Question

Use Darwin’s three postulates to assess whether a trait will evolve due to natural selection. Explain why the “ st ruggle for existence ” is so important for evolution through natural selection. Contrast evolution through natural selection (ENS) with neutral evolutionary processes.

Answer 1

Ans)

Darwin's theory of evolution by natural selection is the logical outcome of three postulates:

(1) individuals within species are variable

(2) some of these variations are heritable

(3) individuals that reproduce the most are those with the most favorable variations

From one generation to the next, the struggle for resources (what Darwin called the “struggle for existence”) will favour individuals with some variations over others and thereby change the frequency of traits within the population. This process is natural selection. In order for natural selection to operate on a trait, the trait must possess heritable variation and must confer an advantage in the competition for resources. If one of these requirements does not occur, then the trait does not experience natural selection.

Natural selection operates by comparative advantage, not an absolute standard of design. As natural selection acts by competition for resources, it adapts the inhabitants of each country only in relation to the degree of perfection of their associates.

Natural Selection is the process by which evolutionary changes occur in living organisms over millions of years. According to Darwin's theory of evolution, the organisms well adapted to their environment survive better than those who are not and are able to pass on their genes to many more offspring. As this process repeats over hundreds of thousands of years and the less-fit organisms become extinct, it appears as if nature 'selects' certain organisms over others in the same environment to continue.

A neutral mutation is one that does not affect an organism's ability to survive and reproduce. The neutral theory allows for the possibility that most mutations are deleterious, but holds that because these are rapidly removed by natural selection, they do not make significant contributions to variation within and between species at the molecular level.