1. 16-3 The Process of Speciation
Interactive pgs

2. 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)

3. 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

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

5. 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

6. 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

8. 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