we want to conduct an experiment to test the adaptive function of a polar bear's fur. we want to compare the fitness of bears with their natural coat, and bears with coats that evolved in a different environment. to do this comparison, we capture a number of polar bears so that we can manipulate their coats. for our treatment group, we shave the polar bears and glue on a coat of grizzly bear fur. an appropriate control for this treatment would be to: