This is the exchange of oxygen and carbon dioxide between an organism and its environment.

What is the answer for the complicated molecules that make up living things usually contain carbon. why is carbon so important in these molecules?

Rue or false siblings look simila rbecause they each have some traits of their parents.

All but one describes an effect of aging on the digestive system. a) decreased acid secretion b) decreased elasticity of stomach c) capacity to resist damage decreases d) food remains in stomach for less time