Why do stars seem to move in the sky

Stars move in the sky because the earth is spinning and orbiting on its axis. Because we are moving in the sky the stars move as well because the earth is spinning. That is also why the clouds move in the sky.

(I'm sorry if my answer is bad :<)

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).