Which system of the body breaks down food into forms that the body can use?
excretory system
digestive system
reproductive system
respiratory system

The correct answer would be the digestive system.

The main function of the digestive system is to break down the complex food substances into simpler absorb-able form.

It is achieved by mechanical and biochemical degradation of the food.

The whole process of the digestive system can be classified into five steps ingestion, digestion, absorption, assimilation, and egestion.

Usually, polysaccharides are converted into monosaccharides (such as glucose), proteins are converted into amino acids, and fats are converted to fatty acids and glycerol.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.  

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.