How many species of spiders do you see?
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How many species of spiders do you see?
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Vocabulary so we are all on the same page…
Species: group of organisms that breed with one another and produce fertile offspringShare a common gene pool, largest gene pool
possible
Speciation – formation of a new speciesThe shared gene pool is eventually split
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Reproductive IsolationReproductive Isolation – when members of
two populations can no longer interbreed and produce fertile offspring
New species form when organisms are reproductively isolated.
REPRODUCTIVE ISOLATION is the KEY to SPECIATION!
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First a little story about our friend the squirrel…
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Geographic IsolationPopulations become
separated by geographic barriers such as rivers, mountains, or other bodies of water.
The Grand Canyon
Kaibab SquirrelAbert Squirrel
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The Gene Pools must separate to become a new species
There is no gene flow between the populations
AND
Over time, the populations respond to new variations and natural selection as separate units
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Speciation
Reproductive IsolationGeographical Isolation Temporal IsolationBehavioral Isolation
The squirrels
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Reduction of gene flow
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Temporal IsolationTemporal Isolation – occurs when two or
more subspecies reproduce at different times
Day Blooming/Night Blooming
Eastern and Western Spotted Skunks
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Speciation
Reproductive IsolationGeographical Isolation Temporal Isolation Behavioral Isolation
The squirrels
The Skunks
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Behavioral IsolationBehavioral Isolation –capable of
interbreeding BUT have different reproductive strategies
Western Meadowlark
Eastern Meadowlark
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Speciation
Reproductive IsolationGeographical Isolation Temporal Isolation Behavioral Isolation
The squirrels
The Meadowlarks
The Skunks
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What type of Isolation is under way? http://www.pbs.org/wgbh/nova/beta/evolution/evolution-action-salamanders.ht
ml
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How many species of spiders do you see?
THE HAPPY FACE SPIDERS!Look different but CAN
interbreed!
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What about the ligers and mules?
Are there any other gray areas for the definition of a species?
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Testing the Speciation Hypothesis in nature1995 Hurricane brought the Iguana iguana
species to a new island in the Caribbean
Will it go extinct?Will the gene pool remain unchanged?Will it respond to new selection
pressures and become reproductivelyIsolated?
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Testing the Speciation Hypothesis ArtificiallySeparate cages act as what?
Develop food preferences
Mate and lay eggs on different food sources
Can lead to the start of what?
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Test your understanding-Explain how geographical and reproductive isolation work together with mutations to cause variation within a species and possibly speciation.