最早可以歸類於為魚類的生物是軟軀體的脊索動物，在寒武紀首次出現，雖然沒有真脊柱，但是有脊索，因此其動作較其他脊索動物更加靈活。魚在古生代繼續演化，產生很多不同的物種，其中許多都是盾皮魚綱，有骨甲防止成為其他動物的食物。第一個有下顎的魚出現在志留紀，而許多的魚已經變成強大的肉食動物，而不再成為節肢動物的食物。
Fish belonging to the vertebrate phylum subphylum. Characterized by aquatic animals have gills, lack limbs and limb at the end of fingers. Most people put into vertebrate fish (53%), birds (18%), reptiles (12%), mammals (9%), amphibians (8%) of the five categories. According to the late Canadian scholar Nelson (1994 年) statistics, known at the time, about 28,000 kinds of fish, accounting for more than half of the named invertebrates and fish, new species continue to be discovered. Named the world about 32,100 kinds of species. [1]
Fish include hagfish, lampreys, and cartilaginous fish bony fish, including many species have become extinct. Fish are cold-blooded, their body temperature will vary with the external ambient temperature, but like the great white shark and tuna can be maintained at a temperature higher temperatures [2] [3]. In most of the water has fish. Almost all of the aquatic environment has fish, from mountain streams (such as trout) and even ultra-deep waters to the deep ocean deep with (like Saccopharyngiformes and monkfish) belt. Fish species have more variability [4] than other vertebrates.
Fish is one of the important human resources, especially food fish. May be used at sea fisherman fishing fishing methods may also be used in aquaculture farming methods. Humans may also be because the entertainment, or want to make aquarium keeping and fish in an aquarium show or fishing. In some cultures fish once a symbol of God or religion, but also a lot of art, books or movie theme.
Fish the word is used in a negative way tabulated definition excludes Tetrapod (such as amphibians, reptiles, birds, mammals), which are the same ancestral species. Fish is Paraphyly, no proper system of taxa in taxonomy.
The earliest fish classified as soft-bodied creatures of chordates, first appeared in the Cambrian, although not really the spine, but there notochord, so its action is more flexible than other chordates. Fish continue to evolve in the Paleozoic, producing many different species, many of which are Placodermi, prevent bone armor become food for other animals. The first one has a jaw fish appeared in the Silurian, and many of the fish has become a powerful predator, rather than become arthropod food.
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