1. Schedule Cultural connection Pre-test Foraging for Candy Lunch
HHMI video
Galapagos finch activity
Measure study skins
Analyze Bumpus data

2. Learning objectives Identify and apply Darwin’s postulates
Measure traits in birds
Analyze data and determine whether natural selection is likely to act on a trait
Predict whether a trait will evolve

3. Evolution
What is it?

4. Change over time
Evolution
time
Phenotype

5. Natural selection
Individuals that are able to survive to produce more offspring will have higher fitness

6. Pre-test No need to include your name No expectations
Just allows us to gauge understanding

7. Candy activity Grab one of the tools (spoons, tweezers, chopsticks)
Collect as much candy as you can in the time you have
Graph the amount of candy collected for each tool

8. Evolution case study: beak shape
Peter and Rosemary Grant
Peter and Rosemary Grant are researchers from Princeton who have been studying the Darwin Finches since the 1970s. The Galapagos are a perfect place for this kind of research -- not only are the islands remote making disperal events rare, the size of the islands is also important.
Researchers at Princeton, started studying the finches in the early 70’s
Geospiza fortis –
medium ground finch

9. Darwinian sieve there is variation in our initial population
not all pieces make it through sieve
the pieces that do make it through sieve are not random

10. Darwinian sieve what about heritability?
will evolution have occurred if the trait isn’t heritable?
imagine if small boxes can also make big box offspring, would the size of boxes change over time?
what if box size is heritable?

11. Natural selection IF
THEN evolution will occur

12. Natural selection IF THEN evolution will occur
1. individuals in a population are variable
2. these variations are, at least in part, inherited by offspring
3. some individuals leave more offspring than others
4. who leaves more offspring is not random
THEN evolution will occur

13. Darwin’s finches
We can see how the different species of ground finches are specialized to eat different sized seeds. Could we see how selection may have driven this differentiation by looking a seed size preferences with in one species?

14. Postulate 1: Variation in beak depth?
Needed to measure many, many finches

15. Postulate 2: Is it heritable?
Must know parents of birds: most birds must be banded.
Want small island.
Why not the same between 76, 78??

16. Selection event: drought
Typically 130mm of rain, in 1977 only 24mm
Here, severe mortality: it was a drought. Fewer seeds available.

17. Selection event: drought
Seeds left were very hard!
Tribulus seeds
Number and type of seeds decreased

18. Postulate 3: Variable numbers surviving to reproduce?
Over 20 months 84% disappeared before breeding
Need a small island, non-migrating population.

19. Postulate 4: Correlation between trait and descendants?
Change in scale
Why didn’t the largest survive?
Why did some small beaks survive?
Note change in scale!
Why did a few small birds survive?
Why didn’t the very largest beaked birds survive?
Why did beak size matter?: observed feeding. Timed period to open seeds.

20. What will happen to medium ground finch beak size?

21. Prediction: evolution
Mean beak size of finches hatched in 1976: 8.9 mm
Mean beak size of finches hatched in 1978: 9.7 mm
8.9% increase in one generation!
Fossils: usually 1% change in million yrs
Larger in next generation
Very fast
faster than fossils

22. Want to learn more about the finches?

23. Measuring study skins
Visit each station and use the calipers and rulers to measure each trait for each bird
Choose one trait and create a graph (histogram) showing how many birds have the different sizes of the trait.

24. Bumpus Data Terrible storm, Feb 1, 1898
Hermon Bumpus, professor at Brown University
Brings birds in and measures many traits
Records which birds live and which birds die
First study of natural selection
Inspires Peter and Rosemary Grant

25. Bumpus Data