Genetic variation . Group of answer choices is created by the direct action of natural selection always arises in response to changes in the environment must be present in a population before natural selection can act upon the population tends to be reduced when diploid organisms produce gametes

It must be present in a population before natural selection can act upon the population.

Explanation:

Genetic variation refers to the variations that exists in the DNA of the individuals. These variations are caused mainly by mutation and genetic recombination of the DNA. It helps in the process of evolution. Genetic variations helps in building the mechanisms of change that helps in the process of evolution. Genetic variation is caused highly because of process of sexual reproduction. The offspring exhibit various genetic variation.

not only is it colder, it also becomes darker, less salty, and more dense.