Lecture4

Lecture4 - Mechanisms of Evolution

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I. Speciation A. Types 1. Anagenesis a. Transformation of an unbranched lineage of organisms to a state different from the ancestral population i. Basis for naming a new species 2. Cladogenesis a. Budding of one or more new species from a parent species that continues to exist b. More common pattern of speciation c. Produces more biological diversity B. Biological species concept 1. Characteristics a. Population whose members have the potential to interbreed i. Must be in nature b. Breeding results in the production of viable and fertile offspring c. Cannot produce viable, fertile offspring with other species 2. Species is the largest unit of a population where gene flow is possible 3. Biological species are reproductively isolated from other species in nature C. Other types of species 1. Species can be conceptualized by other means a. Morphology b. Ecology c. Evolution d. Characteristics that maximize successful mating II. Factors that Cause Reproductive Isolation A. Background 1. For discrete species to exist each must be reproductively isolated 2. Most species are isolated by more than a single type of barrier 3. Types of barriers a. Prezygotic i. Impede mating or fertilization ii. Intrinsic b. Postzygotic i. Prevent hybrid from developing into a viable, fertile adult ii. Intrinsic c. Geographic B. Prezygotic barriers a. Habitat isolation i. Two species live in different habitats within the same geographical range Mechanisms of Evolution http://www.rci.rutgers.edu/~uzwiak/GBSummer08/GB102Sum. .. 1 of 4
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Lecture4 - Mechanisms of Evolution

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