Biology

Biology textbook- pg. 80
3) Distinguish between the autotrophic and heterotrophic nature of plants and animals.
Animals have heterotrophic cells; hence, they live off nutrients of other species by eating. Most plants have autotrophic cells, which allow them to generate their own food with photosynthesis.
4) Explain the following statement: ‘All living things depend on plants’.
As animals are heterotrophs, they need to eat other species to survive. If mammals only depended on other mammals, there would be no animal with nutrients. Only plants have self-feeding systems which is similar to ‘free food’ to the animals.
5) Write out the word equation that summarises the process of photosynthesis.
Water + Carbon Dioxide –(with the presence of chlorophyll, starch and sunlight)-> glucose and oxygen.
6) Compare aquatic and terrestrial plants in relation to the site of water and mineral uptake.
In an aquatic environment, water and minerals can be absorbed across the whole surface of the plant. In most terrestrial plants, water and minerals are obtained through root systems, which also anchor the plants in the soil. Plants root need a large surface area over which absorption can occur. They achieve this by having a branching structure, and root hairs just behind the root tips.
7) Explain how the structure of typical leaves and the distribution of specialised tissue within them are adaptations to photosynthesis. Use clearly labelled diagrams in your answers.

Water, air and glucose must move around the leave for it to photosynthesise. The water is transported through the xylem while the glucose is transported through the phloem. The epidermis allows the sunlight to readily penetrate through the leave for photosynthesis.

8) Explain the difference between mechanical and chemical digestion.
Mechanical digestion is the actual physical break down of food into smaller pieces; for example, using teeth to grind food into smaller bits for it to go down throats. Chemical digestion is the chemical break down of foods into smaller pieces; for example, enzymes break down starch into simpler forms or HCI acids in our stomachs help break down food.
9) Identify the structures labelled W, X, Y and Z in the diagram of the herbivore digestive system shown. What is the major function of each structure?
W= stomach, the chamber where chemical digestion of proteins occur. There is also mechanical digestion through the churning of foods.
X= small intestines, the chamber where food is broken down into small enough molecules which are then absorbed through the walls of the digestive system to the blood. Nutrients and water is absorbed.
Y= large intestines, the place where water is absorbed with soluble compounds like vitamins and minerals; undigested food leaves body as faeces via the anus.
Z=caecum, a pouch that is located at the beginning of the large intestine. It receives the faecal material from the ileum, and connects to the ascending colon of the large intestine.
10) Outline the importance of villi and microvilli in the digestive system.
Villi are small, finger-like projections on the surface of the small intestine. They help increase surface area and that helps absorb nutrients from food. Microvilli increase the surface area of cells so that a greater amount of absorption or secretion can take place. They contain important enzymes for digestion also. They also help certain things move such as white cells to the desired location.
11) Compare the digestive system of dogs and koalas. Include a description of their length, complexity and role of different structures.
Koalas have a long large intestine, a regular stomach and an enormous caecum. With this large caecum, the koala is able to solely rely on Eucalyptus as nutrition. It is not as complex as the dog’s digestive system.