How many species of spiders do you see?
Feb 24, 2016
How many species of spiders do you see?
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
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!
First a little story about our friend the squirrel…
Geographic IsolationPopulations become
separated by geographic barriers such as rivers, mountains, or other bodies of water.
The Grand Canyon
Kaibab SquirrelAbert Squirrel
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
Speciation
Reproductive IsolationGeographical Isolation Temporal IsolationBehavioral Isolation
The squirrels
Reduction of gene flow
Temporal IsolationTemporal Isolation – occurs when two or
more subspecies reproduce at different times
Day Blooming/Night Blooming
Eastern and Western Spotted Skunks
Speciation
Reproductive IsolationGeographical Isolation Temporal Isolation Behavioral Isolation
The squirrels
The Skunks
Behavioral IsolationBehavioral Isolation –capable of
interbreeding BUT have different reproductive strategies
Western Meadowlark
Eastern Meadowlark
Speciation
Reproductive IsolationGeographical Isolation Temporal Isolation Behavioral Isolation
The squirrels
The Meadowlarks
The Skunks
What type of Isolation is under way? http://www.pbs.org/wgbh/nova/beta/evolution/evolution-action-salamanders.ht
ml
How many species of spiders do you see?
THE HAPPY FACE SPIDERS!Look different but CAN
interbreed!
What about the ligers and mules?
Are there any other gray areas for the definition of a species?
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?
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?
Test your understanding-Explain how geographical and reproductive isolation work together with mutations to cause variation within a species and possibly speciation.