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Aquatic habitat - hydrosphere. aquatic life aquatic life

The inhabitants of the aquatic environment received a common name in ecology hydrobionts. They inhabit the oceans, continental waters and groundwater. In any reservoir, zones can be distinguished according to the conditions.

In the ocean and its constituent seas, two ecological areas are primarily distinguished: the water column - pelagial and the bottom benthal. The inhabitants of the abyssal and ultra-abyssal depths exist in darkness, at constant temperature and enormous pressure. The entire population of the ocean floor was named benthos.

Basic properties of the aquatic environment.

Density of water is a factor that determines the conditions for the movement of aquatic organisms and pressure at different depths. For distilled water, the density is 1 g/cm3 at 4°C. The density of natural waters containing dissolved salts may be higher, up to 1.35 g/cm 3 . The pressure increases with depth by about 1 x 10 5 Pa (1 atm) for every 10 m on average. The density of water makes it possible to lean on it, which is especially important for non-skeletal forms. The density of the medium serves as a condition for soaring in water, and many hydrobionts are adapted precisely to this way of life. Suspended organisms hovering in water are combined into a special ecological group of hydrobionts - plankton("planktos" - soaring). Plankton is dominated by unicellular and colonial algae, protozoa, jellyfish, siphonophores, ctenophores, winged and keeled mollusks, various small crustaceans, larvae of bottom animals, fish eggs and fry, and many others. Seaweed (phytoplankton) hover passively in the water, while most planktonic animals are capable of active swimming, but to a limited extent .. A special kind of plankton is the ecological group neuston("nein" - to swim) - the inhabitants of the surface film of water on the border with the air. The density and viscosity of water greatly affect the possibility of active swimming. Animals capable of fast swimming and overcoming the force of currents are combined into an ecological group. nekton("nektos" - floating).

Oxygen mode. In oxygen-saturated water, its content does not exceed 10 ml per 1 liter, which is 21 times lower than in the atmosphere. Therefore, the conditions for the respiration of hydrobionts are much more complicated. Oxygen enters the water mainly due to the photosynthetic activity of algae and diffusion from the air. Therefore, the upper layers of the water column, as a rule, are richer in this gas than the lower ones. With an increase in temperature and salinity of water, the concentration of oxygen in it decreases. In layers heavily populated by animals and bacteria, a sharp deficiency of O 2 can be created due to its increased consumption. Near the bottom of water bodies, conditions can be close to anaerobic.

Among aquatic life there are many species that can tolerate wide fluctuations in the oxygen content in water, up to its almost complete absence. (euryoxybionts - "oxy" - oxygen, "biont" - inhabitant). These include, for example, gastropods. Among fish, carp, tench, crucian carp can withstand very low saturation of water with oxygen. However, a number of types stenoxybiont- they can exist only with a sufficiently high saturation of water with oxygen (rainbow trout, trout, minnow).

Salt mode. Maintaining the water balance of hydrobionts has its own specifics. If for terrestrial animals and plants it is most important to provide the body with water in conditions of its deficiency, then for hydrobionts it is no less important to maintain a certain amount of water in the body when it is in excess in the environment. An excessive amount of water in the cells leads to a change in their osmotic pressure and a violation of the most important vital functions. Most aquatic life poikilosmotic: the osmotic pressure in their body depends on the salinity of the surrounding water. Therefore, the main way for aquatic organisms to maintain their salt balance is to avoid habitats with unsuitable salinity. Freshwater forms cannot exist in the seas, marine forms do not tolerate desalination. Vertebrates, higher crayfish, insects and their larvae living in water belong to homoiosmotic species, maintaining a constant osmotic pressure in the body, regardless of the concentration of salts in the water.

Light mode. There is much less light in water than in air. Part of the rays incident on the surface of the reservoir is reflected into the air. The reflection is stronger the lower the position of the Sun, so the day under water is shorter than on land. In the dark depths of the ocean, organisms use the light emitted by living beings as a source of visual information. The glow of a living organism is called bioluminescence. The reactions used to generate light are varied. But in all cases, this is the oxidation of complex organic compounds (luciferins) using protein catalysts (luciferase).

Ways of orientation of animals in the aquatic environment. Living in constant twilight or darkness greatly limits the possibilities visual orientation hydrobionts. In connection with the rapid attenuation of light rays in water, even the owners of well-developed organs of vision orient themselves with their help only at close range.

Sound travels faster in water than in air. Orientation to sound is generally better developed in hydrobionts than visual. A number of species even pick up very low frequency vibrations (infrasounds) , arising when the rhythm of the waves changes, and descends in advance before the storm from the surface layers to the deeper ones (for example, jellyfish). Many inhabitants of water bodies - mammals, fish, mollusks, crustaceans - make sounds themselves. A number of hydrobionts look for food and navigate using echolocation– perception of reflected sound waves (cetaceans). Many perceive reflected electrical impulses , producing discharges of different frequencies when swimming. A number of fish also use electric fields for defense and attack (electric stingray, electric eel, etc.).

For depth orientation hydrostatic pressure perception. It is carried out with the help of statocysts, gas chambers and other organs.

Filtration as a type of food. Many aquatic organisms have a special nature of nutrition - this is the sieving or sedimentation of particles of organic origin suspended in water and numerous small organisms.

Body shape. Most hydrobionts have a streamlined body shape.

An animal that lives in water for a certain amount of time or its entire life. Many insects, such as mosquitoes, mayflies, dragonflies and caddisflies, begin their life cycle as aquatic larvae before developing into winged adults. Aquatic animals can breathe air or obtain oxygen dissolved in water through specialized organs called gills or directly through their skin. Natural conditions and those that live in them can be divided into two main categories: water or.

Aquatic Animal Groups

Most people only think of fish when asked about aquatic animals. However, there are other groups of animals living in the water:

  • mammals such as (whales), sirens (dugongs, manatees) and pinnipeds (true seals, eared seals and walruses). The concept of "aquatic mammal" is also applied to animals with, such as river otters or beavers, leading a semi-aquatic lifestyle;
  • shellfish (eg sea snails, oysters);
  • (for example, corals);
  • (e.g. crabs, shrimp).

The term "aquatic" can be applied to animals that live in both fresh water (freshwater animals) and salt water (marine animals). However, the concept of marine organisms is most often used for animals that live in sea water, that is, in the oceans and seas.

Aquatic life (especially freshwater animals) is often of particular concern to conservationists due to their fragility. They are exposed to overfishing, poaching, and pollution.

frog tadpoles

Most are characterized by an aquatic larval stage, for example, tadpoles in frogs, but adults lead a terrestrial lifestyle near water bodies. Some fish, such as arapaima and walking catfish, also need to breathe air to survive in oxygen-poor water.

Do you know why the hero of the famous cartoon "SpongeBob SquarePants" (or "Spongebob Square Pants") is depicted as a sponge? Because there are aquatic animals called marine. However, sea sponges do not look like a square kitchen sponge like a cartoon character, but have a more rounded body shape.

Fish and Mammals

School of fish near the coral reef

Did you know that there are more species of fish than there are amphibians, birds, mammals and reptiles combined? Fish are aquatic animals because they spend their entire life in water. Fish are cold-blooded and have gills that take oxygen from the water to breathe. In addition, fish are vertebrates. Most fish species can live in either fresh water or sea water, but some fish, such as salmon, live in both environments.

Dugong - an aquatic mammal from the order of sirens

While fish live only in water, mammals can be found on land and in water. All mammals are vertebrates; have lungs; they are warm-blooded and give birth to live young instead of laying eggs. However, aquatic mammals depend on water to survive. Some mammals, such as whales and dolphins, only live in water. Others, such as beavers, are semi-aquatic. Aquatic mammals have lungs but no gills and are unable to breathe underwater. They need to float to the surface at regular intervals to breathe air. If you've ever seen what a fountain of water looks like coming out of a whale's blowhole, then you should know that this is his exhalation, followed by an inhalation before the animal plunges back under the water.

Mollusks, cnidarians, crustaceans

Giant tridacna - the largest representative of bivalve molluscs

Mollusks are invertebrates that have soft muscular bodies without legs. For this reason, many clams have a hard shell to protect their vulnerable body from predators. Sea snails and oysters are examples of shellfish. Squids are also mollusks, but they do not have shells.

swarm of jellyfish

What do jellyfish, sea anemones and corals have in common? All of them belong to cnidarians - a group of aquatic, which are invertebrates, have a special mouth and stinging cells. The stinging cells around the mouth are used to catch food. Jellyfish can move around to catch their prey, but sea anemones and corals are attached to rocks and wait for food to come close to them.

red crab

Crustaceans are aquatic invertebrates with a hard, chitinous outer shell (exoskeleton). Some examples include crabs, lobsters, shrimp and crayfish. Crustaceans have two pairs of antennae (antennae) that help them receive information about their environment. Most crustaceans feed on the floating remains of dead plants and animals.

Conclusion

Aquatic animals live in water and depend on it for survival. There are various groups of aquatic animals, including fish, mammals, molluscs, cnidarians, and crustaceans. They live either in freshwater bodies of water (streams, rivers, lakes and ponds) or in salt water (seas, oceans, etc.), and can be both vertebrates and invertebrates.

Aquatic habitat characteristics and features, its inhabitants.

Habitat - an element of the world used by living organisms for existence.

It has certain conditions and factors to which organisms living in this area must adapt.

There are 4 types:

  • ground-air
  • soil
  • Water
  • Organismic

According to one theory, the first organisms formed 3.7 billion years ago, according to another - 4.1 billion. The first forms of life appeared in the water. The surface of the Earth is 71% filled with water, which is very important for life on the planet as a whole.

Plants and animals cannot exist without water. This is an amazing liquid that can be in three stays. Water is part of everything, a certain percentage of it is contained in the atmosphere, soil and living organisms, minerals, affects weather conditions and climate.

It has the ability to store thermal energy, due to which there are no sharp temperature drops in coastal areas.

Characteristic

The aquatic environment has limited resources of both light and oxygen. The amount of air can be replenished mainly through photosynthesis. The oxygen index directly depends on the depth of the water column, because. light does not penetrate below 270 meters. It is there that red algae grow, absorbing the scattered rays of the sun and converting them into oxygen. Due to the pressure at different depths, organisms can live at certain levels.

Inhabitants and animals

What creatures live in the water is greatly influenced by:

  • water temperature, its acidity and density;
  • mobility (ebb and flow);
  • mineralization;
  • light mode;
  • gas mode (percentage of oxygen content).

A huge variety of representatives of various species of animals and plants lives in the aquatic environment. Mammals can live both on land and in water. From freshwater, one can distinguish such as the hippopotamus, which uses water for cooling purposes, the Amazonian dolphin, which lives in the channels of the Amazon River, and the manatee, which can live in both salt and fresh waters.

Marine mammals include whales, the largest animals on the planet, polar bears, who spend not all their lives in the water, but a significant part; sea ​​lions coming ashore to rest.

From freshwater amphibians, various types can be distinguished: newts; salamander; frogs; worm, crayfish, lobster, and many others. Amphibians do not live in salt water due to the fact that their eggs die even in slightly salty water bodies, and amphibians live in the same place where they breed, although there are exceptions to the rule.

Also, frogs cannot live in salt water due to the fact that they have very thin skin, and salts draw moisture from the amphibian, as a result of which it dies. Reptiles inhabit both fresh and salt water. There are some species of lizards, snakes, crocodiles and turtles that have adapted to this environment.

aquatic plants photo

For fish, the water environment is their home. They can live in brackish or fresh water. Many insects such as mosquitoes, dragonflies, water striders, water spiders and the like live in the aquatic environment.

There are also a lot of plants here. In freshwater reservoirs, lake reeds grow (along the swampy shores), water lilies (swamps, ponds, backwaters), and calamus (in shallow water). In salt water, for the most part, algae and sea grasses (Posidonia, eelgrass) grow.

Aquatic organisms

In addition to multicellular animals, simple unicellular animals also live in water. Plankton or "wandering" cannot move independently. That is why it is carried by the current of both salty and fresh water bodies. The concept of plankton includes both plants (phytoplankton) living on the surface for the sake of sunlight, and animals (zooplankton) living in the entire water column. There are also amoebas, single-celled loners that live wherever there is water.

Introduction

On our planet, living organisms have mastered four habitats. The aquatic environment was the first in which life arose and spread. Only later did the organisms master the ground-air environment, created and populated the soil, and themselves became the fourth specific environment of life. Water as a habitat has a number of specific properties, such as high density, strong pressure drops, low oxygen content, and strong absorption of sunlight. In addition, water bodies and their individual sections differ in salt regime, current speed, and content of suspended particles. For some organisms, the properties of the soil, the mode of decomposition of organic residues, and so on are also important. Therefore, along with adaptations to the general properties of the aquatic environment, its inhabitants must also be adapted to a variety of particular conditions.

Water is a medium that is many times denser than air. Because of this, it exerts a certain pressure on the organisms living in it and at the same time has the ability to support bodies, according to the law of Archimedes, according to which any body in water loses as much weight as the water displaced by it weighs.

All inhabitants of the aquatic environment received in ecology the general name of hydrobionts.

Hydrobionts inhabit the World Ocean, continental water bodies and groundwater.

General characteristics of the aquatic environment

The hydrosphere as an aquatic environment of life occupies about 71% of the area and 1/800 of the volume of the globe. The main amount of water, more than 94%, is concentrated in the seas and oceans. In the fresh waters of rivers and lakes, the amount of water does not exceed 0.016% of the total volume of fresh water. These ratios are constant, although in nature, the water cycle goes on without ceasing (Figure 1).

Figure 1 - The water cycle in nature

aquatic environment adaptation organism

In the ocean with its constituent seas, two ecological regions are primarily distinguished: the water column - the pelagial and the bottom - the benthal. Depending on the depth, the benthal is divided into the sublittoral zone - the area of ​​​​smooth decrease in land to a depth of 200 m, the bathyal - the region of a steep slope and the abyssal zone - the ocean floor with an average depth of 3-6 km. The deeper benthal regions corresponding to the depressions of the oceanic bed (6-10 km) are called the ultra-abyssal. The edge of the coast, flooded during high tides, is called the littoral. The part of the coast above the tide level, moistened by surf splashes, is called the superlittoral (Figure 2).

The open waters of the oceans are also divided into vertical zones corresponding to the benthal zones: epipeligial, bathypeligial, abyssopegial.

Approximately 150,000 animal species, or about 7% of their total number, and 10,000 plant species (8%) live in the aquatic environment.

The share of rivers, lakes and swamps, as noted earlier, is insignificant compared to seas and oceans. However, they create a supply of fresh water necessary for plants, animals and humans.

A characteristic feature of the aquatic environment is its mobility, especially in flowing, fast-flowing streams and rivers. In the seas and oceans, ebbs and flows, powerful currents, and storms are observed. In lakes, water moves under the influence of temperature and wind.

Water is a completely unique medium in many ways. The water molecule, which consists of two hydrogen atoms and one oxygen atom, is remarkably stable. Water is the only compound of its kind that simultaneously exists in a gaseous, liquid and solid state.

Water is not only a life-giving source for all animals and plants on Earth, but is also a habitat for many of them. Among them, for example, are numerous species of fish, including crucians that inhabit the rivers and lakes of the region, as well as aquarium fish in our homes. As you can see, they feel great among aquatic plants. Fish breathe with gills, extracting oxygen from the water. Some species of fish, such as macropods, breathe atmospheric air, so they periodically rise to the surface.

Water is the habitat of many aquatic plants and animals. Some of them spend their whole lives in water, while others are in the aquatic environment only at the beginning of their lives. This can be seen by visiting a small pond or swamp. In the water element, you can find the smallest representatives - unicellular organisms, which require a microscope to consider. These include numerous algae and bacteria. Their number is measured in millions per cubic millimeter of water.


Figure 1 - Vertical zonality of the sea (according to A.S. Konstantinov, 1967)

Completely purified water exists only in laboratory conditions. Any natural water contains many different substances. In "raw water" it is mainly the so-called protective system or carbonic acid complex, consisting of carbonic acid salt, carbonate and bicarbonate. This factor allows you to determine the type of water acidic, neutral or basic - based on its pH value, which from a chemical point of view means the proportion of hydrogen ions contained in water. Neutral water has a pH of 7, lower values ​​indicate that the water is acidic, and higher values ​​indicate that it is alkaline. In limestone areas, the water of lakes and rivers usually has elevated pH values ​​compared to water bodies in those places where the limestone content in the soil is negligible.

If the water of lakes and rivers is considered fresh, then sea water is called salty or brackish. There are many intermediate types between fresh and salt water.

Aquatic inhabitants are amazing animals that have subjugated stormy seas and majestic oceans. The inhabitants of the aquatic environment are a colorful and numerous world, including aquarium fish. They are all so different. Some of them are simply huge, while others are so small that they are almost invisible. Some aquatic inhabitants are fierce predators that pose a great threat, while some, on the contrary, are friendly and do not pose a danger.

Everyone was in a dolphinarium or oceanarium. But everyone who is represented there is the inhabitants of the vast expanses, living in the harsh conditions of the water element. Below you will find articles about the diverse inhabitants of the water world, in which you will learn a lot of new and interesting things about them.

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