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.

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

hope it ,

bioteacher101