Mesopotamia?? I'm not quite sure this is a biology question.
Atria is a large part of the heart so too big for cells; arteries & veins lead away or to the heart.
Capillaries are the smallest vascular structures that allow materials to be exchanged easily between cells.
Answer;
-Allele frequencies
The hardy-weinberg principle states that allele frequencies in a population do not change unless outside factors affect the gene pool.
Explanation;
Hardy-Weinberg principle is a mathematical model that describes how genotype frequencies are established in sexually reproducing organisms.
The Hardy-Weinberg equilibrium is a principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors. The Hardy-Weinberg equilibrium can be disturbed by a number of forces, including mutations, natural selection, nonrandom mating, genetic drift, and gene flow.
Because human DNA is so very long (with up to 80 million base pairs in a chromosome) it unzips at multiple places along its length so that the replication process is going on simultaneously and more accurately.