Fish Essay

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Fishes & Fisheries. 1. Types of fishes 2. Salt water fishes. 3. Sweet water fishes 4. Aquariums (Salt & Sweet) 5. Movies made on fishes. 6. Sport with fishes 7. My home having an aquarium. 8. World largest aquariums. 9. Marine park A fish is any member of a paraphyletic group of organisms that have gills and they do not have limbs with digits. Most fish are cold-blooded, allowing their body temperatures to vary at different temperatures change and hence are found in most places where there is water. They can be found in nearly all aquatic environments, from high mountain streams to the deepest depth of oceans. Fish are an important resource worldwide, especially as food. Commercial fishermen hunt fish in wild fisheries or farm them in ponds or in cages in the ocean. They are also caught for recreation, kept as pets, raised by fishkeepers, and displayed in public marine shows. . The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked atrue spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey ofarthropods. Sharks are called marine predators. Many types of aquatic animals commonly referred to as "fish" are not fish in the sense given above; examples include shellfish, cuttlefish, starfish,crayfish and jellyfish. In earlier times, even biologists did not make a distinction – sixteenth century natural historians classified also

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