The concept of the living environment. Water environment

The habitat of living organisms influences them both directly and indirectly. Creatures constantly interact with the environment, receiving food from it, but at the same time releasing the products of their metabolism.

The environment includes:

• natural - appeared on Earth regardless of human activity;
• technogenic - created by people;
• external is everything that is around the body and also affects its functioning.

How do living organisms change their environment? They promote change gas composition air (as a result of photosynthesis) and take part in the formation of relief, soil, and climate. Thanks to the influence of living beings:

• oxygen content increased;
• the amount of carbon dioxide has decreased;
• the composition of the waters of the World Ocean has changed;
• appeared rocks organic content.

Thus, the relationship between living organisms and their habitat is a strong circumstance that provokes various transformations. There are four distinct living environments.

Ground-air habitat

It includes air and ground parts and is excellent for the reproduction and development of living beings. This is a rather complex and diverse environment, which is characterized by high degree organization of all living things. Soil exposure to erosion and pollution leads to a decrease in the number of living beings. In the terrestrial world, organisms have a fairly well developed external and internal skeleton. This happened because the density of the atmosphere is much less than the density of water. One of the significant conditions for existence is the quality and structure of air masses. They are in continuous motion, so the air temperature can change quite quickly. Living things that live in this environment must adapt to its conditions, so they have developed an adaptation to sudden temperature fluctuations.

The air-terrestrial habitat is more diverse than the aquatic one. Pressure drops are not so pronounced here, but a lack of moisture occurs quite often. For this reason, terrestrial living creatures have mechanisms that help them with the supply of water to the body, mainly in arid areas. Plants develop a strong root system and a special waterproof layer on the surface of the stems and leaves. Animals have an exceptional structure of external integument. Their lifestyle helps maintain water balance. An example would be migration to watering holes. The composition of the air also plays an important role for terrestrial living beings, providing the chemical structure of life. The raw material source for photosynthesis is carbon dioxide. Nitrogen is required to connect nucleic acids and proteins.

Adaptation to the environment

The adaptation of organisms to their environment depends on their place of residence. Flying species have developed a certain body shape, namely:

• light limbs;
• lightweight design;
• streamlining;
• presence of wings for flight.

In climbing animals:

• long grasping limbs, as well as a tail;
• thin long body;
• strong muscles that allow you to pull your body up and throw it from branch to branch;
• sharp talons;
• powerful grasping fingers.

Running living creatures have the following features:

• strong limbs with low mass;
• reduced number of protective horny hooves on the toes;
• strong hind legs and short forelimbs.

In some species of organisms special devices allow them to combine the characteristics of flight and climbing. For example, having climbed a tree, they are capable of long jumps and flights. Other types of living organisms can run fast and also fly.

Aquatic habitat

Initially, the life activity of creatures was associated with water. Its features include salinity, flow, food, oxygen, pressure, light and contribute to the systematization of organisms. Pollution of water bodies has a very bad effect on living creatures. For example, due to a decrease in water level in the Aral Sea, most of the flora and fauna, especially fish, have disappeared. A huge variety of living organisms live in the expanses of water. From water they extract everything they need for life, namely food, water and gases. For this reason, the entire diversity of aquatic living creatures must adapt to the basic features of existence, which are formed by the chemical and physical properties of water. The salt composition of the environment is also of great importance for aquatic inhabitants.

A huge number of representatives of flora and fauna, which spend their lives in suspension, are regularly found in the thickness of the water body. The ability to soar is ensured by the physical properties of water, that is, the force of buoyancy, as well as by the special mechanisms of the creatures themselves. For example, multiple appendages, which significantly increase the surface of the body of a living organism compared to its mass, increase friction with water. The next example of inhabitants of an aquatic habitat is jellyfish. Their ability to stay in a thick layer of water is determined by unusual shape a body that looks like a parachute. In addition, the density of water is very similar to the density of the body of a jellyfish.

Living organisms whose habitat is water, different ways adjusted to the movement. For example, fish and dolphins have a streamlined body shape and fins. They are able to move quickly thanks to the unusual structure of the outer integument, as well as the presence of special mucus, which reduces friction with water. U individual species In beetles that live in an aquatic environment, the exhaust air released from the respiratory tract is retained between the elytra and the body, thanks to which they are able to rapidly rise to the surface, where the air is released into the atmosphere. Most protozoa move using cilia that vibrate, for example, ciliates or euglena.

Adaptations for the life of aquatic organisms

Different habitats for animals allow them to adapt and exist comfortably. The body of organisms is able to reduce friction with water due to the characteristics of the cover:

• hard, smooth surface;
• the presence of a soft layer present on the outer surface of the hard body;
• slime.

Limbs represented:

• flippers;
• membranes for swimming;
• fins.

The shape of the body is streamlined and has a variety of variations:

• flattened in the dorso-abdominal region;
• round in cross section;
• laterally flattened;
• torpedo-shaped;
• teardrop-shaped.

In an aquatic habitat, living organisms need to breathe, so they developed:

• gills;
• air intakes;
• breathing tubes;
• bubbles that replace the lung.

Features of habitat in reservoirs

Water is able to accumulate and retain heat, so this explains the absence of strong temperature fluctuations, which are quite common on land. The most significant property of water is the ability to dissolve other substances in itself, which are subsequently used both for respiration and for nutrition by organisms living in the water element. In order to breathe, oxygen is necessary, so its concentration in water is of great importance. The water temperature in the polar seas is close to freezing, but its stability has allowed the formation of certain adaptations that ensure life even in such harsh conditions.

This environment is home to a huge variety of living organisms. Fish, amphibians, large mammals, insects, mollusks, and worms live here. The higher the water temperature, the less dilute oxygen it contains, which fresh water dissolves better than in sea water. Therefore, few organisms live in tropical waters, while polar waters contain a huge variety of plankton, which is used as food by fauna, including large cetaceans and fish.

Breathing is carried out over the entire surface of the body or through special organs - gills. For successful breathing, regular renewal of water is required, which is achieved by various vibrations, primarily by the movement of the living organism itself or its adaptations, such as cilia or tentacles. Great importance The salt composition of water also supports life. For example, mollusks and crustaceans require calcium to build their shells or shells.

Soil environment

It is located in the upper fertile layer of the earth's crust. It's quite complex and very important component biosphere, which is closely connected with its other parts. Some organisms remain in the soil their entire life, others - half. For plants, soil plays a vital role. What living organisms have mastered the soil habitat? It contains bacteria, animals, and fungi. Life in this environment is largely determined by climatic factors such as temperature.

Adaptations for soil habitats

For a comfortable existence, organisms have special body parts:

• small digging limbs;
• long and thin body;
• digging teeth;
• streamlined body without protruding parts.

The soil may lack air and be dense and heavy, which in turn has led to the following anatomical and physiological adaptations:

• strong muscles and bones;
• resistance to oxygen deficiency.

The body coverings of underground organisms must allow them to move both forward and backward in dense soil without problems, so the following characteristics have evolved:

• short wool, resistant to abrasion and able to be ironed back and forth;
• lack of hair;
• special secretions that allow the body to slide.

Specific sense organs have developed:

• the ears are small or completely absent;
• there are no eyes or they are significantly reduced;
• tactile sensitivity has become highly developed.

It is difficult to imagine vegetation without soil. A distinctive feature of the soil habitat of living organisms is that the creatures are associated with its substrate. One of the significant differences in this environment is the regular formation of organic matter, usually due to dying plant roots and falling leaves, and this serves as a source of energy for the organisms growing in it. The pressure on land resources and environmental pollution negatively affect the organisms living here. Some species are on the verge of extinction.

Organismal environment

The practical impact of humans on the environment affects the size of animal and plant populations, thereby increasing or decreasing the number of species, and in some cases, their death. Environmental factors:

• biotic - associated with the influence of organisms on each other;
• anthropogenic - associated with human influence on the environment;
• abiotic - refers to inanimate nature.

Industry is the largest sector in the economy modern society plays a vital role. It affects the environment at all stages of the industrial cycle, from the extraction of raw materials to the disposal of products due to their further unsuitability. The main types of negative impact of leading industries on the environment of living organisms:

• Energy is the basis for the development of industry, transport, and agriculture. The use of almost every fossil (coal, oil, natural gas, wood, nuclear fuel) negatively affects and pollutes natural systems.
• Metallurgy. One of the most dangerous aspects of its impact on the environment is considered to be the technogenic dispersion of metals. The most harmful pollutants are: cadmium, copper, lead, mercury. Metals enter the environment at almost all stages of production.
• The chemical industry is one of the dynamically developing industries in many countries. Petrochemical production emits hydrocarbons and hydrogen sulfides into the atmosphere. The production of alkalis produces hydrogen chloride. Substances such as nitrogen and carbon oxides, ammonia and others are also released in large volumes.

Finally

The habitat of living organisms influences them both directly and indirectly. Creatures constantly interact with the environment, receiving food from it, but at the same time releasing the products of their metabolism. In the desert, the dry and hot climate limits the existence of most living organisms, just as in the polar regions, only the hardiest representatives can survive due to the cold. In addition, they not only adapt to a particular environment, but also evolve.

Plants release oxygen and maintain its balance in the atmosphere. Living organisms influence the properties and structure of the earth. Tall plants shade the soil, thereby helping to create a special microclimate and redistribute moisture. Thus, on the one hand, the environment changes organisms, helping them improve through natural selection, and on the other, the species of living organisms change the environment.

You already know such concepts as “habitat” and “living environment”. You need to learn to distinguish them. What is “living environment”?

The living environment is a part of nature with a special set of factors, for existence in which different systematic groups of organisms have developed similar adaptations.

There are four main environments of life on Earth: aquatic, ground-air, soil, and living organisms.

Water environment

The aquatic living environment is characterized by high density, special temperature, light, gas and salt regimes. Organisms that live in aquatic environments are called hydrobionts(from Greek hydor- water, bios- life).

Temperature regime of the aquatic environment

In water, temperature changes less than on land due to the high specific heat capacity and thermal conductivity of water. An increase in air temperature of 10 °C causes an increase in water temperature of 1 °C. With depth, the temperature gradually decreases. At great depths, the temperature regime is relatively constant (no higher than +4 °C). In the upper layers, daily and seasonal fluctuations are observed (from 0 to +36 °C). Since the temperature in the aquatic environment varies within a narrow range, most aquatic organisms require a stable temperature. Even small temperature deviations caused, for example, by enterprises discharging warm wastewater are harmful to them. Hydrobionts that can exist under large temperature fluctuations are found only in small bodies of water. Due to the small volume of water in these reservoirs, significant daily and seasonal temperature changes are observed.

Light regime of the aquatic environment

There is less light in water than in air. Some of the sun's rays are reflected from its surface, and some are absorbed by the water column.

A day under water is shorter than a day on land. In summer, at a depth of 30 m it is 5 hours, and at a depth of 40 m - 15 minutes. The rapid decrease of light with depth is associated with its absorption by water.

The boundary of the photosynthesis zone in the seas is at a depth of about 200 m. In rivers it ranges from 1.0 to 1.5 m and depends on the transparency of the water. The clarity of water in rivers and lakes is greatly reduced due to pollution by suspended particles. At a depth of more than 1500 m there is practically no light.

Gas regime of the aquatic environment

In the aquatic environment, the oxygen content is 20-30 times less than in air, so it is a limiting factor. Oxygen enters water due to photosynthesis of aquatic plants and the ability of air oxygen to dissolve in water. When water is stirred, the oxygen content in it increases. The upper layers of water are richer in oxygen than the lower layers. With oxygen deficiency, death occurs ( mass death aquatic organisms). Winter freezes occur when bodies of water are covered with ice. Summer - when due to high water temperature the solubility of oxygen decreases. The reason may also be an increase in the concentration of toxic gases (methane, hydrogen sulfide) formed during the decomposition of dead organisms without access to oxygen. Due to the variability of oxygen concentration, most aquatic organisms are eurybionts in relation to it. But there are also stenobionts (trout, planaria, mayfly and caddisfly larvae) that cannot tolerate a lack of oxygen. They are indicators of water purity. Carbon dioxide dissolves in water 35 times better than oxygen, and its concentration in it is 700 times higher than in air. CO2 accumulates in water due to the respiration of aquatic organisms and the decomposition of organic residues. Carbon dioxide provides photosynthesis and is used in the formation of calcareous skeletons of invertebrates.

Salt regime of the aquatic environment

The salinity of water plays an important role in the life of aquatic organisms. Based on salt content, natural waters are divided into groups presented in the table:

In the World Ocean, salinity averages 35 g/l. The most high content salts in salt lakes (up to 370 g/l). Typical inhabitants of fresh and salt waters are stenobionts. They cannot tolerate fluctuations in water salinity. There are relatively few eurybionts (bream, pike perch, pike, eel, stickleback, salmon, etc.). They can live in both fresh and salt water.

Adaptations of plants to life in water

All plants in the aquatic environment are called hydrophytes(from Greek hydor- water, phyton- plant). Only algae live in salt waters. Their body is not divided into tissues and organs. The algae adapted to changes in the composition of the solar spectrum depending on the depth by changing the composition of their pigments. When moving from the upper layers of water to the deep ones, the color of the algae changes in the sequence: green - brown - red (the deepest algae).

Green algae contain green, orange and yellow pigments. They are capable of photosynthesis under sufficiently high intensity sunlight. Therefore, green algae live in shallow fresh water bodies or in shallow sea waters. These include: spirogyra, ulotrix, ulva, etc. Brown algae, in addition to green, contain brown and yellow pigments. They are able to capture less intense solar radiation at a depth of 40-100 m. Representatives of brown algae are fucus and kelp, which live only in the seas. Red algae (porphyry, phyllophora) can live at depths of more than 200 m. In addition to green, they have red and blue pigments that can capture even slight light at great depths.

In fresh water bodies, mechanical tissue is poorly developed in the stems of higher plants. For example, if you remove a white water lily or a yellow water lily from the water, their stems droop and are not able to support the flowers in an upright position. They rely on water due to its high density. An adaptation to the lack of oxygen in water is the presence of aerenchyma (air-bearing tissue) in plant organs. Minerals are in water, therefore conductive and root system. Roots may be absent altogether (duckweed, elodea, pondweed) or serve to anchor them in the substrate (cattail, arrowhead, chastukha). There are no root hairs on the roots. The leaves are often thin and long or heavily dissected. Mesophyll is not differentiated. The stomata of floating leaves are on the upper side, while those of leaves submerged in water are absent. Some plants are characterized by the presence of leaves different shapes(heterophily) depending on where they are located. Water lilies and arrowheads have different leaf shapes in water and in air.

Pollen, fruits and seeds of aquatic plants are adapted to dispersal by water. They have cork outgrowths or strong shells that prevent water from getting inside and rotting.

Adaptations of animals to life in water

In the aquatic environment, the animal world is richer than the plant world. Thanks to their independence from sunlight, the animals populated the entire water column. Based on the type of morphological and behavioral adaptations, they are divided into the following ecological groups: plankton, nekton, benthos.

Plankton(from Greek planktos- soaring, wandering) - organisms that live in the water column and move under the influence of its current. These are small crustaceans, coelenterates, and the larvae of some invertebrates. All their adaptations are aimed at increasing the buoyancy of the body:

1. increase in body surface due to flattening and lengthening of the shape, development of outgrowths and bristles;
2. decrease in body density due to reduction of the skeleton, the presence of fat drops, air bubbles, and mucous membranes.

Nekton(from Greek nektos- floating) - organisms that live in the water column and lead an active lifestyle. Representatives of nekton are fish, cetaceans, pinnipeds, and cephalopods. They are able to resist the current by adapting to active swimming and reducing body friction. Active swimming is achieved through well-developed muscles. In this case, the energy of the emitted stream of water, the bending of the body, fins, flippers, etc. can be used. Adaptation contributes to the reduction of body friction: streamlined body shape, elasticity of the skin, the presence of
skin scales and mucus.

Benthos(from Greek benthos- depth) - organisms living at the bottom of a reservoir or in the thickness of the bottom soil.

Adaptations of benthic organisms are aimed at reducing buoyancy:

1. weighting of the body due to shells (mollusks), chitinized integuments (crayfish, crabs, lobsters, lobsters);
2. fixation on the bottom with the help of fixation organs (suction cups in leeches, hooks in caddisfly larvae) or a flattened body (stingrays, flounder). Some representatives burrow into the ground (polychaete worms).

In lakes and ponds another one is isolated environmental group organisms - neuston. Neuston- organisms associated with the surface film of water and living permanently or temporarily on this film or up to 5 cm in depth from its surface. Their body is not wetted because its density is less than that of water. Specially designed limbs allow them to move along the surface of the water without plunging (water strider bugs, spinning beetles). A unique group of aquatic organisms is also periphyton— organisms that form a fouling film on underwater objects. Representatives of periphyton are: algae, bacteria, protists, crustaceans, bivalves, oligochaete worms, bryozoans, sponges.

There are four main living environments on planet Earth: aquatic, land-air, soil and living organisms. In the aquatic environment, oxygen is the limiting factor. Based on the nature of their adaptations, aquatic inhabitants are divided into ecological groups: plankton, nekton, and benthos.

Question 1. Name the main features of the life of organisms in the aquatic environment, in the ground-air environment, and in the soil.
The characteristics of the life of organisms in the aquatic environment, the ground-air environment and in the soil are determined by the physical and chemical properties of these living environments. These properties have a significant impact on the action of other factors of inanimate nature - they stabilize seasonal temperature fluctuations (water and soil), gradually change illumination (water) or completely eliminate it (soil), etc.
The hydrosphere, or the water shell of the Earth, makes up about 70% of the Earth's surface. The largest reserves of water are concentrated in the World Ocean (up to 95%), the remaining 5% are in fresh water bodies (lakes, rivers, etc.). A huge number of living organisms live in water, and their typical diversity is much higher than on land. The state of the hydrosphere is the most important factor determining the climatic conditions of various geographical areas. Water is a dense medium compared to air, which has a buoyant force and is good solvent. Therefore, many organisms living in water are characterized by poor development of supporting tissues (aquatic plants, protozoa, coelenterates, etc.), special methods of movement (hovering, jet propulsion), breathing characteristics and adaptations to maintaining a constant osmotic pressure in the cells that form their bodies.
The atmosphere, or the gas envelope of the Earth, consists of a mixture of gases: nitrogen, oxygen, carbon dioxide, ozone and inert gases. The atmosphere has a huge impact on physical, chemical and biological processes on the surface of the earth and in the aquatic environment: oxygen is necessary for all living organisms to breathe; carbon dioxide is a source of carbon during photosynthesis and chemosynthesis; Nitrogen, as a result of the activity of nitrogen-fixing bacteria, is converted into nitrates, which are absorbed by plants. The density of air is much lower than the density of water, so terrestrial organisms have highly developed supporting tissues - the internal and external skeleton.
Lithosphere - hard shell Earth - includes earth's crust And top part mantle. Life in the lithosphere is mainly concentrated in its upper fertile layer - the soil, the depth of which does not exceed several meters. In the structure of the soil, several horizons are distinguished (from top to bottom): the upper one, called the decline, the next - the humus layer, which ensures soil fertility, and the third, consisting mainly of a mixture of sand and clay.
Soil is the top layer of land transformed as a result of the activity of living beings. Between the soil particles there are numerous cavities that can be filled with water or air. Therefore, the soil is inhabited by both aquatic and air-breathing organisms.

Question 2. What adaptations have organisms developed for living in an aquatic environment?
The aquatic environment is denser than the air, which determines adaptations for movement in it. Active movement in water requires a streamlined body shape and well-developed muscles (fish, cephalopods - squid, mammals - dolphins, seals).
Planktonic organisms (floating in water) have adaptations that increase their buoyancy, such as increasing the relative surface of the body due to numerous projections and setae; decrease in density due to the accumulation of fats and gas bubbles in the body (unicellular algae, protozoa, jellyfish, small crustaceans). Organisms living in an aquatic environment are also characterized by adaptations to maintain water-salt balance. Freshwater species have adaptations to remove excess water from the body. This is, for example, served by excretory vacuoles in protozoa. In salt water, on the contrary, it is necessary to protect the body from dehydration, which is achieved by increasing the concentration of salts in the body.
Another way to maintain your water-salt balance is to move to places with a favorable salinity level.
And finally, the constancy of the body’s water-salt environment is ensured by water-impermeable integuments (mammals, higher crayfish, aquatic insects and their larvae).
Plants need light energy from the Sun to live, so aquatic plants live only at those depths where light can penetrate (usually no more than 100 m). With increasing depth of habitat in plant cells, the composition of pigments that take part in the process of photosynthesis changes, which makes it possible to capture parts of the solar spectrum penetrating into the depths.

Question 3. How do organisms avoid the negative effects of low temperatures?
At low temperatures, there is a danger of metabolism stopping, so organisms have developed special adaptation mechanisms to stabilize it.
Plants are least adapted to sudden temperature fluctuations. When the temperature drops sharply below 0 °C, the water in the tissues can turn into ice, which can damage them. But plants are able to withstand small negative temperatures by binding free water molecules into complexes that are incapable of forming ice crystals (for example, by accumulating up to 20-30% sugars or fatty oils in cells). With a gradual decrease in temperature during seasonal climate changes, a period of dormancy begins in the life of many plants, accompanied by either partial or complete death of terrestrial vegetative organs (herbaceous forms), or a temporary cessation or slowdown of the main physiological processes - photosynthesis and transport of substances.
Animals have the most reliable protection Low ambient temperatures result in warm-bloodedness, but not everyone has it. The following ways of adaptation of animals to low temperatures: chemical, physical and behavioral thermoregulation.
Chemical thermoregulation is associated with an increase in heat production with decreasing temperature through the intensification of redox processes. This path requires expense large quantity energy, so animals in harsh climatic conditions need more food. This type of thermoregulation is carried out reflexively.
Many cold-blooded animals are capable of maintaining optimal temperature body due to the work of muscles. For example, in cool weather, bumblebees warm up their bodies by shivering to 32-33 °C, which gives them the opportunity to take off and feed.
Physical thermoregulation is associated with the presence of special body coverings in animals - feathers or hair, which, due to their structure, form an air and environment, since it is known that air is an excellent heat insulator. In addition, many animals living in harsh climatic conditions accumulate subcutaneous fat, which also has thermal insulating properties.
Behavioral thermoregulation is associated with moving in space in order to avoid temperatures unfavorable for life, creating shelters, crowding into groups, changing activity in different time days or years.

Density of water- this is a factor that determines the conditions of movement of aquatic organisms and pressure at different depths. For distilled water, the density is 1 g/cm 3 at 4 °C. The density of natural waters containing dissolved salts can be greater, up to 1.35 g/cm 3 . Pressure increases with depth by an average of 1 × 10 5 Pa (1 atm) for every 10 m.

Due to the sharp pressure gradient in water bodies, aquatic organisms are generally much more eurybathic compared to land organisms. Some species, distributed at different depths, tolerate pressure from several to hundreds of atmospheres. For example, holothurians of the genus Elpidia, worms Priapulus caudatus live from coastal zone to ultra-abyssal. Even freshwater inhabitants, such as ciliates, slipper ciliates, swimming beetles, etc., can withstand up to 6 × 10 7 Pa (600 atm) in experiments.

However, many inhabitants of the seas and oceans are relatively stenobatic and confined to certain depths. Stenobacy is most often characteristic of shallow- and deep-sea species. Only the littoral zone is inhabited by the annelid Arenicola and limpet mollusks (Patella). Many fish, for example from the group of anglers, cephalopods, crustaceans, pogonophora, starfish, etc., are found only at great depths at a pressure of at least 4 10 7 - 5 10 7 Pa (400-500 atm).

The density of water provides the ability to lean on it, which is especially important for non-skeletal forms. The density of the environment serves as a condition for floating in water, and many aquatic organisms are adapted specifically to this way of life. Suspended organisms floating in water are combined into a special ecological group of aquatic organisms - plankton (“planktos” - soaring).

Rice. 39. Increase in the relative body surface of planktonic organisms (according to S. A. Zernov, 1949):

A - rod-shaped:

1 - diatom Synedra;

2 - cyanobacterium Aphanizomenon;

3 - peridine alga Amphisolenia;

4 - Euglena acus;

5 - cephalopod Doratopsis vermicularis;

6 - copepod Setella;

7 - Porcellana larva (Decapoda)

B - dissected forms:

1 - mollusk Glaucus atlanticus;

2 - worm Tomopetris euchaeta;

3 - Palinurus crayfish larva;

4 - larva of monkfish fish Lophius;

5 - copepod Calocalanus pavo

Plankton includes unicellular and colonial algae, protozoa, jellyfish, siphonophores, ctenophores, pteropods and keelfoot mollusks, various small crustaceans, larvae of bottom animals, fish eggs and fry, and many others (Fig. 39). Planktonic organisms have many similar adaptations that increase their buoyancy and prevent them from sinking to the bottom. Such adaptations include: 1) a general increase in the relative surface of the body due to reduction in size, flattening, elongation, development of numerous projections or bristles, which increases friction with water; 2) a decrease in density due to the reduction of the skeleton, the accumulation of fats, gas bubbles, etc. in the body. In diatoms, reserve substances are deposited not in the form of heavy starch, but in the form of fat drops. The night light Noctiluca is distinguished by such an abundance of gas vacuoles and fat droplets in the cell that the cytoplasm in it has the appearance of strands that merge only around the nucleus. Siphonophores, a number of jellyfish, planktonic gastropods, etc. also have air chambers.

Seaweed (phytoplankton) They float in water passively, but most planktonic animals are capable of active swimming, but to a limited extent. Planktonic organisms cannot overcome currents and are transported by them over long distances. Many types zooplankton However, they are capable of vertical migrations in the water column for tens and hundreds of meters, both due to active movement and by regulating the buoyancy of their body. A special type of plankton is an ecological group Neuston (“nein” - swim) - inhabitants of the surface film of water at the border with the air.

The density and viscosity of water greatly influence the possibility of active swimming. Animals capable of fast swimming and overcoming the force of currents are united in an ecological group nekton (“nektos” - floating). Representatives of nekton are fish, squid, and dolphins. Rapid movement in the water column is possible only if you have a streamlined body shape and highly developed muscles. The torpedo-shaped shape is developed in all good swimmers, regardless of their systematic affiliation and method of movement in the water: reactive, due to bending of the body, with the help of limbs.

Oxygen regime. 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 breathing conditions of aquatic organisms are significantly complicated. Oxygen enters water mainly through the photosynthetic activity of algae and diffusion from the air. Therefore, the upper layers of the water column are, as a rule, richer in this gas than the lower ones. As the temperature and salinity of water increase, 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. For example, in the World Ocean, life-rich depths from 50 to 1000 m are characterized by a sharp deterioration in aeration - it is 7-10 times lower than in surface waters, inhabited by phytoplankton. Conditions near the bottom of reservoirs can be close to anaerobic.

Among aquatic inhabitants there are many species that can tolerate wide fluctuations in oxygen content in water, up to its almost complete absence (euryoxybionts - “oxy” - oxygen, “biont” - inhabitant). These include, for example, the freshwater oligochaete Tubifex tubifex and the gastropod Viviparus viviparus. Among fish, carp, tench, and crucian carp can withstand very low oxygen saturation of water. However, a number of types stenoxybiont - they can exist only with sufficiently high oxygen saturation of the water (rainbow trout, brown trout, minnow, eyelash worm Planaria alpina, larvae of mayflies, stoneflies, etc.). Many species are capable of falling into an inactive state when there is a lack of oxygen - anoxybiosis - and thus experience an unfavorable period.

Respiration of aquatic organisms occurs either through the surface of the body or through specialized organs - gills, lungs, trachea. In this case, the integument can serve as an additional respiratory organ. For example, the loach fish consumes an average of 63% of oxygen through its skin. If gas exchange occurs through the integuments of the body, they are very thin. Breathing is also made easier by increasing the surface area. This is achieved during the evolution of species by the formation of various outgrowths, flattening, elongation, and a general decrease in body size. Some species, when there is a lack of oxygen, actively change the size of the respiratory surface. Tubifex tubifex worms greatly elongate their body; hydra and sea anemone - tentacles; echinoderms - ambulacral legs. Many sessile and sedentary animals renew the water around them, either by creating a directed current or by oscillating movements, promoting its mixing. Bivalve mollusks use cilia lining the walls of the mantle cavity for this purpose; crustaceans - the work of the abdominal or thoracic legs. Leeches, bell mosquito larvae (bloodworms), and many oligochaetes sway their bodies, sticking out of the ground.

In some species, a combination of water and air respiration occurs. These include lungfishes, siphonophores discophants, many pulmonary mollusks, crustaceans Gammarus lacustris, etc. Secondary aquatic animals usually retain the atmospheric type of respiration as it is more energetically favorable and therefore require contact with the air, for example, pinnipeds, cetaceans, water beetles, mosquito larvae, etc.

Lack of oxygen in water sometimes leads to catastrophic phenomena - I'm dying, accompanied by the death of many aquatic organisms. Winter freezes often caused by the formation of ice on the surface of bodies of water and the cessation of contact with air; summer- an increase in water temperature and a resulting decrease in oxygen solubility.

Frequent death of fish and many invertebrates in winter is characteristic, for example, of the lower part of the Ob River basin, the waters of which, flowing from the wetlands of the West Siberian Lowland, are extremely poor in dissolved oxygen. Sometimes death occurs in the seas.

In addition to a lack of oxygen, death can be caused by an increase in the concentration of toxic gases in water - methane, hydrogen sulfide, CO 2, etc., formed as a result of the decomposition of organic materials at the bottom of reservoirs.

Salt regime. Maintaining the water balance of aquatic organisms 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 there is an excess of it in the environment. Excessive amounts of water in cells leads to changes in osmotic pressure and disruption 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, and marine forms cannot tolerate desalination. If the salinity of the water changes, animals move in search of favorable environment. For example, when desalinating the surface layers of the sea after heavy rains radiolarians, sea ​​crustaceans Calanus and others descend to a depth of 100 m. Vertebrates, higher crustaceans, insects and their larvae living in water belong to homoiosmotic species, maintaining constant osmotic pressure in the body regardless of the concentration of salts in the water.

In freshwater species, body juices are hypertonic in relation to the surrounding water. They are at risk of excessive watering if the flow of water is not prevented or excess water is not removed from the body. In protozoa this is achieved by the work of excretory vacuoles, in multicellular organisms - by removing water through the excretory system. Some ciliates secrete an amount of water equal to their body volume every 2-2.5 minutes. The cell expends a lot of energy to “pump out” excess water. With increasing salinity, the work of vacuoles slows down. Thus, in Paramecium slippers, at a water salinity of 2.5%o, the vacuole pulsates at intervals of 9 s, at 5%o - 18 s, at 7.5%o - 25 s. At a salt concentration of 17.5% o, the vacuole stops working, since the difference in osmotic pressure between the cell and external environment disappears.

If water is hypertonic in relation to the body fluids of aquatic organisms, they are at risk of dehydration as a result of osmotic losses. Protection against dehydration is achieved by increasing the concentration of salts also in the body of aquatic organisms. Dehydration is prevented by water-impermeable integuments of homoiosmotic organisms - mammals, fish, higher crayfish, aquatic insects and their larvae.

Many poikilosmotic species transition to an inactive state - suspended animation as a result of a lack of water in the body with increasing salinity. This is characteristic of species living in pools of sea water and in the littoral zone: rotifers, flagellates, ciliates, some crustaceans, the Black Sea polychaete Nereis divesicolor, etc. Salt suspended animation- a means to survive unfavorable periods in conditions of variable salinity of water.

Truly euryhaline There are not many species among aquatic inhabitants that can live in an active state in both fresh and salt water. These are mainly species inhabiting river estuaries, estuaries and other brackish water bodies.

Temperature reservoirs are more stable than on land. This is due to the physical properties of water, primarily high specific heat capacity, due to which the receipt or release of a significant amount of heat does not cause too sudden temperature changes. The evaporation of water from the surface of reservoirs, which consumes about 2263.8 J/g, prevents overheating of the lower layers, and the formation of ice, which releases the heat of fusion (333.48 J/g), slows down their cooling.

The amplitude of annual temperature fluctuations in the upper layers of the ocean is no more than 10-15 °C, in continental waters - 30-35 °C. Deep layers of water are characterized by constant temperature. In equatorial waters, the average annual temperature of surface layers is +(26-27) °C, in polar waters it is about 0 °C and below. In hot land-based springs, the water temperature can approach +100 °C, and in underwater geysers, at high pressure on the ocean floor, temperatures of +380 °C have been recorded.

Thus, there is a fairly significant variety of temperature conditions in reservoirs. Between the upper layers of water with seasonal temperature fluctuations expressed in them and the lower ones, where the thermal regime is constant, there is a zone of temperature jump, or thermocline. The thermocline is more pronounced in warm seas, where the temperature difference between external and deep waters is greater.

Due to more sustainable temperature conditions In water, stenothermy is common among hydrobionts to a much greater extent than among the land population. Eurythermal species are found mainly in shallow continental reservoirs and in the littoral zone of seas of high and temperate latitudes, where daily and seasonal temperature fluctuations are significant.

Light mode. There is much less light in water than in air. Some of the rays incident on the surface of a reservoir are 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. For example, a summer day near the island of Madeira at a depth of 30 m - 5 hours, and at a depth of 40 m only 15 minutes. The rapid decrease in the amount of light with depth is associated with its absorption by water. Rays of different wavelengths are absorbed differently: red ones disappear close to the surface, while blue-green ones penetrate much deeper. The twilight in the ocean that deepens with depth is first green, then blue, indigo and blue-violet, finally giving way to constant darkness. Accordingly, green, brown and red algae, specialized in capturing light with different wavelengths, replace each other with depth.

The color of animals changes with depth just as naturally. The inhabitants of the littoral and sublittoral zones are most brightly and variedly colored. Many deep organisms, like cave organisms, do not have pigments. In the twilight zone, red coloration is widespread, which is complementary to the blue-violet light at these depths. Rays of additional color are most completely absorbed by the body. This allows animals to hide from enemies, since their red color in blue-violet rays is visually perceived as black. Red coloring is characteristic of twilight zone animals such as sea bass, red coral, various crustaceans, etc.

In some species that live near the surface of water bodies, the eyes are divided into two parts with different abilities to the refraction of rays. One half of the eye sees in the air, the other in water. Such “four-eyedness” is characteristic of spinning beetles, the American fish Anableps tetraphthalmus, and one of the tropical species of blenny Dialommus fuscus. During low tides, this fish sits in recesses, exposing part of its head from the water (see Fig. 26).

The absorption of light is stronger, the lower the transparency of the water, which depends on the number of particles suspended in it.

Transparency is characterized by the maximum depth at which a specially lowered white disk with a diameter of about 20 cm (Secchi disk) is still visible. The clearest waters are in the Sargasso Sea: the disk is visible to a depth of 66.5 m. In the Pacific Ocean, the Secchi disk is visible up to 59 m, in the Indian Ocean - up to 50, in shallow seas - up to 5-15 m. The transparency of rivers is on average 1-1 .5 m, and in the muddiest rivers, for example in the Central Asian Amu Darya and Syr Darya, only a few centimeters. The boundary of the photosynthetic zone therefore varies greatly in different bodies of water. In the most clean waters euphotic zone, or zone of photosynthesis, extends to depths not exceeding 200 m, crepuscular, or dysphotic, the zone occupies depths of up to 1000-1500 m, and deeper, in aphotic zone, sunlight does not penetrate at all.

The amount of light in the upper layers of reservoirs varies greatly depending on the latitude of the area and the time of year. Long polar nights severely limit the time available for photosynthesis in Arctic and Antarctic basins, and ice cover makes it difficult for light to reach all frozen bodies of water in winter.

In the dark depths of the ocean, organisms use light emitted by living things as a source of visual information. The glow of a living organism is called bioluminescence. Luminous species are found in almost all classes of aquatic animals from protozoa to fish, as well as among bacteria, lower plants and fungi. Bioluminescence appears to have arisen multiple times in different groups at different stages of evolution.

The chemistry of bioluminescence is now quite well understood. 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). Luciferins and luciferases have different structures in different organisms. During the reaction, the excess energy of the excited luciferin molecule is released in the form of light quanta. Living organisms emit light in impulses, usually in response to stimuli coming from the external environment.

Glow may not play a special ecological role in the life of a species, but may be a by-product of the vital activity of cells, as, for example, in bacteria or lower plants. It acquires ecological significance only in animals that have sufficiently developed nervous system and organs of vision. In many species, the luminescent organs acquire very complex structure with a system of reflectors and lenses that enhance radiation (Fig. 40). A number of fish and cephalopods, unable to generate light, use symbiotic bacteria that multiply in the special organs of these animals.

Rice. 40. Luminescence organs of aquatic animals (according to S. A. Zernov, 1949):

1 - a deep-sea anglerfish with a flashlight over its toothed mouth;

2 - distribution of luminous organs in fish of the family. Mystophidae;

3 - luminous organ of the fish Argyropelecus affinis:

a - pigment, b - reflector, c - luminous body, d - lens

Bioluminescence has mainly a signaling value in the life of animals. Light signals can serve for orientation in a flock, attracting individuals of the opposite sex, luring victims, for camouflage or distraction. A flash of light can act as a defense against a predator by blinding or disorienting it. For example, deep-sea cuttlefish, fleeing from an enemy, release a cloud of luminous secretion, while species living in illuminated waters use dark liquid for this purpose. In some bottom worms - polychaetes - luminous organs develop during the period of maturation of reproductive products, and females glow brighter, and the eyes are better developed in males. In predatory deep-sea fish from the order of anglerfish, the first ray of the dorsal fin is shifted to the upper jaw and turned into a flexible “rod” carrying at the end a worm-like “bait” - a gland filled with mucus with luminous bacteria. By regulating the blood flow to the gland and, therefore, the supply of oxygen to the bacterium, the fish can voluntarily cause the “bait” to glow, imitating the movements of the worm and luring in prey.

Water is the first medium of life: life arose in it and most groups of organisms were formed. All inhabitants of the aquatic environment are called hydrobionts. A characteristic feature of aquatic environments is the movement of water, which manifests itself in the form currents(water transfer in one direction) and unrest(deviation of water particles from their original position and subsequent return to it). The Gulf Stream transports 2.5 million m^3 of water per year, which is 25 times more than all the rivers of the Earth combined. In addition, tidal fluctuations in sea level occur under the influence of the attraction of the Moon and the Sun.

In addition to the movement of water to the number important properties of the aquatic environment include density and viscosity, spectrality, dissolved oxygen and mineral content.

Density and viscosity determine, first of all, the conditions for the movement of aquatic organisms. The higher the density of water, the more supportive it becomes, the easier it is to stay in it. Another meaning of density is its pressure on the body. With a deepening of 10.3 m into fresh water and 9.986 m into sea water, the pressure increases by 1 atm. As viscosity increases, resistance to active movement of organisms increases. The density of living tissues is higher than the density of fresh and sea water; therefore, in the process of evolution, aquatic organisms have developed various structures that increase their buoyancy - a general increase in the relative surface of the body due to a decrease in size; flattening; development of various outgrowths (bristles); decrease in body density due to skeleton reduction; accumulation of fat and the presence of a swim bladder. Water, unlike air, has a greater buoyancy force, and therefore the maximum size of aquatic organisms is less limited.

Thermal properties water differs significantly from the thermal properties of air. The high specific heat capacity of water (500 times higher) and thermal conductivity (30 times higher) determine a constant and relatively uniform temperature distribution in the aquatic environment. Temperature fluctuations in water are not as sharp as in air. Temperature affects the speed of various processes.

Light and light mode. The sun illuminates the surfaces of land and ocean with equal intensity, but water’s ability to absorb and scatter is quite high, which limits the depth of light penetration into the ocean. Moreover, rays with different wavelengths are not absorbed equally: red ones are scattered almost immediately, while blue and green ones go deeper. The zone in which the rate of photosynthesis exceeds the rate of respiration is usually called euphotic zone. The lower limit at which photosynthesis is balanced by respiration is usually called compensation point.

Transparency water depends on the content of suspended particles in it. Transparency is characterized by the maximum depth at which a specially lowered white disk with a diameter of 30 cm is still visible. The most transparent waters are in the Sargasso Sea (the disk is visible at a depth of 66 m), in the Pacific Ocean (60 m), and the Indian Ocean (50 m). In shallow seas, transparency is 2-15 m, in rivers 1-1.5 m.

Oxygen- necessary for breathing. In water, the distribution of dissolved oxygen is subject to sharp fluctuations. At night, the oxygen content in water is less. Respiration of aquatic organisms occurs either through the surface of the body or through special organs (lungs, gills, trachea).

Minerals. Sea water mainly contains sodium, magnesium, chlorine, and sulfate ions. Fresh calcium ions and carbonate ions.

Ecological classification of aquatic organisms. More than 150 thousand species of animals and about 10 thousand species of plants live in the water. The main biotopes of aquatic organisms are: the water column ( pelagic) and the bottom of reservoirs ( benthal). There are pelagic and benthic organisms. The pelagic zone is divided into groups: plankton(a set of organisms that are not capable of active movement and move with water flows) and nekton(large animals whose motor activity is sufficient to overcome water currents). Benthos- a set of organisms inhabiting the bottom.

Water environment. - concept and types. Classification and features of the category "Aquatic environment." 2017, 2018.

Ecological system(ecosystem) is a spatially defined set consisting of a community of living organisms (biocenosis), their habitat (biotope), and a system of connections that exchanges matter and energy between them. There are aquatic and terrestrial natural... .