<span>Pulmonary vein
Pulmonary circulation is the movement of blood starting from the heart, where deoxygenated, or carbon dioxide-filled, blood leaves from the right ventricle and through the pulmonary valve, then into the left and right pulmonary arteries and arrives at the lungs. During the process of respiration, the carbon dioxide is released and oxygen is added to the blood. </span>
The uterus protects and nourishes the fetus
The answer is tropical areas. The tropical areas obtain more
radiant energy from the Sun than they lose to space through terrestrial
radiation, and vice versa for polar areas. Earth has an energy remaining in the
tropics and an energy scarcity for the polar areas.
<span>The trait that is ancestral to all chordates is the presence of a notochord...the others are gill slits and nerve chord</span>
The very primitive organism is the oldest because, over time, organisms gradually evolved into more complex organisms. First came the primitive organism, then it evolved into the more complex one, or the younger fossil.
