Answer:
Natural selection is the process through which populations of living organisms adapt and change. Individuals in a population are naturally variable, meaning that they are all different in some ways. This variation means that some individuals have traits better suited to the environment than others.
Answer:
The Sun's rays warm our world, stir air and ocean currents, and catalyze chemical reactions in the atmosphere. The Sun-warmed surface evaporates water to form rain clouds that redistribute fresh water around the world. And sunlight is essential for most life forms that live at Earth's surface.
Explanation:
Energy. A solute can only move against concentration gradients using active transport which requires energy
The atria of the heart merely need to allow blood to flow into the ventricle, and therefore aren't very muscular.
The ventricles of the heart need to actually pump blood to the rest of the body, whether to the lungs or the the rest of the body.
