Fish
Fish or fish is one of the animals cold-blooded vertebrates that live in the water, there are many types of fish more than 27000 Type of vertebrates, making it more diverse. Of fish scales and fins and Glasam (gills) breathes.
Some fish live in fresh water in lakes, rivers, marshes, and others live in salt water in the seas and oceans.
Some fish are small and a length of 1 cm or less and some other large and long may reach a length of 15 meters long and weighing 15 tons, as in the shark and the whale.
More fish species are a major food for humans, and fish species that are more desirable than others, such as carp Carp Cod and cod and herring Herring Sardines, sardines and tuna Tuna.
Most types of fish have bones and some other species such as sharks have no bones are real, but cartilage. Some scientists do not consider them a real fish, but most people let it fish.
Some other species of animals that live in the sea such as starfish Starfish and jellyfish Jellyfish also called fish but not fish, does not contain her bones, as well as other type of aquatic organisms known organisms molluscs with shells, such as shellfish different, and there are crustaceans like shrimp, shrimp and crabs.
Fish Birth
Do not know precisely when I moved invertebrates to vertebrates, because this transition has been since time immemorial than four hundred and fifty million years, in the afternoon Alslori minimum, and is well known that fish are vertebrates first appeared on the Earth's surface, and they were all in the first part of the largest fish armored vehicles.
Even age Alslori Top the types of fish do not exceed in length ten inches, and then began to appear after the types of fish armored top and larger has been possible to find the skeletal remains of Foreign Affairs of the fish are rarely found on the internal structures, can be considered fish round the mouth of contemporary the descendants of those ancient armored fish.
And can not precisely determine the origin of fish armor, but there are likely refers to the platoons can be one of the origin of these fish, the two Jeraptolita one of the row Alheidrvaniat that belong to the Division Algeoffmaouiat such as Hydra and exercise and others, and platoon second is Altreubita "or tri-lobed , scaly animals that belong to the Division of arthropods.
And making it more likely that the probability that both Jerapolita Altreubita and arrived to the maximum stages of development in modern Alslori. Other groups may be branched for these strains, it is likely that the arthropods are the basis for the emergence of fish, in order to live a living organism in the water in the form of a fish, should be available when certain conditions in order to suit with these aquatic environment, in order to ensure the speed of movement in aqueous heavy, and the nature Algeoffmaouiat does not support the possible existence of these conditions, but proved to be arthropods since the age Cambrian in the first periods were old to move and crawl on the bottom of the sea, it is possible that she lived more than one picture, as do some types of crabs so far in the the Indian Ocean.
To live organism properly, you must provide the body to help it to a sense of Downtown around him. As a result of this need for the growth of sense organs, objects that membership could be affected by gravity and light energy, thermal and so on.
Ring the first transition between vertebrates invertebrates to be that they were being very similar to the animal the arrow, was not for this object internal structure, but it came with under the spinal cord to your nervous centers, is a string of cells flexible so-called spermatic cord, and this object primitive, which resembles arrow originated cartilaginous fish first, which later developed into bony fish, and consisted paragraphs on the spermatic cord to protect from the dangers that result from rapid movement, which was required by the life of this fish in the water, then inflation front part of the nervous cord is to be the brain. And grew gills subsequently advanced from the front part of the gastrointestinal tract in Alsuham primitive, who was working as a breathing absorbs oxygen dissolved in water and turns it into the blood.
Because of the evolution sudden great experienced by invertebrates during the era Alslori, it is likely that Altreubita or tri-lobed forced to expand the area of her life, and to increase the speed of movement, so that they can ensure they stay in conflict with other marine organisms, and it seems that some of them managed to be accommodating with the new circumstances.
And require the speed of movement in the water a special form of the body, to achieve the least amount of resistance, and also requires a device helps to rush into the water, a fish was the inevitable consequence of environmental conditions in which they lived fish first. Thus, invertebrates have evolved into a body of fish known Brwosha shaped body that connect directly without the neck. Also started the back gradually in the gradient at the center, until it reaches the end of the brushes when you sin, and it took a list at the end of the body to help speed the movement, was to be be similar fin tail, and supported the appendages fin pectoral rays strong short help the fish to swim fast.
During the Devonian period - since about three hundred and fifty million years - occurred in the earth's crust changes dramatically, resulting in the evolved organisms that existed at the time; to fit the new conditions of life, and when to move fast on the globe periods of heavy rain, and periods of drought and heat, the fish to evolve to match with the surrounding circumstances, was that Taattort to fish lung can build for themselves in the mud Jehra live, and the hole from which entered the atmosphere, and was to remain in their nests, even undergoing drought, and then resume her life in the water when it rains. This was the lungfish belong to the row of hardened fish which grew wings and amphibians, salamanders and frogmarched.
There have been several types of animate Alglasam seine, including two rows lived through eras Alslori and Devonian, are Alonasbeida and was living on the bottom, and have a solid bony shield covering the posterior part the front at the head.
There are qualities in the composition of the body to believe that the thickness of the Lamprey and fish mucous - two of the fish lacking jaws - are direct descendants of the rest of these objects vanished, which entered its size small and can not exceed a few centimeters, and then flourished in the eras Devonian and Carboniferous period minimum, where they found fossils armored fish heads a length of more than six meters, it is likely to be the ancestors of sharks who has been scattered in the variety of fossils eras Alslori the top and the lower Devonian period, which indicates that the shark came after the fish Alglasam seine.
It is believed that the fish origin, a bony fish, the extension of the development of a branch of the shark in the early era Alslori, the oldest species known of this fish is Alhvxiat primary that existed during the Devonian period, reaching the peak of its development during the Carboniferous period, and remained until the end of the Jurassic period, and there are still a few species belong to this initial Alhvxiat live to this day. However, the level to which most of the remaining bony fish that did not appear in the middle periods, and was developed rapidly and is mostly in the Eocene era at the beginning of the modern eras.
And defines three eras in arrears in the periods the old era of fish, a Silurian age to the Devonian and Carboniferous, but the real fish or bone did not reach the peak of her life only in the Carboniferous period did not show types can be compared to fish that are now only in the age of reptiles, which came after, it also did not show factions prevailing only because in the age of Reptiles, which came after, as the factions did not appear because the prevailing only in the age of mammals, the newest geological ages.
There are types of bony fish are now far more than any number of divisions of the other vertebrates, a multiplicity of shapes, sizes and colors as different from each other in many cases, a major difference in installation procedure, and live in all aquatic environments.
General characteristics of fish
Such as other vertebrates, fish have a central structure or spine. Located body cavity that contains the vital organs in the front part of the belly of the fish, but the back, which is located behind the body cavity is composed mostly of muscle and core function is to move the fish in the water and called the tail or the tail. Often covers the fish's body Bhrashv. Covered with skins of fish also layer of mucosal complement to the peel of the preventive functions; it takes fungi and bacteria that might be attached the body of the fish and crippling slipped and fall without being hit by the injury, but if you lose the fish part of the Hrashvha, the microbes can be up to the naked free of the mucus thus exposing the fish to many diseases.
Is also characterized by the presence of fish fins is also supported by the thorns radial cartilage or bone; and fins are individual or double.
Color fish
Fish colors vary between gray, red and bright, brown, which are similar to green, to dark colors, which specializes in the demersal fish, characterized by bony fish is usually the beauty and variety of colors, while the homogeneous color in the cartilaginous fish.
Gain fish colors of pigments Raspp or suspended in special cells with ribs or branches; and polygonal cells contain the yellow pigment, while containing subsidiary of the dye orange, red, brown and black. There are subsidiary other cells, which accumulate crystals reflecting the light of a substance called "guanine", a production of Synovial indigestible, carrying blood to the cells that abound on the belly of the fish is attributed to white and silver.
Different amounts of pigment and crystals of fish to another .. If There have been many cells containing pigment, and the colors were bright and clear; If There have been many cells, crystal, Colour is pale; When the spread of liquid color within the cells completed the color of the fish becoming more and more obvious, and if the accumulated cells of different dyes on each other generate multiple colors, and Guanine can also analyze the light into colors of the spectrum.
The fish can often be similar to their environment, for fear its enemy or prey Tbaght .. Two daughters, some colors of seaweed, and take other forms of coral and colors, and take demersal colors similar to the prevailing colors.
And the spread of light and included layers of water more than four hundred meters, resulting from this is that pelagic fish are bright in color, while the homogeneous color whenever increased in depth to be dimmed at great depths, as well as fade the colors of fish that inhabit caves and caves, water dark, but regains color when exposed light
There are other factors, in addition to light, often affect the colors of fish. Revealed a relationship between fish-eye and color when covered with the lower part of the eye color of the fish became bright, and did not cause the top cover any color change in fish, which indicates that the bottom part of the retina affect the color of the animal. It was also noted that the thickness of Moses can acquire the colors of the bottom yet, to lengthen seen because the fish-eye movement Photos visuals as the optic nerve and then to the brain and the sympathetic nerve that connects all the cells are colored and thus take the fish, the color of the environment in which they live, such as fish reefs.
Heat effect in the colors of fish, causing the spread of the colored fluid within the cells; and the situation of fish health have a significant impact on color.
The changing colors of fish, in particular at the time of mating. It seems perfectly in the male and brighter color, so that it can entice and attract the female, owing to the change in color to the activity of the gonads. Fish and common traits are: development of breeding eggs in the water and cover their body scales and breathing through gills.
