Gills - GCSE Biology Definition

Gills are special organs found in fish and some other water-dwelling creatures that help them breathe underwater. They work by taking oxygen from the water and getting rid of carbon dioxide, much like how human lungs work in air. Gills are usually located on the sides of the animal's head and appear as thin, feathery structures, which gives them a large surface area to absorb oxygen efficiently. When water flows over the gills, small blood vessels inside pick up oxygen and carry it to the rest of the body, helping the animal stay alive and active. Understanding how gills function is important for GCSE Biology as it relates to the study of respiration in different environments.