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 offspring Share a common gene pool, largest gene pool possible Speciation – formation of a new species The shared gene pool is eventually split

Reproductive Isolation Reproductive 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 Isolation Populations become separated by geographic barriers such as rivers, mountains, or other bodies of water. The Grand Canyon Kaibab Squirrel Abert 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 Isolation Geographical Isolation Temporal Isolation Behavioral Isolation The squirrels

Reduction of gene flow

Temporal Isolation Temporal Isolation – occurs when two or more subspecies reproduce at different times Day Blooming/Night Blooming Eastern and Western Spotted Skunks

Speciation Reproductive Isolation Geographical Isolation Temporal Isolation Behavioral Isolation The squirrels The Skunks

Behavioral Isolation Behavioral Isolation –capable of interbreeding BUT have different reproductive strategies Western MeadowlarkEastern Meadowlark

Speciation Reproductive Isolation Geographical Isolation Temporal Isolation Behavioral Isolation The squirrels The Meadowlarks The Skunks

What type of Isolation is under way?

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 nature 1995 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 reproductively Isolated?

Testing the Speciation Hypothesis Artificially Separate 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.