What does looking at old bones and shells tell us about evolution?

Compare the composition of the moon's surface with the composition of the earth's surface.

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?

Eutrophication caused by human nutrient pollution.