Heredity, Natural Selection, and Evolution

Species and Population

How can a population become reproductively isolated?

Reproductive isolation means that individuals of one population are unable to exchange gene sequences (eggs and sperm) with individuals from another. This means that natural selection will work on the isolated population independently from the rest of the species, therefore increasing the likelihood that those isolated organisms will become a separate species. Methods by which this can occur include geographic isolation, habitat isolation, and temporal isolation. In other words, two populations can become physically separated by a barrier like an ocean or mountain range; they can use different parts of the same habitat (birds that visit only the tops of trees as opposed to the lower branches); or they may be active at different times—for example, nocturnal and diurnal insects.


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