Homologous and Analogous organs:

Various biological studies have told us that since their origin, living organisms have undergone changes in their organisation to evolve into new forms. Thus, we can say that more characteristics two species have in common, more closely they will be related.

One way of analysing how closely related two organisms are is by observing their organs.

Some organisms have the same structure of some organs, but use them for same or different purposes. Such organs are called homologous organs. For example, limbs of frog, lizard, human and bird, as you can see from the image:

Note that all these have different functions –

• Limbs of a man are used for grasping
• Frogs use them for jumping
• Lizards use them for running

On the other hand, some organs may have different structures, but are used for the same thing. Such organs are called analogous organs. For example, wings of a bat and a bird.

Fossils:

Preserved traces of living organisms are called fossils. Study of fossils is very important, as it provides evidence for evolution. But the interesting question is, how are fossils formed!?

Usually, when organisms die, their bodies will decompose and be lost. But every once in a while, the body or at least some parts may be in an environment that does not let it decompose completely

Human Evolution:

Excavating, time dating, etc have revealed a lot of information about human evolution. Scientists today know that all humans, irrespective of their colour, are a single species. Not only that, regardless of where we have lived for the past few thousand years, we all come from Africa. It is also not true that human beings evolved from chimpanzees. Rather, both human beings and chimpanzees have a common ancestor from a long time ago. That common ancestor is likely to have been neither human or chimpanzee.