Add to table of contents Speciation graphs Pg. 62 Speciation Pg. 63

Speciation Pg. 63 1. Speciation – the formation of a new species.

A. Geographic isolation – a physical barrier stops species from interbreeding. Ex. Grand Canyon squirrels. Desert tortoise and a new freeway

B. Reproductive isolation – a population becomes genetically different so they can’t interbreed. Ex. Frogs that mate at different times.

2. Population Genetics: the study of evolution from a genetic viewpoint. Most populations have variation amongst their traits. i.e. different heights, skin color, etc. If graphed, looks like a bell

. Natural Selection can cause a shift in traits within a population. Depends on which traits are favorable in that environment. Those traits will increase over time.

4 Different Effects: A. Stabilizing selection – individuals with the average form have the highest fitness. ex. Fur color

B. Directional selection – individuals with 1 extreme variation have greater fitness than the others.

C. Disruptive selection – individuals with either extreme variation have greater fitness than an average. Can lead to a new species.

D. Sexual selection- when female organisms select a mate based on phenotype-May require extreme male traits. i.e. bright colors, unique mating calls, etc.

Attach Embryology to Pg. 60 Attach graphs to page 62

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Add to table of contents Darwin’s Journey Pg. 68 Rates of Speciation Pg. 69

Rates of speciation: A. Gradualism – speciation gradually and at a stable rate.

Rates of speciation: B. Punctuated Equilibrium– speciation occurs suddenly, then not at all. Usually due to natural disasters.