states that each rock layer isolder than the one above it.

Which identifies the main purpose of biological taxonomy?

Which step is not included in the step approach to calculating the greatest common divisor?

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.