Origin of Species

Reproductive isolation can be classified into two categories:Prezygotic Reproductive Isolation - the inability to exchangegenes, even when the two forms live in the same geographic area.Postzygotic Reproductive Isolation - the inability to producehealthy fertile offspring, even though the two forms can mate andproduce a zygote.Within each category there are several modes or mechanisms ofreproductive isolation.Prezygotic isolation includes ecological isolation, behavioralisolation, temporal isolation, mechanical isolation, and gameteincompatibilityPostzygotic isolation includes zygotic inviability and hybridsterility.6