Lecture 10 - Overview The"Mystery of Mysteries Speciation...

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Overview: The “Mystery of Mysteries” Speciation, the origin of new species, is at the focal point of evolutionary theory Evolutionary theory must explain how new species originate and how populations evolve Microevolution consists of adaptations that evolve within a population, confined to one gene pool Macroevolution refers to evolutionary change above the species level
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Concept 24.1: The biological species concept emphasizes reproductive isolation Species is a Latin word meaning “kind” or “appearance” Members of a biological species are reproductively compatible, at least potentially; they cannot interbreed with other populations.
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LE 24-3 Similarity between different species. Diversity within a species.
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Reproductive Isolation Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids Two types of barriers: prezygotic and postzygotic
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Prezygotic barriers impede mating or hinder fertilization if mating does occur: Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gametic isolation
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Habitat isolation: Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers
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LE 24-4a Prezygotic barriers impede mating or hinder fertilization if mating does occur Postzygotic barriers prevent a hybrid zygote from developing into a viable, fertile adult REDUCED HYBRID VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION GAMETIC ISOLATION Reduced hybrid viability Fertilization Viable, fertile offspring Reduced hybrid fertility Hybrid breakdown Mating attempt Gametic isolation Fertilization Mechanical isolation Behavioral isolation Temporal isolation Habitat isolation Individuals of different species
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Temporal Isolation Temporal isolation: Species that breed at different times of the day, different seasons, or different years cannot mix their gametes
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Behavioral Isolation Behavioral isolation: Courtship rituals and other behaviors unique to a species are effective barriers
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Mechanical Isolation Mechanical isolation: Morphological differences can prevent successful mating
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Gametic Isolation Gametic isolation: Sperm of one species may not be able to fertilize eggs of another species
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This note was uploaded on 06/07/2011 for the course BIO 301M taught by Professor Jasper during the Spring '08 term at University of Texas.

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Lecture 10 - Overview The"Mystery of Mysteries Speciation...

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