how many species of spiders do you see?

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.