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Lecture 49

BIOL 1000 Lecture 49: Lecture 49

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Biological Sciences
BIOL 1000
Kevin G.Scott

c78 different species  Signals that attract mates and elaorate mating behaviours that are unique to a species are the most important reproductive barriers  E.g. only recognizing firefly light signals of one’s own kind o 4) Mechanical isolation – female and male sex organs are not compatible 5) Gametic isolation – sperm of one species may not be able to fertilize eggs of another   Important when fertilization is external Postzygotic barriers = operate after hybrid zygotes have formed 1) Most hybrid offspring do not survive 2) Reduced hybrid fertility – hybrid offspring reach maturity and are vigorous but sterile E.g. a mue is a robust but sterile offspring of a female horse & a male  donkey  Cannot produce offspring 3) Hybrid break-down – first generation hybrid offspring are viable and fertile, but when these hybrids mate with each other, offspring are feeble/sterile In Allopatric Speciation, Geographic Isolation Leads to Speciation Key event in origin of new species is the speciation of a population from other populations of the  same species Changes in allele frequencies caused by natural selection, genetic drift, and mutation will not be diluted by alleles entering from other populations (gene flow)  Allopatric speciation = mode of speciation by which initial block to gene flow comes from  a geographic barrier that isolates a population Populations separated by geographic barriers are known as allopatric populations
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