Importance of oxygen in ANIMALS
Oxygen. Know you heard of it, because that's the cause of your breathing. About every system in your body is in work when you take a lung full of oxygen. The animal body is full of CO2 that it considered "dirty blood" in our bodies. The dirty blood gets replaced by the clean blood when you take a lung full of air. The science of it is complicated and we'll take a close look at it in a way most people are able to understand. The reason why when your noses is stuff, you could breath in through your mouth is because your nose and mouth is connected so air could go down, or up, the same tube. The tube air goes down is called the trachea. From there the air would travel down into you heart to lungs. Your blood is going to absorb that air and is going to turn into something we consider, "clean/blue" blood. The blood that contains CO2 coming in from your lungs is going to be replaced by this blood so that blood could get cleaned. The air is being absorbed into your cells, where it enters the mitochondria and it along with ATP helps break down and make energy. After the oxygen is done assisting ATP, it could come out of the cell as CO2, which your body don't need and plants do, so it would start this whole process again. Without the oxygen, the organism would be dead because it doesn't have the oxygen to assist in making energy.
Gas exchange in Clams
Now gas exchange in clams are a little different but somewhat still the same. As a matter of fact, clams still "breath" but they get their air from water, since the spend most of their time in the water. When the clam opens up it's shell, it's cilia and gills start to be put in use. The cilia that is doing the absorbing from the gills. The cilia in the gills absorbs what oxygen the water is carrying and lets go of the water that does have any oxygen from it's shell. Then does the oxygen goes on it's journey through the clams entire body of exchanging gases. The Oxygen exchange starts from the foot/ near the gills, because remember, the foot is the only thing that get stuck out when it opens up it's shell. From there the bloods are being exchanged from dirty to clean, just like in other land animals, and shown in the diagrams below, moves through out the clams body, almost as it would a land animals. You many thing that the clams need for oxygen would be high because the oxygen is traveling the entire body, but that is not the case. Their need for oxygen is very low, which is no wonder they could stay locked up in that shell without opening it for so long.