What means that members of each species compete regularly for food and other necessary resources?

It means that the species, no matter what kind, are driven by some sort of energy, i.e the sun, soil, water, meat, plants etc. Meaning, that as the number of species are increasing, the food supply is becoming rational.

The (circulatory, digestive, excretory) works to break down food eaten before exercising. The (circulatory, digestive, excretory) takes in the nutrients obtained from the food. The body sweats as a mechanism to cool off, because the (circulatory, digestive, excretory) is working to flush out toxins.

Explanation: