1. Key Points About Natural Selection
Natural selection operates within generations; evolution occurs between generations
Natural selection alters the properties of populations.
Natural selection is not forward thinking or directed in
purpose.
3) Natural selection does not exist for the good of a species.

2. Why Evolution by Natural Selection Works
Individuals of populations exhibit genetically
based variation in traits that affect survival and
reproduction.

3. NS and HIV

4. Phenotypic Variation

5. |-- Drought --|

6. |-- Drought --|

8. Hatchlings (1976)
Hatchlings (1978)
Evolution
Occurs
Between
Generations

9. Heritability of Beak Depth in Medium Ground Finches

10. Foraging- Competition Hypothesis
Adaptation
Foraging-
Competition
Hypothesis
Evolution is more than armchair science:
hypotheses must be tested

11. Prediction: If necks evolved for the purpose of foraging at the
tops of trees, that’s where they should preferentially forage.
Even during
drought
conditions

12. Alternative Hypothesis: Necks are used as a weapon.
Simmons and Scheepers 1996
Pratt and
Anderson 1985

13. Things to keep in mind when studying adaptation
Differences among individuals are not always adaptive
Not every trait is an adaptation
Not every adaptation is perfect

14. Tephritid flies: Do they mimic jumping spiders to escape predation?
Phidippus
Zonosemata
Hypothesis 1: No mimicry
Hypothesis 2: Mimicry deters other predators
Hypothesis 3: Mimicry deters jumping spiders

16. 20 spiders tested for each treatment
Jumping spiders
retreated
Jumping spiders
munched