The demarcation of the fish is not handled uniformly and should therefore be explained at first. We want to call all change-warm animals, for which possess a well trained jaw-appliance and their body is fitted primarily at the life in the water, "fish" here. Therefore, we don´t consider the round-mouths (lampreys and Inger) to be one of it but severs her/it/them as jaw-lots.

What now are the characteristics of the fish in the individual one? Have the form of fins its extremity; the skin is covered with sheds mostly, however, she/it can also skin-teeth or bone-sign carries or completely bare is. The respiration normally happens through gills, that are ordered on skeleton-bows at the rear part of the skull.

System approximately 25 000 fish-types is described today. You/they belong to over 400 families and are subdivided in 2 classes with 2 lower classes each: the cartilage-fish, to whom sharks and smelled, sea-dragons and Chimären belong, as well as the bone-fish, who include all remaining and consequently the majority of the present-day fish.

Formation of the fish (tribal-history) the origin of the fish lies in the darkness also still today. Already before 450 million years, during the Silurian-time, different forms of fishings lived on the earth. These belonged to the group of the Plattenhäuter (Placodermi) once. Head, shoulder and stomach were covered with them with bone-plates so that the fore part of these "tank-fish" was like in a knight-armament. A second, just as old group can clearly be distinguished from the Plattenhäutern, the Acanthodier (Acanthodii). Despite her/its/their shark-similar form, they don´t have to do anything with the sharks, rather they correspond to original bone-fishings in many characteristics even if they are not directly in consideration as Ahnformen of the bone-fish. It is very small fish, that in the Permzeit, before 220-280 Mill. Years, equally like the Plattenhäuter went out.

Cartilage-fish already in the ages Devon and Karbon of the earth-antiquity (before 350-280 Mill). Years, the first predecessors of the sharks appeared. This also means, however, that these early cartilage-fish performed only after the original bone-fish. It refutes the old opinion, that is cartilage-fish, the older of the two groups. In the law-time of the Erdmittelalters (before 175-140 Mill). Years, shark-forms, that exist still today, occurred Z for the first time. B. the gray-sharks (type Hexanchus), who belonged to the the most originally living cartilage-fish with it.

Muscle - or Fleischflosser Hochinteressant is the tribal-historical development of the Fleischflosser (lower class Sarcopterygii) with Quastenflossern and lung-fishing; because they form the transition to the quadrupeds or country-vertebrates. The Rhipidistia, that lived in the Devon and Karbon, belonged to the relatives of the Quastenflosser. Her/its/their fins carried muscles, that found base-surfaces of corresponding bones, at the reason. This development meant the beginning of this limbs for the quadruped animals (Tetrapoda). Eusthenopteron from the upper Devon shows already conspicuous agreements with the amphibians (Amphibia) with the poor-similar fin-skeleton, in the construction of the skull and at the fine-construction of the teeth. In the same age like the Rhipidistia, therefore approximately 350 million years ago, also the first lung-fish appeared. Apparently, they severed themselves from the predecessors of the Quastenflosser in the Silurian for a long time previously.

Bone-fish the first Strahlenflosser (Actinopterygii), that we from petrifactions know, are Cheirolepsis from the group of the Urknochenfische (Palaeonisciformes), that comes from the middle Devon. Surely, however, there were older forms of the Urknochenfische before these freshwater-fish as well. Individual sheds point it out from the upper Silurian. A prime of her/its/their development experienced the Knorpelganoiden (Chondrostei) at the threshold between earth-antiquity and Erdmittelalter in the Perm and triad-time (240-175 million years ago).

In the law-time (175-140 million years ago), the more progressive Knochenganoiden (Holostei) gained a climax with many types, that get the light abundantly particularly in petrifactions of the Solnhofener slate. Her/its/their development separated into different directions: The first representatives of the real bone-fish (Teleostei) from the type Leptolepis went on Pholidophoriformes of the Knochenganoiden directly from the order. In 3 different groups, the real bone-fish developed from different trunks of the Knochenganoiden during the law-time.

But only in the Erdneuzeit, that 60 million years ago in the tertiary was introduced, the blustery development of the real bone-fish began. You/they therefore are just as modern as the mammals and form the overpowering majority of the fish with more than 20 000 types today!

Resembles shape and functions of the fish-body the prevalent fish-form a spindle; with fast swimmers, she/it is cigar-nicely protracted and in the cross-section more or less round (numerous sharks, Lachsartige, pikes). Slow fish have an at the side flattened (coral-fish, hatchet-stomachs), from above downward leveled off (flat-fish, smelled), one eel-good (eels, phlegm-fish) protracted or even rounds or cubic form (ball-fish, sea-hare). Some fish deviate also from the horizontal posture and (Schrägsteher, sea-horse-little, snipe-knife-fish) become even slower through it.

Head the head can have molded very differently: Upper jaws (saw-fish, spoon-sturgeon), lower jaws (Halbschnäbler) or both (horn-pikes) can have extended beak-nicely, the mouth-opening is upper-continuous (pike), middle - or (trout) under-constantly (shark). No less, situation and position of the eyes determine the shape of a fish, whether now she/it like with most fish at the head-sides, far in front (spoon-sturgeon), behind (Picasso-handle-fish), or is ordered above (sea-devils, four-eye-fish). Many deep sea-forms have lying telescope-eyes on stalks or in tubes.

Flowed decisively the shape of the fish is influenced also by the type of the fins. There are unpaare, therefore individual in the center line of ordered fins and few-y fins at the body-sides. You/they have different functions, that one from the form and the order can partially recognize. Primarily, they are used for the stabilization of the fish-body and - particularly the tail fluke - to the locomotion. Backs, anuses, and the unpaaren fins are tail fluke. You/they can have subdivided only in the longitudinal direction, unpaarig therefore remain also with the existence of 2 back-fins. Breast and stomach-fins always are few-y, d. h. one each right and left, ordered. You/they correspond to the front and rear-extremities of the remaining vertebrates.

The fins are supported by gristly or bone fin-radiations, that under-structure into different types, can become: So, horny Stützfäden (Elastoïdinfäden) give solid hold to the fins with cartilage-fishings and sturgeons. The bone fin-rays of the bone-fish can consist of undivided, shared or many times shared (feathered) soft-radiations or from hard-radiations, that for the Stachelflosser (Z). B. Perches, typical is. As well as in back and anus-fins, sometimes also in stomach-fins, hard-radiations can form the reason-framework.

Fish move locomotion rarely in the water through one single drive-type. Mostly, it is about mixtures, that are essentially composed from 3 locomotion-manners:

1. Winding movements of the entire body that originates (eel and sea-wolf) through constriction and prolonging of the torso and tail-musculature or at the side beating movements of the tail-stalk to observe especially well with the Picasso-handle-fish in the aquarium);

2. Movement of individual fins (sea-horse-little) Lippfische);

3. Recoil-movement from ago-expressions of the breath-water from the gill-covers as well as. -Slits (particularly with sharks).

4. Further locomotion-types: Ground-inhabitants like the Grundeln push off with the tail-stalk at the ground and "hop" onward. The tremor-eel swims with completely stretched body through undulating movements of the fin-hem. With the Knurrhahn, the 3 lowermost rays of the flippers are independently and not interconnected through the fin-skin. The fish uses her/it/them like legs and "crawls" over the reason with it. The flying fish have strongly increased flippers (partially also stomach-fins), with which they glide after the Herausschnellen from the water through the air.

Most fish carry skin in the skin of the torso sheds, skin-teeth, bone-plates or thorns. Only few fish-forms are bare (catfish, leather-carps), her/its/their skin appears leathery. The sheds don´t form the outer restriction of the skin. You/they are "" roof tile-nicely overlapping in the leather-skin and are covered by the transparent waiter-skin. Through plentiful phlegm-secretion, the waiter-skin becomes slippery: everyone, that tries for the first time to hold on to a fish with the hands, notices this. The crystal-clear phlegm-layer becomes dully through caustic impurity of the waters or when cooking and with it visible, Z. B. with carps or trout "in blue!").

Sheds near the sheds let themselves distinguish 3 types in principle:

1. Tooth or Placoidschuppen with sharks and handle-fishing,

2. Glaze or Ganoidschuppen with sturgeons, cayman-fish and Quastenflosser,

3. Little tile-shed of the higher bone-fish, that in 2 forms, the round things, or Cycloidschuppen and the comb, or Ctenoidschuppen appear.

The tooth-shed of the sharks is especially interesting: Raises a to the back tended little tooth for itself on a Basalplatte, that lies in the leather-skin. This consists of Dentin (tooth-leg) like the mammal-tooth and is coated with a glaze-layer. The glaze-shed consists of bone plates. You/they are coated by a shiny Ganoid or glaze-layer. These sheds are among each other interconnected and so hard that harpoons often bounce off them.

The little tile-shed of the higher bone-fish, as third Schuppentyp, also exists from bones, however they lack the glaze-layer of the Ganoidschuppen. If the rear free edge of these sheds is roundish and smooth, it is about round-shed, like one she/it with herrings, salmon and carps finds. If more exactly the back edge and clearly toothed is, one speaks of comb-shed, that Z. B. occur with the Barschartigen. There are also fish with round - and comb-shed, for example some jag-perches or the real red-tongue (a flat-fish). Occasionally, shed-fields grow together to bigger plates; fish-tanks then are built through it as we know her/it/them from Knurrhähnen, tank-catfish and suitcase-fishing.

Side-line the side-line-organ has his/its name of the course visible with many fishings at both body-sides. One thinks of the light line with the brownish colored codfish or the black side-line, that itself with the cod, behind the gill-covers, over which entire bodies and tail-stalk stretch and finish before the tail fluke, incipient. Here, we have to do it with a system of canals, that stands with the surrounding water through fine openings in the sheds in connection. The cavity of the canal-system is filled with phlegm, at the reason, one discovers Sinneszellen, that in-sticks out into the cavity with a fort-sentence, with microscopic contemplation. Already minimal alterations of the water pressure can register the fish with this organ. It shows above all in cloudy water or with darkness obstacles. That can be also enemies, loot-animals or Artgenossen. Only so it is to be understood that coral-fish around-swim between the narrowest splits and holes without bumping" somewhere or that blind cave-fish as certainly as sighted Artgenossen move in light areas.

Swimming-blister co help of the swimming-blister can adjust fish her/its/their specific weight that of the respective water-depth. The swimming-blister therefore regulates the pressurization if the fish changes into higher or deeper water-layers. So, he/it hovers in the respective "wished" depth without effort. The cartilage-fish, who don´t have any swimming-blister like flat-fish and some other ground-inhabitants, constantly must anarbeiten with swimming-movements against the water pressure accordingly in order to remain in a wished water-depth.

The swimming-blister is an Aussackung of the intestine; often, another connection between swimming-blister and intestine, the duct pneumaticus, exists. Fish with this connection (Physostomen) can the pressurization faster as such carries out that he/it is missing (Physoclisten). Here, the gas-increase takes place or - depositing gradually over a gas-gland, the so-called red body, from the bloodstream. When some fishing, the swimming-blister serves as resonance-ground for the production or reinforcement of sounds, Z. B. with the Knurrhahn, with Umberfischen and frog-fishing.

Gills far most fish breathe through inner gills, that are ordered the pharynx on both sides of lateral. It is thin, strongly supplied with blood and therefore intensively red colored skin-leaves. The water flowed in into the mouth-opening streams past at them and through the gill-columns again out. At the gill-leaves, the gas-exchange, d, takes place. h., the blood picks up oxygen and gives away Kohlendioxid. Some fish-forms can or must breathe in even atmospheric air, according to Z. B. the labyrinth-fish, the tremor-eel or the lung-fish. Kleinschuppige types can breathe also through the skin. With the mud-jumpers, the gas-exchange takes place at country through Aussackungen of the mouth and gill-cave.

Reproduction so big the empire of the fish with 25 000 types is, there are so many deviations from the normal forms of the reproduction. Most fish set aside a large number of eggs all at once into the water, they "spawn." The spawn is inseminated (outer fertilization) by the male in the free water afterwards. An inner fertilization through mating takes place with all viviparous fish, Z. B. with numerous shark-types and viviparous tooth-carps. Here, the seedlings develop in the uterus of the female. Cat-sharks smelled and also have an inner fertilization. However, the eggs are set aside into the water.

Many fish undertake at the spawn-time of prolonged hikes to particular spawn-places. Some groups of the sea shift into the freshwater (salmon) on that occasion, others of the freshwater in the sea (river-eels). The number of the all at once cast-off eggs is very different, she/it hands 6 million from 20 with cat-sharks, 3000 with trouts, and more with the codfish, up to 25 million with the Leng.

The seedling-development lasts 5 days, with the carp 14 days, with the sturgeon with the salmon until 5 months and with the cat-shark until 8 months. The young hatching from the eggs often carry another yolk-sack as food-reserve around (herrings, Dorschartige) with itself. Eels and flat-fish go through an especially strong shape-change (so-called metamorphosis) of the larva up to the ready fish.

Brood-care It gives numerous forms of brood-care; a flat nest-hollow, that builds Stichlingsmännchen, near the Lachsartigen is dug out an artistic nest, in which the eggs are inserted. With the sea-wolf, the female lies down around wreath-shaped about the spawn together-adhesive in an egg-bale and turns the bale regularly (oxygen-supply). The Spritzsalmler sets aside his/its eggs outside the water; so that they don´t dry up, the fish sprays her/it/them with water. The female of the Seepferdchens puts his/its eggs into a brood-bag at the stomach of the male, in which the young-fish still remain some time also after slipping. Some colorful-perches, but also other fish, so-called mouth-breeders, take the eggs into the mouth-cave; also the slipped young-fish-little use the parental mouth-cave as place of refuge. The boys of the discus-fish live from a slimy secretion at the body of the parents.