Why can different species not interbreed?
1 Answer
Members of one species is reproductively isolated from members of another species. (Thus species is naturally defined category.) Though invisible to us, there are several factors which act as reproductive barriers between two species.
Explanation:
- Envirnmental barriers such as water bodies or mountains are external factors, but species isolation takes place mostly due to various biological factors.
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I would say biological factors are genetically determined. Thus a change in reproductive behaviour, or in structure of coital organs, are new variations added to the gene pool due to mutation. Organisms with new variations would prefer to mate only with those organisms having complementary variations.
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Likewise the fertilizin/antifertilizin chemistry may change and sperms of some organisms would no longer be able to fertilise eggs of other individuals. Such incopatibility may also happen in plants where pollen of one group of plants may not germinate on stigma of others.
- Sometimes a hybrid is formed, but the hybrid remains sterile.
- Chromosomes of different species also differ and could not form homologous pairs.
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