Answer:
Genetic variation refers to differences in the genetic makeup of individuals in a population. Genetic variation is necessary in natural selection. In natural selection, organisms with environmentally selected traits are better able to adapt to the environment and pass on their genes.
I think it might be B. not 100% sure but I think it's B.
Answer:
pressure changes of alternating contraction and relaxation during the cardiac cycle.
Explanation:
Opening and closing of heart valves are regulated by changes in the blood pressure of various heart chambers during the cardiac cycle. During atrial systole, the higher blood pressure in the atria opens both AV valves and forces the blood to enter the ventricles. The semilunar valves are closed. During ventricular systole, the higher blood pressure in the ventricles opens both semilunar valves to allow the blood to enter the pulmonary trunk and aorta. At this time, both the atrioventricular valves are closed.
Answer:
The organism halfway up is the evolutionary ancestor of the one at the top of the branch. The one halfway up shares some characteristics with the one on the top. Hence the connection in the diagram.
Explanation:
A branching tree diagram is a set of groups within groups, with the organisms at the bottom having the fewest shared characteristics and the ones at the top having the most.