Origin of Species

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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
Ecological isolation occurs whentwo species live in the same areabut do not encounter each otherbecause they exploit differentportions of the same habitat.Until recently lions and tigers hadoverlapping ranges in India. Theydid not mate, in part, becauselions live in open areas, and tigersprefer forests. They can, and willmate, and produce offspring inzoos. In nature, they are goodbiological species.7
Page 1 and 2: Evolution IIIThe Origin of SpeciesN
Page 3 and 4: The question is sometimes more diff
Page 5: The biological species concept - a
Page 9 and 10: Temporal isolation occurs when two
Page 11 and 12: Hybrid sterility isolates species.
Page 13 and 14: The geographic isolationmay involve
Page 15 and 16: Speciation can also occur within th
Page 17 and 18: Anagenesis and cladogenesis combine
Page 19: “Nothing in biology makes senseex

Origin of Species

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