Diversity in the Living World

UNIT I
Diversity in the Living World

CHAPTER 1
The Living World

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 What is Living
 Diversity in the living world
 Taxonomic Categories
 Taxonomical Aids

The living world is very wonderful. It contains wide range of life forms.
1.1 What is living – Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli.
Living organisms exhibit following distinctive characteristics.

All Living Organisms grow:
 Twin characters of growth are increase in (a) mass and (b) number of individuals. Cell division leads to growth of an organism.
 External Growth is shown in non-living bodies where the accumulation of material on the surface takes place thereby increasing the mass.
 Internal Growth is a process in which the mass of living bodies grows by cell division.
 Growth - by Cell Division
Animals – It is up to a certain age
Plants – Continues through out their life span

All Living Organisms Reproduce:
 Organisms reproduce or replicate both by sexual and asexual means.
 In unicellular organisms growth and reproduction are synonymous.
 Organisms such as sterile working bees, mules are living but don’t reproduce. So it can’t be a defining factor for life.
 No non-living organism is capable of reproducing itself.

Metabolism
 All living organisms are made up of chemicals.
 These chemicals are constantly being made and changed into other bio-molecules. These conversions are chemical reactions or metabolic reactions.
 Thousands of metabolic reactions occur simultaneously in all the living organisms. The sum total of all the chemical reactions inside our body is metabolism.
 Cellular organization of body is the defining feature of life forms.

Consciousness
 The most obvious and technically complicated feature of all living organisms is their ability to sense their surroundings and environment and respond to these environmental stimuli