Chapter 24 Notes

Chapter 24 Notes - Chapter 24 • • Two basic patterns of...

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Chapter 24 Two basic patterns of evolutionary change Anagenesis - the accumulation of changed within a single gene pool Cladogenesis - the splitting of a single gene pool into two or more separate pools Figure 24.2 What is a Species? Species is a Latin word meaning "kind" or "appearance" Biologists compare morphology, physiology, biochemistry, and DNA sequence when grouping organisms Gene flow between populations holds the phenotype of population together Similarity between different species Diversity within a species The Biological Species Concept Our old friend Ernst Mayr proposed the BSC: "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups" - Mayr 1942 Reproductive Isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring Hybrids are the offspring of crosses between different species. Barriers to Gene Flow Reproductive isolation can be classified by whether factors act before or after fertilization Prezygotic barriers block fertilization from occurring by: Impeding different species from attempting to mate Preventing the successful completion of mating Hindering fertilization if mating is successful
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Postzygotic barriers - Often prevent the hybrid zygote from developing into a viable, fertile adult Prezygotic and Postzygotic Barriers Habitat Isolation : Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers Figures 24.4 Temporal Isolation : Species that bred at different times of the day, different seasons, or different years cannot mix their gametes
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This note was uploaded on 06/11/2008 for the course BIOL 2108 taught by Professor Davis during the Spring '08 term at Kennesaw.

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Chapter 24 Notes - Chapter 24 • • Two basic patterns of...

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