Plant and animal cells differ in a variety of ways. Notice when you compare the model cells, plant cells contain chloroplasts and animal cells do not. What is the function of this organelle found in plant cells?

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays

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.

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.