The Great Diversity of Fish
reflects different adaptations that enable fish to live in the oceans and fresh water. Fish vary in size and shape, and can be divided in 3 main groups (above).
Fish by the Numbers
According to FishBase, 34,300 species of fish had been described as of September 2020. That is more than the combined total of all other vertebrate species: mammals, amphibians, reptiles and birds. Fish species diversity is roughly divided equally between marine (oceanic) and freshwater ecosystems.
All fish have in common 3 characteristics
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The great diversity of fish and their main characteristics
- In addition to the absence of jaws, modern agnathans are characterised by absence of paired fins. e.g. lampreys
- They are jawed vertebrates with paired fins, scales, and skeletons made of cartilage rather than bone. e.g. sharks and rays
- have skeletons primarily composed of bone tissue, as opposed to cartilage. Is the largest class of vertebrates in existence today with ~ 28,000 species e.g. guppies, clown fish
- Are a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide.
- Fish have an internal skeleton either made of bone or cartilage. That is one important characteristic that differentiate fish groups; Bony fish and Cartilaginous fish.
- Blood passes only once through the heart in each complete circuit of the body except for lungfish.
- They are fish, but they have a horse-like head, a monkey-like tail and a kangaroo-like pouch. They have a few things in common with chameleons as well – they can move their eyes around, and change their skin colour!
- Entices prey close with the glowing lure that comes from luminous bacteria that live in it.
- Their leafy camouflage and spiny fins keep large fish from snacking on them. They slurp up their food, using their long snout like a drinking straw.
Osteichthyes (Bony fish)
Single – loop blood circulation