Q. 4 B4.0( 8 Votes )

(a) Define ‘speciation’. Explain how speciation occurs.

(b) Will geographical isolation be major factor in the speciation of a self-pollinating plant species? Give reason for your answer.

Answer :

(a) The process by which new species develop from the pre-existing ones is known as speciation.

A number of ways leads to speciation:


1. Geographical separation of a population, leading to reproductive isolation and thus, speciation.


2. Lack of gene flow between two groups of a population results in speciation.


3. Occurrence of variations in organisms due to natural selection.


4. Due to random change n gene frequency (genetic drift), the organisms are unable to reproduce with each other, resulting in speciation.


There can be more ways like DNA changes, the change in the number of chromosomes, the inability of the germ cells of two isolated groups to fuse with each other, etc. which can lead to speciation.


Thus, new species come into existence.


(b) Geographical isolation signifies the separation of two populations of a species.


A self-pollinating plant possesses both the male and female parts of a flower, required for pollination.


Pollination occurs between the reproductive organs of the same flower, so geographical isolation is not at all significant in the speciation of a self-pollinating plant.


Moreover, new gene variants will not be introduced in the population due to geographic isolation.


On the other hand, accumulation of variations occurs in cross-pollinating plants due to geographical isolation.


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