Gills are used by fish for gas exchange. The structure of gills is a feathery shape that increases the surface area and allows for maximum efficiency.
Gills
Gills are used by fish for gas exchange. The structure of gills is a feathery shape that increases the surface area and allows for maximum efficiency.
Fish (like all animals) must take in oxygen and release carbon dioxide (gas exchange). Remember that oxygen is required for cellular respiration and releasing energy from food. Gills are a major part of a fish's respiratory system. An animal's respiratory system is the combination of all the organs and tissues in the animal that are involved in gas exchange. Oxygen gas, which is produced in water ecosystems from plants and algae, is dissolved in the water. Fish use their gills as a site for collecting this oxygen gas and passing it into their blood.
If you have ever seen a fish picked up by its mouth with its gills spread, as in the picture above, you will notice the bright red color. This is because of the rich blood supply that flows through the gills. Many tiny blood vessels in the gills allow the oxygen gas to diffuse from the water into the fish's blood. The blood moves through the vessels, which carry oxygen to the fish's cells.
At the same time, blood vessels carry carbon dioxide gas from the cells' cellular respiration back to the gills. The gills then diffuse the carbon dioxide gas out of the blood, through the gills, and into the water.
Remember, diffusion is the movement of a substance from areas of high concentration to areas of low concentration. The oxygen and carbon dioxide gas move from high to low concentrations, and this process requires no energy. As the blood vessels release carbon dioxide gas waste, they are picking up the needed oxygen gas.
Pretty cool cycle, isn't it?
As you're looking for your fish, does your fish have a means of pumping the water over their gills, or does your fish have to swim constantly to move water over its gills?