Bio1510Chapter 24

Bio1510Chapter 24 - Chapter 24 The Origin of Species...

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Chapter 24: The Origin of Species Concept 24.1: The biological species concept emphasizes reproductive isolation The biological species concept states that a species is a group whose members have the potential to produce viable, fertile offspring only within that group. Gene flow between populations holds the phenotype of a population together Reproductive isolation: Biological factors that prevent two species from producing fertile offspring. Hybrids: Offspring that are the result of the mating of two separate species. Prezygotic barriers block fertilization from occurring by: Habitat isolation: Species of different rarely interact and have little chance of mating. Temporal isolation: Species that breed at different times of the day, seasons, or years cannot mix gametes. Behavioral isolation: Courtship ritual and other behaviors that attract mates unique to a species prevents mating with other species. Mechanical isolation: Morphological differences prevent a mating if attempted. Gametic isolation: A sperm may not be able to fertilize the egg of another species. Postzygotic barriers prevent the hybrid zygote from developing into a viable, fertile adult: Reduced hybrid viability: The interaction of the genes from interspecies parents impairs a hybrid’s development or survival. Reduced hybrid fertility: Hybrids of even the best traits could end up being sterile. Hybrid breakdown : Some hybrids may be viable and fertile, but when they mate with one another or a parent species, the offspring are sterile or feeble. Limitations of the Biological Species Concept
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This note was uploaded on 01/25/2011 for the course BIO 1510 taught by Professor Unknown during the Spring '07 term at Georgia Tech.

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Bio1510Chapter 24 - Chapter 24 The Origin of Species...

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