Question

Describe the basics of Endler’s guppy study (what did he discover and how did he test it?), AND explain how selection in the guppy study differed from that which the finches on Daphne Major experienced following the drought.

Answer 1

American zoologist John Endler tested Darwin’s theory with common aquarium fish guppy. He discovered guppies with differential colouration and spottings. some guppies with vivid colours and large spots while the others with light drab colour and small spots at different parts of the water stream. He observed that the colour pattern of male guppy is related to its predator stress. Male guppies with bright colour and large spots have a reproductive advantage in attracting the female, besides which it also catch the attention of the predator fish. So male guppies living in streams where there were many predators tend to possess light colouration and small spots. In absence of the predator, guppies tend to possess bright colours.

In Endler's guppy study, the frequency of predator is selecting the colour of the male fish. Here natural selection drives in favour of the male in terms of escaping from predator vs attracting the female. The finches in Daphne major has no predators or competitors. The medium ground finch evolution is only influenced by the weather, so the availability of food.

Normally, the medium ground finch are variable in size and shape which has the stubby beaks and eats mostly seeds. when drought occurred, the larger beak size gain advantage in utilising alternate food, and they survived. Due to differential survivability, they gain the reproductive advantage and hence evolved into new species.