Fish definition

Systems of classification

Morphography includes the systematic exploration and tabulation of the facts involved in the recognition of all the recent and extinct kinds of animals and their distribution in space and time. (1) The museum-makers of old days and their modern representatives the curators and describers of zoological collections, (2) early explorers and modern naturalist travelers and writers on zoo-geography, and (3) collectors of fossils and palaeontologists are the chief varieties of zoological workers coming under this heading. Gradually, since the time of Hunter and Cuvier, anatomical study has associated itself with the more superficial morphography until today no one considers a study of animal form of any value which does not include internal structure, histology and embryology in its scope.

The real dawn of zoology after the legendary period of the Middle Ages is connected with the name of an Englishman, Edward Wotton, born at Oxford in 1492, who practised as a physician in London and died in 1555. He published a treatise De differentiis animalium at Paris in 1552. In many respects Wotton was simply an exponent of Aristotle, whose teaching, - with various fanciful additions, constituted the real basis of zoological knowledge throughout the Middle Ages. It was Wotton's merit that he rejected the legendary and fantastic accretions, and returned to Aristotle and the observation of nature.

The most ready means of noting the progress of zoology during the 16th, 17th and 18th centuries is to compare Aristotle's classificatory conceptions of successive.

6. Read and translate the text.

A typical fish is cold-blooded; has a streamlined body that allows it to swim rapidly; extracts oxygen from the water using gills or an accessory breathing organ to enable it to breath atmospheric oxygen; has two sets of paired fins, usually one or two (rarely three) dorsal fins, an anal fin, and a tail fin; has jaws; has skin that is usually covered with scales; and lays eggs that are fertilized internally or externally.

To each of these there are exceptions. Tuna, Swordfish, and some species of sharks show some warm-blooded adaptations, and are able to raise their body temperature significantly above that of the ambient water surrounding them. Streamlining and swimming performance varies from highly streamlined and rapid swimmers which are able to reach 10-20 body-lengths per second (such as tuna, salmon, and jacks) through to slow but more maneuverable species such as eels and rays that reach no more than 0.5 body-lengths per second. Many groups of freshwater fish extract oxygen from the air as well as from the water using a variety of different structures. Lungfish have paired lungs similar to those of tetrapods, gouramis have a structure called the labyrinth organ that performs a similar function, while many catfish, such as Corydoras extract oxygen via the intestine or stomach. Body shape and the arrangement of the fins is highly variable, covering such seemingly un-fishlike forms as seahorses, pufferfish, anglerfish, and gulpers. Similarly, the surface of the skin may be naked (as in moray eels), or covered with scales of a variety of different types usually defined as placoid (typical of sharks and rays), cosmoid (fossil lungfishes and coelacanths), ganoid (various fossil fishes but also living gars and bichirs, cycloid, and ctenoid (these last two are found on most bony fish. There are even fishes that spend most of their time out of water. Mudskippers feed and interact with one another on mudflats and are only underwater when hiding in their burrows. The catfish Phreatobius cisternarum lives in underground, phreatic habitats, and a relative lives in waterlogged leaf litter.

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