A relationship in which one species benefits while the other species is harmed is known as

It is known as a parasitic relationship.

Explanation:

Parasitic relationships are exactly what you described. We see these sorts of relationships in nature in worms for instance.

When a worm attaches to a host, it oftentimes leeches off the host's blood for nutrients and the like. In this manner, the worm benefits while the host gets weaker and loses nutrition.

Other examples include ticks and leeches.

answer; polycythemia is the correct answer;

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).