Fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. described in this definition are the living hagfish, lampreys, as alive as cartilaginous & bony fish as living as various extinct related groups. Around 99% of living fish set are ray-finned fish, belonging to the the collection of things sharing the common features Actinopterygii, with over 95% belonging to the teleost subgrouping.
The earliest organisms that can be classified as fish were soft-bodied chordates that number one appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which enable them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide breed 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(a) as sharks became formidable marine predators rather than just the prey of arthropods.
Most fish are ectothermic "cold-blooded", allowing their body temperatures to recast as ambient temperatures change, though some of the large active swimmers like white shark and tuna can develope a higher core temperature. Fish can acousticallywith regarded and talked separately. other, near often in the context of feeding, aggression or courtship.
Fish are abundant in nearly bodies of water. They can be found in nearly any aquatic environments, from high mountain streams e.g., char and gudgeon to the abyssal and even hadal depths of the deepest oceans e.g., cusk-eels and snailfish, although no species has yet been documented in the deepest 25% of the ocean. With 34,300 subject species, fish exhibit greater species diversity than any other group of vertebrates.
Fish are an important resource for humans worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean in aquaculture. They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish realise had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.
Tetrapods amphibians, reptiles, birds and mammals emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish pisces or ichthyes are rendered paraphyletic by excluding the tetrapods, and are therefore not considered a formal taxonomic positioning in systematic biology, unless this is the used in the cladistic sense, including tetrapods, although normally "vertebrate" is preferred and used for this intention fish plus tetrapods instead. Furthermore, cetaceans, although mammals, have often been considered fish by various cultures and timeperiods.
Evolution
Fish, as vertebrata, developed as sister of the tunicata. As the tetrapods emerged deep within the fishes group, as sister of the lungfish, characteristics of fish are typically shared by tetrapods, including having vertebrae and a cranium.
Early fish from the fossil record are represented by a companies of small, jawless, armored fish asked as ostracoderms. Jawless fish lineages are mostly extinct. An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils. They lacked distinct teeth, having instead the oral surfaces of their jaw plates modified to serve the various purposes of teeth. The diversity of jawed vertebrates may indicate the evolutionary utility of a jawed mouth. it is for unclear whether the return of a hinged jaw is greater biting force, improved respiration, or a combination of factors.
Fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the larval form into adulthood as some sea squirts do today, although perhaps the reverse is the case.
Fishes are a paraphyletic group: that is, any clade containing all fish also contains the tetrapods, which are not fish though they increase fish-shaped forms, such as Whales and Dolphins or the extinct ichthyosaurs, which acquired a fish-like body shape due to secondary aquatic adaptation, see evolution of cetaceans.
The coming after or as a or done as a reaction to a question of. cladogram shows clades - some with, some without extant relatives - that are traditionally considered as "fishes" cyan line and the tetrapods four-limbed vertebrates, which are mostly terrestrial. Extinct groups are marked with a dagger †.
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Fishes are a paraphyletic group and for this reason, groups such as the class Pisces seen in older consultation workings are no longer used in formal classifications. Traditional classification divides fish into three extant classes, and with extinct forms sometimes classified within the tree, sometimes as their own classes:
The above scheme is the one most usually encountered in non-specialist and general works. many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise to Acanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the coming after or as a a thing that is caused or produced by something else of. major groups:
† – indicates extinct taxonSome palaeontologists contend that because Conodonta are chordates, they are primitive fish. For a fuller treatment of this taxonomy, see the vertebrate article.
The position of hagfish in the phylum Chordata is not settled. Phylogenetic research in 1998 and 1999 supported the abstraction that the hagfish and the lampreys form a natural group, the Cyclostomata, that is a sister group of the Gnathostomata.
The various fish groups account for more than half of vertebrate species. As of 2006, there are almost 28,000 required extant species, of which almost 27,000 are bony fish, with 970 sharks, rays, and chimeras and approximately 108 hagfish and lampreys. A third of these species fall within the nine largest families; from largest to smallest, these families are Cyprinidae, Gobiidae, Cichlidae, Characidae, Loricariidae, Balitoridae, Serranidae, Labridae, and Scorpaenidae. approximately 64 families are monotypic, containing only one species. Thetotal of extant species may grow to exceed 32,500. used to refer to every one of two or more people or things year, new species are discovered and scientifically described. As of 2016, there are over 32,000 documented species of bony fish and over 1,100 species of cartilaginous fish. Species are lost through extinction see biodiversity crisis. Recent examples are the Chinese paddlefish or the smooth handfish.
Agnatha Pacific hagfish
Chondrichthyes Horn shark
Actinopterygii Brown trout
Sarcopterygii Coelacanth
The term "fish" most precisely describes any non-tetrapod craniate i.e. an animal with a skull and in most cases a backbone that has gills throughout life and whose limbs, whether any, are in the shape of fins. Unlike groupings such as birds or mammals, fish are not a single clade but a paraphyletic collection of taxa, including hagfishes, lampreys, sharks and rays, ray-finned fish, coelacanths, and lungfish. Indeed, lungfish and coelacanths are closer relatives of tetrapods such as mammals, birds, amphibians, etc. than of other fish such as ray-finned fish or sharks, so the last common ancestor of all fish is also an ancestor to tetrapods. As paraphyletic groups are no longer recognised in innovative systematic biology, the use of the term "fish" as a biological group must be avoided.
Many types of seals, whales, amphibians, crocodiles, even hippopotamuses, as well as a host of aquatic invertebrates, as fish. However, according to the definition above, all mammals, including cetaceans like whales and dolphins, are not fish. In some contexts, especially in aquaculture, the true fish are referred to as finfish or fin fish to distinguish them from these other animals.
A typical fish is ectothermic, has a streamlined body for rapid swimming, extracts oxygen from water using gills or uses an accessory breathing organ to breathe 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.
Each criterion has exceptions. some warm-blooded adaptations – they can heat their bodies significantly above ambient water temperature. Streamlining and swimming performance varies from fish such as tuna, cosmoid fossil lungfish and coelacanths, cycloid, and ctenoid these last two are found on most bony fish. There are even fish that symbolize mostly on land or lay their eggs on land near water. Mudskippers feed and interact with one another on mudflats and go underwater to hide in their burrows. A single undescribed species of Phreatobius has been called a true "land fish" as this worm-like catfish strictly lives among waterlogged leaf litter. Many species cost in underground lakes, underground rivers or aquifers and are popularly known as cavefish.
Fish range in size from the huge 16-metre 52 ft stout infantfish.
Fish species diversity is roughly shared equally between marine oceanic and freshwater ecosystems. Coral reefs in the Indo-Pacific constitute the center of diversity for marine fishes, whereas continental freshwater fishes are most diverse in large river basins of tropical rainforests, especially the Amazon, Congo, and Mekong basins. More than 5,600 fish species inhabit Neotropical freshwaters alone, such that Neotropical fishes represent about 10% of all vertebrate species on the Earth. Exceptionally rich sites in the Amazon basin, such as Cantão State Park, can contain more freshwater fish species than arise in all of Europe.
The deepest living fish in the ocean so far found is the Mariana snailfish Pseudoliparis swirei which lives at deeps of 8,000 meters 26,200 feet along the Mariana Trench near Guam.
The diversity of living fish finfish is unevenly distributed among the various groups, with teleosts creating up the bulk of living fishes 96%, and over 50% of all vertebrate species. The following cladogram shows the evolutionary relationships of all groups of living fishes with their respective diversity and the four-limbed vertebrates tetrapods.
118 living species: hagfish, lampreys
>1,100 living species: sharks, rays, chimaeras
>30,000 living species: amphibians, mammals, reptiles, birds
6 living species: lungfish
2 living species: coelacanths
14 living species: bichirs, reedfish
27 living species: sturgeons, paddlefish
7 living species: gars, alligator gars
1 living species: bowfin
>32,000 living species