pl What happens when we disturb one of the biogeochemical cycles?
a. the global ecosystem becomes stressed and experiences imbalance
b. stuff gets messed up
c. plants and animals die
d. the global ecosystems experience homeostasis

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.