If a population grows larger than the carry capacity of an ecosystem, the

If the population is larger than the environment can support, more will die until the population size is back to or lower than the environment can support.

The answer is B I guessed and got it right

the answer is:

carbon dioxide

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).