CBSE - IX - Biology - Diversity in Living Organisms
How is classification related to evolution? How do the previous body designs affect all other subsequent designs?
- The principles of classification help us to trace the evolutionary relationships of the species around us.
- The similarities amongst the organisms allow us to group them into broad groups. The grouping can be done based on a certain set of characteristics.
- As time passed, certain characteristics began to influence the body design. Once the new body design came into existence, changes began to occur in it which in turn brought about new changes.
- The characteristics which came into existence earlier are likely to be more primitive than those which arise later.
- Most of the organisms have arisen by the accumulation of changes in their body design. The organisms which possess these favourable changes survive better in the long run.
- There are certain groups of organisms that have ancient body designs and are referred to as primitive or lower organisms. Some organisms have acquired their body designs relatively recently and are called advanced or higher organisms.
- The terms primitive and advanced do not clearly reflect the evolution of the organisms and hence, we often refer to them as older and younger organisms respectively.
- There is a strong possibility that complexity within the organisms increases with an increase in the evolutionary time. Hence, we can say that older organisms are relatively simpler, while younger organisms are more complex.
- We can build up small groups of species with recent common ancestors, then super groups of these groups with more distant common ancestors and so on.
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