Concept of evolution. r Role of variations in evolution. fSalient features of Lamarckism. - Salient Features of Darwinism. — Evidences in support of Evolution

From the discussion in previous chapter you have learnt that living things exist in great variety. There are about 2 % million different kinds of iF living things mostly alive while many in fossil (preserved) forms. However, ” despite their variety, they have many features in common. For instance, there are fundamental similarities in their chemical structure. All living things contain carbon, hydrogen, oxygen, nitrogen, etc. which are organized an into molecules of proteins, carbohydrates, lipids. Moreover, the process ot ® breaking down of food to release energy is almost identical in all living organisms. Not only in chemistry, there exist similarities in morphology also such as rats with mice, turtle with tortoise, frog with toad, etc. 

Similarities discussed above and yet numerous others suggest that species are interrelated in some way, and some species are more closely interrelated than the others. 

The great variety of forms leads to many questions such as: 

How living things vary from each other? 

Have they always been like this? 

Did the great variety of life forms appear with time? 

Why many living things could not continue their existence and becam? 

To account for the answers of such questions through careful and painstaking scientific work, biologists lead to the idea of organic evolutio which explains that present day living beings have developed or modifie 

from the simpler ancestral forms during the course of time through? gradual and continual process of modification. 

The theory of organic evolution not only explains how living thing? have become so varied, it also explains their basic similarities as well. fof instance, if the present day organisms originated from the same ancestor that is, the earliest living things, it is thus not surprising that all liv things share the fundamental similarities. y