What is the classification of fish? Classification of fish What are the classifications of fish

Jawless: The spine is cylindrical and lifelong and has no upper and lower jaws. The gills originating from the endoderm are sac-shaped, so they are also called cysts; The brain is well developed, generally with 10 pairs of cranial nerves; There are pairs of visual and auditory organs.

The inner ear has 1 or 2 semicircular canals. There is a heart, red blood; The epidermis is made up of multiple layers of cells. The even-fins are underdeveloped, and some archaeotic beetle fishes have pectoral fins.

The classification of jawless is different, and it is generally divided into: hagfish, headfish, lamprey, and finned turtles.

Jawed: upper and lower jaws. most have pectoral and pelvic fins; The endoskeleton is well developed, the adult notochord is degenerate, with a spine, and rarely a bony exoskeleton.

The inner ear has 3 semicircular canals. Gill are formed by ectodermal tissue. It is composed of shieldfish, cartilaginous fishes, echinosaurs and bony fishes.

Among them, there are only fossil species of the class Shieldfish and Acanthida. It is distributed all over the world, mainly inhabiting low-latitude sea areas, and some species inhabit freshwater. The extant species belong to the subclass Plategill and the Holocephalic subclass.

There are about 600 species of plategill subclass, about 180 species in China, and most of them in the South China Sea. There are about 30 species in 3 families and 6 genera in the whole subclass, and about 5 species in 3 genera and 2 families in China. The endoskeleton of the bony fish class is ossified, with bony sutures, and the head is often covered with membranous bones, and the body is covered with hard or bony scales.

It is the most abundant branch of living fishes, which can be divided into three subclasses: total finned subclass, lungfish subclass and radial fin subclass. Radial-finned fishes.

The class is the largest taxa. Among them, perciformes have the most species, except for cypriniformes, which are distributed in freshwater and salmoniformes, which are mostly anadromous fishes, and the other orders are mainly distributed in the ocean. Herring and cod are the highest in world fishery production today, followed by cod, which accounted for nearly half of the world's total fishery production that year.

There are more than 2,000 species of bony fish in China's coastal waters and more than 700 species of freshwater bony fish.

It can be classified according to body type.

1. There are more than 20,000 species of fish in the world. Among them, there are about 73 species of roundmouths, about 800 species of cartilaginous fishes, and about 20,000 species of bony fishes. There are about 3,000 species of fish in China. Among them, there are more than 2,100 species of marine fish and about 1,010 species of freshwater fish.

2. The order of fish classification is the same as that of other organisms, and under the phylum Chordates, it is divided into subphylum, general order, class, subclass, order, suborder, family, family, subfamily, genus, subgenus, species and subspecies. Its basic unit is the species, which is composed of similar species into an order larger than the first order.

3. Species are reproductive units, which are composed of continuous and intermittent populations; Species are evolutionary units and taxonomic units.

4. Subspecies is the only taxonomic order below the species, and it is also the reproductive unit of the species, and the subspecies has certain morphological characteristics and geographical distribution, and is a population formed after the individuals within the species are fully isolated geographically and reproductively.

There are two classifications of fish:

1. According to the water quality of life, it can be divided into freshwater fish and saltwater fish.

2. According to the living climate, it can be divided into tropical fish, temperate fish and cold fish.

Common freshwater fish include catfish, monk fish, etc., and common saltwater fish include yellow croaker, plum fish, rice fish, hairtail, shark, grouper, yellow fish, mackerel, plaice, etc.

Common tropical fish include colored fish, mosquito-eating fish, cranemouth fish, etc., temperate fish such as red crucian carp, mid-late slag goldfish, Japanese koi, etc., and cold ribbon fish such as anchovies.

Fish is a body covered with bone scales, gills to breathe, with fins as locomotor organs and by the upper and lower jaw feeding ection of ectothermic aquatic vertebrates, belonging to the chordate phylum in the vertebrate subphylum, the general people divide the vertebrate into fish, birds, reptiles, mammals, amphibians five categories.

Fish, cows, sheep, horses, pigs, chickens, ducks, geese, mosquitoes, flies, cockroaches, bats, cats, dogs, birds, ants, snakes, shrimps, turtles, turtles, frogs, crabs, centipedes, rats, rabbits, geckos, snails, butterflies, moths, beesheds, dragonflies.

Fishes are ectothermic aquatic vertebrates that swim and feed by the upper and lower jaws by respiring with gills, swimming through the swing of the tail and trunk of the chain plum, and feeding by the upper and lower jaws, and belong to the vertebrate subphylum of the phylum Chordates, and generally people divide vertebrates into five categories: fish (53%), birds (18%), reptiles (12%), mammals (9%), and amphibians (8%).

According to the statistics of the late Canadian scholar Nelson in 1994, there are 24,618 species of fish in the world, accounting for half of the named vertebrates, and new species of fish are constantly being discovered, with an average of about 150 species per year, and more than 1,500 species should have increased in more than ten years, and about 32,100 species have been named in the world.

River fish include blue saury, wheat ear fish, and black fish.

Fishes are diothermal-tempered aquatic vertebrates that swim and feed with their upper and lower jaws by respiring with their gills, swinging their tails and trunks, and feeding on their upper and lower jaws, and belong to the vertebrate subphylum of the phylum Chordates, and generally divide vertebrates into five categories: fish (53%), birds (18%), reptiles (12%), locusts, mammals (9%), and amphibians (8%). According to the statistics of the late Canadian scholar Nelson in 1994, there are 24,618 species of fish in the world, accounting for more than half of the named vertebrates, and new species of fish are constantly being discovered, with an average of about 150 species per year, and more than 1,500 species should have increased in more than ten years, and there are about 32,100 species of named fish species in the world.

Fish are mainly divided into: tropical fish, temperate fish and cold ribbon fish.

Aquatic fish are divided into: freshwater fish and saltwater fish.

Fish are mostly cold-blooded, and a few are warm-blooded, breathing with gills and having jaws and fins. Extant fish can be divided into two main groups: cartilaginous fishes (such as sharks, etc.) and bony fishes (fishes with linear and wavy fins).

The fishes of both groups were the first to emerge from the Early Devonian. One of the more advanced species of thread-finned fish, called bony fish, began to evolve during the Jurassic period and became the fish with the largest number of individuals. There are also several extinct species of fish.

Classification of fish.

Fishes belong to the phylum chordata and the subphylum vertebrata in the phylum chordates. This door encompasses many animals with a wide variety of styles in terms of appearance, living habits and habitat conditions. Wenchang fish looks like a fish, the notochord and neural tube run through the whole body, lifelong retention, no head, no vertebrae, no cartilage and hard bones, the heart is a beating abdominal blood vessel, and it belongs to the cephalochordate subphylum cephalochordata in classification.

But by the definition of fish: a true fish is a group of ectothermic vertebrates that usually use fins to aid body balance and gills for gas exchange in the water. Broadly speaking, the cephalic chordate fishichomorph Wenchang fish is also classified as fish.

The book Taxonomy of Fishes includes the Wenchang fish in the class Amphioxi. The total number of fish in the world accounts for about half of the entire vertebrate population, with about 22,396 species and subspecies, belonging to 4 classes (hagfish myxini, cephalaspidomorphi, chondrichthyes and osteichthyes) 57 orders, 479 families and 3848 genera; There are 4 classes, 45 orders, 299 families, 1214 genera, about 3166 species and subspecies in China. Scientific research on fishes is believed to have begun with the Greek scholar Aristotle (384-322 BC), who recorded 115 species of fish living in the Aegean Sea.

In the 17th century, due to the progress of geography, the field of ichthyology was greatly expanded, and in terms of classification, it entered the natural classification from artificial classification. In the 18th century, the Swedish scientist Linnaeus (author of the book "Natural Systems", established the binomial method, recorded 2,600 species of fish, and laid the foundation for fish taxonomy. In the middle of the 19th century, the progress of fish morphology research, and the late 19th century, due to the need for fishery production to deepen the study of fish migration, reproduction, occurrence and growth, fish taxonomy developed rapidly, and many schools of thought were formed over the past 100 years.

There are generally two ways to classify fish: one is to use one or several characteristics of the external morphology and habits of fish as the classification standard, which does not involve kinship and the basic structure and evolutionary relationship of fish; The other is to rely on the morphology, ecology, physiology, occurrence, and fossil evolution relationship of fish to classify, that is, natural classification. With the development of science and technology, there are new classification methods such as cell classification, chemical classification, and molecular classification.

At present, the more famous fish taxonomic schools in the world are: the Berg classification system, the Russ and Lindberg classification system (on which the Ichthyes of China is based) belong to the comprehensive systematics school or the evolutionary systematics school; The Nelson classification system belongs to the branch school of systems (on which the Taxonomy of Fish is based) and is currently accepted by most fish scholars; There is also the school of numerical taxonomy.

Genus and species of the family family:

Class: Bony Fishes and Cartilaginous Fishes.

Cartilaginous fish: the number is very small, there are rays, sharks, sturgeons, etc. (the bones are a bit like the crispy bones of pigs we eat) Bony fish: common carp (carp), perch (perch, tilapia), catfish (black spotted catfish, catfish) and other cypriniformes The best difference between cypriniformes and perciformes is dorsal fin, one cypriniformes, and two perciformes.

There are also families and genera below, which are very complex, so if you are interested, you can study them yourself.

The extant fish are divided into two major categories: cartilaginous and bony.

Cartilaginous fish, no hard bones for life, and the endoskeleton is composed of cartilage. Most of the body surface is scaled. Gill intervals are well developed and there is no gill cover.

In the bony fish system, the bones are hardened into hard bones to varying degrees. The body surface is covered with hard, round, or ctenophoric scales, and a few species are degenerate without scales. ** The mucus glands are well developed.

The gill septum is partially or completely degenerated, the gills do not open directly outside the body, they are covered by a bony gill cover, and the water flowing out of the gill slit is drained through the posterior edge of the gill cover, and most of them have a swim bladder.

Modern fish portion.

BAI is divided into two categories, one is soft DU

The bony fish, one type is the bony fish. The skeleton of the cartilaginous fish is composed of cartilage, and although the vertebrae are partially ossified, the right is to lack true bones. They are relatively high animals in the ocean, first appeared in the Devonian period, and have been steadily developing until modern times.

The sharks, rays, stingrays, and silver sharks that we can see in the aquarium are all cartilaginous fish. Cartilaginous fish do not have swim bladders, so they can only swim constantly to keep their bodies floating, ensuring that they take in oxygen from oxygen-rich seawater, and if they stop swimming, they will sink to the bottom of the sea, which has low oxygen content and is difficult to survive.

Sharks are a type of cartilaginous fish.

Bony fish is a highly developed vertebrate animal in the water, which is very widely distributed, whether it is in the ocean, rivers, lakes, caves, and even hot springs, it can be found in the body, and it is the most common fish. Bony fish is also the most successful fish of all the fish that live in the water, and there are more than 20,000 species of bony fish out of a total of 50,000 modern vertebrates. The grass carp, crucian carp, carp, etc., which we usually eat, are all bony fish.

The main characteristic of bony fish is the high ossification of the bones (scleroforming into bones), and even the scales are ossified. In addition, most bony fish have a swim bladder, which can be used to control the rise and fall of the body in the water through the contraction of the swim bladder, and in an oxygen-deficient environment, the swim bladder can also assist breathing.

Bony fish are common in life.

The above content refers to Milley's children's book "A Brief History of Life".