1. Do Now
Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur?
A. fewer mutations
B. limited food resources
C. limited beak variations
D. overproduction of offspring

2. Let’s brainstorm some things that could be considered a “Pressure”
Predators
Food Sources
Water Sources
Shelter
Mate Selection
When a trait dies off, it is considered selected against. The surviving trait is considered selected for.
Come up with an example of each.

3. Definition: Movement of alleles from one population to another
How it works: When animals migrate and breed in the new population the traits of both populations are passed on
Gene Flow

4. Lots of gene flow results in: Similar populations (genetically)

5. Gene Flow
Limited gene flow results in: Different populations (genetically) that could evolve into different species

6. Definition: Changes in allele frequencies due to chance alone
How it works: Some alleles may increase in frequency while others may decrease or become eliminated from the population.
Genetic Drift

7. Genetic Drift
Bottleneck effect: genetic drift that occurs after an event drastically reduces the size of a population

8. Genetic Drift
Founder Effect: genetic drift that occurs after a small number of individuals colonize a new area

9. Genetic Drift
Negative effects: population loses genetic variation, so they are less likely to be able to adapt to a changing environment

10. Sexual Selection
Definition: Process which certain traits increase mating success and become more common in the population

11. Sexual Selection
How it works: Females mate with males that display certain traits, so those traits get passed on to offspring

12. Sexual Selection
Intrasexual: competition/fighting among males for females
Intersexual: males display certain traits to attract females

13. Describe the difference between gene flow and genetic drift.
Exit Ticket
Describe the difference between gene flow and genetic drift.