Speciation_web

Speciation_web - What is a Species? Species Concepts 1....

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What is a Species?
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 Species Concepts 1. Biological* 2. Morphological* 3. Recognition 4. Cohesion 5. Ecological 6. Evolutionary Two main concepts
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Morphological* species concept: "members of a species are individuals that look similar to one another." Basis for Linneaus' original classification - still broadly accepted and applicable today. *Morphology refers to the form & structure of an organism or any of its parts.
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Problems: Many situations in which individuals look similar, but don’t mate with one another. Even within a species, individuals can look very different depending on stage of life cycle (e.g. tadpole & adult frog)
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The Biological Species Concept “a group of actually or potentially interbreeding individuals who are reproductively isolated from other such groups.” - emphasizes that a species is an evolutionary unit. Members share genes with other members of their species, and not with members of other species.
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There are situations (and taxa) for which the Biological Species Concept is inadequate. Examples: Fossils, asexual organisms, species that remain distinct despite ability to interbreed or exchange genes through intermediates, members of a species that live in different places? So, biologists have other species concepts: (each has advantages & disadvantages)
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 Species Concepts 1. Biological 2. Morphological 3. Recognition 4. Cohesion 5. Ecological 6. Evolutionary See your text for additional info (page 476)
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   Reproductive Isolating Barriers / Mechanisms: 1. Prezygotic  Isolating Barriers / Mechanisms 2. Postzygotic  Isolating Barriers / Mechanisms prevent fertilization reduced reproduction Mechanisms: intrinsic to organisms
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   Reproductive Isolating  Barriers / Mechanisms: 1. Prezygotic   a. geographic isolation b. habitat isolation –  parasites on diff. Hosts  c. behavioral isolation –  frogs with diff. calls d. temporal isolation –  moths w / sim. pheromones  e. mechanical isolation –  f. gametic isolation –  molec. recognition of sperm  Prevent fertilization
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   Reproductive Isolating  Barriers / Mechanisms: 2. Postzygotic        a. hybrid inviability –  hybrid frog eggs/larvae  fail to complete development     b. hybrid infertility – 
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This note was uploaded on 02/12/2009 for the course BIO 102 taught by Professor Bick during the Spring '09 term at Pace.

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Speciation_web - What is a Species? Species Concepts 1....

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