Respiratory System

The respiratory system performs exchange between gases. The molecules of oxygen and carbon dioxide are exchanges, this process changes oxygen to carbon dioxide. Our respiratory system is responsible to clean out the bacteria or dust we breath in. Every living organism has that system, but in different shape and form, like how some have lungs while others have gills.

Earthworm

The earthworms' respiratory system is very different compared to other mammals, but the purpose is the same, get the oxygen and take out the carbon dioxide. Earthworms do not have lungs or gills like other mammals, but instead they breathe by using their moist skin. By diffusing air through their skin, worms are able to breathe like every other mammal. Their moist skin is need, so that diffusion can happen without a problem. The skin covers the whole body of the worm, so it is much more easy for the worm to take in oxygen an give out carbon dioxide.  

Crayfish 

The crayfish has evolutionary advantage of being able to breathe underwater because of their gills, which it helps the crayfish to breathe. Also most of what crayfish eats is in the water, so it is easier for the crayfish. The crayfish's gills are located on the outside of the body between the crayfish body wall and carapace. When one of the swimmerets were pulled out, you can see that the crayfish's gills is attached to the walking leg. So whenever the crayfish walks the gills will spread out giving space so that oxygen can enter them. The gills are attached therefore when the crayfish walks, it can breathe at the same time. In the crayfish, there is a pocket like thing that lets the crayfish store its water so that when it walks on land and still breath because it needs water in order to survive.

Frog 

There are three main components to a frog's respiratory system. The First is the lungs, for pulmonary respiration. The second is the skin, for cutaneous. Finally the third one is the mouth, for buccal respiration. The most oxygen they get is from their skin. The frog have lungs that help them breathe. Once the nostrils of the frog breathes in the oxygen, it goes through the windpipe and down to the lungs. The frog can use its' mouth to breathe too. The skin of the frog is also is not really for protection, but instead it is for taking in oxygen. A lot of blood vessels are running through the skin of the frog and can help take in oxygen, which goes to the red blood cells. Whenever the frog swims, the oxygen in the water is instantly collected by the skin, so it  can stay underwater for a long period of time.  

Rat 

The rat's respiratory system  only has two lungs. The rat does not need anything else, like the human. Unlike the frog, the rat does not have to hold its breathe or get oxygen from its' skin. Rats use only their lungs to breathe, but when something bad happens, they on have one source to help them live. When the rat breathes the oxygen taken in are transported throughout the body by the red blood cells and at the same time the red blood cell  tries to rid of the carbon dioxide.