Scientists can classify plants into two major groups based on the reproductive structures of the plants. What are these two groups called?
A. seedless and seed plants
B. hybrid and heirloom plants
C. water plants and land plants
D. flowering and nonflowering plants

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.