On an island, finches that fed on large, hard seeds had large beaks. finches with small beaks fed on small, soft seeds. a drought changed the vegetation on the island. after this period, the number of seeds declined. the decrease in small, soft seeds was greater than the decrease in large, hard seeds. what are two ways the decrease in seed availability will affect the population of birds on the island?

This is similar to the research undertaken by grant and colleagues where they tried to observe evolution in a relatively short amount of time (i.e., in about two years).one of the first ways the drought and seed availability will affect the finch population will be the decline in numbers of the finches with small beaks and even possible extinction if conditions prove to be impassable for them. this is because they will be unable to eat the large seeds.the second effect of the condition is the natural selection of the finches with the larger beaks that enable them to eat the large seeds on the island. in the research i have mentioned above, they actually found a significant increase in beak size after only a few  generations of finches thus providing evidence for evolution and natural selection.

The answer is ozone layer.