1. Darwin proposed the theory of Natural selection.
2. Nature only selects or decides which organism should survive or perish in nature.
3. The organism with useful traits will survive and the organisms having harmful traits are going to perished or eliminated from its environment.
4. For example, a group of twelve red beetles live in a bush of green leaves.
5. They will grow their population by sexual reproduction.
6. So they generate variations in their population. Let us assume crows eat the red beetles more the population of red beetles slowly reduced.
7. Crows eat these red beetles and their population slowly reduces.
8. During this time a colour variation arises by the sexual reproduction.
9. So that there appears one beetle that is green in colour instead of red.
10. Moreover this green colour beetle passes its colour to its offsprings; so that all its progeny are green.
11. Crows cannot see the green coloured beetles on green leaves of the bushes and therefore crows cannot eat them.
12. The crows can see the red beetles and eat them as a result, there are more and more green beetles than red ones which decrease in their number.
13. The variation of green colour beetle gave a survival advantage to green beetles’ than red beetles. They were naturally selected.
