In broad terms, finches. In specific terms, he observed how over time, the beak sizes and shapes of said finches changed to adapt to the food sources available.
I hope I was able to help. Best of luck.
<span>Insects are found in almost all ecosystems on Earth, with the rarity being oceans. While some species, such as coconut crabs, sand hoppers, woodlice and pill bugs dwell on land, crustaceans are generally found in water — and usually oceanic — regions. Adapting to their habitat, many insect species evolved wings — two pairs for most and one pair for others. A tracheal system is also present for breathing. Crustaceans, on the other hand, breathe using gill-like mechanisms.</span>
That's a hard one but I would go with A unwanted transpitation. Hope that helped :)
