Sea otters are important predators of sea urchins, an animal that eats giant brown kelp in continental shelf zones where they form huge kelp beds. it was observed that the removal of sea otters from the west coast led to an increase in the sea urchin population. these sea urchins fed on the large kelp fronds, destroying the kelp beds that serve as an important source of food and protection for spawning fish. what role does the sea otter play in this case?

dominant species

invasive species

keystone species

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.