Characteristics of a population changes over the years for their survival in nature. This can be justified with these examples:

(a) To gain survival advantage: the best example is provided by the peppered moth in order to survive these moths then changed their colour to grey and now blended perfectly with soot coated trees.

(b) Due to accidental survival: Beetles are of two colour either red or blue. It was seen that elephants crushed all the red coloured beetle but not blue hence this example shows accidental survival.

(c) Temporary change of characteristics: Speciation of any plant or animal to the modern one is an example of temporary change of characteristics so as to bring about a finally best-suited species.