Read the following and answer the question. 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?
a.) dominant species
b.) invasive species
c.) keystone species

The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required? a. the bacteriophage used in the experiments was a t2 phage. b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment. c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. d. establishing the identity of the genetic material required observation of two phage generations.