Chapter 24 - CR

Chapter 24 - CR - Chapter 24 The Origin of Species 1 of 25...

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1 of 25 of 25 Chapter 24 Chapter 24 The Origin of Species
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2 of 25 of 25 The origin of species The origin of species The origin of new species, or speciation Evo. theory focuses on speciation since appearance of new species is the source of biological diversity Evolutionary theory Must explain how new species originate in addition to how populations evolve Micro evolution: Changes of allele frequencies within 1 gene pool Macro evolution Refers to evolutionary change above the species level (present in many species…ex. Feathers)
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3 of 25 of 25 2 Patterns of Change 2 Patterns of Change Anagenesis Changes accumulate within one species until it transitions to be a species with different characteristics Cladogenesis (branching) 1 gene pool splits into multiple, separate pools which differentiate into new species Increases the number of species present (b) Cladogenesis (a) Anagenesis Figure 24.2
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4 of 25 of 25 The biological species concept The biological species concept Emphasizes reproductive isolation Reproductive Isolation : The existence of biological factors that impede members of two species from producing viable , fertile hybrids Is a combination of various reproductive barriers Species A population or group of populations whose members: 1. Can interbreed with members of the same species 2. Are unable to interbreed with AND produce viable offspring with members of other populations
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5 of 25 of 25 Similarity between different species. The eastern meadowlark ( Sturnella magna, left) and the western meadowlark ( Sturnella neglecta, right) have similar body shapes and colorations. Nevertheless, they are distinct biological species because their songs and other behaviors are different enough to prevent interbreeding should they meet in the wild. (a) Diversity within a species. As diverse as we may be in appearance, all humans belong to a single biological species ( Homo sapiens ), defined by our capacity to interbreed. (b) Figure 24.3 A, B
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6 of 25 of 25 2 types of barriers 2 types of barriers 1. Pre zygotic barriers Impede mating between species or hinder the fertilization of ova if members of different species attempt to mate a. Habitat : Species live in different habitats in the same area and so rarely encounter each other b. Temporal : Species breed at different times (can be day, season, or even year) c. Behavior : Different courtship rituals prevent mating d. Mechanical : Morphological differences prevent mating e. Gametic Isolation : Sperm unable to fertilize eggs of another species (ex. pH not right; can’t penetrate egg membrane)
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7 of 25 of 25 2 types of barriers 2 types of barriers 1. Post zygotic barriers Often prevent the hybrid zygote from developing into a viable, fertile adult a. Reduced Hybrid Viability : Hybrids do not fully
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This note was uploaded on 04/07/2008 for the course BIO 103 taught by Professor Mannino during the Fall '08 term at Long Island U..

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Chapter 24 - CR - Chapter 24 The Origin of Species 1 of 25...

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