The smallest particle of an element is the .

Variety of living organisms; includes genetic, species, and ecological types.

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.

Support mangrove trees out of the water. a) pneumatophores b) prop roots c) sand dunes d) tide supports