16-3 The Process of Speciation Interactive pgs. 404-410

What is speciation? It is the formation of a new species A species is a group of organisms that can breed with one another and produce fertile offspring. Different species have different gene pools (groups of alleles)

How to become reproductively isolated… (cannot interbreed) Behavior Isolation Capable of interbreeding but different courting rituals Eastern and Western meadowlarks have different songs Geographic Isolation Separation by geographic barriers : rivers or mountains Natural selection works separately on each group Temporal Isolation Reproduction during different times of the year

Behavioral Isolation: Different Mating Calls Geographic Isolation: Separated by a Boundary Temporal Isolation: Reproduce during different times of the year

Peter and Rosemary Grant’s Research on the Galapagos Finches Tested 2 Hypotheses There must be inheritable variation in beak size and shape The difference in beaks must produce differences in fitness leading to nat. selection Studied the medium ground finch on Daphne Major (one of the islands) They caught and measured almost every medium ground finch on the island

What they found… Variation Natural Selection Rapid Evolution Many different characteristics showed bell shaped distribution of polygenic traits Natural Selection Beak shape determined survival during a drought. Largest beaks most likely to survive Rapid Evolution As food supply changed so did the fluctuation of beak size over a period of a few decades

Speciation in Darwin’s Finches 1. Founders Arrive From South America and populate an island (species A) 2. Separation of Populations Some birds cross to another island & become isolated 3. Changes in the Gene Pool Population on the new island evolves due to different environmental conditions (species B) 4. Reproductive Isolation A few birds (B) cross back to island 1 and cannot mate with original population 5. Ecological Competition Species A and B compete for food and resources. Species C may evolve 6. Continued Evolution Process continues leading to the formation of 13 different species of finches