Chapter 22 - Chapter 22 The Origin of Species I Biological...

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Chapter 22 The Origin of Species I. Biological Species A. Definition of species Populations whose genes are actually or potentially exchanged through interbreeding reproductively isolated, mate, reproduce, and produce viable offspring. 1. Geographic variation within species 2. Populations of species may exhibit variation still considered the same species 3. Many species live together (sympatric) What mechanisms keeps species separate? B. Reproductive Isolating Mechanisms (Two Types) 1. Prezygotic isolating mechanisms : prevent zygote formation a. Ecological isolation = habitat isolation b. Behavioral isolation c. Temporal isolation
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d. Mechanical isolation e. Gametic isolation 2. Postzygotic isolating mechanisms a. Hybrid sterility b. Hybrid inviability C. Problems with the biological species concept 1. Geographically isolated species can’t mate 2. Some organisms reproduce asexually 3. Fossils 4. Genetic analysis is discovering more hybridization
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II. How species form Isolating mechanisms evolve slowly over time, and are probably
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Chapter 22 - Chapter 22 The Origin of Species I Biological...

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