Vertebrates_Concept_4
Magnets
Magnets
Most fish spend their entire lives in water; with the water providing for all their needs, It contains the sources of food that they eat, supplies them with oxygen and maintains the temperature that they require. Oxygen dissolves readily into water: the action of waves on a beach causes oxygen in the air to be mixed into the water .Plants photosynthesising underwater will also release oxygen.
Fish have developed gills to filter oxygen out of water in a similar way to the way our lungs filter oxygen out of air. The fish will take a gulp of water and then force the water out through slits in the sides of its head, causing the water to pass over its gills. The gills consist of many thin tissue surfaces or membranes that are full of blood vessels. As the water passes over these membranes, the oxygen is absorbed into the blood supply and carbon dioxide is passed into the water.
Some fish, such as tuna, are unable to gulp water and force it through their gills: they rely on a constant flow of water through their gills (caused by their own movement through the water) to breathe. If they stop swimming,,they will not be able to breathe and wiill die,
Most children are aware that they inhale air . Some even appreciate that the most important part of air for breathing is oxygen. But when it comes to water-dwelling animals, confusion and misunderstanding set in. Some animals dwell in the water but still need to surface for air; but what about those animals that live wholly in water — how can they breathe where we cannot? Understanding how gills work will heip to clear up this confusion, and prepare them for later work on amphibian metamorphosis and on mammalian respiration .
Gill — a set of thin membranes that absorb oxygen from water; allowing fish and other aquatic animals to 'breathe' underwaten
Sharks have to keep swimming in order to breathe so they have to swim and sleep at the same time.
The whale shark. (which is: a shark not a whale) is the largest species of fish, it. can grow up to 12.5m long,
Fish breathe water.
it's not water as such that the fish take in when they breathe: its the oxygen that is mixed into the water. In a simiiar sense, we take in the oxygen that is a part of the air. All animals require oxygen, and they extract it either from the mixture of gases that is air or from oxygenated water. It is basically the same respiratory process (breathing oxygen), but in a different medium.
Do lungfish breathe in water?
Young lungfish have external gills: feather-like organs that extract oxygen from the water. These degenerate with age and finally drop off forcing the lungfish to surface in order to obtain oxygen from the air. Fish have an organ called a swim bladder which they can inflate by gulping in air; it helps them to maintain their buoyancy without having to swim all the time, In lungfish, this bladder has evolved the ability to absorb oxygen from air. They move around on land rather like eels or snakes, This is probably the way that all vertebrate air-breathing animals evolved.
Children can explore the variation in fish through video and other information sources:
www.bbc.co.uk/naturefanimals/by/fish
www.nhm.ac.uk/nature-online/life/reptiles-amphibians-fish/index.html
www.nhm.ac.uk/kids-only/life/life-sea/index.html