Question

Mention four main postulates of Darwin's theory.

Answer 1

1. Overproduction: Living beings, both plants and animals, have an innate desire to produce their own progeny so that their race may continue. It has been observed that more individuals are produced to increase the chances of their survival. However, regardless of the rate of reproduction of a species under natural conditions, the number of individuals of each species remains roughly constant over a long period of time in a fairly stable environment.
2. Struggle for existence: According to Darwin, individuals multiply in a geometric ratio, whereas space and food remain almost constant. This leads to a struggle for existence among the organisms. In this struggle, there is intense competition between organisms for favourable shelter, climate, food supply, and breeding places. Competition may be between members of the same species (intraspecific) or different species (interspecific).
3. Variation: The struggle for existence among the organisms has compelled them to adapt themselves according to the conditions so that they can utilise natural resources and survive successfully. Because of the adaptations, it is difficult to find any of the two individuals alike. Even the progeny of the same parents are not exactly alike in all respects. Such differences are known as variations. Without variations, changes could not occur, and hence, there would be no possibility of evolution occurring. Certain variations that once appeared in the parent generation continue to appear in the progeny, generation after generation.
4. Survival of the fittest: During the struggle for existence, only those individuals who have advantageous adaptations or variations can survive. Individuals or races without these variations will be routed out. Nature selects only those variations that are suitable. This is what Darwin termed natural selection.