1. Variation in beak shapes
You just determined that the beak depth of Geospiza scandens changed over the course of 37 years. There are a few hypotheses as to why this is the case. One reason may be
2. The drought of winter 1976/1977
a drought in 1976 and 1977 that resulted in the death of the plants that produce small seeds on the island. The larger seeds required deeper beaks to crack them, so large-beaked birds survived and then reproduced. If this is the case, it stands to reason that the length of the beak might also change over time. Importantly, if the length and depth change at the same rate,
3. Beak geometry
the beak has the same shape; it just gets bigger. But if the beak length and beak depth change differently, the shape of the beak changes. In the next few exercises, you will investigate how beak length and depth change together. That means it's time for some linear regression! As a hint,
4. Hint
the draw_bs_pairs_linreg function you wrote will be helpful in computing confidence intervals this of your linear regression parameters.
5. Let's practice!
Now, off you go, back to your analysis! -