Many body systems work together for proper functioning of the body and to maintain internal homeostasis. The works to break down food eaten before exercising. The takes in the nutrients obtained from the food. The body sweats as a mechanism to cool off, because the is working to flush out toxins.

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:

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs