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

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

Evolution What is it?

Change over time Evolution time Phenotype

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

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

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

Evolution case study: beak shape http://www.hhmi.org/biointeractive/origin-species-beak-finch 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

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

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?

Natural selection IF THEN evolution will occur

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

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?

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

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??

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

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

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

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.

What will happen to medium ground finch beak size?

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

Want to learn more about the finches?

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.

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

Bumpus Data