The Astyanax mexicanus fish live in the deep dark caves of northeast Mexico. They are closely related to a fish that lives on the surface of the water that has lots of light. Researchers have discovered two phenotypes for a gene for sight, those who have eyes as adults and those who eyes are missing and are blind (blindness is a mutation). The blindness is caused by an overreactive allele that although causes eye loss, it also develops extremely powerful jaws, large teeth, and abundant taste buds that helps the blind fish find food in the water (compared to those fish with eyes). Those fish who are sighted are not has good for capturing their prey and rarely survive in the caves. These fish produce around 10 -20 eggs but are eaten by a lot of other fish found in the darkness. Please write all answers in proper sentences.

a) What type of natural selection occured based on the fish that are blind? Explain your answer. [1]

b) What type of speciation is this (allopatric or sympatric)? Explain your answer. [1]

c) What is the selective pressure for these cave fish? Explain your answer. [1]

d) What is the selective advantage for these cave fish? Explain you answer. [1]

e) Using Darwin’s five ideas of Evolution by Natural Selection, explain the development of blindness in fish using ONE PARAGRAPH.