(a) Explain Darwinian theory of evolution with the help of one suitable example. State the two key concepts of the theory (pls dont give answer given in prev year paper solution). andproper explaination

Darwinian theory of evolution.

Theory of evolution by means of natural selection and survival of the fittest. 

Darwin and Wallace proposed that natural selection is the mechanism by which new species arise from pre existing ones. Natural selection states that there is "struggle for existence" within a population and variation exists within all population. The continuous competition between individuals for environmental resources creates a 'struggle for existence' and this struggle makes sure that certain organisms would fail to survive or reproduce. This would eliminate less suited organisms and better adapted organisms would survive and pass on their traits to next generation leading to evolution.

Consider the following example:

• A small population of beetles live in a bushy area with green leaves. Crows eat these beetles. As a result, variation occurs in these beetles due to sexual reproduction. Due to the occurrence of variation, the colour of one progeny beetle changes from red to green.

What is the advantage of this variation to green beetles?

The green beetle can hide itself in leaves to escape from being eaten by crows. Thus, the variation provides a survival advantage to the beetle.

Hence, the red beetles are rendered more vulnerable. Their chances of survival to reproduce are lesser in comparison to green beetles. This leads to an increase in the population of green beetles.

Variation in population by natural selection

This type of variation, which increases the survival value of an organism, is naturally selected.

The two key concepts are natural selection and survival of the fittest: