One theory suggests that giant woolly mammoths became extinct when the ice age ended and the climate became warmer. Why might this environmental change have led to their extinction? A. hey didn’t die off, their traits changed to match the new climate
B. Their traits were best suited for a cold climate

well, you see. the answer to your question is quite simple. the thing that is big, powerful, and over 9,000 is your mom.

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).