How did Darwin explain the similarities between organisms in South America and the Galápagos islands? He suggested that identical organisms were in both places.

He suggested that a few organisms came to the islands from the mainland and changed over time.
He suggested that all the organisms originated in North America.

He suggested that a small number of organisms broke off the island and populated South America and changed over time.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.