Discuss theory of natural selection proposed by darwin.

Explanation

Darwin.s Theory of Natural Selection
Charles Robert Darwin (1809-1882), a British naturalist went on world voyage on board the ship HMS Beagle to study animal and plant diversity. Later on Darwin published a book entitled .On the Origin of Species by Means of Natural Selection. embodying his observations and conclusions in 1859. The main postulates of Darwin.s theory of natural selection are
(i) Overproduction or Prodigality of reproduction which indicates the enormous fertility rate in organisms.
(ii) Limiting factors, i.e. the resources like food, space, etc. remain limited in an environment.
(iii) Struggle for existence Limited resources cause struggle among species. This occurs at three levels
(a) Intraspecific struggle among the individuals of same species.
(b) Interspecific struggle among the individuals of different species.
(c) Environmental struggle of living forms against the environmental conditions.
(iv) Variations and heredity The dissimilarity between organisms is attributed to variations. These variations allow better adjustment of some individuals to their environment.
(v) Survival of the fittest The organisms which adapt well In the environment due to favourable variations will be selected by nature and will survive more in nature. The organisms unfit to survive are gradually eliminated. This is called natural selection.
(vi) Origin of new species (Speciation) As a result of struggle for existence, variability and inheritance, species become better adapted to their environment. These beneficial adaptations are preserved and accumulated in the Individuals of species one generation after next.
This results into the origin of a new species.