LIFE SCIENCE

Detailed explanation-1: -This is ‘natural selection’. Consider the giraffe, for example. A Darwinian theory of evolution posits that it was through random variation that some giraffes had longer necks than others. Thanks to their long necks, they were able to reach leaves high up in the trees in their environment.

Detailed explanation-2: -This higher fitness results in less genetic variation in the population. Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in “neck wrestling” contests.

Detailed explanation-3: -An example of directional selection is giraffe neck lengths. The environment created a selection pressure which favored giraffes with longer necks who could reach more food in the trees. At the same time, there was selection pressure against giraffes with shorter necks.

Detailed explanation-4: -Since the days of Charles Darwin, the long necks of giraffes have been a textbook example of evolution. The theory goes that as giraffe ancestors competed for food, those with longer necks were able to reach higher leaves, getting a leg-or neck-up over shorter animals.