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The shared trait of breathing via gills in bony fish and cartilaginous fish is a famous example of symplesiomorphy. Bony fish are more closely related to terrestrial vertebrates, which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the sharks, rays, and the other cartilaginous fish. Their kind ...
Many aquatic animals have developed gills for respiration which are specifically adapted to their function. In fish, for example, they have: A large surface area to allow as much oxygen to enter the gills as possible because more of the gas comes into contact with the membrane; Good blood supply to maintain the concentration gradient needed
Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The gills push the oxygen-poor water out through openings in the sides of the pharynx.
The majority of marine gastropods breathe through a single gill, supplied with oxygen by a current of water through the mantle cavity. This current is U-shaped, so that it also flushes waste products away from the anus , which is located above the animal's head, and would otherwise cause a problem with fouling.
They typically breathe by extracting oxygen from water through gills. Fish use fins to propel and stabilise themselves in the water. Over 33,000 species of fish have been described as of 2017, [ 1 ] of which about 20,000 are marine fish.
In fish and some molluscs, the efficiency of the gills is greatly enhanced by a countercurrent exchange mechanism in which the water passes over the gills in the opposite direction to the flow of blood through them. This mechanism is very efficient and as much as 90% of the dissolved oxygen in the water may be recovered.
Fish do consume water, but not necessarily like humans. All living species on Earth need water to survive, including our aquatic friends. Fish do consume water, but not necessarily like humans. ...
However, non-facultative fish must respire at the surface even in normal dissolved oxygen levels because their gills cannot extract enough oxygen from the water. Many air breathing freshwater teleosts use ABOs to effectively extract oxygen from air while maintaining functions of the gills.