8. chemoreceptors in the circulatory system detect changes in circulating pco2. if co2 concentrations get too high, the rate of ventilation increases. why does this make sense?

because as bigger the concentration of carbon dioxide in blood is less oxygen present.

Explanation:

In human body the exchange among carbon dioxide and oxygen is constant, there need to be an equilibrium among them, if there is a considerable increase of carbon dioxide, that could be due:

1.- Because there is no enter of oxygen in the body.

2.- Suddenly there is an unusual production of carbon dioxide from the body.

In both cases this situation is not healthy for the body, so like a survival mechanism, the body will try to increase the ventilation rate to get more oxygen to the body.

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.