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Both evolution and classification are interlinked:

→ Classification of species is reflection of their evolutionary relationship.
→ The more characteristic two species have in common the more closely they are
related.
→ The more closely they are related, the more recently they have a common ancestor.
→ Similarities among organisms allow us to group them together and to study their
characteristic.

 We can thus build up small groups of species with recent common ancestors,
then super-groups of these groups with more distant common ancestors, and so
on.
 In theory, we can keep going backwards like this until we come to the notion of a
single species at the very beginning of evolutionary time.

TRACING EVOLUTIONARY RELATIONSHIPS

Homologous Organs
 Homologous organs are defined as the organs of different animals that are
having a similar structure but differ in their functions.
 Example of homologous organs are the forelimbs of frog, man, and the flippers of
the whale.
 The structure of these animals are the same but the functions are different.

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