Water as a habitat for organisms characteristics. Aquatic habitat

HABITAT AND THEIR CHARACTERISTICS

Living conditions various types organisms are very diverse. Depending on where representatives of different species live, they are affected by various complexes environmental factors. On our planet, we can distinguish several main living environments, which vary greatly in terms of living conditions:

Aquatic habitat

· Ground-air environment habitat

· Soil as a habitat

In the process of historical development, living organisms have mastered four habitats. The first is water. Life originated and developed in water for many millions of years. The second - ground-air - plants and animals arose on land and in the atmosphere and rapidly adapted to new conditions. Gradually transforming the upper layer of land - the lithosphere, they created a third habitat - soil, and themselves became the fourth habitat.

Aquatic habitat - hydrosphere

Water covers 71% of the globe's area and makes up 1/800 of the volume of land or 1370 m3. The bulk of water is concentrated in the seas and oceans - 94-98%, in polar ice contains about 1.2% water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps. These relationships are constant, although in nature the water cycle continues without ceasing.

About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is only 7 and 8% of the total world population, respectively. total number species of the Earth. Based on this, it was concluded that evolution on land was much more intense than in water.

All aquatic inhabitants, despite differences in lifestyle, must be adapted to the main features of their environment. These features are determined, first of all, physical properties of water:

Density,

· Thermal conductivity,

Ability to dissolve salts and gases

· Vertical movements of water,

Light mode

Hydrogen ion concentration (pH level)

Density water determines its significant buoyant force. This means that the weight of organisms in water is lighter and it becomes possible to conduct permanent life in the water column without sinking to the bottom. A collection of small species that are not capable of fast active swimming and are suspended in water is called plankton.

Plankton(planktos - wandering, soaring) - a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water bodies only) algae, plant flagellates, peridineans, etc.) and small animal organisms (zooplankton: small crustaceans, of the larger ones - pteropods mollusks, jellyfish, ctenophores, some worms) living at different depths, but not capable of active movement and resistance to currents.

Due to the high density of the environment and the presence of plankton in the aquatic environment, a filtration type of nutrition is possible. It is developed in both swimming (whales) and sessile aquatic animals (sea lilies, mussels, oysters). Straining suspended matter from water provides such animals with food. A sedentary lifestyle would be impossible for aquatic inhabitants if it were not for the sufficient density of the environment.

The density of distilled water at a temperature of 4 0 C is equal to 1 g/cm 3 . The density of natural waters containing dissolved salts can be greater, up to 1.35 g/cm 3 .

Due to the high density of water, pressure increases greatly with depth. On average, for every 10 m of depth, pressure increases by 1 atmosphere. Deep-sea animals are able to withstand pressure that is thousands of times higher than land pressure (flounder, stingrays). They have special adaptations: a body shape flattened on both sides, massive fins. The density of water makes it difficult to move in it, so fast-swimming animals must have strong muscles and a streamlined body shape (dolphins, sharks, squids, fish).

Thermal mode. For aquatic environment characterized by less heat gain, because a significant part of it is reflected, and an equally significant part is spent on evaporation. Water has a high heat capacity. Consistent with the dynamics of land temperatures, water temperatures exhibit smaller fluctuations in daily and seasonal temperatures. Therefore, aquatic inhabitants do not have to adapt to severe frosts or 40 degree heat. Only in hot springs can the water temperature approach the boiling point. Moreover, reservoirs significantly equalize the temperature in the atmosphere of coastal areas. In the absence of an ice shell, the seas have a warming effect on the adjacent land areas in the cold season, and a cooling and moistening effect in the summer.

Characteristic feature The aquatic environment is its mobility, especially in flowing, fast-flowing streams and rivers. There are ebbs and flows in the seas and oceans, powerful currents, storms. In lakes, the water temperature moves due to temperature and wind. Temperature changes in flowing waters follow its changes in the surrounding air and have a smaller amplitude.

In lakes and ponds of temperate latitudes, the water is clearly divided into three layers:

With a further increase in temperature, the upper layers of water become less dense and no longer sink down - summer stagnation sets in. In autumn, surface waters cool again to 4 0 C and sink to the bottom, causing secondary mixing water masses with temperature equalization.

The range of water temperatures in the World Ocean is 38° (from -2 to +36°C), in fresh water bodies – 26° (from -0.9 to +25°C). With depth, the water temperature drops sharply. Up to 50 m there are daily temperature fluctuations, up to 400 m – seasonal fluctuations, deeper it becomes constant, dropping to +1-3°C (in the Arctic it is close to 0°C).

Thus, in water as a living environment, on the one hand, there is a fairly significant variety of temperature conditions, and on the other hand, the thermodynamic features of the aquatic environment (high specific heat capacity, high thermal conductivity, expansion during freezing) create favorable conditions for living organisms.

Light mode. The intensity of light in water is greatly weakened due to its reflection by the surface and absorption by the water itself. This greatly affects the development of photosynthetic plants. The less transparent the water, the more light is absorbed. Water transparency is limited by mineral suspensions and plankton. It decreases with the rapid development of small organisms in summer, and in temperate and northern latitudes– also in winter, after the ice cover has been established and covered with snow on top.

In the oceans, where the water is very transparent, 1% of light radiation penetrates to a depth of 140 m, and in small lakes at a depth of 2 m only tenths of a percent penetrates. Rays different parts spectrum are absorbed differently in water; red rays are absorbed first. With depth it becomes darker, and the color of the water first becomes green, then blue, indigo and finally blue-violet, turning into complete darkness. Hydrobionts also change color accordingly, adapting not only to the composition of light, but also to its lack - chromatic adaptation. In light zones, in shallow waters, green algae (Chlorophyta) predominate, the chlorophyll of which absorbs red rays, with depth they are replaced by brown (Phaephyta) and then red (Rhodophyta).

Light penetrates only to a relatively shallow depth, so plant organisms (phytobenthos) can exist only in the upper horizons of the water column. At great depths there are no plants, and deep-sea animals live in complete darkness, uniquely adapting to this way of life.

Daylight hours are much shorter (especially in deep layers) than on land. The amount of light in the upper layers of reservoirs varies with the latitude of the area and the time of year. Thus, long polar nights greatly limit the time suitable for photosynthesis in the Arctic and Antarctic, and ice cover makes it difficult for light to reach all frozen bodies of water in winter.

Gas mode. The main gases in water are oxygen and carbon dioxide. The rest are of secondary importance (hydrogen sulfide, methane).

Limited quantity oxygen is one of the main difficulties in the life of aquatic inhabitants. The total oxygen content in the upper layers of water (what is it called?) is 6-8 ml/l or in 21 times lower than in the atmosphere (remember the numbers!).

Oxygen content is inversely proportional to temperature. As the temperature and salinity of water increase, the concentration of oxygen in it decreases. In layers heavily populated by animals and bacteria, oxygen deficiency may occur due to increased oxygen consumption. Thus, in the World Ocean, life-rich depths from 50 to 1000 meters 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.

In bodies of water there can sometimes be freezes– mass death of inhabitants due to lack of oxygen. The reasons are stagnant conditions in small reservoirs. Covering the surface of a reservoir with ice in winter, polluting the reservoir, increasing water temperature. When the oxygen concentration is below 0.3-3.5 ml/l, the life of aerobes in water is impossible.

Carbon dioxide. Ways of carbon dioxide entering water:

· Dissolution of carbon contained in the air;

· Respiration of aquatic organisms;

· Decomposition of organic residues;

· Release from carbonates.

The water shell of our planet(the totality of oceans, seas, continental waters, ice sheets) is called the hydrosphere. In a broader sense, the hydrosphere also includes groundwater, ice and snow in the Arctic and Antarctic, as well as atmospheric water and water contained in living organisms.

The bulk of the water in the hydrosphere is concentrated in the seas and oceans, the second place is occupied by groundwater, the third is the ice and snow of the Arctic and Antarctic regions. The total volume of natural waters is approximately 1.39 billion km 3 (1/780 of the planet's volume). Water covers 71% of the globe's surface (361 million km2).

Water reserves on the planet (% of total number) were distributed as follows:

Water — component all elements of the biosphere, not only bodies of water, but also air, living beings. This is the most abundant natural compound on the planet. Without water, neither animals, nor plants, nor humans can exist. For the survival of any organism, a certain amount of water is required daily, so free access to water is a vital necessity.

The liquid shell covering the Earth distinguishes it from its neighboring planets. The hydrosphere is important for the development of life not only in a chemical sense. Its role is also great in maintaining a relatively constant climate, which has allowed life to reproduce for more than three billion years. Since life requires that the prevailing temperatures be in the range from 0 to 100 °C, i.e. within the limits that allow the hydrosphere to remain largely in the liquid phase, we can conclude that the temperature on Earth has been relatively constant throughout most of its history.

The hydrosphere serves as a planetary accumulator of inorganic and organic matter, which is brought into the ocean and other bodies of water by rivers, atmospheric flows, and is also formed by the reservoirs themselves. Water is the great distributor of heat on Earth. Heated by the Sun at the equator, it transfers heat through giant streams of sea currents in the World Ocean.

Water is part of minerals, is found in the cells of plants and animals, influences the formation of climate, participates in the cycle of substances in nature, contributes to the deposition of sedimentary rocks and the formation of soil, and is a source of cheap electricity: it is used in industry, agriculture and for household needs.

Despite the seemingly sufficient amount of water on the planet, the fresh water necessary for human life and many other organisms is sorely lacking. Of the total amount of water in the world, 97-98% is salt water seas and oceans. Of course, use this water in everyday life, agriculture, industry, for production food products impossible. And yet something else is much more serious: 75% of fresh water on Earth is in the form of ice, a significant part of it is groundwater, and only 1% is available to living organisms. And people mercilessly pollute these precious crumbs and carelessly consume them, while water consumption is constantly increasing. Pollution of the hydrosphere occurs primarily as a result of the discharge of industrial, agricultural and household waste into rivers, lakes and seas. waste water.

Fresh waters- not only an irreplaceable drinking resource. The lands irrigated by them produce about 40% of the world's harvest; Hydroelectric power plants produce approximately 20% of all electricity; Of the fish consumed by people, 12% are river and lake species.

The characteristics of the aquatic environment stem from the physical and chemical properties of water. Thus, the high density and viscosity of water are of great environmental importance. The specific gravity of water is comparable to that of the body of living organisms. The density of water is approximately 1000 times the density of air. Therefore, aquatic organisms (especially actively moving ones) encounter a large force of hydrodynamic resistance. For this reason, the evolution of many groups of aquatic animals went in the direction of the formation of body shapes and types of movement that reduced drag, which led to a decrease in energy consumption for swimming. Thus, a streamlined body shape is found in representatives of various groups of organisms living in water - dolphins (mammals), bony and cartilaginous fish.

The high density of water also contributes to the fact that mechanical vibrations (vibrations) propagate well in it. This was important in the evolution of sensory organs, spatial orientation and communication between aquatic inhabitants. Four times greater than in air, the speed of sound in an aquatic environment determines more high frequency echolocation signals.

Due to the high density of the aquatic environment, many of its inhabitants are deprived of the obligatory connection with the substrate, which is characteristic of terrestrial forms and is caused by gravitational forces. There is a whole group of aquatic organisms (both plants and animals) that spend their entire lives floating.

Water has an exceptionally high heat capacity. The heat capacity of water is taken as unity. The heat capacity of sand, for example, is 0.2, and that of iron is only 0.107 of the heat capacity of water. The ability of water to accumulate large reserves of thermal energy allows smoothing out sharp temperature fluctuations on the coastal areas of the Earth at different times of the year and at different times of the day: water acts as a kind of temperature regulator on the planet.

What animals live in the aquatic environment? You are interested in this question and want to find an answer to it, then in this article you will definitely get the information you need.

Animals that live in aquatic environments

The world of aquatic inhabitants is very diverse. Although there is not as much oxygen in the aquatic environment as in the air-terrestrial environment, animals have adapted to provide themselves with this vital gas. So, fish absorb oxygen dissolved in water using gills. Dolphins and whales They live in an aquatic environment, but provide themselves with oxygen outside of it. To do this, they rise to the surface of the water from time to time to inhale air.

They live in fresh water bodies beavers, their thick coat has the property of not allowing water to pass through, that is, impenetrable.

Feathers birds living in an aquatic environment is covered with a substance that does not allow it to become saturated with water.

The aquatic environment has become a factor that influenced the structure of the organs of movement, for example, fish move with the help of fins; waterfowl, beavers, frogs- using limbs that have membranes between the fingers.

Seals and walruses have wide flippers. On ice they are quite slow, because their mass does not allow them to move quickly, but in water they are very agile and fast.

Swimming beetles have legs that resemble oars.

In the oceans at a depth of more than 1 km there is complete darkness. Only those organisms that have adapted to such conditions live there. Some of them have special special organs that have the ability to glow blue, green or yellow.

At a depth of 2-3 km live fish called « monkfish", or anglerfish, because their body is covered with plaques and spines, and their mouth is incredibly large, characteristic of regular fish. From dorsal fin The “bar” grows and a “fishing rod” hangs over, at the end of which there is a luminous organ. Anglers use this as bait, since this moving point attracts the attention of organisms that swim past, and the “devil,” in turn, carefully pulls the “fishing rod” to his mouth and simply swallows the prey in a matter of seconds. Some types of fish have such “fishing rods” in their mouths, so when hunting they swim with their mouths open.

HABITAT AND THEIR CHARACTERISTICS

Aquatic habitat

Water covers 71% of the earth's area. The bulk of water is concentrated in the seas and oceans - 94-98%, polar ice contains about 1.2% of water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps.

About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is respectively only 7 and 8% of the total number of species on Earth.

In the seas-oceans, as in the mountains, vertical zoning is expressed. The pelagic - the entire water column - and the benthic - the bottom - differ especially greatly in ecology. The water column, the pelagic zone, is vertically divided into several zones: epipeligal, bathypeligal, abyssopeligal and ultraabyssopeligal(Fig. 2).

The warm seas and oceans (40,000 species of animals) in the equator and tropics are characterized by the greatest diversity of life; to the north and south, the flora and fauna of the seas are hundreds of times depleted. As for the distribution of organisms directly in the sea, the bulk of them are concentrated in the surface layers (epipelagic) and in the sublittoral zone. Depending on the method of movement and stay in certain layers, sea creatures are divided into three environmental groups: nekton, plankton and benthos.

Nekton (nektos - floating) - actively moving large animals that can overcome long distances and strong currents: fish, squid, pinnipeds, whales. In fresh water bodies, nekton includes amphibians and many insects.

Plankton (planktos - wandering, soaring) - a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water bodies only) algae, plant flagellates, peridineans, etc.) and small animal organisms (zooplankton: small crustaceans, of the larger ones - pteropods mollusks, jellyfish, ctenophores, some worms) living at different depths, but not capable of active movement and resistance to currents. Plankton also includes animal larvae, forming special group – Neuston . This is a passively floating “temporary” population of the uppermost layer of water, represented by various animals (decapods, barnacles and copepods, echinoderms, polychaetes, fish, mollusks, etc.) in the larval stage. The larvae, growing up, move into the lower layers of the pelagel. Above the neuston is located plaiston - these are organisms in which the upper part of the body grows above water, and the lower part in water (duckweed - Lemma, siphonophores, etc.). Plankton plays an important role in the trophic relationships of the biosphere, because is food for many aquatic inhabitants, including the main food for baleen whales (Myatcoceti).

Benthos (benthos – depth) – bottom hydrobionts. It is represented mainly by attached or slowly moving animals (zoobenthos: foraminephores, fish, sponges, coelenterates, worms, mollusks, ascidians, etc.), more numerous in shallow water. In shallow water, benthos also includes plants (phytobenthos: diatoms, green, brown, red algae, bacteria). At depths where there is no light, phytobenthos is absent. Rocky areas of the bottom are richest in phytobenthos.

Thermal mode. The aquatic environment is characterized by less heat gain, because a significant part of it is reflected, and an equally significant part is spent on evaporation. Consistent with the dynamics of land temperatures, water temperatures exhibit smaller fluctuations in daily and seasonal temperatures. Moreover, reservoirs significantly equalize the temperature in the atmosphere of coastal areas. In the absence of an ice shell, the seas have a warming effect on the adjacent land areas in the cold season, and a cooling and moistening effect in the summer.

The range of water temperatures in the World Ocean is 38° (from -2 to +36°C), in fresh water bodies – 26° (from -0.9 to +25°C). With depth, the water temperature drops sharply. Up to 50 m there are daily temperature fluctuations, up to 400 – seasonal, deeper it becomes constant, dropping to +1-3°C. Since temperature regime in reservoirs is relatively stable, their inhabitants are characterized by stenothermicity.

Due to to varying degrees heating of the upper and lower layers throughout the year, ebbs and flows, currents, and storms constantly mix the water layers. The role of water mixing for aquatic inhabitants is extremely important, because at the same time, the distribution of oxygen and nutrients within reservoirs is equalized, ensuring metabolic processes between organisms and the environment.

In stagnant reservoirs (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature throughout the reservoir becomes uniform, i.e. comes homothermy. In summer and winter as a result of a sharp increase in heating or cooling upper layers mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation is stagnation(summer or winter). In summer, lighter warm layers remain on the surface, located above heavy cold ones (Fig. 3). In winter, on the contrary, there is warmer water in the bottom layer, since directly under the ice the temperature of surface waters is less than +4°C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4°C.

The absorption of light is stronger, the lower the transparency of the water, which depends on the number of particles suspended in it (mineral suspensions, plankton). It decreases with the rapid development of small organisms in summer, and in temperate and northern latitudes even in winter, after the establishment of ice cover and covering it with snow on top.

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 most clear waters- in the Sargasso Sea: the disk is visible to a depth of 66.5 m. In the Pacific Ocean, the Secchi disk is visible 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 only a few centimeters.

In the oceans, where the water is very transparent, 1% of light radiation penetrates to a depth of 140 m, and in small lakes at a depth of 2 m only tenths of a percent penetrates. Rays from different parts of the spectrum are absorbed differently in water; red rays are absorbed first. With depth it becomes darker, and the color of the water first becomes green, then blue, indigo and finally blue-violet, turning into complete darkness. Hydrobionts also change color accordingly, adapting not only to the composition of light, but also to its lack - chromatic adaptation. In light zones, in shallow waters, green algae (Chlorophyta) predominate, the chlorophyll of which absorbs red rays, with depth they are replaced by brown (Phaephyta) and then red (Rhodophyta). At great depths, phytobenthos is absent.

Plants adapted to the lack of light by developing large chromatophores, as well as increasing the area of assimilating organs (leaf surface index). Deep-sea algae are characterized by strongly dissected leaves and thin, translucent leaf blades. Semi-submerged and floating plants are characterized by heterophylly - the leaves above the water are the same as those of land plants, they have a solid blade, the stomatal apparatus is developed, and in the water the leaves are very thin, consisting of narrow thread-like lobes.

Animals, like plants, naturally change their color with depth. In the upper layers they are brightly colored in different colors, in the twilight zone ( sea bass, corals, crustaceans) are painted in colors with a red tint - it is more convenient to hide from enemies. Deep-sea species lack pigments. In the dark depths of the ocean, organisms use light emitted by living beings as a source of visual information. bioluminescence.

High density(1 g/cm3, which is 800 times the density of air) and water viscosity ( 55 times higher than that of air) led to the development of special adaptations of aquatic organisms :

1) Plants have very poorly developed or completely absent mechanical tissues - they are supported by water itself. Most are characterized by buoyancy due to air-carrying intercellular cavities. Characterized by active vegetative reproduction, the development of hydrochory - the removal of flower stalks above the water and the distribution of pollen, seeds and spores by surface currents.

2) In animals living in the water column and actively swimming, the body has a streamlined shape and is lubricated with mucus, which reduces friction when moving. Developed devices to increase buoyancy: accumulations of fat in tissues, swim bladders in fish, air cavities in siphonophores. In passively swimming animals, the specific surface area of the body increases due to outgrowths, spines, and appendages; the body is flattened, and skeletal organs are reduced. Different methods of locomotion: bending of the body, using flagella, cilia, jet mode of locomotion (cephalopods).

In benthic animals, the skeleton disappears or is poorly developed, body size increases, vision reduction is common, and tactile organs develop.

Currents. A characteristic feature of the aquatic environment is mobility. It is caused by ebbs and flows, sea currents, storms, at different levels elevation marks of river beds. Adaptations of hydrobionts:

1) In flowing reservoirs, plants are firmly attached to stationary underwater objects. The bottom surface is primarily a substrate for them. These are green and diatom algae, water mosses. Mosses even form a dense cover on fast riffles of rivers. In the tidal zone of the seas, many animals have devices for attaching to the bottom (gastropods, barnacles), or hide in crevices.

2) In fish of running waters, the body is round in diameter, and in fish that live near the bottom, as in benthic invertebrate animals, the body is flat. Many have attachment organs to underwater objects on the ventral side.

Salinity of water.

Natural reservoirs are characterized by a certain chemical composition. Carbonates, sulfates, and chlorides predominate. In fresh water bodies, the salt concentration is no more than 0.5 ‰ (with about 80% being carbonates), in the seas - from 12 to 35 ‰ (mainly chlorides and sulfates). When the salinity is more than 40 ppm, the water body is called hypersaline or oversaline.

1) In fresh water (hypotonic environment), osmoregulation processes are well expressed. Hydrobionts are forced to constantly remove water penetrating into them; they are homoyosmotic (ciliates “pump” through themselves an amount of water equal to its weight every 2-3 minutes). In salt water (isotonic environment), the concentration of salts in the bodies and tissues of hydrobionts is the same (isotonic) with the concentration of salts dissolved in water - they are poikiloosmotic. Therefore, the inhabitants of salt water bodies do not have developed osmoregulatory functions, and they were unable to populate fresh water bodies.

2) Aquatic plants are able to absorb water and nutrients from water - “broth”, the entire surface, so their leaves are strongly dissected and conductive tissues and roots are poorly developed. The roots serve mainly for attachment to the underwater substrate. Most freshwater plants have roots.

Typically maritime and typically freshwater species– stenohaline, do not tolerate significant changes in water salinity. There are few euryhaline species. They are common in brackish waters (freshwater pike perch, pike, bream, mullet, coastal salmon).

5th grade biology report on the topic of an organism’s habitat

Answers:

Each organism lives in a specific environment. Everything that surrounds a living being is called its habitat. There are four main habitats on Earth that have been developed and inhabited by organisms. These are water, ground-air, soil and, finally, organisms (the environment formed by living organisms themselves). Each habitat has its own special living conditions to which organisms adapt. This explains the wide variety of living organisms on our planet. Water serves as a habitat for many organisms. From water they get everything they need for life.

Aquatic habitat.

Aquatic organisms are very diverse, but all their structural features and adaptations are determined by physical and chemical properties waterWater has a buoyant force. This property allows many organisms to float in the water column. These include both small plants and animals, and fairly large organisms, such as jellyfish. Active swimmers (fish, dolphins, whales, etc.) have a streamlined body shape, and their limbs are in the form of fins or flippers. Many aquatic organisms lead a sedentary or even attached lifestyle, for example, coral polyps. Water is able to accumulate and retain heat, so there are no such sharp temperature fluctuations in water as on land. Animals have populated the entire thickness of the water, right down to the deepest ocean depressions. Plants live only in the upper layers of water, where sunlight penetrates. The salt composition of water is of great importance for aquatic organisms.

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, in order to exist 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.

Aquatic 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. Part sun rays is reflected from its surface, and part is 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 of aquatic organisms).

Aquatic habitat - hydrosphere

Winter freezes occur when bodies of water are covered with ice. Summer - when due high temperature water, 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 highest salt content is 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 small 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 in stems higher plants poorly developed mechanical tissue. 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 found in water, so the conductive and root systems are poorly developed. 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 having leaves of different shapes (heterophily) depending on where they are found. 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 durable 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 thickness of the water. By 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:

increase in body surface due to flattening and lengthening of the shape, development of outgrowths and bristles;
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 ejected stream of water, bending of the body, fins, flippers, etc. can be used. Adaptations contribute to reducing body friction: streamlined body shape, elasticity skin, availability on
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:

weighting of the body due to shells (mollusks), chitinized integuments (crayfish, crabs, lobsters, lobsters);
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 ecological group of organisms is identified - 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.

Minsk Educational Institution “Gymnasium No. 14”

Abstract on biology on the topic:

“ WATER - HABITAT”

Prepared by a student of grade 11 “B”

Maslovskaya Evgenia

Teacher:

Bulva Ivan Vasilievich

1. Aquatic habitat – hydrosphere.

2. Water – unique environment.

3. Ecological groups of hydrobionts.

4. Modes.

5. Specific adaptations of hydrobionts.

6. Filtration as a type of nutrition.

7. Adaptation to life in drying up water bodies.

8. Conclusion.

1. Aquatic environment - hydrosphere

In the process of historical development, living organisms have mastered four habitats. The first is water. Life originated and developed in water for many millions of years. Water covers 71% of the globe's area and makes up 1/800 of the volume of land or 1370 m3. The bulk of water is concentrated in the seas and oceans - 94-98%, polar ice contains about 1.2% of water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps. These relationships are constant, although in nature the water cycle continues without ceasing (Fig. 1).

About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is respectively only 7 and 8% of the total number of species on Earth. Based on this, it was concluded that evolution on land was much more intense than in water.

In the seas-oceans, as in the mountains, vertical zoning is expressed. The pelagic - the entire water column - and the benthic - the bottom - differ especially greatly in ecology.

The water column, the pelagial, is vertically divided into several zones: epipeligal, bathypeligal, abyssopeligal and ultraabyssopeligal (Fig. 2).

Depending on the steepness of the descent and the depth at the bottom, several zones are also distinguished, which correspond to the indicated pelagic zones:

- littoral - the edge of the coast, flooded during high tides.

- supralittoral - the part of the coast above the upper tidal line, where the surf splashes reach.

- sublittoral - a gradual decrease in land to 200m.

- bathyal - steep depression of land (continental slope),

- abyssal - a gradual decrease in the bottom of the ocean floor; the depth of both zones together reaches 3-6 km.

- ultra-abyssal - deep-sea depressions from 6 to 10 km.

2. Water is a unique environment.

Water is a completely unique medium in many respects. The water molecule, consisting of two hydrogen atoms and one oxygen atom, is surprisingly stable. Water is a unique compound that exists simultaneously in gaseous, liquid and solid states.

Water is not only a life-giving source for all animals and plants on Earth, but is also a habitat for many of them. These include, for example, numerous species of fish, including crucian carp 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 through gills, extracting oxygen from the water. Some fish species, 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 entire lives in water, while others are in the aquatic environment only at the beginning of their lives. You can verify this by visiting a small pond or swamp. IN water element You can find the smallest representatives - single-celled organisms, which require a microscope to view. These include numerous algae and bacteria. Their number is measured in millions per cubic millimeter of water.

Other interesting property water consists in acquiring a very dense state at a temperature above the freezing level; for fresh water, these parameters are 4 °C and 0 °C, respectively.

Water as a habitat (page 1 of 3)

This is critical for the survival of aquatic organisms during the winter. Thanks to this same property, ice floats on the surface of the water, forming a protective layer on lakes, rivers and coastal areas. And this same property contributes to the thermal stratification of water layers and the seasonal turnover of water masses in lakes in areas with cold climates, which is very important for the life of aquatic organisms. The density of water provides the ability to lean on it, which is especially important for non-skeletal forms. The support of the environment serves as a condition for soaring in water, and many hydrobionts are adapted precisely to this way of life. Suspended organisms floating in water are combined into a special ecological group of aquatic organisms - plankton.

Completely purified water exists only in laboratory conditions. Any natural water contains a lot various substances. In "raw water" this is mainly the so-called protective system or carbonic complex, consisting of a 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 the water. U neutral water pH=7, lower values indicate increased acidity of the water, and higher values indicate that it is alkaline. In limestone areas, the water of lakes and rivers usually has higher pH values compared to reservoirs in places where the limestone content in the soil is insignificant

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

3. Ecological groups of hydrobionts.

Ecological groups of hydrobionts. The warm seas and oceans (40,000 species of animals) in the equator and tropics are characterized by the greatest diversity of life; to the north and south, the flora and fauna of the seas are hundreds of times depleted. As for the distribution of organisms directly in the sea, the bulk of them are concentrated in the surface layers (epipelagic) and in the sublittoral zone. Depending on the method of movement and stay in certain layers, marine inhabitants are divided into three ecological groups: nekton, plankton and benthos.

Nekton (nektos - floating) are actively moving large animals that can overcome long distances and strong currents: fish, squid, pinnipeds, whales. In fresh water bodies, nekton includes amphibians and many insects.

Plankton (planktos - wandering, soaring) is a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water bodies only) algae, plant flagellates, peridinea, etc.) and small animal organisms (zooplankton: small crustaceans, of the larger ones - pteropods, jellyfish, ctenophores, some worms), living at different depths, but not capable of active movement and resistance to currents. Plankton also includes animal larvae, forming a special group - neuston. This is a passively floating “temporary” population of the uppermost layer of water, represented by various animals (decapods, barnacles and copepods, echinoderms, polychaetes, fish, mollusks, etc.) in the larval stage. The larvae, growing up, move into the lower layers of the pelagel. Above the neuston there is a pleiston - these are organisms in which the upper part of the body grows above water, and the lower part in water (duckweed - Lemma, siphonophores, etc.). Plankton plays an important role in the trophic relationships of the biosphere, because is food for many aquatic inhabitants, including the main food for baleen whales (Myatcoceti).

In lakes, zoobenthos is less abundant and diverse than in the sea. It is formed by protozoa (ciliates, daphnia), leeches, mollusks, insect larvae, etc. The phytobenthos of lakes is formed by free-floating diatoms, green and blue-green algae; brown and red algae are absent.

Rooted coastal plants in lakes form clearly defined belts, species composition and the appearance of which is consistent with environmental conditions in the land-water boundary zone. In the water near the shore, hydrophytes grow - plants semi-submerged in water (arrowhead, whitewing, reeds, cattails, sedges, trichaetes, reeds). They are replaced by hydatophytes - plants immersed in water, but with floating leaves (lotus, duckweed, egg capsules, chilim, takla) and - further - completely submerged (pondweed, elodea, hara). Hydatophytes also include plants floating on the surface (duckweed).

The high density of the aquatic environment determines the special composition and nature of changes in life-supporting factors. Some of them are the same as on land - heat, light, others are specific: water pressure (increases with depth by 1 atm for every 10 m), oxygen content, salt composition, acidity. Due to the high density of the environment, the values of heat and light change much faster with the altitude gradient than on land.

4. Modes.

Temperature reservoirs are more stable than on land. This is due to the physical properties of water, primarily its high specific heat capacity, due to which the receipt or release of a significant amount of heat does not cause too sudden changes in temperature. The amplitude of annual temperature fluctuations in the upper layers of the ocean is no more than 10-150C, in continental waters - 30-350C. Deep layers of water are characterized by constant temperature. In equatorial waters the average annual temperature of the surface layers is +26...+270C, in polar waters it is about 00C and below. 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 stronger.

Due to the more stable temperature regime of water, stenothermy is common among aquatic organisms 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.

Water covers 71% of the globe's area and makes up 1/800th of the land volume. The bulk of water is concentrated in the seas and oceans - 94–98%, polar ice contains about 1.2% of water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps. These relationships are constant, although in nature the water cycle continues without ceasing.

About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is respectively only 7 and 8% of the total number of species on Earth.

In the World Ocean, as in the mountains, vertical zoning is pronounced. The pelagic - the entire water column - and the benthic - the bottom - differ especially greatly in ecology. Zoning is especially clearly manifested in lakes of temperate latitudes (Fig. 2.1). In the water mass as a habitat for organisms, 3 vertical layers can be distinguished: epilimnion, metalimnion and hypolimnion. The waters of the surface layer, the epilimnion, warm up and mix in summer under the influence of wind and convection currents. In autumn, surface waters, cooling and becoming denser, begin to sink, and the temperature difference between the layers equalizes. With further cooling, the waters of the epilimnion become colder than the waters hypolimnion. In spring, the reverse process occurs, ending with a period of summer stagnation. The bottom of lakes (benthal) is divided into 2 zones: a deeper zone - profundal, approximately corresponding to the part of the bed filled with waters of the hypolimnion, and a coastal zone - littoral, usually extending inland to the limit of macrophyte growth. According to the transverse profile of the river, a coastal zone is distinguished - ripal and an open zone - medial. In the open zone, current speeds are higher and the population is quantitatively poorer than in the coastal zone.

Ecological groups of hydrobionts.

The warm seas and oceans (40,000 species of animals) in the equator and tropics are characterized by the greatest diversity of life; to the north and south, the flora and fauna of the seas are hundreds of times depleted. As for the distribution of organisms directly in the sea, the bulk of them are concentrated in the surface layers (epipelagic) and in the sublittoral zone. Depending on the method of movement and stay in certain layers, marine inhabitants are divided into three ecological groups: nekton, plankton and benthos.

Plankton (planktos - wandering, soaring) is a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water bodies only) algae, plant flagellates, peridinea, etc.) and small animal organisms (zooplankton: small crustaceans, of the larger ones - pteropods, jellyfish, ctenophores, some worms), living at different depths, but not capable of active movement and resistance to currents. Plankton also includes animal larvae, forming a special group - neuston. This is a passively floating “temporary” population of the uppermost layer of water, represented by various animals (decapods, barnacles and copepods, echinoderms, polychaetes, fish, mollusks, etc.) in the larval stage. The larvae, growing up, move into the lower layers of the pelagel. Above the neuston is pleiston - these are organisms in which the upper part of the body grows above the water, and the lower part in the water (duckweed, egg capsules, water lilies, etc.). Plankton plays an important role in the trophic relationships of the biosphere, because is food for many aquatic inhabitants, including the main food for baleen whales.

Benthos (benthos – depth) – hydrobionts of the bottom. It is represented mainly by attached or slowly moving animals (zoobenthos: foraminephores, fish, sponges, coelenterates, worms, brachiopods, ascidians, etc.), more numerous in shallow water. In shallow water, benthos also includes plants (phytobenthos: diatoms, green, brown, red algae, bacteria). At depths where there is no light, phytobenthos is absent. Along the coasts there are flowering plants of zoster, rupiah. Rocky areas of the bottom are richest in phytobenthos. In lakes, zoobenthos is less abundant and diverse than in the sea. It is formed by protozoa (ciliates, daphnia), leeches, mollusks, insect larvae, etc. The phytobenthos of lakes is formed by free-floating diatoms, green and blue-green algae; brown and red algae are absent. Taking root coastal plants in lakes form clearly defined belts, the species composition and appearance of which are consistent with the environmental conditions in the land-water boundary zone. Hydrophytes grow in the water near the shore - plants semi-submerged in water (arrowhead, whitewing, reeds, cattails, sedges, trichaetes, reeds). They are replaced by hydatophytes - plants immersed in water, but with floating leaves (lotus, duckweed, egg capsules, chilim, takla) and - further - completely submerged (pondweed, elodea, hara). Hydatophytes also include plants floating on the surface (duckweed).

Thermal mode.

The aquatic environment is characterized by less heat gain, because a significant part of it is reflected, and an equally significant part is spent on evaporation. Consistent with the dynamics of land temperatures, water temperatures exhibit smaller fluctuations in daily and seasonal temperatures. Moreover, reservoirs significantly equalize the temperature in the atmosphere of coastal areas. In the absence of an ice shell, the seas have a warming effect on the adjacent land areas in the cold season, and a cooling and moistening effect in the summer.

The range of water temperatures in the World Ocean is 38° (from –2 to +36°С), in fresh water bodies – 26° (from –0.9 to +25°С). With depth, the water temperature drops sharply. Up to 50 m there are daily temperature fluctuations, up to 400 – seasonal, deeper it becomes constant, dropping to +1–3°C (in the Arctic it is close to 0°C). Since the temperature regime in reservoirs is relatively stable, their inhabitants are characterized by stenothermism. Minor temperature fluctuations in one direction or another are accompanied by significant changes in aquatic ecosystems. Examples: a “biological explosion” in the Volga delta due to a decrease in the level of the Caspian Sea - the proliferation of lotus thickets (Nelumba kaspium), in southern Primorye - the overgrowth of whitefly in oxbow rivers (Komarovka, Ilistaya, etc.) along the banks of which woody vegetation was cut down and burned.

Due to varying degrees of heating of the upper and lower layers throughout the year, ebbs and flows, currents, and storms, constant mixing of water layers occurs. The role of water mixing for aquatic inhabitants (aquatic organisms) is extremely important, because at the same time, the distribution of oxygen and nutrients within reservoirs is equalized, ensuring metabolic processes between organisms and the environment.

In stagnant reservoirs (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature throughout the reservoir becomes uniform, i.e. homothermy occurs. In summer and winter, as a result of a sharp increase in heating or cooling of the upper layers, the mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation is called stagnation (summer or winter). In summer, lighter warm layers remain on the surface, located above heavy cold ones. In winter, on the contrary, there is warmer water in the bottom layer, since directly under the ice the temperature of surface waters is less than +4°C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4°C.

During periods of stagnation, three layers are clearly distinguished: the upper (epilimnion) with the sharpest seasonal fluctuations in water temperature, the middle (metalimnion or thermocline), in which a sharp jump in temperature occurs, and the bottom (hypolimnion), in which the temperature changes little throughout the year. During periods of stagnation, oxygen deficiency occurs in the water column - in the bottom part in summer, and in the upper part in winter, as a result of which fish kills often occur in winter. In stagnant reservoirs (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature throughout the reservoir becomes uniform, i.e. homothermy occurs. In summer and winter, as a result of a sharp increase in heating or cooling of the upper layers, the mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation is called stagnation (summer or winter). In summer, lighter warm layers remain on the surface, located above the heavier cold ones. In winter, on the contrary, there is warmer water in the bottom layer, since directly under the ice the temperature of surface waters is less than +4°C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4°C.

Light mode.

The intensity of light in water is greatly weakened due to its reflection by the surface and absorption by the water itself. This greatly affects the development of photosynthetic plants. The less transparent the water, the more light is absorbed. Water transparency is limited by mineral suspensions and plankton. It decreases with the rapid development of small organisms in summer, and in temperate and northern latitudes even in winter, after the establishment of ice cover and covering it with snow on top. In small lakes, only tenths of a percent of light penetrates to a depth of 2 m. With depth it becomes darker, and the color of the water first becomes green, then blue, indigo and finally blue-violet, turning into complete darkness. Hydrobionts also change color accordingly, adapting not only to the composition of light, but also to its lack - chromatic adaptation. In light zones, in shallow waters, green algae (Chlorophyta) predominate, the chlorophyll of which absorbs red rays, with depth they are replaced by brown (Phaephyta) and then red (Rhodophyta). At great depths, phytobenthos is absent. Plants have adapted to the lack of light by developing large chromatophores, which provide a low point of compensation for photosynthesis, as well as by increasing the area of assimilating organs (leaf surface index). Deep-sea algae are characterized by strongly dissected leaves and thin, translucent leaf blades. Semi-submerged and floating plants are characterized by heterophylly - the leaves above the water are the same as those of land plants, they have a solid blade, the stomatal apparatus is developed, and in the water the leaves are very thin, consisting of narrow thread-like lobes. Animals, like plants, naturally change their color with depth. In the upper layers they are brightly colored in different colors, in the twilight zone (sea bass, corals, crustaceans) they are painted in colors with a red tint - it is more convenient to hide from enemies. Deep-sea species lack pigments.