Notice that natural selection does not refer to individuals changing their characteristics. Rather,
natural selection results in a higher proportion of individuals that have an adaptation.
18a. Suppose that the sea level decreased in the open ocean, making shallow seas, allowing for
the growth of coral in tropical regions. What do you think would happen to the sea turtle
population? First, make your prediction of the population of sea turtles at the beginning with
higher sea levels, then after it becomes a coral reef. Be sure to include red, orange, yellow and
blue sea turtles.
18b. Next, think about a different scenario. Suppose that natural selection over many
generations had eliminated all the red, orange and yellow sea turtles in the open ocean habitat
so the population in this habitat only had blue sea turtles. After that, the sea level decreased in
the open ocean, making shallow seas, allowing for the growth of coral in tropical regions. Would
natural selection for sea turtle color occur? Why or why not?
18c. Based on this example, explain why evolution by natural selection can only occur if there is
variation in a trait.
19a. Suppose that your class repeated the simulation, but this time all the hunters were
blind-folded so they could only find sea turtles by touch. In each habitat, what fraction of the
sea turtles would be blue at the end of the simulation? (Remember that at the beginning of the
simulation 25% of the sea turtles were red, 25% were yellow, 25 Orange, and 25% blue.)
Open Ocean:
Coral Reef:
19b. Explain your reasoning.