If polar bears and brown bears can breed it means that they come from a common ancestor population. Now imagine that this ancestor population had brown coats and lived in forests that were covered in snow in the winter and that were close to seas that iced over in winter.

Describe a process by which some of the ancestor population could have become today's brown bears and some polar bears.

The response is the basis for vaccination. primary secondary tertiary none of the above

Which example describes a mutualistic relationship between organisms? young wasps prey on caterpillars. crabs eat the remains of dead fish. tapeworms feed on food in the intestines of cats ants protect a tree on which they feed.

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.