of benzene is 353 K. f Boiling point of toluene is 384 K. f he difference in their boiling points T is 31 K.
thermometer
fractionating column
water condenser
flask benzene and toluene mixture
cooling water flows into condenser
distillate bunsen burner
warm water flows out of condenser
ACTIvITy –3.11 f ake a mixture of alcohol and water in a distillation flask. T
WE ObSERvE
f Close the distillation flask with a one holed rubber cork and fit a thermometer. f Fit a condenser. f Heat the mixture slowly. f lcohol vapourises first and gets condensed in the condenser and is collected. A f Water remains in the flask. 48
IS MATTER AROUND US PURE?
MORE TO KNOW
FILTRATION PROCESSES ADOPTED IN vARIOUS FIELDS:
1. Carbon filter:
Powdered charcoal can be formed in such a way as to be full of tiny holes, which serves as a filter. As air is drawn through the holes, the charcoal traps gases and chemicals . Such carbon filters are put in the gasmasks used by soldiers and fire fighters.
2. Air-Conditioning filter:
It circulates the air with fans and removes dust from air.
3. Automobile filter:
Filters in the fuel line clean the fuel but they can block the flow of fuel when they get clogged with dirt.
4. Water filter:
Particles of matter suspended in water are removed by the use of chemicals like chlorine, potash alum and powdered carbon and filtered through beds of sand or porous separation.
Identification of element, compound and mixture.
Matter IF NO
Is it uniform throughout?
IF yES
Homogeneous
Heterogeneous mixture
IF NO
IF yES
Does it have a variable composition? Homogeneous mixture (Solution)
Pure substance
IF NO
Can it be separated into simpler substance? Element Compound
IF yES
49
SCIENCE
CHEMISTRY EvALUATION
SECTION – A Choose the correct answer:
CHAPTER - 3
1. The lead in the pencil we use is made of a material called graphite. Graphite is a mixture of ________ (carbon and clay, clay and nitrogen) 2. Pure water is a compound. It contains 11.19% by mass of hydrogen and oxygen ________ by mass. (88.81% , 31.81%) 3. Coins are mixtures of solid in solid. Smoke is a mixture of ________ (solid in gas, gas in solid) 4. Some pair of items are given below. Could you identify the incorrect pair? a) Air - - - - gas in gas solid in liquid gas in liquid. liquid in liquid b) Seawater d) Amalgam
c) Soft drinks
5. Components of a given matter can be separated by various purifying techniques. Components of liquid air can be separated by adopting ________ physical method. (fractional distillation , distillation , sublimation) SECTION – b 6. ometimes I am hard and cold. Sometimes I am difficult to hold. But, I am always S present in air. Who am I? 7. Pure substance contains a single type of particles. Is sea water pure or not? justify. 8. In a compound two or more elements are combined in a fixed ratio by mass. Mention any two properties of a compound? 9. omogeneous mixture contains a single type of phase. Heterogeneous mixture H contains different types of phases. quote one example for each type. 10. hen a solid camphor is exposed to air, it changes into gaseous state. It is a W physical change. Name the process that takes place? Could you give another example for such a process. 11.(a) eparation of a mixture containing water and kerosene can be done by S use of ________ (distillation , separating funnel) (b) _______ (sublimation, chromatography) process is used to separate _ common salt and ammonium chloride. 50
IS MATTER AROUND US PURE?
12. liquid ‘A’ has a boiling point of 353 K and another liquid ‘B’ has a boiling point of A 384K. Both are miscible with each other. They are separated by “fractional distillation”. Justify the reason for using fractional distillation method. SECTION – C 13. In mixtures, components are combined in any ratio. . 15. eterogeneous mixture is separated by decantation. What is meant by decantation H Process? 16. In what way does an element differ from a compound? 17. Write a short note on chromatography. SECTION – D 18. What are heterogeneous mixtures? Mention their types with examples. 19. Classify the following as solution, heterogeneous mixture, compound or element. i. Sodium ii.Glucose v. Common salt 20. Alchohol is mixed with water. Write briefly the separation of the components. 21. How does the process of decantation differ from filtration? 22. How are immiscible liquids separated? iii. Lemon juice iv. Coal dust in sand (a) How does a mixture differ from a compound? (b) What are the types of mixtures? (c) Write an example for each type.
14. All matters in the universe exist in three states namely solid, liquid and gas. (a) Why do solid substances have definite shape? (b) Write any two properties of a solid substance.
(c) Will the solid substance expand on heating? Why?
ASSESSMENT ACTIvITy
1.Water purification experiment
Know about the natural way of purifying dirty water. you can make your own sand and gravel filter and use it to clean a sample of dirty water. use a large, empty can. Punch eight holes around the bottom of the can with a big nail. Place about 8cm (3 inches) of pebbles in the bottom of the can, and cover the pebbles with the same amount of sand. 51
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CHEMISTRY
Collect some muddy water from a puddle or pond. Hold the can over the bowl and pour the muddy water into the can. Look at the water that comes through the can. It is much clearer than the water you had poured in. Muddy water being poured in
CHAPTER - 3
Can Sticks to support the can
Sand Pebbles
2. Discussion
Aim : o enable the students to T know the components of the mixtures used in daily life. Name the components of the mixtures listed below. Mixtures 1. Air 2.Crude oil 3.Milk 4.Aerated drinks 5.Stainless steel
Components
3. Classification
Aim : o enable the students to classify the mixtures as homogeneous or T heterogeneous. Method of preparation of mixture Sugar is added to water Both sugar and salt are added to water Smoke in air Mixture containing rice and wheat Type of mixture obtained
4.Comparative learning
Aim : o enable the students to understand the method of purification involved in T separating components of a mixture. Type of mixture Salt solution Mixture containing petrol and kerosene Mixture containing kerosene in water Common salt and powdered camphor Water containing fine sand 52 Method of purification
IS MATTER AROUND US PURE?
5. opy the following table and write an example of a mixture in each empty C box. For example, coffee is a mixture of solid and liquid.
Solid Solid Liquid Gas Liquid Coffee Gas
6. Identify the physical states of the following
Matter Ice Air Water rice Oxygen Physical state
7. uppose a ship gets wrecked on an island in the Pacific Ocean. The S passengers, however, manage to bring plenty of firewood, match boxes and some pots ashore. Describe, with the help of diagrams, how the passengers can obtain drinking water from the salty ocean water. 8. mixture of chalk powder and salt can be separated by combining more A than one method. Salt is soluble in water, whereas chalk powder is not. The steps of separation are given below. Arrange them in correct order. i) Filtration removes the insoluble chalk powder. iii) Evaporation of the salt solution removes water. iv) Add the salt and chalk powder mixture to water. v) The chalk powder is then dried in sunlight. ii) Stir well. The salt dissolves in water.
Further reFerence
Books: General Chemistry (Second Edition) - Jean B.Umland & Jon M.Bellama West publishing company http://www.khanacademy.org
Websites : http://www.tutorvista.com
53
SCIENCE
ATOMIC STRUCTURE
4.1. IsCoVERy of THE D NuClEus
Need to study the structure of the atom
John Dalton proposed the idea of the atom as the smallest possible particle of any substance. He never worked with small particles of solids but actually he worked with gases, how they mix with each other, how they form compounds and how they dissolve in water etc. While working with all this he discovered that whenever elements combine to form more than one compound, the ratio of the masses of elements in the compounds are small whole number ratios of each other, which led him to the idea that the smallest particle of one substance was combining with the smallest part of another substance in a fixed quantities. The development of modern atomic theories is an excellent example of how science progresses. Many scientists contribute their knowledge for the development. New experiments lead to either changes in the old theories or even to new theories.Theories are useful in providing the basis for further work. Although, J.J.Thomson’s atomic theory explained electrical neutrality of atoms, it could not reveal the presence of nucleus in an atom, which was later proposed by Ernest Rutherford in 1909.
Rutherford’s contribution
Rutherford observed what happens to alpha particles projected at a thin metal foil.
Ernest Rutherford (1871-1937)
Ernest Rutherford, a British physicist probed atoms with alpha particles. He was known as the “father of nuclear physics”. He was awarded Nobel prize for his contribution in structure of atom in 1908.
4.2. uTHERfoRD’s R ExpERIMENT
A stream of alpha particles was made to pass through a thin gold foil of about 4x10-5 cm thickness. Most of the alpha particles did go through the foil in a straight line. some alpha particles were deflected through an average angle of 90o .Rarely the path of 1 in 20,000 alpha particles scored a direct hit on the nucleus and returned by an angle of 180o.
schematic diagram showing alpha particles bombarding one gold atom. The nucleus of the gold atom is shown in the centre.
1 2
1. Not scattered at all 2. slightly scattered
3. More scattered 4. Returned at 180o MORE TO KNOW 3 Alpha particles are helium 4 ions He2+ .The mass of an alpha particle is about 8000 times the mass of an electron. Velocity of alpha particles is about 2x107 m/s.
Alpha particles
55
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CHEMISTRY from this experiment, he concluded that there is a heavy positive charge occupying small volume, at the centre of an atom.
CHAPTER - 4 continuously lose energy. due to the loss of energy, path of electron may reduce and finally the electron should fall into nucleus. If it happens so, atom becomes unstable. But atoms are stable. hence Rutherford’s theory does not explain the stability of atom.
Nucleus
4.3. RutheRfoRd’s model of atom f atom has a very small nucleus at the centre. f there is large empty space around the nucleus. f entire mass of an atom is due to the mass of nucleus. f electrons are distributed in vacant space around the nucleus. f the electrons are moving in circular paths around the nucleus.
electron
electrons
Nucleus
MORE TO KNOW Imagine a small boy swinging a stone on the end of a string around him. the stone is able to occupy a larger volume because it is moving rapidly. similarly the electrons in an atom are able to occupy a larger volume because they are moving very fast. Neils Bohr (1885 - 1962)
MORE TO KNOW James Chadwick was one of Rutherford’s students.
4.3.1. lImItatIoNs according to electromagnetic theory, a moving electron should accelerate and AcTiviTy – 4.1 WE dO
We divide into groups and have a discussion about the following. In Rutherford’s experiment,
1.Why did the majority of alpha particles pass through the foil unaffected? 2.Why were very few alpha particles deflected? 3.Is the size of nucleus small or large with respect to the size of atom? 56
Neils Bohr was born on october 7, 1885 in Copenhagen, denmark. he was also an outstanding soccer player. he worked with Rutherford at the university of manchester. Bohr’s theory became the basis for modern physics known as Quantum mechanics.Bohr received the Nobel Prize for physics in 1922.
ATOMIC STRUCTURE
4.4. BoHR’s MoDEl of AToM
Neils Bohr modified Rutherford’s atom model and put forth the following postulates. f n atoms, the electrons revolve I around the nucleus in stationary circular paths. These paths are called orbits or shells or energy levels. f s long as electrons revolve in the A same orbit, it does not lose or gain energy. f he circular orbits are numbered as T 1, 2, 3, 4 or designated as K, l, M, N shells. These numbers are referred to as principal quantum numbers (n). f maller the size of orbit, smaller is s the energy of the orbit. f s we move away from the nucleus, A energy of the orbit is constantly increasing. f aximum number of electrons that M can be accommodated in an energy level (n) is given by 2n2 . f hen an electron absorbs energy, W it jumps from lower energy level to higher energy level. f hen an electron returns from higher W energy level to lower energy level, it gives off energy.
Third energy - level (M-shell)
second energy - level (l-shell) first energy - level (K-shell)
Orbit orbit is defined as the path, by which electrons revolve around the nucleus. dAlTON, ThOMSON, RUThERfORd ANd NEIlS BOhR - ATOM MOdElS
Dalton
Thomson
Rutherford Neils bohr
n = 1 (K shell) n = 2 (l shell)
4.5. DIsCoVERy of NEuTRoNs
In 1932, James Chadwick observed that when beryllium was exposed to alpha particles, particles with about the same mass as protons were emitted.. These emitted particles carried no electrical charge. Hence they were called as neutrons.
Beryllium + alpha ray carbon + neutron
n = 3 (M shell)
57
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CHEMISTRY
Beryllium
CHAPTER - 4
4.6.1. oMposITIoN of C NuClEus
Electrons have negligible mass. Hence the mass of an atom mainly depends on the mass of the nucleus. Nucleus of an atom consists of two components. They are protons and neutrons. protons are positively charged. protons repel each other because of their like-charges. Hence, more than one proton cannot be packed in a small volume to form a stable nucleus unless neutrons are present. Neutrons reduce the repulsive force between positively charged protons and contribute to the force that holds the particles in the nucleus together. proton Alpha particles Neutron Charge detector indicating no charge
MORE TO KNOW Number of neutrons = Mass number - Number of protons or Number of Electrons (Atomic number) Neutrons are particles with no charge i.e. neutral particles. Neutrons are present in the nuclei of all atoms except hydrogen atom. Mass of a neutron is almost equal to the mass of a proton. Atoms of the same element with different number of neutrons are called isotopes. Neutron is also regarded as a sub-atomic particle.
Neutron
4.6. HARACTERIsTICs of C fuNDAMENTAl pARTIClEs physical and chemical properties of elements and their compounds can be explained by the fundamental particles of an atom. The fundamental particles of an atom are: protons: They are positively charged particles. They are present inside the nucleus. Electrons: They are negatively charged particles. They revolve around the nucleus in circular orbits. Neutrons: They are neutral particles. They are present inside the nucleus. 58
Nucleus
oTHER suBAToMIC pARTIClEs Besides Electrons, protons and Neutrons, there are many sub-atomic particles such as; f Mesons f positrons f Neutrinos f Quarks f pions f Gluons
ATOMIC STRUCTURE
Characteristics of sub-atomic particles
Electron mass Charge in units 9.1x10-28 g -1 Proton 1.672x10-24 g +1 Neutron James Chadwick 1.674x10-24 g 0
Discovered by J.J. Thomson and H.A.Lorentz e. Goldstein
Nucleons
The elementary particles such as protons and neutrons are collectively referred to as nucleons. Thus mass number of atom is equal to the total number of nucleons in the nucleus of an atom.
4.7. ATomIC NumBer ANd mAss NumBer
Atomic number (Z)
Atomic number of an atom can be defined as the total number of protons present in the nucleus of the atom or the number of electrons present outside the nucleus of an atom. Thus the atomic number of hydrogen would be one and that for helium would be two. The symbol for Atomic number is Z. No two elements have the same atomic number; hence it is unique to each element. The atomic numbers of some elements are given in the table below:element Atomic number H 1 He 2 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11
Mass number (A)
element Atomic number mass number ACTIvITy – 4.2
H 1 1
He 2 4
Li 3 7
Be 4 9
B 5 11
C 6 12
N 7 14
o 8 16
F 9 19
Ne 10 20
Na 11 23
mg 12 24
WE DO
MORE TO KNOW
A has 11 protons, 11 electrons and 12 neutrons. B has 15 protons, 15 electrons and 16 neutrons. C has 4 protons, 4 electrons and 5 neutrons. We identify the elements A, B and C. 59
In lighter atoms, one neutron per proton is enough. Heavier atoms with more protons in the nucleus need more neutrons in the nucleus, for the nucleus to be stable. Thus the stability of the nucleus is determined by the Neutron-Proton ratio.
SCIENCE
Mass number (A) is defined as, the sum of the number of protons and neutrons present in the nucleus of an atom of an element. For example the mass number of sodium is 23 which implies that the total number of protons and neutrons in the sodium atom is 23. The number of neutrons can be obtained by subtracting the atomic number from the mass number (12 for sodium). The mass numbers of some elements are given in the table below:-
CHEMISTRY
AcTIvITy – 4.3 I dO
CHAPTER - 4 4.8. ISotoPeS
Proton 3
I complete the following table
Atomic number 5 11 15 10 number of protons number of electrons
Species Boron Sodium Phosphorus Neon
Neutron
Li 7
Li 6 3
Isotopes of lithium
Representation of Atomic number and Mass number
Atomic number (Z)
X
Mass number(A)
For example, Atomic number of nitrogen is 7. Mass number of nitrogen is 14. Representation:
14
American scientist, t.W.Richards observed to his amazement that Lead samples collected in different places differed in atomic mass. this suggested that all atoms of an element are not exactly alike. It is clear that atoms of an element have the same chemical properties.But they may differ in their masses. Isotopes are atoms of an element that differ in mass numbers, but have the same atomic number.
7
AcTIvITy – 4.4
N
I dO
From the following elements, I find which have the same number of neutrons. 1. Lithium - 3 Li 7 2. Carbon 3. Nitrogen 4. Beryllium 5. oxygen 6C 7N 12 14
Characteristics of isotopes f Isotopes of an element differ in mass numbers only. f Difference in mass number is due to difference in number of neutrons. f Isotopes of an element have the same chemical properties. f However, variation in physical properties are noted in isotopes. f elements having isotopes exhibit fractional atomic mass. AcTIvITy – 4.5 I dO
8 4 Be 16 8o
MORE TO KNOW Chlorine has fractional atomic mass. Chlorine-35 exists by 75% Chlorine-37 exists by 25% Average atomic mass of chlorine is,
{ }{ }
(i) I calculate the number of neutrons in the isotopes. (a) 1H1, 1H2, 1H3 (b) 17Cl35,
17Cl 37
75 x35 25 x37 + = 35.5 100 100
(ii) My inference________________ 60
ATOMIC STRUCTURE
Electron Proton Neutron
Protium atom (Common hydrogen) Element Isotope Protium Deuterium Tritium Chlorine Carbon Uranium Chlorine-35 Chlorine-37 Carbon-12 Carbon-14 Uranium-235 Uranium-238
Deuterium atom (Heavy hydrogen) Isotopes of Hydrogen
Representation
1 1H 2 1H 2 1D 3 1H 3 1T 17
Tritium atom (Radioactive hydrogen)
aCtIvIty – 4.7
I do
(or) (or)
Hydrogen
cl35 37 17cl
12 235 238
From the given average atomic mass, I find which element does exist with least number of isotopes. f Chlorine-35.5 f Hydrogen-1.008 f Oxygen-16.0
14 6C 92U 92U
6C
4.9. ElECtRoNIC CoNfIguRatIoN of atomS
It is known that atoms consist of a positively charged nucleus with protons and neutrons in it. Negatively charged particles called electrons constantly revolve around the nucleus in set of orbits. The electron orbits are numbered as 1, 2, 3, etc, starting from the orbit closest to the nucleus. These orbits are also called K, l, m, N shells, as mentioned in the atom model proposed by Niels Bohr. The maximum number of electrons in an orbit is given by 2n2, where n is the orbit number. Shell number or energy level First shell (K) Second shell (L) Third shell (M) Fourth shell (N) maximum number of electrons(2n2) 2(12) = 2 2(22) = 8 2(32) = 18 2(42) = 32
aCtIvIty – 4.6 The element bromine following isotopes. has
I do the
49.7% of Bromine-79 and 50.3% of Bromine-81
Based on this I calculate the average atomic mass of Bromine.
Uses of Isotopes
Many isotopes find use in medical field. f Iron-59 isotope is used in the treatment of anaemia. f Iodine-131 isotope is used for treatment of goitre. f Cobalt-60 isotope is used in the treatment of cancer. f Phosphorous-32 isotope is used in eye treatment. f Carbon-11 isotope is used in brain scan.
61
SCIENCE
CHEMISTRY
It must be understood that the second orbit begins to fill with electrons only after the first orbit is filled. The third orbit begins to fill only after the second orbit is filled. But the fourth orbit commences even before the third orbit is completely filled. The reason for this lies in the concept of quantum numbers. Thus the term electronic configuration or electronic structure refers to the way, the electrons are arranged around the nucleus. Most of the properties of elements and their compounds depend on their electronic configurations. To write electronic configuration, the principal quantum number of the shells must be known. This number describes the number of orbits present in the atom. let us consider sodium atom. Atomic number of sodium = Total number of electrons in sodium = 11 Orbit wise distribution of electrons Orbit Number of electrons 1. (K-Shell) 2n2 =2x12=2 electrons 2. (l-Shell) 2n2 =2x22=8 electrons 3. (M-Shell) Remaining=1 electron The electronic distribution in sodium is 2, 8, 1.
Sodium atom
CHAPTER - 4 some elements and their electronic configurations
Electron distribution
Element
Atomic Number
Electron dot structure
Hydrogen
1
1
(H)
Helium
2
2
(He)
lithium
3
2,1
(Li)
-
-
Beryllium
4
2,2
(Be)
- Boron
11P 12N
5
2,3
(B)
-
MORE TO KNOW Much of the experimental evidence for electronic configuration comes from atomic spectra. 62
Carbon
6
2,4
(C)
ATOMIC STRUCTURE
Some elements and their electronic configurations
Electron distribution Electron distribution
Atomic Number
Atomic Number
Element
Electron dot structure
Element
Electron dot structure
Nitrogen
(N)
7
2,5
Aluminium 13
(Al)
2,8,3
Oxygen
(O)
8
2,6
Silicon
(Si)
14
2,8,4
Fluorine
(F)
9
2,7
Phosphorus
(P)
15
2,8,5
Neon
(Ne)
10
2,8
Sulphur
(S)
16
2,8,6
Sodium
(Na)
11
2,8,1
Chlorine
(Cl)
17
2,8,7
Magnesium
(Mg)
12
2,8,2
Argon
(Ar)
18
2,8,8
63
SCIENCE
CHEMISTRY
ACTIvITy – 4.8 I write the electron distribution
Element lithium Boron fluorine Magnesium phosphorous Atomic number 3 5 9 12 15 Electron distribution l M K
CHAPTER - 4
I dO
Illustration lithium (Atomic number:3) has the electronic distribution, (n=1) K shell 2 (electron) (n=2) l shell 1 (remaining electron) outer most shell is ‘l’. The valence electron = 1 The valency of lithium = 1
4.9.1. AlENCE ElECTRoNs AND V VAlENCy
The number of electrons in the outer energy level (orbit) of an atom are the ones that can take part in chemical bonding. These electrons are referred to as the valence electrons. The outermost shell or orbit of an atom is known as valence shell or valence orbit. The electrons present in the outer shell are called valence electrons. The number representing the valence electrons is used to calculate the valency of the element. This valency is regarded as the combining capacity of elements. ACTIvITy – 4.9
When the number of electrons in the outermost shell is close to its full capacity, (such as 8 for l shell) valency is then determined by subtracting the valence electron number from the full capacity of 8. Valency = 8-valence electrons for example fluorine(atomic number: 9) has the electron distribution, n 1 2 shell K l electrons 2 7
outer shell (l) has 7 electrons which is close to the full capacity of 8. Hence valency = (8 -7) = 1 I dO
I calculate the valence electrons and determine the valency. Element Hydrogen Boron Carbon Magnesium Aluminium Atomic number 1 5 6 12 13 Valence electrons Valency
64
ATOMIC STRUCTURE
EvAlUATION
SECTION - A Choose the correct answer T 1. otal number of electrons, that can be accommodated in an orbit is given by 2 (n = 1, 2, 3....). Maximum number of electrons, that can be present in first orbit is 2n ________. (8, 2, 18) 2. oldstein discovered protons. It is present in the nucleus. Charge on the protons G are ________ (negative, positive, neutral). 3. subatomic particle is revolving around the nucleus in orbits. It is A negatively charged. It was discovered by J.J.Thomson. The particle is _______. (proton, neutron, electron) 4. umber of neutrons present in 3li7 is 4. The number of neutrons present in 8o16 N element is _______. (8, 7, 6) 5. ucleus of an atom has two components. They are proton and ________ N (positron, neutron, electron) 6. he sum of the number of protons and neutrons present in the nucleus is T called mass number. find the number of protons in the following element. (11, 23, 12) Element sodium (Na) Mass number 23 Number of protons ? Number of neutrons 12
7. tomic number and mass number of 17Cl35 are 17 and 35 respectively. The number A of protons present in it is _______ (17, 35, 18) 8. ______________________ isotope is used for the treatment of goitre. _ (Iodine – 131, phosphorus – 32, Iron – 59) 9. he electron distribution of fluorine is 2, 7. The valency of the element is ________ T (7, 2, 1) 10. lectron distribution of sodium is 2, 8, 1. The valency of the element is _______ E (2, 8, 1) 11. very atom has equal number of protons and electrons. Both are oppositively E charged. Neutron is electrically neutral. The nature of atom is _______ (positive, negative, neutral) SECTION - B 12. Electrons in an atom revolve around the nucleus in circular stationary paths. a) Who proposed such a statement? b) What is the name of the circular path? 13. K shell of 7N14 has 2 electrons. How many electrons are present in the l shell? 65
SCIENCE
CHEMISTRY
CHAPTER - 4
14. x 35 is a gaseous element. Its atomic number is 17. Its mass number is 35. 17 find out the number of electrons, protons and neutrons. 15. any Isotopes are used in medical field. M a) Which isotope is used for the treatment of anaemia? b) Which one is used in eye treatment? 16. Write the electron distribution in the following elements.
Element Atomic number K Electron distribution l M
Boron Magnesium
5 12
2 -
8
-
17. find the valence electrons and valency.
Element Atomic number valence electron valency
Carbon Aluminium
6(2,4) 13(2,8,3)
I 18. n the elements given here identify (a) Mass number (b) Atomic number (c) Number of protons (d) Number of Electrons (e) Number of Neutrons
2
He4, 3li7, 5B10, 6C12, 13Al27
19. opy and complete the table by adding the missing information for uranium C isotope.
Isotope Uranium- 235 Uranium- 238 Symbol
92u 235
Number of Protons 92 92
Number of Neutrons 143
Number of Electrons 92
SECTION - C 20. Name the elements with completely filled orbits.
Element Atomic Number Electron distribution
Nitrogen Neon Magnesium sulphur Argon
7 10 12 16 18
66
ATOMIC STRUCTURE
21. Correlate the facts with properties. (i) (ii) (iii) (iv) (v) More dense part of an atom Chargeless particle outermost orbit Number of electrons in outermost orbit Number of protons valency Atomic number nucleus Valence shell
Neutron proton 22. How many electrons can be accommodated in K, l and M shells? 2 3. What are the fundamental particles of an atom? Name all the subatomic particles. 2 4. What are isotopes? Draw the isotopes of Hydrogen. SECTION - d 25. hat are alpha particles? How are they useful in the determination of nucleus of W an atom? 26. Write briefly the atomic model concept proposed by Rutherford. 27. list the limitations of Rutherford’s atom model. 28. state the postulates of Bohr’s atom model? 29. Give experimental evidence about the discovery of neutron. 30. How is valency of an element predicted? 31. Give orbitwise electronic configuration of i. Carbon (Atomic Number - 6) iii. Magnesium (Atomic Number - 12) iv. phosphorus (Atomic Number - 15) v. Argon (Atomic Number - 18) ii. fluorine (Atomic Number - 9)
67
SCIENCE
CHEMISTRY
1. Assignment
ASSESSMENT ACTIvITy
CHAPTER - 4
Aim : o enable the students to know about the role of neutrons in the nucleus. T In lighter atoms protons and neutrons are equal in numbers. In heavier atoms they are not equal in numbers. list out the reasons.
2. project :
Aim : To construct the model of an atom C onstruct the model of an atom using available materials. your model should have the correct number of shells, and the correct number of electrons in each shell. use different colour codes to represent electrons, protons and neutrons(Choose any atom of your choice)
3. Discussion
A im : o enable the students to find out the major similarities and differences T between Rutherford and Neils Bohr atom models Similarities differences
4. Album
Aim: To enable the students to draw the atomic models. Draw the atomic models of Dalton, Thomson, Rutherford and Neils Bohr.
5. How do you assume about the shape of an atom to be? Tick your choice square shape Rectangular shape Circular shape spherical shape Elliptical shape
Further reFerence
Books: Atomic Structure Advanced Inoganic Chemistry Satya prakash, GD Tuli - S.Chand & Company Ltd Websites : http://www.shodor.org http://www.chemguide.co.uk.
68
STANDARD NINE
TERM I VOLUME 3
SCIENCE SOCIAL SCIENCE
NOT FOR SALE
Untouchability is Inhuman and a Crime
A Publication Under Free Textbook Programme of Government of Tamilnadu
Department of School Education
© Government of Tamilnadu
First Edition - 2013
(Published under Uniform System of School Education Scheme in Trimester Pattern)
Textbook Prepared and Compiled by
State Council of Educational Research and Training
College Road, Chennai - 600 006.
Textbook Printing
Tamilnadu Textbook Corporation
College Road, Chennai - 600 006.
This book has been printed on 80 G.S.M Maplitho Paper
Price : Rs.
Printed by Web Offset at :
Textbook available at
www.textbooksonline.tn.nic.in
ii
CONTENTS
UNIT TOPIC PAGE NO. (1 - 122)
SCIENCE
BIOLOGY 1. 2. Animal kingdom Cells CHEMISTRY 3. 4. Is matter around us pure? Atomic structure PHYSICS 5. 6. 7. Measuring instruments Motion Liquids Practicals
3 24
39 54
69 81 101 114
iii
CONTENTS
UNIT TOPIC SOCIAL SCIENCE HISTORY 1. 2. 3. Ancient Civilizations Intellectual Awakening in 6th Century B.C. Medieval Age GEOGRAPHY 1. 2. 3. 4. 5. Tamil Nadu Physiography of Tamil Nadu Climate of Tamil Nadu Resources of Tamil Nadu Tamil Nadu - Agriculture CIVICS 1. The Union Government ECONOMICS 1. Demand and Supply 233 220 162 169 177 189 205 124 142 151 PAGE NO. (123 - 236)
iv
SCIENCE
STANDARD NINE
TERM I
SCIENCE
1
Note to the teacher… As we present this revised edition of the Science Textbook, we would like to express our deepest gratitude to the learners and the teaching community for their enthusiastic responses. In science some concepts could be subjected to change from time to time as new theories and principles are constantly being evolved. We have tried to present facts and concepts of science (both concrete and abstract) in a visually appealing manner without detracting from the content. Activity based learning is now accepted as the basis of science education. These activities should be regarded as a means for open-ended investigation rather than for verification of principles/content given in the textbook has been designed to facilitate low cost activities and experiments using locally available materials. With a view to streamlining the activities, we have now segregated them into three groups: y I Do y We Do - activities to be done by an individual learner. - activities to be done by a group of learners and
y We Observe - activities to be demonstrated by the teacher. The third group of activities have a higher degree of difficulty or require careful handling as it may involve dealing with chemicals, electricity etc., The “More to know” snippets in the text represents some unusual and interesting facts or information in which the students need not be examined. The evaluation section is nothing but another space for learning in a different manner. As the focus is on understanding, rote learning is to be discouraged thoroughly. Application of learnt ideas, problem solving skills and critical thinking is to be encouraged. There could be scope for more than one answer to a question, which should be acknowledged always. To facilitate further reference, books and websites have been suggested at the end of each lesson. Suggestions and constructive criticism are most welcome. Valuable suggestions will be duly incorporated. - Authors sciencetextbook@gmail.com
2
BIOLOGY
Introduction
CHAPTER - 1
There are millions and millions of different organisms living along with us and around us. Could we remember all by their names? Biologists have helped us achieve this by sorting all living things into meaningful groups. Animals originated approximately 600 million years ago. More than 2 million existing varieties of animals have been identified. Of these more than 12,72,000 are invertebrates and fewer than 62,000 species are vertebrates. The system of sorting living organisms into various groups based on similarities and differences is called classification. taxon is the kingdom and the smallest is the species.
Kingdom
Phylum
Class
TAXONOMY
The branch of biology dealing with identification, description, nomenclature and classification of living organisms is called taxonomy. Biological classification helps us to identify organisms and also recognize those already classified. Carolus Linnaeus classified organisms based on the similarities and differences into small groups called taxa.
Order
Family
Genus
Species
Units of Taxonomy
Levels of classification
According to the order of arrangement the different levels of taxa (singular taxon) are Kingdom, Phylum, Class, Order, Family, Genus and Species.The largest
Criteria for classification
1. Grade of organisation – animals are grouped into unicellular and multicellular based on the number of cells.
MORE TO KNOW Carolus Linnaeus, the Swedish Botanist is regarded as the father of modern taxonomy. (1707-1778) 4 Aristotle, the father of Zoology was the first to classify animals based on their similarities and differences. (384-322 BC)
ANIMAL KINGDOM
c. Eucoelomate – Animals with a true coelom (eg. Earth worm) Acoelomate ectoderm mesoderm endoderm
Pseudocoelomate ectoderm mesoderm endoderm coelom
2. Germ layers – Germ layers are collection of cells formed during development of an embryo. These layers give rise to different organs as the embryo become an adult. Based on the number of layers the multicellular animals are classified into diploblastic (two germ layers ectoderm,endoderm) and triploblastic (three germ layers - ectoderm, mesoderm and endoderm) animals. 3. Symmetry – it refers to the arrangement of body parts around a central axis. Based on symmetry, animals are classified into a. Asymmetrical. eg. Amoeba b. Radially symmetrical. eg. Hydra c. Bilaterally symmetrical. eg. Earth worm 4. Coelom – the fluid filled space between the body wall and digestive tract is called coelom. Based on the nature of coelom, animals are divided into a. Acoelomate – Animals without a coelom. eg. Tape worm b. Pseudocoelomate – Animals with a false coelom. eg. Round worm 5
Eucoelomate ectoderm mesentery endoderm mesoderm coelom
a. Poikilothermic animals – whose body temperature varies with that of environment. eg. Fish, frog b. Homeothermic animals – whose body temperature always remains constant and slightly higher than the environment. eg. Birds, man Animals are classified into two major groups, namely invertebrates and vertebrates based on the absence or presence of back bone (Vertebral column)
SCIENCE
5. Body temperature – animals are classified into two groups on the basis of their ability to regulate their body temperature into
BIOLOGY
CHAPTER - 1 actIvIty – 1.1 I DO
1.1. Invertebrates
Invertebrates are classified into nine phyla namely 1. Phylum Protozoa (eg. Amoeba) 2. Phylum Porifera (eg. Sponges) 3. Phylum Coelenterata (eg. Hydra) 4. Phylum Platyhelminthes (eg. Tape worm) 5. Phylum Aschelminthes (eg. Roundworm) 6. Phylum Annelida (eg. Earthworm) 7. Phylum Arthropoda (eg. Cockroach) 8. Phylum Mollusca (eg. Snail) and 9. Phylum Echinodermata (eg. Starfish)
I collect a sample of water from a fresh water pond and I prepare a micro slide. Afterwards adding a drop of methylene blue stain to the water. After I view the slide under a microscope, I try to find an amoeba.
2. Phylum Porifera
These are non-motile marine animals attached to some solid support such as rocks or shells. These are multicellular animals with perforated(having holes) bodies. The cells are loosely arranged without the formation of tissues.The pores lead to a canal system which helps in circulating water throughout the body to bring in food and oxygen. They possess an internal skeleton made up of calcareous or silicious spicules. Reproduction is both by asexual (budding or gemmule formation) or sexual method (fusion of male and female gametes). eg. Sycon, Sponges
1. Phylum Protozoa
These are generally unicellular microscopic animals. Locomotion takes place by cilia, flagella or pseudopodia. Mode of nutrition may be holozoic, saprozoic or parasitic. They reproduce asexually by binary or multiple fission and sexually by conjugation. eg. Amoeba, Paramoecium
Cilia Contractile vacuole
Micro nucleus Macro nucleus Food vacuole
Sponges
3. Phylum Coelenterata
Paramoecium
These animals are aquatic with radial symmetry. They may be sessile(Polyps) or free floating(medusa). There is a 6
ANIMAL KINGDOM distinct body cavity called coelenteron or gastro vascular cavity. The body bears slender, flexible tentacles around the mouth. The tentacles at their tip bears stinging cells called cnidoblasts which have poisonous barbs to sting their prey. They are used for protection and for attack. Reproduction takes place either by asexual (budding or fission) or by sexual method (by gametes). eg. Sea anemone, Hydra
4. Phylum Platyhelminthes (flat worms)
These are flat, leaf like, ribbon like organisms. They are triploblastic, bilaterally symmetrical and acoelomate animals. These are either free living (eg. Planaria) or parasitic (eg. Tape worm). Parasites have organs of attachment such as hooks and suckers. They are mostly hermaphrodites (i.e. male and female sex organs are present in the same individual). eg. Planaria, Liverfluke
Tape worm Planaria
Sea anemone
MORE TO KNOW
5. Phylum Aschelminthes (round or thread worms)
The body is cylindrical, unsegmented and protected by a resistant cuticle. The animals are bilaterally symmetrical, triploblastic and pseudocoelomate. Circulatory and respiratory systems are absent. Sexes are separate(male and female) and fertilization is internal(inside the body). These are familiar as parasitic worms causing elephantiasis (filarial worm) and ascariasis (ascaris).
The Australian sea wasp or box jelly fish (Chironex fleckeri) is the most venomous coelenterate in the world. It has enough poison to kill about sixty people. ACTIvITy – 1.2 I DO
I observe a permanent slide of hydra under a microscope. I observe the mouth, tentacles and basal disc of hydra and I draw a neat labelled diagram. 7
Ascaris
SCIENCE
BIOLOGY
6. Phylum Annelida
Do you know about vermicompost? Which animal plays a vital role in vermicomposting?
CHAPTER - 1
Earthworm
The body is elongated, cylindrical and segmented (i.e. the body is divided into compartments called segments). They move with the help of setae and parapodia. They exhibit cephalisation (formation of a distinct head) and metamerism (segmental repetition of identical organs). eg. Earthworm, leech
Butterfly
7. Phylum Arthropoda
Do you know which is the largest phylum? Do you know which is the most successful group of animals on earth? Arthropods are the largest group of organisms and insects are the most successful group of animals. It includes crustaceans (eg. crab, prawn), insects (eg. butterfly, cockroach), arachnids (eg. spider, scorpion) and myriapods
(centipedes and millipedes). These forms have jointed legs with a chitinous exoskeleton. The jointed limbs are used for locomotion, feeding and sensing. Their body is also segmented and grouped together to form head, thorax and abdomen. It is covered by a hard, firm external skeleton made up of a strong substance called chitin. Arthropods possess compound eyes. They have open type of circulation where blood vessels are absent and the body fluid circulates in the body cavity, bathing all the organs.
Scorpion
MORE TO KNOW EARThWORMS are referred to as “Farmer’s Friend”? Why? Earthworm plays a vital role in improving the fertility of the soil. It ploughs the land and assists in the recycling of organic matter for the efficient growth of the plants. The soil system is loosened, stirred up and aerated by the vertical migration of earthworms. hIRUDIN - is a naturally occurring protein in the salivary glands of Leeches that has a blood anticoagulant property. Hence blood fails to clot ensuring continuous flow of blood when the leech sucks the blood. This property is widely used in the field of medicine and used in the treatment of blood clotting disorders and in the development of anticoagulant pharmaceuticals . 8
ANIMAL KINGDOM
8. Phylum Mollusca
Molluscs form the second largest group of organisms. Body is soft, unsegmented and without appendages. It is surrounded by a thin, fleshy structure called mantle which secretes a hard calcareous shell. They move around with the help of a muscular foot. Respiration is usually by gills called ctenidia. eg. snail, mussel, oysters
9. Phylum Echinodermata
These are marine organisms. Their skin is covered by calcareous spines. Echinoderms are unique because they have a system of water-filled canals inside the body. These canals project out in the form of hundreds of tube feet on the underside of their body. A starfish moves with the help of tubefeet. Tube feet have suction cups at their ends and are powered by muscles and hydraulic force from the water-vascular system. The water-vascular system also helps in the exchange of gases, internal transport of nourishment, and excretion. eg.starfish, sea cucumber
Mussels
Starfish
Biodiversity of India
India has an immense variety of plants and animals. It is a home to 2000 species of fishes, 182 species of amphibians, 453 species of reptiles, 1200 species of birds and 350 species of mammals. India ranks within the top 10 countries in the world in the biodiversity of vertebrates. Complete the following paragraph :
MORE TO KNOW Insects form one of the most successful groups of animals. More than a million species of insects are known today. ACTIvITy – 1.3 I DO
I make a list of any five poisonous invertebrates.
All animals have one common characteristic ________. The invertebrates are animals that do not have ________.The largest invertebrate group is ________ . Animals with a soft body covered with one or two hard shells are ________. The spiny skinned organisms are ________.
9
SCIENCE
BIOLOGY
CHAPTER - 1
1.2. VERTEbRATES
The Vertebrates are the most advanced group of organisms on Earth. These animals are larger in size than the invertebrates. They are coelomate , triploblastic and bilaterally symmetrical. They have a strong and flexible vertebral column made of a chain of cylindrical bones. Vertebrates also show characteristics that include body segmentation, closed blood circulation and presence of a well developed internal skeleton. They also have well developed brain. How do vertebrates differ from invertebrates? Sl.No. 1. 2. 3. Invertebrates They do not have a back bone. They include both unicellular and multicellular organisms. Vertebrates They have a distinct back bone. They include only multicellular organisms.
They have different types of They have two pairs of limbs for locomotory organs such as locomotion. pseudopodia, flagella, cilia, etc., Organisms may be free living or parasitic. Systems are simple in organisation. Reproduction is by asexual or sexual methods. All organisms are free living. Systems are complex and highly organised. Reproduction is only by sexual method.
4 5. 6.
Vertebrates are classified into five classes as follows. 1. Pisces. 2. Amphibia 3. Reptilia 4. Aves 5. Mammalia
1. Pisces
These are aquatic animals and their skin is covered with over lapping scales which form the exoskeleton. The Endoskeleton is made up of either cartilage (tough, flexible tissue) eg. Shark or bone eg. Catla. The body is streamlined. Respiration is by gills which are covered by lid-like structure called an operculum on either side. Heart is two chambered (one auricle and one ventricle). These are poikilothermic animals. They are either oviparous or viviparous. 10
Lion fish
2. Amphibia
Amphibians are poikilothermic vertebrates which can live on land as well as in water (dual life). Body is divisible into head and trunk. Skin is moist and slimy and helps in exchange of gases for respiration. The heart is three chambered (two auricles and one
ANIMAL KINGDOM
MORE TO KNOW Unforgiving fish? The stone fish is a highly poisonous fish in the world. The poison is carried in its skin and in sacs attached to razor sharp spines along its back. When attacked or even accidentally stepped on, the stone fish pushes its spines into the predator and releases the poison into the wounds which usually results in paralysis or death. MORE TO KNOW Amphibians are good indicators of environmental changes. They breathe partially through their skin which makes them sensitive to radiation, pollution and habitat destruction. Scientists believe amphibians can show the first signs of environmental emergencies. In the last 20 years, the number of amphibian species have declined, with some species becoming extinct due to acid rain, ozone depletion and chemical pollution.
Salamander
ventricle). Respiration is by gills (tadpole), skin and lungs (adult). Fertilisation is external(outside the body). They are oviparous (egg laying) showing complete metamorphosis. eg. Frogs, Toads and Salamanders
How to distinguish frogs from toads?
S.No. 1 2 3 4 5 6 TOAD Short hind legs. Rough, warty skin. Spends little time in water. FROG Long hind legs. Moist, smooth skin. Spends more time in water.
Walks and makes short hops. Jumps. Toothless. Webless hind feet. Teeth in upper jaw. Webbed hind feet.
MORE TO KNOW The drug derived from the extract of Poison arrow frog (Epipedobates tricolor) works as a powerful painkiller. It has the same benefits of morphine but without any side effects.
11
SCIENCE
BIOLOGY
3. Reptilia
CHAPTER - 1
These are poikilothermic creeping or crawling terrestrial animals and their body is covered with dryskin or epidermal scales. A thin membrane called the tympanum represents the ear. Heart is three chambered. They breathe through lungs. They are oviparous. Development is direct and the young ones resemble their parents. eg. Snakes, Turtles, Lizards
Indian Cobra
MORE TO KNOW The slowest reptile The fastest reptile World’s fastest snake The world’s longest snake Largest poisonous snake Smallest reptile Largest reptile Giant tortoise of Galapagos islands. Spiny-tailed Iguana of Costa Rica. The black mamba of Africa A reticulated python King Cobra. mini meleon Komodo dragon.
4. Aves
Birds are characterized by the presence of feathers, modified forelimbs (wings), beak and air filled bones (pneumatic bones). These are homeothermic and oviparous which lay cledoic eggs (with shell) with large amount of yolk (reserve food). The hind limbs are modified for walking, swimming or clasping. The heart is four chambered. Fertilization is internal. Pigeon, Crow and Sparrow are examples of birds that we commonly see flying around us. Ostrich, penguin, emu and cassowary are examples of birds that do not fly.
Peacock
Owl
12
ANIMAL KINGDOM
Vedanthangal Birds Sanctuary
It is one of the spectacular breeding grounds in India. It is located in Kancheepuram District of Tamilnadu (about 75 km from Chennai). The bird life (residents and visitors) include Cormarants, Darters, Herons, Egrets, Open billed stork, Spoon bills, white ibis, Little grebe, Blackwinged suits, Grey pelican etc. November to February is the ideal season to visit the sanctuary. MORE TO KNOW f Woodpeckers not only peck the wood for insects but can also hear the sound of insects crawling inside the wood. f Penguins can survive freezing cold temperatures because of a thick layer of the fat below their skin which act as heat insulator. f Owls can easily hunt in darkness, since their eye balls are elastic and can be focused instantly at any distance. They can widely open their pupil to allow more light to enter.
Vedanthangal birds sanctuary
MORE TO KNOW
Echolocation in Bats
Echolocation is also called bio sonar which is used by several animals like bats. These animals emit ultrasound waves and listen to the echoes of those calls that return from various object in the surroundings. They use these echoes to locate, range and identify the objects. It is used for navigation and for hunting in total darkness.
5. Mammalia
Mammals are Homeothermic vertebrates characterised by presence of milk producing glands (mammary glands). Their skin has hair as well as sweat and oil glands. Heterodont dentition (different types of teeth), external ears or pinnae, diaphragm (muscle which separate thorax and abdomen), four chambered heart, pulmonary respiration (lungs), internal fertilization and viviparity are other salient features. Rat, Cat, Whale, Dolphin, Elephant, Monkey and Man are examples of mammals. Bat is an example of a flying mammal. 13
Dolphins
SCIENCE
BIOLOGY
ACTIVITY – 1.4
CHAPTER - 1
I DO
I visit the zoo and note down the different animals and their feeding habits. ACTIVITY – 1.5 1. A marine invertebrate that has a porous body: ___________________ 2. A marine invertebrate that has a soft body and a shell:___________________ 3. A homoeothermic vertebrate with modified fore limbs: ___________________ 4. A marine invertebrate that is covered with spines :___________________ 5. An invertebrate that has a segmented body and jointed limbs: ______________ 6. A vertebrate that has fur and feeds its young with milk : ___________________ 7. A vertebrate that has dry scaly skin : ___________________ 8. An invertebrate that has a long, segmented body without any limbs: ___________________ I DO
1.3. VARIOUS MODES OF REPRODUCTION IN ANIMALS
Lion with cub Hippopotamus with young one
Reproduction is the capacity of an organism to produce young ones of their own kind. Living things reproduce to ensure the continuation of their species. All animals have the ability to reproduce. The process of reproduction can be asexual or sexual. Sl.No. 1. Asexual Reproduction It involves a single parent. Sexual Reproduction It involves two parents (male and female) each capable of producing gametes. It involves the fusion of male and female gametes [(i.e.) Sperm and ovum] resulting in the formation of zygote.
2.
It does not involve the fusion of gametes.
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ANIMAL KINGDOM
Asexual Reproduction
In asexual reproduction, new individuals are formed from a single parent. A single celled organism may simply divide and give rise to independent daughter cells. Some of the ways in which organisms reproduce asexually are multiple fission, binary fission, budding, gemmule formation and sporulation. Each daughter nucleus is surrounded by cytoplasm and plasma membrane and thus a number of daughter cells are formed. Each cell separates and leads an independent life.
Budding (eg. Hydra)
Binary fission (eg. Paramoecium)
Paramoecium is an unicellular organism which reproduces by binary fission. In this process a constriction appears at the centre which divides the nucleus and cytoplasm into two parts. Thus a single paramoecium is divided into two daughter cells.
Hydra with bud
Constriction
Nuclear Division
Gemmules (eg. Sponges)
Gemmules are internal buds found in sponges and are resistant to unfavourable condition. These buds have an outer thick layer with numerous air spaces and two inner chitinous layers. On the onset of favourable conditions, the cell mass comes out of the gemmule through an opening called the micropyle. Later the cell mass develops into a young sponge. ACtIvIty – 1.6 I DO
Daughter Paramoecia
Binary fission in Paramoecium
Multiple Fission (eg. Amoeba)
Many protozoans reproduce by multiple fission under unfavourable condition. In this process, the nucleus of the parent cell divides repeatedly to form a number of daughter nuclei.
I observe a micro slide of binary fission in amoeba. 15
SCIENCE
Hydra reproduces asexually by budding. During budding the body wall of hydra produces an outgrowth (bud) due to repeated cell division at one specific site. This bud gradually grows in size and develops a mouth and tentacles at the free end. Soon a constriction appears at the point of contact and the daughter hydra gets separated from the mother and leads an independent life.
BIOLOGY
CHAPTER - 1
Advantages of Asexual reproduction
1. It requires only one parent. 2. It does not involve gametes and fertilization. 3. The young ones have identical characteristics of their parents.
Disadvantages of Asexual reproduction
1. Offspring do not show much variation from parents. This reduces the chances of having a variety that could lead to formation of new species after hundreds of years. 2. Undesirable characters are transfered from parent to offspring without any change.
Gemmule
Spore and cyst formation (eg. Plasmodium)
This type of reproduction is common among protozoan parasites such as plasmodium (malarial parasite). This method is also called sporulation. During unfavourable conditions, the protoplasm is condensed and covered by a thick, protective covering called the cyst. When conditions are favourable, the cyst gets dissolved. The protoplasm regains its original nature and undergoes multiple fission giving rise to numerous independent daughter cells. This process is called sporulation. MORE TO KNOW
Sexual reproduction
Sexual reproduction involves the production of sex cells or gametes. The male organism gives rise to male gamete or sperm and the female organism gives rise to the female gamete or the ovum. In sexual reproduction the male and female gametes fuse together to form a single cell called the zygote. The zygote grows to be a new adult. Gametes are produced in organs that are generally referred to as the gonads. The male gonad is the testis and the female gonad is the ovary. If an organism carries any one type of gonad it is said to be a unisexual organism. In this case the sexes are said to be separate: male and female. Bisexual organisms, also referred to as hermaphrodites, are those that possess both testis and ovary in the same body. Hydra and Tapeworm are examples of bisexual organisms. Unicellular organisms like Paramoecium are also known to reproduce sexually. Two Paramoecia come together, establish a bridge-
Regeneration
Animals like Sponges, Hydra, Planaria and Starfish exhibit regeneration. It is a complex process which involves the repair of damaged cells or tissues or redevelopment of severed part or formation of whole body from a small fragment.
Autotomy
It refers to the power of self cutting of body parts for defence. Examples – Regeneration of arms in Starfish, regeneration of tail in House Lizard. 16
ANIMAL KINGDOM like connection and exchange genetic material. Each of them separate and divide independently to give rise to daughter cells . This method of sexual reproduction is called conjugation. reproductive organ is the ovary which produce the ova or eggs. A sperm and an egg fuse to form a zygote. The fusion of sperm and ovum is called fertilization. The zygote further develops into an embryo and later becomes an adult.
1 2 3 4 6
7
1.4. FERTILIZATION
Fertilization is a process of fusion of haploid male and female gamete to form a diploid zygote.
5
Types of fertilization
The two types of fertilization are, (a) External fertilization – The fusion of the gametes occurs outside the body of the animal. (eg. Frogs, Echinoderms) (b) Internal fertilization – The fusion of the gametes occur within the body of the female parent. (eg. Reptiles, Birds and Mammals)
Conjugation in Paramoecium
SExUAL REPRODUCTION Schematic representation of sexual reproduction
Male Female
1.5. VIVIPAROUS ANIMALS
Testis Ovary In Viviparous animals, example Mammals, a zygote develops into an embryo that grows inside the mother and receives nourishment directly from the mother. After a period of time the mother gives birth to young ones that resemble the adult.
Sperm (n)
Ovum (n)
Zygote (2n)
Embryo
Young individual In higher organisms, two individuals of a species (male and female) are involved in sexual reproduction. The male reproductive organ is the testis which produce the sperms. The female 17
SCIENCE
BIOLOGY
CHAPTER - 1
1.6. OVIPAROUS ANIMALS
Oviparous animals lay eggs laden with yolk. These eggs are laid outside after the process of internal fertilization (e.g. Reptiles and insects). The embryonic development takes place outside the body of the mother. Land dwelling animals lay eggs with shell (cledoic eggs). The shell gives protection and prevents desiccation. Aquatic animals lay eggs without a shell(noncledoic eggs) MORE TO KNOW Ovoviviparous animals In these animals the embryos develop inside the eggs that are retained within the mother’s body until they are ready to hatch. The young ones are nourished by the egg yolk and there is no placental connection. eg. Vipers
Cledoic eggs
Non cledoic eggs
changes which transform the young ones into adults are known as metamorphosis. MORE TO KNOW Moulting hormone Moulting hormone or ecdysone or juvenile hormones are secreted by the neuro secretory cells of the brain and controls moulting in insects. Types of metamorphosis
1.7. YOUNG ONES TO ADULT
The young ones which emerge from the egg either has resemblance or no resemblance with the adult. The young one has to pass through morphological, anatomical and physiological changes and get transformed into an adult. These Life cycle of Grasshopper
1. Incomplete metamorphosis
Among animals where the young ones resemble the adult, growth in size takes place. In arthropods the shell covering the body is shed periodically, to match the growth of the animal. Life cycle of Grasshopper: The newly hatched young ones resembles the adult except in size, wings and reproductive organs. The young ones which hatch out of the egg (nymphs) undergo several intermediary stages through successive moultings to become an adult. Egg Nymph Adult e.g Grasshopper, Mayfly
Nymphs Eggs Adult
18
ANIMAL KINGDOM
Eggs Larva
Pupa Adult
Complete metamorphosis
Life cycle of Butterfly size. Then the larva enters a resting stage the pupa and develops a pupal case (cocoon) around it. After a period of time, the adult or imago emerges out of the cocoon. Larva Pupa Adult Egg e.g. Butterfly, Silk moth.
2. Complete metamorphosis
Life cycle of Butterfly The young ones are strikingly different from the adults and the process of development starts with larva which hatches out of the egg. It is worm like and termed as caterpillar. The larva feeds voraciously on leaves and increase in
EVALUATION
Section – A Think and answer
1. The arrangement of body parts in an organism is known as symmetry. Classify organisms based on symmetry. 2. Reptilia → Pisces → Aves → Mammalia → Amphibia Arrange in correct sequence according to the evolutionary trend. 3. Coelenterates have a special mechanism to protect themselves from their enemies. Explain how? 4. Some Platyhelminthes are parasites. Mention any two adaptations. 5. Frogs can live on land and in water. Mention any two adaptations. 19
SCIENCE
BIOLOGY
Section – B
CHAPTER - 1
6. Millions of organisms inhabit the earth. They are classified and placed under different groups. Mention the need for classification. 7. a) Match the organisms with their locomotory organs. b) Correlate the locomotory organs with their mode of existence. Organisms Paramoecium Fishes Frogs Aves Mammals Locomotory organs Limbs Webbed feet Wings Fins Cilia
8. The eggs of birds are Cledoic (shell) and contains yolk. Mention the role of the shell and yolk in birds. 9. Most of the birds can fly. List the structural adaptations which enable them to fly. 10. Earthworms can increase soil fertility. Justify. 11. Both the Sperm and Ovum contains haploid set (n) of chromosomes. Give reason. 12. In insects during metamorphosis, the outer skin is cast off periodically. Name the process and mention its significance.
Section C
13. Match the following columns A, B and C to make meaningful sequences: One is done for you: Birds lay eggs that are cledoic a). Column A Platyhelminthes Frogs hydra birds grasshopper b). Column A Tapeworm Earthworm Starfish Paramoecium Mussels eggs nematocyst parasites amphibious nymph Column B Vermi compost Spiny Skin Locomotion Shell Hooks and suckers 20 Column B Column C protection molting cledoic Hooks and suckers gills and lungs Column C Calcareous spines Parasite Soft body Organic farming Cilia
ANIMAL KINGDOM
Section D Answer the following in not more than two sentences:
14. Mammals are homeotherms. List the vertebrate classes that are poikilotherms. 15. Fertilization is internal in mammals. Name a group that have external fertilization 16. Nymphs undergo a process to become an adult grasshopper. Define it. 17. Frogs and toads are different but they are in the same group - amphibians. Are spider and mosquito related? How? 18. Insects are the most successful group of animals. List the reasons.
Section E Answer in a paragraph
19. How do poikilotherms adapt to change in the environmental temperatures. Give an example. 20. Taxonomy is the science of classification. Imagine you are a biologist and make a list of criteria how you would classify a pearl oyster. 21. Young insects undergo changes to become adults. Define this change. Compare the life cycle of a grasshopper with that of a butterfly.
SUGGESTED ACTIVITIES Activity • Cut a paper into seven pieces. • Write seven units of taxonomy in the chart pieces. • Fix a double side tape at the back of each chart pieces. • Fix the units of Taxonomy in the correct order on a chart paper. • Submit it for assessment. Activity • Prepare the branches of evolutionary tree with paper. • Fix the pictures of animals according to their evolution. • Let the students make an evolutionary tree for vertebrates. 21 Learning by doing Learning by doing
• Collect the pictures of different classes of animals of vertebrates.
SCIENCE
BIOLOGY
Activity
CHAPTER - 1
Observation
• While you are visiting your native village, observe natural hatching phenomenon of hen. • Write a paragraph about natural hatching. Activity • Observe ten animals in your locality. • Write down the common names of above animals. • Find out the zoological names of the above animals with the help of Website, or senior students or parents. Assignment
Common Names
Zoological Names
Activity Observe any two animals in your locality and enlist its parental care.
Observation
Assessment activity Class Topic Activity :9 : Animal Kingdom : Individual
Method of Assessment : Preparation of worksheet Aim: To Identify and differentiate between Invertebrate and Vertebrate animals Materials required: Pictures, Photos and preserved animals of Invertebrates and Vertebrates. Procedure: • • • • Ask the students to observe the animal pictures carefully. Ask them about the locomotary organs of the animals. Ask them about their mode of nutrition. Teacher explains the mode of reproduction of animals.
Conclusion: The students learn to identify the invertebrates and Vertebrates. 22
ANIMAL KINGDOM
Sl. No. Name of the animal Housefly Earthworm Starfish Hen Fish Frog Invertebrates Verterbrates
Remedial Activities: 1. Show additional animals pictures of animals from books and websites. Ask students to identify Invertebrates and vertebrates. 2. By using the permanent charts of organ system of animals, the teacher explains the complexity of organ system. Life Skills Through this activity the life skill such as creative thinking, co-operation and interpersonal relationship are developed. Assignment Activity Prepare a table and write the classification for the following animals. (Cockroach, Cat, Dog, Lion, Tiger) Name of the animal Kingdom Phylum Class Order Family Genus Species
Further reFerence
Books: 1. Developmental Biology - Arumugam.N, Saras Publications. 2. A Manual of Zoology, VolumeI& II - Ekambaranatha Iyar, E.K. and T.N.Ananthakrishnan, Viswanathan &Co. 3. Invertebrates - Barnes, R.D.,W.B.Saunders Publications.
Websites : http://www.worldanimal.net http://www.animaltrial.com
23
SCIENCE
Cells 2.1. PROKARYOTIC AND eUKARYOTIC Cells
Cells are the smallest functional unit in a living organism. Based on the complexity of organization, especially nuclear organization, the cells are classified into two types. 1) Prokaryotic cells. 2) Eukaryotic cells.
Cell wall Ribosomes Flagella DNA Cell membrane
1. Prokaryotic cells
Cells which lack a well organized nucleus are called prokaryotic cells. eg. Bacteria and blue green algae (Cyano Bacteria). Their DNA (Deoxyribo nucleic Acid) is not enclosed by a nuclear membrane. They also lack membrane bound organelles. The organisms which possess prokaryotic cells are called Prokaryotic organisms or Prokaryotes. They are considered to be primitive organisms.
Capsule
2. Eukaryotic Cells
The cells of all plants (except a few Bacteria and Cyano Bacteria) and animals possess a well organized nucleus they are called Eukaryotic cells. Their genetic material is enclosed by a nuclear
A Prokaryotic cell (Bacteria)
membrane. They possess membrane bound organelles like Endoplasmic reticulum, golgi body, mitochondria, plastids and vacuoles. The organisms which possess eukaryotic cells are called Eukaryotic organisms or Eukaryotes.
Differences between Prokaryotic cell and Eukaryotic cell
Prokaryotic Cell It is generally smaller (1-10 microns) in size It lacks a well organized nucleus as its nuclear material is not surrounded by a nuclear membrane. It has a single chromosome Nucleolus is absent It lacks membrane bound cell organelles. Cell division occurs by fission or budding. Mitotic and meiotic divisions are absent Ribosomes are smaller 25 eukaryotic Cell It is comparatively larger (5-100 microns) in size. It contains a well organized nucleus as its nuclear material is surrounded by a nuclear membrane. It has more than one chromosome. Nucleolus is present It possesses membrane bound cell organelles. Cell division takes place by mitosis and meiosis. Ribosomes are larger
1.
2. 3. 4. 5. 6. 7.
sCIeNCe
sl. No.
BIOLOGY
AcTiviTy – 2.1 f f f f
CHAPTER - 2 i DO
I take a drop of curd and put it on a slide and I stain it with saffranin. I heat the back of the slide for few minutes. I observe the slide under compound microscope. My observation : The bacteria seen in the microscope is a _________ (Prokaryotic cell/Eukaryotic cell) MORE TO KNOW
f The study of cell is not possible without a microscope. Robert Hooke in 1665 coined the term cell and discovered the cellular structure of cork. f Anton van Leeuwenhoek (1674), studied the structure of bacteria, protozoa, etc. under the simple microscope which he himself designed. f Robert Brown, a Scottish botanist, discovered that all cells contain nucleus.
Ultra structure of a Plant Cell
f Purkinje coined the term, ‘protoplasm’ for the living substance present inside the cell.
Compound Microscope
2.2 STRUCTURAL ORGANIZATION OF A CELL
Ribosome Cell wall Vacuole Plasma membrane Smooth endoplasmic reticulum Nucleus
Cytoplasm Chloroplast
Golgi apparatus
Nucleolus Rough endoplasmic reticulum
Mitochondrion
Amyloplast
Ultra structure of a Plant cell
26
Cells
Smooth endoplasmic reticulum
Golgi apparatus
Cytoplasm
Centrioles Ribosome
Nucleolus Nucleus
Rough endoplasmic reticulum Vacuole
Microvilli
Plasma Membrane Lysosome
Mitochondrion
Ultra structure of an Animal cell
A study of the diagrams of Plant cell and Animal cell shows the following differences:
Sl.No. 1. 2. 3. 4. 5. 6. 7.
Plant cell is larger than animal cell. Animal cell is comparatively smaller in size. Plant cell has large vacuoles which Animal cell usually lacks vacuoles. occupy more space in the cell. Even if they are present, they occur in minute sizes. Centrosome is present only in the All the animal cells of some lower plants. centrosomes. cells have
Lysosomes are found only in the Lysosomes are found in all animal eukaryotic plant cells. cells. Plant cell contains plastids. Plastids are absent Mostly, starch is the storage Glycogen is the storage material. material.
27
sCIeNCe
Plant cell Animal cell Plant cell has an outer rigid cell Animal cell lacks a cell wall. wall which is made up of cellulose.
BIOLOGY
ACTIvITY – 2.2
CHAPTER - 2
I DO
I Imagine that a cell is like a large swimming pool….and I dive into it…How would I feel? What interesting things would I possibly find floating around me? I talk about it in my classroom or I write a story about it.
2.3. Cell MeMBRANe AND Cell WAll
Cell Membrane (Plasma membrane or Plasmalemma)
The contents of the cell are enclosed by a thin, delicate living membrane called cell membrane. It is the outer boundary of the cell. Cell membrane is flexible and is made up of a continuous bilayer of lipid molecules and protein molecules. All cell organelles are also bound by a similar membrane. The cell wall consists of three layers namely, middle lamella, primary wall and secondary wall. The middle lamella is a thin amorphous cement like layer between two adjacent cells. Primary wall is the first formed wall of the cell and is produced inner to the middle lamella. The secondary wall is a thick layer found inner to the primary wall.
Functions
1. ell wall gives a definite shape to the C plant cells. 2. t gives rigidity and provides I mechanical strength to the cell. I 3. t protects the protoplasm against injury. I 4. t also plays an important role in the transfer of materials between cells.
Functions f lasma membrane selectively P regulates the entry and exit of the substances into and out of the cell. Therefore, it is called a selectively permeable membrane or semipermeable membrane. f t provides an outer boundary to the I cell and protects the cell from injury. f t allows the flow of materials and I information between different organelles of the same cell, as well as between the adjacent cells. f t provides some organic connections I between the adjacent cells.
2.3.1. CYTOPlAsM
Cytoplasm is the jellylike, translucent, homogeneous substance that fills up a cell. It consists of vital molecules such as carbohydrates, lipids, proteins, amino acids, minerals and water. The cytoplasm moves around slowly carrying the organelles around in a process called cytoplasmic streaming. It helps to keep the cell organelles dynamic and in motion. The portion of cytoplasm immediately below the cell membrane is gel-like and is called ectoplasm. The
CELL WALL
Cell wall is present only in plant cells. It is a rigid protective covering outside the plasma membrane. Presence of cell wall in plant cells distinguishes them from animal cells. Most of the plant cell walls are made up of cellulose.
28
Cells
ACTIvITY – 2.3 I cut a small piece of onion and separate a peel. I place the peel on a glass slide in a drop of water and I put a drop of saffranin or methylene blue on the peel. I wash it in water to remove the excess stain and I put a drop of glycerine and cover it with a coverslip. I observe it under the microscope. My observation about the onion cell : ______________________ ___________________________________________________ ____________________________________________________ I DO
cytoplasm between the ectoplasm and nuclear membrane is liquefied and is called endoplasm. The cytoplasm together with the nucleus is referred to as the protoplasm. metabolism. The cell organelles are embedded within the cytoplasm. Each organelle performs specific functions in the cell.
a) ough endoplasmic reticulum : R
They are found in cells which synthesize proteins. This type of endoplasmic reticulum possesses rough walls because the ribosomes are attached to it. They are found in cells which synthesize lipid. The walls are smooth as ribosomes are not attached to its membrane.
Cytoplasm is the seat of cellular
b) mooth endoplasmic reticulum: S
2.3.2. Cell ORGANelles
A cell performs a variety of functions. To understand the functioning of the cell, it is necessary to know briefly about the structure of cell organelles.
Functions
1. ndoplasmic Reticulum (ER) provides E large surface area for the metabolic activities of the cell. R 2. ough endoplasmic reticulum plays an important role in protein synthesis. 3. mooth endoplasmic reticulum is S involved in the synthesis of steroids, hormones and lipids.
Endoplasmic Reticulum
Endoplasmic reticulum is a complex and interconnected system of membrane bound channels and tubules. It is spread throughout the cytoplasm and is continuous with the plasma membrane and nuclear membrane. There are two types of Endoplasmic Reticulum. a. ough Endoplasmic Reticulum. R (RER) b. mooth Endoplasmic Reticulum. S (SER)
Golgi Complex or Golgi apparatus The Golgi apparatus was first described by Camillo Golgi. Golgi complex consist of saucer-like cisternae, compartments called network of interconnecting tubules, vesicles and vacuoles at the peripheral regions. In plant cells, Golgi apparatus is referred to as dictyosomes.
29
sCIeNCe
BIOLOGY
CHAPTER - 2
MORe TO KNOW Lysosomes are involved in the destruction of aged and wornout cellular organelles. Therefore they are also called demolition squads or scavangers or cellular housekeepers.
Cisterna
Ribosomes
Ribosomes are small granular structures made up of ribonucleic acids Vesicles (RNA) and proteins. They occur free in the cytoplasm as well as attached to the Golgi complex outer surface of the rough endoplasmic Functions reticulum. Each ribosome consists of 1. olgi apparatus is involved in the G two subunits – a small subunit and a formation of lysosomes. large subunit. At the time of protein I 2. t is also responsible for the synthesis synthesis many ribosomes get attached of cell wall and cell membrane. to messenger RNA and form a structure called polyribosome or polysome.
Lysosomes
Lysosomes are small membrane bound 40S Subunit vesicles which contain powerful digestive enzymes. These serve as intracellular digestive system, hence they are called digestive bags. They are produced by the joint activity of Endoplasmic reticulum 60S Subunit 50S Subunit and Golgi apparatus. If the membrane of 70S Ribosome 80S Ribosome Lysosome happens to get ruptured, the enzymes of Lysosome would digest the entire cellular structure causing death of There are two types of ribosomes the cell. So Lysosomes are called ‘suicide a. 0S – Ribosome. It is small and 7 bags’. consists of 30S and 50S subunits. It is seen in prokaryotic cells. Functions b. 0S – Ribosome. It is made up of 8 1. ysosomes are involved in the L 40S and 60S subunits. It is seen intracellular digestion of food in eukaryotic cells. particles ingested by the cell through endocytosis. Functions 2. he lysosomes of WBCs (White blood T Ribosomes play an important role in cells) destroy pathogens and other protein synthesis. So they are called, foreign particles and thus take part in ‘protein factories’ of the cell. natural defence of the body. 30
30S Subunit
Cells
Vacuoles
Vacuoles are fluid– filled sacs bound by a single membrane called tonoplast. They are found, more in plant cells than in animal cells. Mature plant cells are found to have one large vacuole that almost fills up the entire cell. They may play the part of a contractile vacuole where excess water and waste is excreted from a cell. They also function as food vacuoles where they engulf material. For example, in Amoeba, the food vacuole engulfs food items and digests it using digestive juices. Vacuoles of plants are filled with cell sap containing minerals, sugars, amino acids and dissolved waste products. also contains the DNA and ribosomes. This makes it a unique organelle
Function
( M itochondria synthesize energy rich compounds such as ATP.
Outer membrane Inner membrane
DNA Mitochondrion
Cristae
Functions
1. acuoles store and concentrate V mineral salts as well as nutrients. 2. hey maintain proper osmotic pressure T in the cell for its turgidity.
Plastids
Plastids are disc or oval shaped organelles which occur in plant cells only. Plastids are of three types. They are Leucoplasts, Chromoplasts and Chloroplasts. 1. leucoplasts: These are colourless plastids which store food in the form of starch, lipids and proteins 2. hromoplasts: These are yellow or C reddish in colour due to the presence of pigments other than chlorophyll. Chromoplasts provide colour to many flowers and fruits. 3. hloroplasts: These are green C coloured plastids which possess the photosynthetic pigment chlorophyll which is present in leaves.
Mitochondria
Mitochondria are globular or cylindrical organelles. Each mitochondrion is bound by two membranes – an outer continuous membrane and an inner membrane thrown into folds called cristae. These cristae divide the inner chamber incompletely. The inner chamber is filled with homogenous dense material called the matrix. The cristae have pin headed bodies called F1 particles or Oxysomes which play an important role in respiration. The matrix of mitochondria contains enzymes necessary for the oxidation of food during respiration and release of energy in the form of ATP(Adenosine Triphosphate) molecules. Therefore mitochondria are called power houses of the cell. The mitochondria contain proteins and lipids. The mitochondrial matrix
Structure of chloroplast
Each chloroplast consists of a double membraned envelope and a matrix. The inner membrane is arranged along the length of the plastids as lamellae. At certain regions, the lamellae are thickened and appear like pile of coins. 31
sCIeNCe
BIOLOGY
Outer Membrane Granum Lumen
CHAPTER - 2
The nucleoplasm has two types of nuclear structures i) the nucleolus and, ii) chromatin. The nucleolus is a spherical body rich in protein and RNA. It is the site of ribosome formation. There may be one or more nucleoli in the nucleoplasm.
The chromatin is a network of fine threads composed of genetic material Inner Membrane DNA (Deoxyribonucleic acid) and Stroma Thylakoids proteins. During cell division chromatin is condensed into thick cord like Chloroplast structures called Chromosomes. The chromosomes contain genes and each These are called the grana. Each granum gene is responsible for one hereditary consists of disc shaped membranous character of the organism. Genes sacs called thylakoids. Inside these contain information for inheritance of grana, the chlorophyll is located. The traits or characters from parents to the non-thylakoid portion of the matrix is offsprings of the next generation. called stroma. It contains a number of enzymes involved in photosynthesis.
Centrosome
Centrosome is present in animal cells and in certain lower plants. It is absent in prokaryotic cells and in higher plant cells. It is located in the cytoplasm, just outside the nucleus. It contains a pair of small, hollow granules called centrioles.
Ribosomes
Chromatin Nucleolus Nucleoplasm Nuclear Envelope
Functions
Centrioles play an important role in the formation of spindle fibres during cell division.
2.4. NUCleUs
A nucleus is commonly seen as a spherical structure surrounded by a double membrane called the nuclear envelope. Nuclear envelope encloses a ground substance called nucleoplasm or karyolymph. The nuclear envelope has a large number of holes or ‘pores’ called nuclear pores. They allow the movement of molecules across the nuclear envelope in and out of the nucleus.
Functions:
Nucleus
1. ucleus controls all the metabolic N activities of the cell. 2. t controls the inheritance of characters I from parents to offsprings. 3. t controls cell division. I
2.4.1. ChROMOsOMes
Chromosomes are thread-like condensed chromatin fibres which contain hereditary information and are visible only during cell division.
32
Cells
Chromatid Centromere Arms Centromere Centromere
Arms Chromatid
Metacentric
Telomere
Submetacentric Acrocentric Telocentric
Structure of chromosome
Types of chromosomes
ACTIvITy – 2.4
WE DO
ACTIvITy – 2.5
WE DO
Each chromosome consists of two similar structures called chromatids. Both the chromatids are joined at a particular point called centromere.
Types of chromosomes
Based on the location of the centromere, the chromosomes are of four types. 1.Metacentric Chromosome: The centromere lies in the middle of the chromosome and the two arms are almost equal in length. It is a V-shaped chromosome.
f We prepare models of types of chromosomes, using Coloured paper / Coloured threads / China clay. f We display them in the classroom and discuss. f Also we display and explain them in the science club.
DNA Structure
Chromosomes are made of a long series of structures called genes. Genes are made of nucleic acids like DNA (Deoxyribonucleic acid) or RNA(Ribonucleic acid). DNA is the genetic material in most of the organisms 33
SCIENCE
f Let the students divide themselves into 5 groups. f etthefirstgroupdrawthestructure L of Endoplasmic Reticulum. Write a note on the structure and functions and display for other students. f Let the second group draw the structure of Golgi body. Write a note on the structure and functions and display for other students. f etthethird,fourthandfifthgroups L draw the structures of Ribosomes, Mitochondrion and Chloroplast respectively. Write a note on the structure and function of them, and display for other students. f Let all the students discuss and understand the structure and functions of cell organelles.
2.Submetacentric Chromosome: The centromere lies slightly away from the middle of the chromosome and hence, its one arm is slightly shorter than the other. It is a ‘J’ shaped chromosome. 3. Acrocentric chromosome: The centromere lies near the end and hence, one arm is very short and the other arm is very long. It is a rodshaped chromosome. Chromosome: The 4. Telocentric centromere lies at one end of the chromosome, and hence, there is only one arm on one side. It is also a rodshaped chromosome.
BIOLOGY and higher organisms. DNA is made up of millions of nucleotides. Each nucleotide is made up of a pentose sugar, a phosphate group and a nitrogenous base. The nitrogenous bases are of two kinds- Purines and Pyrimidines. Adenine and Guanine are the purines and Thymine and Cytosine are the pyrimidines. The helical(spiral) structure of DNA was proposed by Watson and Crick. DNA is a double stranded structure in which the two strands are coiled around each other forming a double helix. The backbone of the helix is formed of sugar and phosphate molecules. The nitrogenous bases are attached to sugar molecules. The two poly-nucleotide strands are held together by hydrogen bonds between specific pairs of purines and pyrimidines. aCTiviTy – 2.6
CHAPTER - 2
We Do
f We devide into groups and draw the diagram of the structure of DNA in a cardboard with the help of our textbook. f We fill the two strands of DNA with coloured threads. f We fix the coloured matchsticks between the two strands as seen in the diagram and label the parts with the help of textbook. f We display it in the classroom and discuss about the structure of DNA.
2.5. Cell Types
Division
anD
Adenine
Thymine
One of the most important characteristics of a living being is its ability to reproduce. The process of reproduction involves an increase in the number of cells by cell division. New cells can arise from pre-existing cells only through the process of cell division. Cell multiplication is needed for growth, development and repair of the body. Cells divide by three different methods. They are Amitosis, Mitosis and Meiosis. In each case, division of nucleus occurs before the division of cytoplasm.
Amitosis (Direct division)
Guanine
Cytosine
DNA Backbone
DNA structure
Amitosis is a simple method of cell division. It is also called direct cell division. The nucleus elongates and develops a constriction around its middle. The constriction gradually deepens and finally divides the nucleus into two daughter nucleus. This is followed by the constriction of the cytoplasm to form two daughter cells. This type of cell division is common in prokaryotes. (e.g. Bacteria, Amoeba) 34
Cells
Mitosis (or) Indirect cell division:
Mitosis takes place in somatic cells (body cells other than sperm and ovum). It is a division that produces two identical daughter cells, each containing the same number of chromosomes as in the parent cell. It is a continuous process and takes place in four phases. These are Prophase, Metaphase, Anaphase and Telophase.
Nuclear Membrane Centromere Cell wall
Interphase
Spindle fibres
Prophase
Interphase Before a cell undergoes mitotic division, it prepares itself for the division. This phase is called interphase. The chromatin material duplicates due to duplication of nucleic acids. This results in the formation of two chromatids.
Prophase f hromatin network begins to coil C and appears as long thread-like structures called chromosomes. f ach chromosome appears as two E chromatids that lie side by side and are joined at a point called centromere. f pindle fibres appear from the poles S and develop towards the centre. Nuclear membrane and nucleolus start disappearing.
Chromatid
Metaphase
Anaphase
Daughter cells Early Telophase Late Telophase
Chromosome
Nucleolus
Metaphase f he nuclear membrane totally T disappears. f hromatids become shorter and C thicker. f he chromatids move to the centre of T the cell along with their centromeres. f pindle fibres get attached to the S centromere.
Mitosis
Anaphase f The centromere of each chromosome divides into two and separates the chromatids. f he sister chromatids are pulled apart T towards the poles by the contraction of the spindle fibres. f ach chromatid gets a portion E of centromere, it becomes a chromosome. 35
sCIeNCe
BIOLOGY
Telophase
f he daughter chromosomes reach T the poles. f he nucleolus and nuclear membrane T reappear and thus two daughter nuclei are formed at the two poles of the cell. f he spindle fibres disappear. T f hese stages bring about the T division of the nucleus and this is called karyokinesis. This is followed by the division of the cytoplasm.
CHAPTER - 2
In plant cells, the cytoplasmic division occurs by the formation of a cell plate at the centre of the cell between the two daughter nuclei. Thus at the end of mitosis, two identical daughter cells are formed.
Meiosis
Meiosis is a type of cell division which takes place in the reproductive cells of organisms. Unlike mitosis, meiosis results in four daughter cells each having half the number of chromosomes of the parent cell. These daughter cells become part of specialized reproductive cells called gametes (a sperm or an ovum). They are involved in sexual reproduction.
Cytokinesis
The division of cytoplasm is called cytokinesis.
evAlUATION
Section A Choose the correct answer
1. ower house of the cell P (chloroplast, nucleus, mitochondrion, lysosome). 2. he membrane of vacuole T (cell membrane, nuclear membrane, plasma lemma, tonoplast). 3. The organelle that destroys worn-out cells (centrosome, vacuole, lysosome, chromosome) 4. The cell division that form gametes (mitosis, amitosis, meiosis, both mitosis and meiosis).
Section B
5. Complete the table: Name of the chromosome 1. Metacentric 2. 3. Acrocentric 4. Telocentric Shape of the chromosome 1. 2. ‘J’ shaped chromosome 3. 4.
6. he mitochondria is referred to as the ‘powerhouse’ of a cell. What makes it a T unique organelle? 7. Vacuoles are fluid-filled sacs. How does it play a part in excretion and nutrition?
36
Cells
8. ook at the given picture. Identify the phase of cell division. What happens to the L cell immediately after this stage?
9. ook at the given picture. Describe the changes in the nuclear material from stage L A to stage B.
A
B
10. Meiosis gives rise to gametes. How is it different from mitosis? 11. enes are the physical basis of heredity. How are chromosomes, genes and G DNA connected? Explain. 12. Read the following statements and correct them. i) Golgi apparatus was first described by Watson and Crick.
Section C
13. A) Draw a mind-map of the parts of a cell. B) Fill in the blanks. i) Division of cytoplasm is known as ________. ii) Prokaryotic cells do not have well organized _______.
Further reFerence
Books: 1. Plant Physiology 2004 - Salisbury F.B and Ross C.W, Wadsworth publishers. 2. Cell Biology, Genetics, Molecular Biology, Evolution & Ecology - 2008 - Agarwal V.K and Verma P.S., S.Chand Publishers. 3. Life Science 1990 - Silver Burdett K Ginn Publications.
Websites : http://www.sciencecentral.com http://www.botany.org http://www.khanacademy.org
37
sCIeNCe
ii) Cell wall is present in animal cells.
BIOLOGY sUGGesTeD ACTIvITIes (CCe)
CHAPTER - 2
I. Discussion • Draw the diagram of Plant cell in one part of the chart and Animal cell in the other part. • Observe them and discuss. • Differentiate the Plant cell from the Animal cell. • Fill up the following worksheet.
sl.No.
1. 2. 3.
Plant Cell
Cell wall is ________ _____________ are present. Vacuoles are __________ in size.
Animal Cell
Cell wall is ________ _____________ are absent. Vacuoles are __________ in size.
II. Activity based learning • • • • • • • • Let the students divide themselves into two groups A and B. Let the group A draw the structure of a plant cell on a cardboard. Let the group B draw the structure of an animal cell on a cardboard. From the cardboards, cut out portions showing the cell organelles. The cut out portions of the cell organelles are to be coloured with sketch pen. Let the group A fix the relevant organelles in the empty spaces of the animal cell. Let the group B fix the relevant cell organelles in the empty spaces of the plant cell. Discuss the structure of plant cell and animal cell after the cell organelles are fixed correctly.
III. Power point presentation • Prepare a power point presentation showing pictures of cell organelles and explain about any one organelle. Iv. Display • • • • • Draw the diagrams of different stages of Mitotic cell division in a chart. Fix a bead as the Nucleus. Use different coloured threads for chromosomes and spindle fibres. Observe the different stages and discuss. Write a note on every stage and display the chart.
v. Dictionary preparation • Collect scientific terms from the lesson. • With the help of Science Dictionary or Encyclopedia from your school library, find their meanings and write them down. • Arrange them in alphabetical order and submit. vI. You can do it • Take a suitable white PET bottle according to the diameter of the convex lens, cut top and bottom portion to a particular length. • Fix the lens at the top of the bottle. • Keep the object (e.g. pollen grain) in a horizontal surface and keep the bottle over it. • Observe the object through the lens. • Can you see the structure of pollen grain through the simple microscope you have prepared? • If so, let your friends also use it to observe the plant parts.
38
CHEMISTRY
Matter
The entire world around us that we can see, touch and feel is made up of matter. The sweet smelling fresh air that we breathe, the beautiful flowers and trees around us, the tasty fruits that we eat, the pets that we love, the roof and walls that make up our homes, the ground that we walk on, why even our own bodies are all made up of matter. Matter occupies space. In other words matter has volume. Some are large and some are small. The quantity of matter contained in any object is referred to as mass. Hence each matter is characterized by mass and volume. All matter exists in one of the three states - solid, liquid or gas. These are often referred to as the three physical states of matter. Classification of matter: 1. ccording to physical state as solid, A liquid and gas. 2. ccording to its composition as A element, compound and mixture.
CHAPTER - 3
Physical states of matter
Solid: Solids have a definite shape and a definite volume. They take a lot of energy to change the shape. They are rigid and not compressed appreciably even at high pressures. They usually have high densities and expand only very slightly when heated. In a solid, the molecules are held tightly together in definite arrangements. Liquid: Liquids have no definite shape and they take the shape of the container. They have a definite volume. They are not appreciably compressed by moderate pressures. They expand more than solids on heating and change into the gaseous state. They have lower densities than solids. Gas: Gases have no definite shape. They take the shape of the containing vessel. Gases have no definite volume. They have the property to fill the entire space available to them. They are easily compressed by even small pressures and also expand more than liquids on heating. They have low densities.
Solid
Liquid
Gas
40
IS MATTER AROUND US PURE?
Purity of Matter
Substances rarely exist in a pure form in nature. Often they are mixed with many other substances or materials. Their physical properties and chemical properties are either altered or are not clearly visible because of the presence of other substances. A pure substance is a distinct type of matter that has the same properties (physical and chemical) throughout the sample. elements in compounds are chemically bonded to each other. The physical and chemical properties of such compounds do not resemble the properties of any of the constituent elements. For example when hydrogen gas and oxygen gas are stored together in a container in the ratio 2:1, under certain conditions they would explosively combine to form water which is a liquid and has physical and chemical properties that are totally different from those of either hydrogen or oxygen. Water is a chemical compound. A molecule can be broken down chemically into atoms of the constituent elements. (figure (c)).
Elements, Compounds and Mixtures
According to its composition matter can be classified as element, compound and mixture.
Elements
An element is a type of substance that cannot be broken down chemically. When it is pure, the smallest unit of an element that displays all the properties of that element is an atom. Atoms of the same element may be visualized as similar looking tiny little objects (figure (a) below) each particle having the same physical and chemical properties as well. Many elements especially gases do not exist as single atoms. They exist in clusters (usually identical clusters of two or three atoms) as shown in figure (b) below. Examples of such elements are hydrogen, oxygen etc.
(c) Compound
3.1. MIxTurES
When two or more substances are mixed together and the substances retain their individual original identities, the combination is called a mixture. For example if you mix sand and water, sand retains its own properties and water retains its own properties. In a mixture, two or more substances are brought together and no chemical reaction takes MORE TO KNOW The purity of a substance is often determined by measuring its physical properties. For example, a colourless, odourless, tasteless liquid which at atmospheric pressure, boils at 100o C, freezes at 0o C and has a density of 1.0 g cm-3 is water. A pure substance can exist as element or compound. 41
(a) Atoms
(b) Molecules
Compounds
Compounds are substances resulting from the chemical combination of two or more elements in fixed proportions. The
SCIENCE
CHEMISTRY place. For example if hydrogen and oxygen, in any ratio are mixed together in a container gently at low temperatures in the absence of a spark, no chemical reaction would take place and the mixture would display the physical and chemical properties of hydrogen and oxygen. Types of mixtures Solid in solid Solid in liquid Solid in gas Liquid in solid
CHAPTER - 3
Examples Coins, alloys Sea water Smoke(carbon particles in air) Amalgam (metal + Mercury) Alcohol and water Cloud, fog Gas adsorbed by charcoal Soda drinks Air WE DO
3.2. HArACTErISTICS OF C MIxTurES
Mixtures may consist of substances in the same or different physical states. For example, bronze is an alloy consisting of the two solid metals, copper and tin; both are in the solid state. Most common solutions are mixtures of a solid in a liquid. For example salt dissolved in water. Mixtures are not pure substances since they are neither single type of distinct matter nor do they display single set of physical and chemical properties throughout the whole sample. As shown in figure (d) below, we can imagine mixtures to be different types of atoms or molecules held together but essentially retaining their individual physical and chemical properties. In mixtures, elements are physically mixed in any ratio and no new compound is formed. The substances making up a mixture are called constituents or components.
Liquid in liquid Liquid in gas Gas in solid Gas in liquid Gas in gas ACTIvITy –3.1
Left - Sulphur and Iron right - Iron sulphide
We mix iron powder and sulphur powder in a china dish. In another dish, we take the same substances and heat them strongly. We bring a magnet closely. Iron powder is attracted by the magnet and the compound iron sulphide is not. Now we distinguish a mixture and a compound. MORE TO KNOW The lead in your pencil is actually a form of carbon called graphite mixed with clay.
(d) Mixture 42
IS MATTER AROUND US PURE?
ACtIvIty –3.2 WE do sameproportionsinwhichtheyoccur at a place, and when this is done, no energychangesarenoticed. f The components of air can be separated by a physical method such as fractional distillation of liquid air. f iquid air does not have a definite L boiling point. It boils over a range of temperature between -196OC and -183OC. f If air is a compound, the composition of air expelled from humans should not be different from the composition of air around us. But it is known that during respiration, exhaled air has lower percentage of oxygen than ordinaryair. ACtIvIty –3.3 I do I classify the following into mixture or compound. (i) Alloys (ii) Smoke (iii) Juice (iv) Milk (v) Common salt (vi) Coffee (vii) Carbon dioxide (viii) Ice cream.
Is air around us pure? We discuss the reasons in groups.
Law of constant composition
A pure compound always contains the same elements combined together in the same definite proportions by weight irrespective of its method of preparation.
Is water a mixture or a compound?
Water is a compound because of the following reasons. f It is homogeneous. f t has definite physical constants I such as boiling point, freezing point, density,etc. f The properties of water are entirely different from those of its constituents, i.e, hydrogen and oxygen. f aterhasadefinitecompositionby W mass. TheratioofH:Obymassis1:8.
Composition of inhaled air and exhaled air during respiration.
Inhaled Air Contains78% nitrogen. Contains20% oxygen. Contains0.03% Carbon dioxide. Containsvery little moisture. Exhaled Air Contains78% nitrogen. Contains16% oxygen. Contains4%Carbon dioxide. Contains appreciable amount of moisture. in mass % 75.50% 23.20% 1.0% 0.046% Negligible Negligible
Is air a mixture or a compound?
Air is a mixture because of the following reasons. f irdoesnothaveafixedcomposition. A The composition of air varies from place to place. f rtificialaircanbemadebymixing A the various components of air in the
Composition of air
Gas Nitrogen Oxygen Argon Carbon dioxide Neon Helium 43
SCIENCE
CHEMISTRY
3.2.1. DIFFErENCES BETWEEN MIxTurE AND COMPOuND Mixture Elements are physically mixed in any ratio and no new compound is formed. They have no sharp or definite melting point, boiling point, density etc. A mixture exhibits the properties of its constituent or component elements. They are either homogeneous or heterogeneous in nature.
CHAPTER - 3
Compound Elements are chemically combined in a fixed ratio to form a new compound. They have definite melting point, boiling point, density etc. Property of a compound is different from its constituent or component elements. They are always homogeneous in nature.
Constituents of a mixture can be Constituents of a compound cannot be separated by physical methods like separated by physical methods. filtration, magnetic separation etc.
3.3. TyPES OF MIxTurES
There are two types of mixtures. They are, 1. Homogeneous mixture 2. Heterogeneous mixture H 3.3.1. OMOGENEOuS MIxTurES AND THEIr TyPES
There are three types of homogeneous mixtures. Solid homogeneous mixture - Alloys Liquid homogeneous mixture - lcohol in A water Gaseous homogeneous mixture - Air
Homogeneous Mixtures
Homogeneous mixtures consist of a uniform distribution of the substances throughout the mixture. Samples taken from any part of the mixture would have the same ratio of the ingredient substances and same physical and chemical properties although the properties of different samples may be different. Air is a homogeneous mixture of nitrogen,oxygen, argon and other traces of gases. All the ingredients of homogeneous mixtures necessarily have to be in the same state. Homogeneous mixtures are called solutions. ACTIvITy –3.4 I DO
Salt in water A cup of tea
ACTIvITy –3.5 f mix a drop of ink in water. I f observe whether I
I DO
the colour of the solution is uniform throughout.
Aspirin is a medicine for headache. It is composed of 60% carbon, 4.5% hydrogen and 35.5% oxygen by mass, regardless of its source. I observed that aspirin is a __________(mixture/compound) 44
f conclude that I it is a _______ (homogeneous mixture/ heterogeneous mixture)
IS MATTER AROUND US PURE?
3.3.2. HeTerogeneouS mIxTureS and THeIr TypeS Heterogeneous mixtures do not have a uniform composition. For example if you take dilute buttermilk in a vessel and keep it undisturbed at one place for some time then the particles settle to the bottom and the water comes to the top. The composition is not uniform. Ingredients of a heterogeneous mixture need not necessarily be in the same state, gas, liquid or solid. Solid - solid heterogeneous mixture mixture of sugar and salt Solid - liquid heterogeneous mixture ice cubes in water gas - gas heterogeneous mixture smoke in air. Liquid - liquid heterogeneous mixture kerosene in water. ACtIvIty –3.6 (i) Tea (ii) Ink (iii) Fruit salad (iv) Sugar solution ACtIvIty –3.7 I do
f I mix a spoonful of sand in water. f I try to see the particles of sand. f I observe whether the particles are evenly distributed in the mixture. f I write my conclusion about the nature of the mixture prepared.
I do
I classify each of the following as homogeneous or heterogeneous mixture
CLaSSIFICaTIon oF maTTer
Matter
Mixtures fVariable composition. f easily separated by physical methods. fNo definite physical constants.
Pure Substances fConstant composition. f not easily separated by physical methods. fHave definite physical constants.
Homogeneous Mixtures
Heterogeneous Mixtures
Elements f Contain atoms of the same kind.
Compounds f Contain two or more elements in a definite ratio by mass.
f Have the same f do not have the same composition composition throughout. throughout. f Components are f Components are distinguishable. indistinguishable.
45
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CHEMISTRY
3.4. EPArATION OF DIFFErENT S COMPONENTS OF A MIxTurE
Mixtures can be separated by simple physical procedures. To be able to separate the ingredients of a mixture we would need to know the physical properties of the individual ingredients. using the properties that are distinct and different, we can separate them. For example if both the ingredients of a mixture are soluble in water then we cannot separate the ingredients. However if we know that the melting point of two ingredients is different then we can use that knowledge to separate the ingredients. A good knowledge of physical properties is therefore very important.
CHAPTER - 3
S 3.4.1. EPArATION OF MIxTurES By SuBLIMATION Sublimation is defined as a process, in which a substance in solid state is directly converted into vapour state. At high temperature, the molecules of volatile solid move far away from each other making the solid substance into vapour.
1
2
1. Solid molecules evaporate 2. Iodine crystal vapourises
3. Sublimation of dry ice (carbon dioxide in ice form)
Separation of heterogeneous mixture
1. ecantation: used to separate a liquid D from a solid (present as large particles) that does not dissolve in it. 2. iltration: used to separate a liquid F from a solid (present as very small particles) which does not dissolve in the liquid. 3. ublimation: used to separate S a volatile solid substance from a mixture containing a non-volatile solid substance. 4. eparating funnel: used to separate S two completely immiscible liquids. ACTIvITy –3.8 I DO An equal quantity of fine salt and wheat flour are added into the beaker containing water and stirred well. The solubility of flour and salt in water are observed. The flour settles at the bottom of the beaker. I can now mention a suitable method of separation of flour from the salt. 46
3
Consider a mixture containing common salt and camphor. Both common salt and camphor are solid substances. Common salt is a non-volatile substance. It does not undergo sublimation. Camphor undergoes sublimation. Hence camphor can be separated from common salt by sublimation. ACTIvITy –3.9 WE ObSERvE
W e take a mixture containing common salt and camphor in a china dish placed over a stand and an inverted funnel is kept over it. The funnel stem is closed by means of cotton and the china dish is heated. The observations are recorded.
IS MATTER AROUND US PURE? cotton plug inverted funnel
immiscible liquids are usually separated by using a device named “separating funnel”. consider a mixture containing kerosene and water. both the liquids are immiscible with each other. by using a separating funnel, one liquid can be separated from the other. less denser liquid remains in the upper layer while high denser liquid remains in the lower layer. ACTIvITy –3.10 WE ObSERvE f take a mixture kerosene and water. containing
solidified camphor
vapours of camphor mixture of salt and camphor
f pour the mixture into a separating funnel. f close the mouth of the separating funnel. f Shake it for 10 minutes. MORE TO KNOW Solids that undergo sublimation are camphor, naphthalene, benzoic acid, iodine and ammonium chloride.
3.4.2. Separation of a mixture
f Hold the funnel in a stand for 15 minutes. f observe the changes. f note the lower and upper layers. f What is the principle behind it? Separation of HomogeneouS mixture
containing immiScible liquidS
1. distillation: used to separate a nonvolatile solid and a volatile liquid present together in a solution. 2. fractional distillation: used for separating funnel separating a mixture containing two or more liquids with an appreciable kerosene difference in their boiling points. 3. chromatography: Separation of two or water more dissolved solids can be carried out by chromatography. it can be used to separate samples as small as stop cock a picogram (10-12 g) and as large as several ions. it involves the distribution of solutes between a moving phase and a non-moving phase or stationary phase. 47
SCIENCE
CHEMISTRY
3.4.3. EPArATION OF A MIxTurE S CONTAINING MISCIBLE LIquIDS Fractional distillation is a suitable method for separation of a mixture containing miscible liquids. It works on the principle that the two liquids should vary in their boiling points by 25 K. f onsider a mixture containing two C liquids namely benzene and toluene.
CHAPTER - 3 f oth the liquids are miscible with B one another. f hey can be separated by fractional T distillation. f Boiling point of benzene is 353 K. f Boiling point of toluene is 384 K. f he difference in their boiling points T is 31 K.
thermometer
fractionating column
water condenser
flask benzene and toluene mixture
cooling water flows into condenser
distillate bunsen burner
warm water flows out of condenser
ACTIvITy –3.11 f ake a mixture of alcohol and water in a distillation flask. T
WE ObSERvE
f Close the distillation flask with a one holed rubber cork and fit a thermometer. f Fit a condenser. f Heat the mixture slowly. f lcohol vapourises first and gets condensed in the condenser and is collected. A f Water remains in the flask. 48
IS MATTER AROUND US PURE?
MORE TO KNOW
FILTRATION PROCESSES ADOPTED IN vARIOUS FIELDS:
1. Carbon filter:
Powdered charcoal can be formed in such a way as to be full of tiny holes, which serves as a filter. As air is drawn through the holes, the charcoal traps gases and chemicals . Such carbon filters are put in the gasmasks used by soldiers and fire fighters.
2. Air-Conditioning filter:
It circulates the air with fans and removes dust from air.
3. Automobile filter:
Filters in the fuel line clean the fuel but they can block the flow of fuel when they get clogged with dirt.
4. Water filter:
Particles of matter suspended in water are removed by the use of chemicals like chlorine, potash alum and powdered carbon and filtered through beds of sand or porous separation.
Identification of element, compound and mixture.
Matter IF NO
Is it uniform throughout?
IF yES
Homogeneous
Heterogeneous mixture
IF NO
IF yES
Does it have a variable composition? Homogeneous mixture (Solution)
Pure substance
IF NO
Can it be separated into simpler substance? Element Compound
IF yES
49
SCIENCE
CHEMISTRY EvALUATION
SECTION – A Choose the correct answer:
CHAPTER - 3
1. The lead in the pencil we use is made of a material called graphite. Graphite is a mixture of ________ (carbon and clay, clay and nitrogen) 2. Pure water is a compound. It contains 11.19% by mass of hydrogen and oxygen ________ by mass. (88.81% , 31.81%) 3. Coins are mixtures of solid in solid. Smoke is a mixture of ________ (solid in gas, gas in solid) 4. Some pair of items are given below. Could you identify the incorrect pair? a) Air - - - - gas in gas solid in liquid gas in liquid. liquid in liquid b) Seawater d) Amalgam
c) Soft drinks
5. Components of a given matter can be separated by various purifying techniques. Components of liquid air can be separated by adopting ________ physical method. (fractional distillation , distillation , sublimation) SECTION – b 6. ometimes I am hard and cold. Sometimes I am difficult to hold. But, I am always S present in air. Who am I? 7. Pure substance contains a single type of particles. Is sea water pure or not? justify. 8. In a compound two or more elements are combined in a fixed ratio by mass. Mention any two properties of a compound? 9. omogeneous mixture contains a single type of phase. Heterogeneous mixture H contains different types of phases. quote one example for each type. 10. hen a solid camphor is exposed to air, it changes into gaseous state. It is a W physical change. Name the process that takes place? Could you give another example for such a process. 11.(a) eparation of a mixture containing water and kerosene can be done by S use of ________ (distillation , separating funnel) (b) _______ (sublimation, chromatography) process is used to separate _ common salt and ammonium chloride. 50
IS MATTER AROUND US PURE?
12. liquid ‘A’ has a boiling point of 353 K and another liquid ‘B’ has a boiling point of A 384K. Both are miscible with each other. They are separated by “fractional distillation”. Justify the reason for using fractional distillation method. SECTION – C 13. In mixtures, components are combined in any ratio. . 15. eterogeneous mixture is separated by decantation. What is meant by decantation H Process? 16. In what way does an element differ from a compound? 17. Write a short note on chromatography. SECTION – D 18. What are heterogeneous mixtures? Mention their types with examples. 19. Classify the following as solution, heterogeneous mixture, compound or element. i. Sodium ii.Glucose v. Common salt 20. Alchohol is mixed with water. Write briefly the separation of the components. 21. How does the process of decantation differ from filtration? 22. How are immiscible liquids separated? iii. Lemon juice iv. Coal dust in sand (a) How does a mixture differ from a compound? (b) What are the types of mixtures? (c) Write an example for each type.
14. All matters in the universe exist in three states namely solid, liquid and gas. (a) Why do solid substances have definite shape? (b) Write any two properties of a solid substance.
(c) Will the solid substance expand on heating? Why?
ASSESSMENT ACTIvITy
1.Water purification experiment
Know about the natural way of purifying dirty water. you can make your own sand and gravel filter and use it to clean a sample of dirty water. use a large, empty can. Punch eight holes around the bottom of the can with a big nail. Place about 8cm (3 inches) of pebbles in the bottom of the can, and cover the pebbles with the same amount of sand. 51
SCIENCE
CHEMISTRY
Collect some muddy water from a puddle or pond. Hold the can over the bowl and pour the muddy water into the can. Look at the water that comes through the can. It is much clearer than the water you had poured in. Muddy water being poured in
CHAPTER - 3
Can Sticks to support the can
Sand Pebbles
2. Discussion
Aim : o enable the students to T know the components of the mixtures used in daily life. Name the components of the mixtures listed below. Mixtures 1. Air 2.Crude oil 3.Milk 4.Aerated drinks 5.Stainless steel
Components
3. Classification
Aim : o enable the students to classify the mixtures as homogeneous or T heterogeneous. Method of preparation of mixture Sugar is added to water Both sugar and salt are added to water Smoke in air Mixture containing rice and wheat Type of mixture obtained
4.Comparative learning
Aim : o enable the students to understand the method of purification involved in T separating components of a mixture. Type of mixture Salt solution Mixture containing petrol and kerosene Mixture containing kerosene in water Common salt and powdered camphor Water containing fine sand 52 Method of purification
IS MATTER AROUND US PURE?
5. opy the following table and write an example of a mixture in each empty C box. For example, coffee is a mixture of solid and liquid.
Solid Solid Liquid Gas Liquid Coffee Gas
6. Identify the physical states of the following
Matter Ice Air Water rice Oxygen Physical state
7. uppose a ship gets wrecked on an island in the Pacific Ocean. The S passengers, however, manage to bring plenty of firewood, match boxes and some pots ashore. Describe, with the help of diagrams, how the passengers can obtain drinking water from the salty ocean water. 8. mixture of chalk powder and salt can be separated by combining more A than one method. Salt is soluble in water, whereas chalk powder is not. The steps of separation are given below. Arrange them in correct order. i) Filtration removes the insoluble chalk powder. iii) Evaporation of the salt solution removes water. iv) Add the salt and chalk powder mixture to water. v) The chalk powder is then dried in sunlight. ii) Stir well. The salt dissolves in water.
Further reFerence
Books: General Chemistry (Second Edition) - Jean B.Umland & Jon M.Bellama West publishing company http://www.khanacademy.org
Websites : http://www.tutorvista.com
53
SCIENCE
ATOMIC STRUCTURE
4.1. IsCoVERy of THE D NuClEus
Need to study the structure of the atom
John Dalton proposed the idea of the atom as the smallest possible particle of any substance. He never worked with small particles of solids but actually he worked with gases, how they mix with each other, how they form compounds and how they dissolve in water etc. While working with all this he discovered that whenever elements combine to form more than one compound, the ratio of the masses of elements in the compounds are small whole number ratios of each other, which led him to the idea that the smallest particle of one substance was combining with the smallest part of another substance in a fixed quantities. The development of modern atomic theories is an excellent example of how science progresses. Many scientists contribute their knowledge for the development. New experiments lead to either changes in the old theories or even to new theories.Theories are useful in providing the basis for further work. Although, J.J.Thomson’s atomic theory explained electrical neutrality of atoms, it could not reveal the presence of nucleus in an atom, which was later proposed by Ernest Rutherford in 1909.
Rutherford’s contribution
Rutherford observed what happens to alpha particles projected at a thin metal foil.
Ernest Rutherford (1871-1937)
Ernest Rutherford, a British physicist probed atoms with alpha particles. He was known as the “father of nuclear physics”. He was awarded Nobel prize for his contribution in structure of atom in 1908.
4.2. uTHERfoRD’s R ExpERIMENT
A stream of alpha particles was made to pass through a thin gold foil of about 4x10-5 cm thickness. Most of the alpha particles did go through the foil in a straight line. some alpha particles were deflected through an average angle of 90o .Rarely the path of 1 in 20,000 alpha particles scored a direct hit on the nucleus and returned by an angle of 180o.
schematic diagram showing alpha particles bombarding one gold atom. The nucleus of the gold atom is shown in the centre.
1 2
1. Not scattered at all 2. slightly scattered
3. More scattered 4. Returned at 180o MORE TO KNOW 3 Alpha particles are helium 4 ions He2+ .The mass of an alpha particle is about 8000 times the mass of an electron. Velocity of alpha particles is about 2x107 m/s.
Alpha particles
55
SCIENCE
CHEMISTRY from this experiment, he concluded that there is a heavy positive charge occupying small volume, at the centre of an atom.
CHAPTER - 4 continuously lose energy. due to the loss of energy, path of electron may reduce and finally the electron should fall into nucleus. If it happens so, atom becomes unstable. But atoms are stable. hence Rutherford’s theory does not explain the stability of atom.
Nucleus
4.3. RutheRfoRd’s model of atom f atom has a very small nucleus at the centre. f there is large empty space around the nucleus. f entire mass of an atom is due to the mass of nucleus. f electrons are distributed in vacant space around the nucleus. f the electrons are moving in circular paths around the nucleus.
electron
electrons
Nucleus
MORE TO KNOW Imagine a small boy swinging a stone on the end of a string around him. the stone is able to occupy a larger volume because it is moving rapidly. similarly the electrons in an atom are able to occupy a larger volume because they are moving very fast. Neils Bohr (1885 - 1962)
MORE TO KNOW James Chadwick was one of Rutherford’s students.
4.3.1. lImItatIoNs according to electromagnetic theory, a moving electron should accelerate and AcTiviTy – 4.1 WE dO
We divide into groups and have a discussion about the following. In Rutherford’s experiment,
1.Why did the majority of alpha particles pass through the foil unaffected? 2.Why were very few alpha particles deflected? 3.Is the size of nucleus small or large with respect to the size of atom? 56
Neils Bohr was born on october 7, 1885 in Copenhagen, denmark. he was also an outstanding soccer player. he worked with Rutherford at the university of manchester. Bohr’s theory became the basis for modern physics known as Quantum mechanics.Bohr received the Nobel Prize for physics in 1922.
ATOMIC STRUCTURE
4.4. BoHR’s MoDEl of AToM
Neils Bohr modified Rutherford’s atom model and put forth the following postulates. f n atoms, the electrons revolve I around the nucleus in stationary circular paths. These paths are called orbits or shells or energy levels. f s long as electrons revolve in the A same orbit, it does not lose or gain energy. f he circular orbits are numbered as T 1, 2, 3, 4 or designated as K, l, M, N shells. These numbers are referred to as principal quantum numbers (n). f maller the size of orbit, smaller is s the energy of the orbit. f s we move away from the nucleus, A energy of the orbit is constantly increasing. f aximum number of electrons that M can be accommodated in an energy level (n) is given by 2n2 . f hen an electron absorbs energy, W it jumps from lower energy level to higher energy level. f hen an electron returns from higher W energy level to lower energy level, it gives off energy.
Third energy - level (M-shell)
second energy - level (l-shell) first energy - level (K-shell)
Orbit orbit is defined as the path, by which electrons revolve around the nucleus. dAlTON, ThOMSON, RUThERfORd ANd NEIlS BOhR - ATOM MOdElS
Dalton
Thomson
Rutherford Neils bohr
n = 1 (K shell) n = 2 (l shell)
4.5. DIsCoVERy of NEuTRoNs
In 1932, James Chadwick observed that when beryllium was exposed to alpha particles, particles with about the same mass as protons were emitted.. These emitted particles carried no electrical charge. Hence they were called as neutrons.
Beryllium + alpha ray carbon + neutron
n = 3 (M shell)
57
SCIENCE
CHEMISTRY
Beryllium
CHAPTER - 4
4.6.1. oMposITIoN of C NuClEus
Electrons have negligible mass. Hence the mass of an atom mainly depends on the mass of the nucleus. Nucleus of an atom consists of two components. They are protons and neutrons. protons are positively charged. protons repel each other because of their like-charges. Hence, more than one proton cannot be packed in a small volume to form a stable nucleus unless neutrons are present. Neutrons reduce the repulsive force between positively charged protons and contribute to the force that holds the particles in the nucleus together. proton Alpha particles Neutron Charge detector indicating no charge
MORE TO KNOW Number of neutrons = Mass number - Number of protons or Number of Electrons (Atomic number) Neutrons are particles with no charge i.e. neutral particles. Neutrons are present in the nuclei of all atoms except hydrogen atom. Mass of a neutron is almost equal to the mass of a proton. Atoms of the same element with different number of neutrons are called isotopes. Neutron is also regarded as a sub-atomic particle.
Neutron
4.6. HARACTERIsTICs of C fuNDAMENTAl pARTIClEs physical and chemical properties of elements and their compounds can be explained by the fundamental particles of an atom. The fundamental particles of an atom are: protons: They are positively charged particles. They are present inside the nucleus. Electrons: They are negatively charged particles. They revolve around the nucleus in circular orbits. Neutrons: They are neutral particles. They are present inside the nucleus. 58
Nucleus
oTHER suBAToMIC pARTIClEs Besides Electrons, protons and Neutrons, there are many sub-atomic particles such as; f Mesons f positrons f Neutrinos f Quarks f pions f Gluons
ATOMIC STRUCTURE
Characteristics of sub-atomic particles
Electron mass Charge in units 9.1x10-28 g -1 Proton 1.672x10-24 g +1 Neutron James Chadwick 1.674x10-24 g 0
Discovered by J.J. Thomson and H.A.Lorentz e. Goldstein
Nucleons
The elementary particles such as protons and neutrons are collectively referred to as nucleons. Thus mass number of atom is equal to the total number of nucleons in the nucleus of an atom.
4.7. ATomIC NumBer ANd mAss NumBer
Atomic number (Z)
Atomic number of an atom can be defined as the total number of protons present in the nucleus of the atom or the number of electrons present outside the nucleus of an atom. Thus the atomic number of hydrogen would be one and that for helium would be two. The symbol for Atomic number is Z. No two elements have the same atomic number; hence it is unique to each element. The atomic numbers of some elements are given in the table below:element Atomic number H 1 He 2 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11
Mass number (A)
element Atomic number mass number ACTIvITy – 4.2
H 1 1
He 2 4
Li 3 7
Be 4 9
B 5 11
C 6 12
N 7 14
o 8 16
F 9 19
Ne 10 20
Na 11 23
mg 12 24
WE DO
MORE TO KNOW
A has 11 protons, 11 electrons and 12 neutrons. B has 15 protons, 15 electrons and 16 neutrons. C has 4 protons, 4 electrons and 5 neutrons. We identify the elements A, B and C. 59
In lighter atoms, one neutron per proton is enough. Heavier atoms with more protons in the nucleus need more neutrons in the nucleus, for the nucleus to be stable. Thus the stability of the nucleus is determined by the Neutron-Proton ratio.
SCIENCE
Mass number (A) is defined as, the sum of the number of protons and neutrons present in the nucleus of an atom of an element. For example the mass number of sodium is 23 which implies that the total number of protons and neutrons in the sodium atom is 23. The number of neutrons can be obtained by subtracting the atomic number from the mass number (12 for sodium). The mass numbers of some elements are given in the table below:-
CHEMISTRY
AcTIvITy – 4.3 I dO
CHAPTER - 4 4.8. ISotoPeS
Proton 3
I complete the following table
Atomic number 5 11 15 10 number of protons number of electrons
Species Boron Sodium Phosphorus Neon
Neutron
Li 7
Li 6 3
Isotopes of lithium
Representation of Atomic number and Mass number
Atomic number (Z)
X
Mass number(A)
For example, Atomic number of nitrogen is 7. Mass number of nitrogen is 14. Representation:
14
American scientist, t.W.Richards observed to his amazement that Lead samples collected in different places differed in atomic mass. this suggested that all atoms of an element are not exactly alike. It is clear that atoms of an element have the same chemical properties.But they may differ in their masses. Isotopes are atoms of an element that differ in mass numbers, but have the same atomic number.
7
AcTIvITy – 4.4
N
I dO
From the following elements, I find which have the same number of neutrons. 1. Lithium - 3 Li 7 2. Carbon 3. Nitrogen 4. Beryllium 5. oxygen 6C 7N 12 14
Characteristics of isotopes f Isotopes of an element differ in mass numbers only. f Difference in mass number is due to difference in number of neutrons. f Isotopes of an element have the same chemical properties. f However, variation in physical properties are noted in isotopes. f elements having isotopes exhibit fractional atomic mass. AcTIvITy – 4.5 I dO
8 4 Be 16 8o
MORE TO KNOW Chlorine has fractional atomic mass. Chlorine-35 exists by 75% Chlorine-37 exists by 25% Average atomic mass of chlorine is,
{ }{ }
(i) I calculate the number of neutrons in the isotopes. (a) 1H1, 1H2, 1H3 (b) 17Cl35,
17Cl 37
75 x35 25 x37 + = 35.5 100 100
(ii) My inference________________ 60
ATOMIC STRUCTURE
Electron Proton Neutron
Protium atom (Common hydrogen) Element Isotope Protium Deuterium Tritium Chlorine Carbon Uranium Chlorine-35 Chlorine-37 Carbon-12 Carbon-14 Uranium-235 Uranium-238
Deuterium atom (Heavy hydrogen) Isotopes of Hydrogen
Representation
1 1H 2 1H 2 1D 3 1H 3 1T 17
Tritium atom (Radioactive hydrogen)
aCtIvIty – 4.7
I do
(or) (or)
Hydrogen
cl35 37 17cl
12 235 238
From the given average atomic mass, I find which element does exist with least number of isotopes. f Chlorine-35.5 f Hydrogen-1.008 f Oxygen-16.0
14 6C 92U 92U
6C
4.9. ElECtRoNIC CoNfIguRatIoN of atomS
It is known that atoms consist of a positively charged nucleus with protons and neutrons in it. Negatively charged particles called electrons constantly revolve around the nucleus in set of orbits. The electron orbits are numbered as 1, 2, 3, etc, starting from the orbit closest to the nucleus. These orbits are also called K, l, m, N shells, as mentioned in the atom model proposed by Niels Bohr. The maximum number of electrons in an orbit is given by 2n2, where n is the orbit number. Shell number or energy level First shell (K) Second shell (L) Third shell (M) Fourth shell (N) maximum number of electrons(2n2) 2(12) = 2 2(22) = 8 2(32) = 18 2(42) = 32
aCtIvIty – 4.6 The element bromine following isotopes. has
I do the
49.7% of Bromine-79 and 50.3% of Bromine-81
Based on this I calculate the average atomic mass of Bromine.
Uses of Isotopes
Many isotopes find use in medical field. f Iron-59 isotope is used in the treatment of anaemia. f Iodine-131 isotope is used for treatment of goitre. f Cobalt-60 isotope is used in the treatment of cancer. f Phosphorous-32 isotope is used in eye treatment. f Carbon-11 isotope is used in brain scan.
61
SCIENCE
CHEMISTRY
It must be understood that the second orbit begins to fill with electrons only after the first orbit is filled. The third orbit begins to fill only after the second orbit is filled. But the fourth orbit commences even before the third orbit is completely filled. The reason for this lies in the concept of quantum numbers. Thus the term electronic configuration or electronic structure refers to the way, the electrons are arranged around the nucleus. Most of the properties of elements and their compounds depend on their electronic configurations. To write electronic configuration, the principal quantum number of the shells must be known. This number describes the number of orbits present in the atom. let us consider sodium atom. Atomic number of sodium = Total number of electrons in sodium = 11 Orbit wise distribution of electrons Orbit Number of electrons 1. (K-Shell) 2n2 =2x12=2 electrons 2. (l-Shell) 2n2 =2x22=8 electrons 3. (M-Shell) Remaining=1 electron The electronic distribution in sodium is 2, 8, 1.
Sodium atom
CHAPTER - 4 some elements and their electronic configurations
Electron distribution
Element
Atomic Number
Electron dot structure
Hydrogen
1
1
(H)
Helium
2
2
(He)
lithium
3
2,1
(Li)
-
-
Beryllium
4
2,2
(Be)
- Boron
11P 12N
5
2,3
(B)
-
MORE TO KNOW Much of the experimental evidence for electronic configuration comes from atomic spectra. 62
Carbon
6
2,4
(C)
ATOMIC STRUCTURE
Some elements and their electronic configurations
Electron distribution Electron distribution
Atomic Number
Atomic Number
Element
Electron dot structure
Element
Electron dot structure
Nitrogen
(N)
7
2,5
Aluminium 13
(Al)
2,8,3
Oxygen
(O)
8
2,6
Silicon
(Si)
14
2,8,4
Fluorine
(F)
9
2,7
Phosphorus
(P)
15
2,8,5
Neon
(Ne)
10
2,8
Sulphur
(S)
16
2,8,6
Sodium
(Na)
11
2,8,1
Chlorine
(Cl)
17
2,8,7
Magnesium
(Mg)
12
2,8,2
Argon
(Ar)
18
2,8,8
63
SCIENCE
CHEMISTRY
ACTIvITy – 4.8 I write the electron distribution
Element lithium Boron fluorine Magnesium phosphorous Atomic number 3 5 9 12 15 Electron distribution l M K
CHAPTER - 4
I dO
Illustration lithium (Atomic number:3) has the electronic distribution, (n=1) K shell 2 (electron) (n=2) l shell 1 (remaining electron) outer most shell is ‘l’. The valence electron = 1 The valency of lithium = 1
4.9.1. AlENCE ElECTRoNs AND V VAlENCy
The number of electrons in the outer energy level (orbit) of an atom are the ones that can take part in chemical bonding. These electrons are referred to as the valence electrons. The outermost shell or orbit of an atom is known as valence shell or valence orbit. The electrons present in the outer shell are called valence electrons. The number representing the valence electrons is used to calculate the valency of the element. This valency is regarded as the combining capacity of elements. ACTIvITy – 4.9
When the number of electrons in the outermost shell is close to its full capacity, (such as 8 for l shell) valency is then determined by subtracting the valence electron number from the full capacity of 8. Valency = 8-valence electrons for example fluorine(atomic number: 9) has the electron distribution, n 1 2 shell K l electrons 2 7
outer shell (l) has 7 electrons which is close to the full capacity of 8. Hence valency = (8 -7) = 1 I dO
I calculate the valence electrons and determine the valency. Element Hydrogen Boron Carbon Magnesium Aluminium Atomic number 1 5 6 12 13 Valence electrons Valency
64
ATOMIC STRUCTURE
EvAlUATION
SECTION - A Choose the correct answer T 1. otal number of electrons, that can be accommodated in an orbit is given by 2 (n = 1, 2, 3....). Maximum number of electrons, that can be present in first orbit is 2n ________. (8, 2, 18) 2. oldstein discovered protons. It is present in the nucleus. Charge on the protons G are ________ (negative, positive, neutral). 3. subatomic particle is revolving around the nucleus in orbits. It is A negatively charged. It was discovered by J.J.Thomson. The particle is _______. (proton, neutron, electron) 4. umber of neutrons present in 3li7 is 4. The number of neutrons present in 8o16 N element is _______. (8, 7, 6) 5. ucleus of an atom has two components. They are proton and ________ N (positron, neutron, electron) 6. he sum of the number of protons and neutrons present in the nucleus is T called mass number. find the number of protons in the following element. (11, 23, 12) Element sodium (Na) Mass number 23 Number of protons ? Number of neutrons 12
7. tomic number and mass number of 17Cl35 are 17 and 35 respectively. The number A of protons present in it is _______ (17, 35, 18) 8. ______________________ isotope is used for the treatment of goitre. _ (Iodine – 131, phosphorus – 32, Iron – 59) 9. he electron distribution of fluorine is 2, 7. The valency of the element is ________ T (7, 2, 1) 10. lectron distribution of sodium is 2, 8, 1. The valency of the element is _______ E (2, 8, 1) 11. very atom has equal number of protons and electrons. Both are oppositively E charged. Neutron is electrically neutral. The nature of atom is _______ (positive, negative, neutral) SECTION - B 12. Electrons in an atom revolve around the nucleus in circular stationary paths. a) Who proposed such a statement? b) What is the name of the circular path? 13. K shell of 7N14 has 2 electrons. How many electrons are present in the l shell? 65
SCIENCE
CHEMISTRY
CHAPTER - 4
14. x 35 is a gaseous element. Its atomic number is 17. Its mass number is 35. 17 find out the number of electrons, protons and neutrons. 15. any Isotopes are used in medical field. M a) Which isotope is used for the treatment of anaemia? b) Which one is used in eye treatment? 16. Write the electron distribution in the following elements.
Element Atomic number K Electron distribution l M
Boron Magnesium
5 12
2 -
8
-
17. find the valence electrons and valency.
Element Atomic number valence electron valency
Carbon Aluminium
6(2,4) 13(2,8,3)
I 18. n the elements given here identify (a) Mass number (b) Atomic number (c) Number of protons (d) Number of Electrons (e) Number of Neutrons
2
He4, 3li7, 5B10, 6C12, 13Al27
19. opy and complete the table by adding the missing information for uranium C isotope.
Isotope Uranium- 235 Uranium- 238 Symbol
92u 235
Number of Protons 92 92
Number of Neutrons 143
Number of Electrons 92
SECTION - C 20. Name the elements with completely filled orbits.
Element Atomic Number Electron distribution
Nitrogen Neon Magnesium sulphur Argon
7 10 12 16 18
66
ATOMIC STRUCTURE
21. Correlate the facts with properties. (i) (ii) (iii) (iv) (v) More dense part of an atom Chargeless particle outermost orbit Number of electrons in outermost orbit Number of protons valency Atomic number nucleus Valence shell
Neutron proton 22. How many electrons can be accommodated in K, l and M shells? 2 3. What are the fundamental particles of an atom? Name all the subatomic particles. 2 4. What are isotopes? Draw the isotopes of Hydrogen. SECTION - d 25. hat are alpha particles? How are they useful in the determination of nucleus of W an atom? 26. Write briefly the atomic model concept proposed by Rutherford. 27. list the limitations of Rutherford’s atom model. 28. state the postulates of Bohr’s atom model? 29. Give experimental evidence about the discovery of neutron. 30. How is valency of an element predicted? 31. Give orbitwise electronic configuration of i. Carbon (Atomic Number - 6) iii. Magnesium (Atomic Number - 12) iv. phosphorus (Atomic Number - 15) v. Argon (Atomic Number - 18) ii. fluorine (Atomic Number - 9)
67
SCIENCE
CHEMISTRY
1. Assignment
ASSESSMENT ACTIvITy
CHAPTER - 4
Aim : o enable the students to know about the role of neutrons in the nucleus. T In lighter atoms protons and neutrons are equal in numbers. In heavier atoms they are not equal in numbers. list out the reasons.
2. project :
Aim : To construct the model of an atom C onstruct the model of an atom using available materials. your model should have the correct number of shells, and the correct number of electrons in each shell. use different colour codes to represent electrons, protons and neutrons(Choose any atom of your choice)
3. Discussion
A im : o enable the students to find out the major similarities and differences T between Rutherford and Neils Bohr atom models Similarities differences
4. Album
Aim: To enable the students to draw the atomic models. Draw the atomic models of Dalton, Thomson, Rutherford and Neils Bohr.
5. How do you assume about the shape of an atom to be? Tick your choice square shape Rectangular shape Circular shape spherical shape Elliptical shape
Further reFerence
Books: Atomic Structure Advanced Inoganic Chemistry Satya prakash, GD Tuli - S.Chand & Company Ltd Websites : http://www.shodor.org http://www.chemguide.co.uk.
68
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