Alleles can disappear from a population through natural selection. This relates to the most fit phenotype because the breed with the desirable trait, or the most fit, will live and produce off spring. Eventually the less desirable trait and its corresponding allele will disappear after multiple generations pass. If the environment does not change alleles of non desirable traits will disappear. <span />
D is the answer because I had to answer the same question
The heart has 4 chambers, 2 upper chambers and 2 lower chambers. Blood passes through a valve before leaving each chamber of the heart.
