A wide variety of fish species living in oceans, lakes, rivers and streams have evolved over millions of years and adapted to their preferred environments over long periods.
Fish are classified according to their salinity level tolerance. Freshwater fish such as goldfish and saltwater fish such as tuna are fish that can withstand a fairly narrow salinity range and are known as “stenohalin” (shorthand: narrow; Olaya: salt) species. Fish of this breed cannot live in waters with a different degree of salinity than in their natural environment.
Fish that can tolerate a wide range of salinity at certain periods of their life cycle are called “örihalin” (Eurus: wide) species. Fish such as salmon, eels, sea fish, striped bass, and flounder can live or survive in a wide range of salinity degrees, ranging from freshwater and light saltwater to seawater. For example, fish may need to undergo a gradual adjustment or acclimatization process in order to withstand high changes in salinity.
It is claimed that when the newly formed Earth cooled enough, the rain began to fall continuously. This rainfall filled the first oceans with fresh water. The continuous evaporation and subsequent condensation of ocean water fell as rain on large pieces of land. This caused the oceans to become salty at the end of several billion years. As rainwater floated between the soil and washed the soil, it dissolved many minerals such as sodium, potassium and calcium and added them back to the oceans.
Vertebrates (fish, birds, mammals, amphibians and reptiles) have a unique and common trait. The salt content in the blood of each is almost the same. Vertebrate blood has a salinity of up to 9 grams per liter (about 0.9 percent salt solution). Almost 77 percent of the salts in the blood are sodium and chlorine, while the rest is made up of bicarbonate, potassium and calcium. Sodium, potassium and calcium salts are very important for the normal functioning of the heart, nerve and novelistic tissues.
Fish that can tolerate a wide range of salinity at certain periods of their life cycle are called “örihalin” (Eurus: wide) species. Fish such as salmon, eels, sea fish, striped bass, and flounder can live or survive in a wide range of salinity degrees, ranging from freshwater and light saltwater to seawater. For example, fish may need to undergo a gradual adjustment or acclimatization process in order to withstand high changes in salinity.
It is claimed that when the newly formed Earth cooled enough, the rain began to fall continuously. This rainfall filled the first oceans with fresh water. The continuous evaporation and subsequent condensation of ocean water fell as rain on large pieces of land. This caused the oceans to become salty at the end of several billion years. As rainwater floated between the soil and washed the soil, it dissolved many minerals such as sodium, potassium and calcium and added them back to the oceans.
Vertebrates (fish, birds, mammals, amphibians and reptiles) have a unique and common trait. The salt content in the blood of each is almost the same. Vertebrate blood has a salinity of up to 9 grams per liter (about 0.9 percent salt solution). Almost 77 percent of the salts in the blood are sodium and chlorine, while the rest is made up of bicarbonate, potassium and calcium. Sodium, potassium and calcium salts are very important for the normal functioning of the heart, nerve and novelistic tissues.
If the salinity of ocean water is diluted to about a quarter of its normal density, it will have almost the same degree of salinity as fish blood and contain similar ratios of sodium, potassium, calcium, and chloride. The similarities between the salt content of vertebrate blood and diluted seawater bring to mind the strong evolutionary relationship between vertebrates, as well as the connection to primordial (primitive) oceans.
Indeed, when the oceans were about a third as salty as today's, it seems likely that vertebrate life began to evolve. As the oceans became saltier and vertebrates evolved more, several groups of vertebrates, such as birds, mammals, reptiles and amphibians, left the oceans to live on large chunks of land, bringing seawater with them as blood. They balanced the Salt density in their blood with the salts they provided by drinking fresh water and the nutrients they ate.
Fish, on the other hand, remained in the aquatic environment. They had two options to adapt: either stay in low-salinity environments, such as a bay or river mouth, or develop mechanisms to replace water that mixes with seawater [from their bodies] due to osmosis (transition), and also to remove salts that penetrate their bodies from oceans that become increasingly salty. In order to live in fresh water, they had to replace the salts mixed with the water due to diffusion (transition, spread) and dispose of the excess water they absorbed from the environment. In order for fish to survive in these different circles, kidney function also had to change accordingly. Ultimately, the gills developed the ability to discharge salts from the body into seawater and absorb salts from fresh water.
In seawater, fish have to drink salt water to replenish the liquids they have lost, and then throw excess salts out of their bodies. For this reason, his kidneys produce small amounts of liquid containing a high density of salt. Freshwater fish, on the other hand, produce large amounts of dilute urea, low in Salt. High levels of calcium in the environment help reduce salt loss in freshwater environments, through gills and body surfaces. If the water is slightly salty or low in Salt, less work falls on the kidneys to balance the constant amounts of salt in the blood.
Indeed, when the oceans were about a third as salty as today's, it seems likely that vertebrate life began to evolve. As the oceans became saltier and vertebrates evolved more, several groups of vertebrates, such as birds, mammals, reptiles and amphibians, left the oceans to live on large chunks of land, bringing seawater with them as blood. They balanced the Salt density in their blood with the salts they provided by drinking fresh water and the nutrients they ate.
Fish, on the other hand, remained in the aquatic environment. They had two options to adapt: either stay in low-salinity environments, such as a bay or river mouth, or develop mechanisms to replace water that mixes with seawater [from their bodies] due to osmosis (transition), and also to remove salts that penetrate their bodies from oceans that become increasingly salty. In order to live in fresh water, they had to replace the salts mixed with the water due to diffusion (transition, spread) and dispose of the excess water they absorbed from the environment. In order for fish to survive in these different circles, kidney function also had to change accordingly. Ultimately, the gills developed the ability to discharge salts from the body into seawater and absorb salts from fresh water.
In seawater, fish have to drink salt water to replenish the liquids they have lost, and then throw excess salts out of their bodies. For this reason, his kidneys produce small amounts of liquid containing a high density of salt. Freshwater fish, on the other hand, produce large amounts of dilute urea, low in Salt. High levels of calcium in the environment help reduce salt loss in freshwater environments, through gills and body surfaces. If the water is slightly salty or low in Salt, less work falls on the kidneys to balance the constant amounts of salt in the blood.
After all, fish adapted to seawater, sweet or little salt water, or kept these environments abode for themselves because each environment gave different species a competitive advantage. For example, it is claimed that fish can get rid of their external parasites by entering and exiting fresh and salty waters. It also provided different salinity environments, new and abundant food sources, escape from predators, and even thermal shelter (constant heat) possibilities.