Which function of the muscular system is best illustrated by the heart pumping blood throughout the body?

Contraction and relaxation of the heart is the function of the muscular system whereby illustrated by the pumping of the blood by the heart throughout the body. Though everyone is not aware, the constant contraction and relaxation of the muscles help fight gravity, that is why the muscular system is a great help in maintaining good posture.

He proposed that natural selection is the primary mechanism of evolution.

Explanation:

Lets look at this question like this:

If you have a white deer in a green forest, the wolves who prey on deer would automatically go for that white deer. The white deer is easier to locate rather one who would blend in their environment. (A brown deer) With the theory of natural selection, the survival of the fittest would make it in their environment. Passing their genetics to their offsprings.