. Explain the following: (a) Speciation (b) Natural Selection
Ans.(i) Speciation. The process by which new species develop from the existing species is known as speciation.
The important factor s which could lead to the formation of new species are:
-Geographical isolation of a population caused by various types of barriers like
mountain ranges, rivers, sea etc. The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.
-Genetic drift caused by drastic changes in the frequencies of particular genes by change alone.
-Variations caused in individuals due to natural selection.
(ii) Natural selection. Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their off springs and those characteristic which do not help are not passed on.