Why did the united states ban the use of ddt

The united states banned the use of ddt because it was running from the farmers fields into rivers and the fish were absorbing the chemicals. Eagles and other birds would eat fish out of the rivers and because they were infected with the chemicals, the bird also was infected. When the birds would lay their eggs the shell would be really thin and they would sit on the eggs to warm them and the shell would break. This is the reason why the Bald Eagle became endangered.

c.more precipitation,but only when emission levels.

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).