“When cells touch, they should stop replicating” is a general way to describe external cell regulation. Explain why it is necessary for cells to have external cell regulation factors.

As soon as possible this assignment is due in 5 minutes atoms in a molecule are bonded together by sharing, gaining, or a. photons b. protons c. neutrons d. energy f. electrons

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.

Compare the shapes of the bones of the human skull with the shapes of the bones of the human leg. how do the shapes differ? why are the shapes important?