Bb-Chap.16-Lect.FA10 (1)

Bb-Chap.16-Lect.FA10 (1) - What is a Species? Defined as a...

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1 What is a Species? Defined as a group of (actually or potentially) interbreeding natural populations, which are reproductively isolated from other such groups Biological Species” Concept Limitations : Cannot determine species identity among asexually reproducing organisms (e.g. bacteria) or among fossils (e.g. dinosaurs) Often difficult to observe whether members of different groups interbreed
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2 Appearance Can Be Misleading Organisms that are similar in appearance sometimes belong to different species Organisms that differ in appearance may belong to the same species Examples (birds): Two species of flycatcher: difficult to tell apart —but don’t interbreed Previously distinct species of warbler: slight physical differences, but do interbreed where ranges overlap (thus single species)
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3 Alternatives to the Biological Species Concept Refer to Chapter 18 : textbook pgs. 344, 346, 351. “Phylogenetic Species” Concept “phylogeny” = evolutionary history of a species Defines a species as the smallest group of individuals that share a single common ancestor , forming one branch on a “tree” diagram “Molecular Systematics” Using DNA sequence data to infer evolutionary relationships (Fig. E18-1, textbook pg. 346)
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4 How Is Reproductive Isolation Between Species Maintained? Reproductive isolation occurs when members of one population are unable to interbreed with members of another Pre mating isolating mechanisms prevent mating between species Post mating isolating mechanisms prevent formation of viable, fertile offspring after mating has occurred
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6 Pre mating Isolating Mechanisms Geographically separated populations aren’t necessarily distinct species May be able to mate if geographic barrier was removed; difficult to determine Kaibab & Abert squirrels live in geographically separate areas of Grand Canyon, but are still very
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Bb-Chap.16-Lect.FA10 (1) - What is a Species? Defined as a...

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