BI111 Chapter Notes - Chapter 22.2/22.3: Disruptive Selection, Gene Flow, Peripatric Speciation
Document Summary
Two categories of reproductive isolation; prezygotic and postzygotic. Prezygotic factors act before the fertilization of an egg. Postzygotic factors come into play after fertilization. Prezygotic factors prevent fertilization from taking place where as postzygotic factors result in the failure of the fertilized egg to develop into a fertile individual. Most species are reproductively isolated by prezygotic isolating factors that can take many different forms. Behaviourally isolated means that individuals mate only with other individuals based on specific behaviours. Prezygotic reproductive isolation of humans and chimps is behavioural. Prezygotic isolation in plants can be from incompatibility between the incoming pollen and he receiving flower so fertilization fails to take place. Incompatibilities between the games of two different species is called gametic isolation. Mechanical incompatibility is when sex cannot be performed because of anatomy. Plants and animals can also be isolates in space by geographic or ecological isolation. Sometimes the zygote may be perfectly viable and other times it may not be.
