Animals are spread over almost the entire surface of the Earth. Due to their mobility, ability to adapt evolutionarily to colder living conditions, due to their lack of direct dependence on sunlight, animals occupied more habitats than plants. However, it should be remembered that animals depend on plants, since plants serve as a source of food for them (for herbivores, and predators eat herbivores).

Here in the context of animal habitats we will understand animal living environment.

In total, four animal habitats can be distinguished. These are 1) ground-air, 2) water, 3) soil and 4) other living organisms. When talking about the ground-air environment of life, it is sometimes divided into ground and, separately, air. However, even flying animals sooner or later land on the ground. In addition, while moving on the ground, the animal is also in the air. Therefore, the ground and air environments are combined into one ground-air environment.

There are animals that live in two environments at once. For example, many amphibians (frogs) live both in water and on land, a number of rodents live in the soil and on the surface of the earth.

Ground-air habitat

The land-air environment contains the most animal species. The land turned out to be, in a sense, the most convenient environment for their life. Although in evolution, animals (and plants) arose in water and only later came to the surface.

Most worms, insects, amphibians, reptiles, birds and mammals live on land. Many species of animals are capable of flight, so they spend part of their lives exclusively in the air.

For terrestrial animals air environment usually characterized by high mobility and good vision.

It is typical for the ground-air environment big variety living conditions (tropical forests and temperate forests, meadows and steppes, deserts, tundras and much more). Therefore, animals in this living environment are characterized by great diversity; they can differ greatly from each other.

Aquatic habitat

The aquatic habitat differs from the air habitat in its greater density. Here animals can afford to have very massive bodies (whales, sharks), as the water supports them and makes their bodies lighter. However, it is more difficult to move in a dense environment, which is why aquatic animals most often have a streamlined body shape.

Almost no sunlight penetrates into the depths of the sea, so deep-sea animals may have poorly developed visual organs.

Aquatic animals are divided into plankton, nekton and benthos. Plankton floats passively in the water column (for example, unicellular organisms), nekton- these are actively swimming animals (fish, whales, etc.), benthos lives on the bottom (corals, sponges, etc.).

Soil habitat

Soil as a habitat is very different high density and lack of sunlight. Here animals do not need organs of vision. Therefore, they are either not developed (worms) or reduced (moles). On the other hand, temperature changes in the soil are not as significant as on the surface. The soil is home to many worms, insect larvae, and ants. There are also soil inhabitants among mammals: moles, mole rats, and burrowing animals.

WATER ENVIRONMENT

The aquatic environment of life (hydrosphere) occupies 71% of the globe's area. More than 98% of the water is concentrated in the seas and oceans, 1.24% is the ice of the polar regions, 0.45% is the fresh water of rivers, lakes, and swamps.

There are two ecological areas in the world's oceans:

water column - pelagic, and the bottom - benthal.

The aquatic environment is home to approximately 150,000 species of animals, or about 7% of their total number, and 10,000 species of plants – 8%. The following are distinguished: ecological groups of aquatic organisms. Pelagial - inhabited by organisms divided into nekton and plankton.

Nekton (nektos - floating) - This is a collection of pelagic actively moving animals that do not have a direct connection with the bottom. These are mainly large animals that can overcome long distances and strong water currents. They are characterized by a streamlined body shape and well-developed organs of movement (fish, squid, pinnipeds, whales) B fresh water In addition to fish, nekton includes amphibians and actively moving insects.

Plankton (wandering, floating) - This is a set of pelagic organisms that do not have the ability for rapid active movements. They are divided into phyto- and zooplankton (small crustaceans, protozoa - foraminifera, radiolarians; jellyfish, pteropods). Phytoplankton – diatoms and green algae.

Neuston– a set of organisms that inhabit the surface film of water at the border with the air. These are the larvae of decapods, barnacles, copepods, gastropods and bivalves, echinoderms, and fish. Passing through the larval stage, they leave the surface layer, which served them as a refuge, and move to live on the bottom or pelagic zone.

Plaiston – this is a collection of organisms, part of the body of which is above the surface of the water, and the other in the water - duckweed, siphonophores.

Benthos (depth) - a collection of organisms that live at the bottom of water bodies. It is divided into phytobenthos and zoobenthos. Phytobenthos - algae - diatoms, green, brown, red and bacteria; off the coasts flowering plants– zostera, rupiah. Zoobenthos – foraminifera, sponges, coelenterates, worms, mollusks, fish.

In the life of aquatic organisms, an important role is played by the vertical movement of water, density, temperature, light, salt, gas (oxygen and carbon dioxide content) regimes, and the concentration of hydrogen ions (pH).

Temperature: It differs in water, firstly, by less heat influx, and secondly, by greater stability than on land. Part of the thermal energy arriving at the surface of the water is reflected, while part is spent on evaporation. 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. Temperature changes in flowing waters follow its changes in the surrounding air, differing in smaller amplitude.

In lakes and ponds of temperate latitudes, the thermal regime is determined by the well-known physical phenomenon– water has a maximum density at 4 o C. The water in them is clearly divided into three layers:

1. epilimnion- the upper layer whose temperature experiences sharp seasonal fluctuations;

2. metalimnion– transitional layer of temperature jump, there is a sharp temperature difference;

3. hypolimnion- a deep-sea layer reaching to the very bottom, where the temperature changes slightly throughout the year.

In summer, the warmest layers of water are located at the surface, and the coldest ones are located at the bottom. This type of layer-by-layer temperature distribution in a reservoir is called direct stratification. In winter, as the temperature drops, reverse stratification: the surface layer has a temperature close to 0 C, at the bottom the temperature is about 4 C, which corresponds to its maximum density. Thus, the temperature increases with depth. This phenomenon is called temperature dichotomy, observed in most lakes in the temperate zone in summer and winter. As a result of temperature dichotomy, vertical circulation is disrupted - a period of temporary stagnation begins - stagnation.

In spring, surface water, due to heating to 4C, becomes denser and sinks deeper, and in its place more water rises from the depths. warm water. As a result of such vertical circulation, homothermy occurs in the reservoir, i.e. for some time the temperature of the entire water mass equalizes. With a further increase in temperature, the upper layers become less and less dense and no longer sink down - summer stagnation. In autumn, the surface layer cools, becomes denser and sinks deeper, displacing warmer water to the surface. This occurs before the onset of autumn homothermy. When cooling surface waters Below 4C they become less dense and again remain on the surface. As a result, water circulation stops and winter stagnation occurs.

Water is characterized by significant density(800 times) superior to air) and viscosity. IN On average, in the water column, for every 10 m of depth, pressure increases by 1 atm. These features affect plants in the fact that they develop very little or not at all. mechanical fabric, so their stems are very elastic and bend easily. Most aquatic plants are characterized by buoyancy and the ability to be suspended in the water column; in many aquatic animals, the integument is lubricated with mucus, which reduces friction when moving, and the body takes on a streamlined shape. Many inhabitants are relatively stenobatic and confined to certain depths.

Transparency and light mode. This especially affects the distribution of plants: in muddy water bodies they live only in the surface layer. The light regime is also determined by the natural decrease in light with depth due to the fact that water absorbs sunlight. At the same time, rays with different wavelengths are absorbed differently: red ones are absorbed most quickly, while blue-green ones penetrate to significant depths. The color of the environment changes, gradually moving from greenish to green, blue, indigo, blue-violet, replaced by constant darkness. Accordingly, with depth, green algae are replaced by brown and red ones, the pigments of which are adapted to capture solar rays of different wavelengths. The color of animals also naturally changes with depth. Brightly and variously colored animals live in the surface layers of water, while deep-sea species are devoid of pigments. The twilight habitat is inhabited by animals painted in colors with a reddish tint, which helps them hide from enemies, since the red color in blue-violet rays is perceived as black.

The absorption of light in water is stronger, the lower its transparency. Transparency is characterized by extreme depth, where a specially lowered Secchi disk (a white disk with a diameter of 20 cm) is still visible. Hence, the boundaries of photosynthesis zones vary greatly in different bodies of water. In the cleanest waters, the photosynthetic zone reaches a depth of 200 m.

Salinity of water. Water is an excellent solvent for many mineral compounds. As a result, natural reservoirs have a certain chemical composition. Highest value have sulfates, carbonates, chlorides. The amount of dissolved salts per 1 liter of water in fresh water bodies does not exceed 0.5 g, in seas and oceans - 35 g. Freshwater plants and animals live in a hypotonic environment, i.e. an environment in which the concentration of dissolved substances is lower than in body fluids and tissues. Due to the difference in osmotic pressure outside and inside the body, water constantly penetrates into the body, and freshwater hydrobionts are forced to intensively remove it. In this regard, their osmoregulation processes are well expressed. In protozoa this is achieved by the work of excretory vacuoles, in multicellular organisms - by removing water through excretory system. Typically marine and typically freshwater species do not tolerate significant changes in water salinity - stenohaline organisms. Eurygalline - freshwater pike perch, bream, pike, from the sea - the mullet family.

Gas mode The main gases in the aquatic environment are oxygen and carbon dioxide.

Oxygen- the most important environmental factor. It enters water from the air and is released by plants during photosynthesis. Its content in water is inversely proportional to temperature; with decreasing temperature, the solubility of oxygen in water (as well as other gases) increases. In layers heavily populated by animals and bacteria, oxygen deficiency may occur due to increased oxygen consumption. Thus, in the world’s oceans, 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.

Carbon dioxide - dissolves in water about 35 times better than oxygen and its concentration in water is 700 times higher than in the atmosphere. Provides photosynthesis of aquatic plants and participates in the formation of calcareous skeletal formations of invertebrate animals.

Hydrogen ion concentration (pH)– freshwater pools with pH = 3.7-4.7 are considered acidic, 6.95-7.3 – neutral, with pH 7.8 – alkaline. In fresh water bodies, pH even experiences daily fluctuations. Sea water is more alkaline and its pH changes much less than fresh water. pH decreases with depth. The concentration of hydrogen ions plays a large role in the distribution of aquatic organisms.

Ground-air habitat

A feature of the land-air environment of life is that the organisms living here are surrounded by a gaseous environment characterized by low humidity, density and pressure, and high oxygen content. Typically, animals in this environment move on the soil (hard substrate) and plants take root in it.

In the ground-air environment, the operating environmental factors have a number of characteristic features: higher light intensity compared to other environments, significant temperature fluctuations, changes in humidity depending on geographical location, season and time of day. The impact of the factors listed above is inextricably linked with the movement of air masses - wind.

In the process of evolution, living organisms of the land-air environment have developed characteristic anatomical, morphological, physiological adaptations.

Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment.

Air. Air as an environmental factor is characterized by a constant composition - oxygen in it is usually about 21%, carbon dioxide 0.03%.

Low air density determines its low lifting force and insignificant support. All inhabitants of the air are closely connected with the surface of the earth, which serves them for attachment and support. The density of the air environment does not provide high resistance to organisms when they move along the surface of the earth, but it makes it difficult to move vertically. For most organisms, staying in the air is associated only with settling or searching for prey.

The low lifting force of air determines the maximum mass and size of terrestrial organisms. The largest animals living on the surface of the earth are smaller than the giants of the aquatic environment. Large mammals (the size and mass of a modern whale) could not live on land, as they would be crushed by their own weight.

Low air density creates little resistance to movement. The ecological benefits of this property of the air environment were used by many land animals during evolution, acquiring the ability to fly. 75% of the species of all terrestrial animals are capable of active flight, mainly insects and birds, but flyers are also found among mammals and reptiles.

Thanks to the mobility of air and the vertical and horizontal movements of air masses existing in the lower layers of the atmosphere, passive flight of a number of organisms is possible. Many species have developed anemochory - dispersal with the help of air currents. Anemochory is characteristic of spores, seeds and fruits of plants, protozoan cysts, small insects, spiders, etc. Organisms passively transported by air currents are collectively called aeroplankton by analogy with planktonic inhabitants of the aquatic environment.

The main ecological role of horizontal air movements (winds) is indirect in enhancing and weakening the impact on terrestrial organisms of such important environmental factors as temperature and humidity. Winds increase the release of moisture and heat from animals and plants.

Gas composition of air in the ground layer the air is quite homogeneous (oxygen - 20.9%, nitrogen - 78.1%, inert gases - 1%, carbon dioxide - 0.03% by volume) due to its high diffusivity and constant mixing by convection and wind flows. However, various impurities of gaseous, droplet-liquid and solid (dust) particles entering the atmosphere from local sources can have significant environmental significance.

High oxygen content contributed to increased metabolism in terrestrial organisms, and based on high efficiency oxidative processes gave rise to animal homeothermy. Oxygen, due to its constantly high content in the air, is not a factor limiting life in terrestrial environment. Only in places, under specific conditions, is a temporary deficiency created, for example in accumulations of decomposing plant residues, reserves of grain, flour, etc.

Edaphic factors. Soil properties and terrain also affect the living conditions of terrestrial organisms, primarily plants. The properties of the earth's surface that have an ecological impact on its inhabitants are called edaphic environmental factors.

The nature of the plant root system depends on the hydrothermal regime, aeration, composition, composition and structure of the soil. For example, the root systems of tree species (birch, larch) in areas with permafrost are located at shallow depths and spread out wide. Where there is no permafrost, the root systems of these same plants are less spread out and penetrate deeper. In many steppe plants, the roots can reach water from great depths; at the same time, they also have many surface roots in the humus-rich soil horizon, from where the plants absorb elements of mineral nutrition.

The terrain and the nature of the soil affect the specific movement of animals. For example, ungulates, ostriches, and bustards living in open spaces need hard ground to enhance repulsion when running fast. In lizards that live on shifting sands, the toes are edged with a fringe of horny scales, which increases the surface of support. For terrestrial inhabitants that dig holes, dense soils are unfavorable. The nature of the soil in some cases influences the distribution of terrestrial animals that dig burrows, burrow into the soil to escape heat or predators, or lay eggs in the soil, etc.

Weather and climatic features. Living conditions in the ground-air environment are also complicated by weather changes. Weather is the continuously changing state of the atmosphere at the earth's surface, up to an altitude of approximately 20 km (the boundary of the troposphere). Weather variability is manifested in a constant variation in the combination of environmental factors such as air temperature and humidity, cloudiness, precipitation, wind strength and direction, etc. Weather changes, along with their regular alternation in the annual cycle, are characterized by non-periodic fluctuations, which significantly complicates the conditions for the existence of terrestrial organisms. The weather affects the life of aquatic inhabitants to a much lesser extent and only on the population of the surface layers.

Climate of the area. The long-term weather regime characterizes the climate of the area. The concept of climate includes not only the average values of meteorological phenomena, but also their annual and diurnal cycle, deviations from it and their recurrence. The climate is determined by the geographical conditions of the area.

The zonal diversity of climates is complicated by the action of monsoon winds, the distribution of cyclones and anticyclones, the influence of mountain ranges on the movement of air masses, the degree of distance from the ocean and many other local factors.

For most terrestrial organisms, especially small ones, it is not so much the climate of the area that is important as the conditions of their immediate habitat. Very often, local environmental elements (relief, vegetation, etc.) change the regime of temperature, humidity, light, air movement in a particular area in such a way that it differs significantly from climatic conditions terrain. Such local climate modifications that develop in the surface layer of air are called microclimate. Each zone has very diverse microclimates. Microclimates of arbitrarily small areas can be identified. For example, a special regime is created in the corollas of flowers, which is used by the inhabitants living there. A special stable microclimate occurs in burrows, nests, hollows, caves and other closed places.

Precipitation. In addition to providing water and creating moisture reserves, they can play other ecological roles. Thus, heavy rainfall or hail sometimes have a mechanical effect on plants or animals.

The ecological role of snow cover is especially diverse. Daily temperature fluctuations penetrate into the snow depth only up to 25 cm; deeper the temperature remains almost unchanged. With frosts of -20-30 C under a layer of snow of 30-40 cm, the temperature is only slightly below zero. Deep snow cover protects renewal buds and protects green parts of plants from freezing; many species go under the snow without shedding their foliage, for example, hairy grass, Veronica officinalis, etc.

Small land animals lead an active lifestyle in winter, making entire galleries of tunnels under the snow and in its thickness. A number of species that feed on snow-covered vegetation are even characterized by winter reproduction, which is noted, for example, in lemmings, wood and yellow-throated mice, a number of voles, water rats, etc. Grouse birds - hazel grouse, black grouse, tundra partridge - burrow in the snow for the night.

Winter snow cover makes it difficult for large animals to obtain food. Many ungulates (reindeer, wild boars, musk oxen) feed exclusively on snow-covered vegetation in winter, and deep snow cover, and especially the hard crust on its surface that occurs during icy conditions, doom them to starvation. Snow depth may limit the geographic distribution of species. For example, real deer do not penetrate north into those areas where the snow thickness in winter is more than 40-50 cm.

Light mode. The amount of radiation reaching the Earth's surface is determined by the geographic latitude of the area, the length of the day, the transparency of the atmosphere and the angle of incidence of the sun's rays. Under different weather conditions, 42-70% of the solar constant reaches the Earth's surface. Illumination on the Earth's surface varies widely. It all depends on the height of the Sun above the horizon or the angle of incidence of the sun's rays, the length of the day and weather conditions, and the transparency of the atmosphere. Light intensity also fluctuates depending on the season and time of day. In certain regions of the Earth, the quality of light is also unequal, for example, the ratio of long-wave (red) and short-wave (blue and ultraviolet) rays. Short-wave rays are known to be absorbed and scattered by the atmosphere more than long-wave rays.

Soil as a habitat

The soil is a loose thin surface layer of land in contact with the air. The soil is not just solid, like most rocks of the lithosphere, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore it develops extremely diverse conditions favorable for the life of many micro- and macroorganisms. Temperature fluctuations in the soil are smoothed out compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a humidity regime intermediate between water and the ground environment. The soil concentrates reserves of organic and mineral substances supplied by dying vegetation and animal corpses. All this determines the greater saturation of the soil with life.

The heterogeneity of soil conditions is most pronounced in the vertical direction. With depth, a number of the most important environmental factors affecting the life of soil inhabitants change dramatically. First of all, this relates to the structure of the soil. It distinguishes three main horizons, differing in morphological and chemical properties: 1) upper humus-accumulative horizon, in which organic matter accumulates and is transformed and from which some of the compounds are carried down by washing waters; 2) the influx horizon, or illuvial, where the substances washed out from above settle and are transformed, and 3) the parent rock, or horizon, the material of which is transformed into soil.

The size of the cavities between soil particles, suitable for animals to live in, usually decreases rapidly with depth. For example, in meadow soils the average diameter of cavities at a depth of 0-1 mm is 3 mm; 1-2 cm 2 mm, and at a depth of 2-3 cm - only 1 mm; deeper the soil pores are even smaller.

Moisture in the soil is present in various states: 1) bound (hygroscopic and film) firmly held by the surface of soil particles; 2) capillary occupies small pores and can move along them in different directions; 3) gravitational fills larger voids and slowly seeps down under the influence of gravity; 4) vaporous is contained in the soil air.

The composition of soil air is variable. With depth, the oxygen content in it decreases greatly and the concentration of carbon dioxide increases. Due to the presence of decomposing organic substances in the soil, the soil air may contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or intensive rotting of plant residues, completely anaerobic conditions may occur in some places.

Fluctuations in cutting temperature only on the soil surface. Here they can be even stronger than in the surface layer of air. However, with every centimeter deeper, daily and seasonal temperature changes become less and less and at a depth of 1-1.5 m they are practically no longer traceable.

All these features lead to the fact that, despite the great heterogeneity of environmental conditions in the soil, it acts as a fairly stable environment, especially for soil organisms. The steep moisture gradient in the soil profile allows soil organisms to provide themselves with a suitable ecological environment through minor movements.

Soil inhabitants, depending on their size and degree of mobility, can be divided into several groups:

1. Microbiota- these are soil microorganisms that form the main link of detrital the food chain, represent a kind of intermediate link between plant residues and soil animals. These are green and blue-green algae, bacteria, fungi and protozoa. These are aquatic organisms, and the soil for them is a system of micro-reservoirs. They live in soil pores filled with gravitational or capillary moisture, and part of the life can, like microorganisms, be in an adsorbed state on the surface of particles in thin layers of film moisture.

2. Mesobiota is a collection of relatively small, easily removed from the soil, mobile animals (soil nematodes, small insect larvae, mites, etc.). The sizes of soil mesobiota representatives range from tenths to 2-3 mm. For this group of animals, the soil appears as a system of small caves. They have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows them to breathe through the integument of the body. Animals usually experience periods of soil flooding with water in air bubbles. Air is retained around their body due to the non-wetting of the integument, which in most of them is equipped with hairs and scales.

Animals of meso- and microbiotypes are able to tolerate winter freezing of the soil, which is especially important, since most of them cannot move down from layers exposed to negative temperatures.

3) Macrobiota– these are large soil animals, with body sizes from 2 to 20 mm (insect larvae, centipedes, earthworms, etc.). They move in the soil, expanding natural wells by moving apart soil particles or digging new passages. Both methods of movement leave an imprint on the external structure of animals. Gas exchange of most species of this group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument.

Burrowing animals can move away from layers where an unfavorable environment occurs. By winter and during drought, they concentrate in deeper layers, mostly a few tens of centimeters from the surface.

4) Megabiota- These are large shrews, mainly mammals. Many of them spend their entire lives in the soil (golden moles in Africa, moles in Eurasia, marsupial moles in Australia). They create entire systems of passages and burrows in the soil. Adaptation to a burrowing underground lifestyle is reflected in the appearance and anatomical features of these animals: they have underdeveloped eyes, a compact ridged body with a short neck, short thick fur, strong compact limbs with strong claws.

In addition to the permanent inhabitants of the soil, a separate ecological group is often distinguished among large animals burrow inhabitants(badgers, marmots, gophers, jerboas, etc.). They feed on the surface, but reproduce, hibernate, rest, and escape danger in the soil.

Walking through a forest or meadow, you hardly think that you are... in ground-air environment. But this is exactly what scientists call the house for living beings, which is formed by the surface of the earth and the air. Swimming in a river, lake or sea, you find yourself in aquatic environment- another richly populated natural home. And when you help adults dig up the soil in the garden, you see the soil environment under your feet. There are also many, many diverse residents here. Yes, there are three wonderful houses around us - three habitat, with which the fate of the majority of organisms inhabiting our planet is inextricably linked.

Life in each environment has its own characteristics. IN ground-air environment there is enough oxygen, but often there is not enough moisture. There is especially little of it in the steppes and deserts. Therefore, plants and animals of arid places have special adaptations for obtaining, storing and economically using water. Just remember a cactus that stores moisture in its body. There are significant temperature changes in the land-air environment, especially in areas with cold winters. In these areas, the entire life of organisms changes noticeably throughout the year. Autumn leaf fall, the departure of migratory birds to warmer regions, the change of fur of animals to thicker and warmer ones - all these are adaptations of living beings to seasonal changes in nature.

For animals living in any environment, movement is an important problem. In the ground-air environment, you can move on the ground and in the air. And animals take advantage of this. The legs of some are adapted for running (ostrich, cheetah, zebra), others - for jumping (kangaroo, jerboa). Of every hundred animal species living in this environment, 75 can fly. These are most insects, birds and some animals (bats).

IN aquatic environment something, and there is always enough water. The temperature here varies less than the air temperature. But oxygen is often not enough. Some organisms, such as trout fish, can only live in oxygen-rich water. Others (carp, crucian carp, tench) can withstand a lack of oxygen. In winter, when many reservoirs are covered with ice, fish may die - mass death from suffocation. To allow oxygen to penetrate the water, holes are cut in the ice.

There is less light in the aquatic environment than in the air-terrestrial environment. In the oceans and seas at a depth below 200 m - the kingdom of twilight, and even lower - eternal darkness. It is clear that aquatic plants are found only where there is enough light. Only animals can live deeper. They feed on the dead remains of various marine inhabitants that “fall” from the upper layers.

The most noticeable feature of many aquatic animals is their swimming adaptations. Fish, dolphins and whales have fins. Walruses and seals have flippers. Beavers, otters, waterfowl, and frogs have membranes between their toes. Swimming beetles have swimming legs that look like oars.

Soil environment- home to many bacteria and protozoa. Mushroom myceliums and plant roots are also located here. The soil was also inhabited by a variety of animals - worms, insects, animals adapted to digging, such as moles. The inhabitants of the soil find in this environment the conditions they need - air, water, mineral salts. True, there is less oxygen and more carbon dioxide here than in the fresh air. And sometimes there is too much water. But the temperature is more even than on the surface. But light does not penetrate deep into the soil. Therefore, the animals inhabiting it usually have very small eyes or no visual organs at all. Their sense of smell and touch help out.

Ground-air environment

In these drawings representatives “met” different environments a habitat. In nature, they would not be able to gather together, because many of them live far from each other, on different continents, in the seas, in fresh water...

The champion in flight speed among birds is the swift. 120 km per hour is his usual speed.

Hummingbirds flap their wings up to 70 times per second, mosquitoes - up to 600 times per second.

The flight speed of different insects is as follows: for the lacewing - 2 km per hour, for the housefly - 7, for the cockchafer - 11, for the bumblebee - 18, and for the hawk moth - 54 km per hour. Large dragonflies, according to some observations, reach speeds of up to 90 km per hour.

Our bats are small in stature. But their relatives, fruit bats, live in hot countries. They reach a wingspan of 170 cm!

Large kangaroos make jumps of up to 9 and sometimes up to 12 m. (Measure this distance on the floor in the classroom and imagine a kangaroo jump. It’s simply breathtaking!)

The cheetah is the fastest-footed of animals. It reaches speeds of up to 110 km per hour. An ostrich can run at speeds of up to 70 km per hour, taking steps of 4-5 m.

Water environment

Fish and crayfish breathe through gills. These are special organs that extract dissolved oxygen from water. A frog, while underwater, breathes through its skin. But animals that have mastered the aquatic environment breathe with their lungs, rising to the surface of the water to inhale. Aquatic beetles behave in a similar way. Only they, like other insects, do not have lungs, but special breathing tubes - tracheas.

Soil environment

The body structure of the mole, zokor and mole rat suggests that they are all inhabitants of the soil environment. The front legs of the mole and zokor are the main tool for digging. They are flat, like shovels, with very large claws. But the mole rat has ordinary legs; it bites into the soil with its powerful front teeth (to prevent soil from getting into the mouth, the lips close it behind the teeth!). The body of all these animals is oval and compact. With such a body it is convenient to move through underground passages.

Test your knowledge

List the habitats you were introduced to in class.
What are the living conditions of organisms in the ground-air environment?
Describe the living conditions in the aquatic environment.
What are the characteristics of soil as a habitat?
Give examples of the adaptation of organisms to life in different environments.

Think!

Explain what is shown in the picture. In what environments do you think the animals whose body parts are shown in the picture live? Can you name these animals?
Why do only animals live in the ocean at great depths?

There are ground-air, water and soil habitats. Each organism is adapted to life in a certain environment.

General characteristics. In the course of evolution, the land-air environment was mastered much later than the aquatic environment. Life on land required adaptations that became possible only with a relatively high level of organization in both plants and animals. A feature of the land-air environment of life is that the organisms that live here are surrounded by air and a gaseous environment characterized by low humidity, density and pressure, and high oxygen content. Typically, animals in this environment move on the soil (hard substrate) and plants take root in it.

In the ground-air environment, the operating environmental factors have a number of characteristic features: higher light intensity compared to other environments, significant temperature fluctuations, changes in humidity depending on the geographical location, season and time of day (Table 5.3).

Table 5.3

Habitat conditions for air and water organisms

(according to D.F. Mordukhai-Boltovsky, 1974)

Conditions a habitat	The importance of conditions for organisms
Conditions a habitat	air environment	aquatic environment
Humidity	Very important (often in short supply)	Does not have (always in excess)
Density	Minor (except for soil)	Large compared to its role for the inhabitants of the air
Pressure	Almost none	Large (can reach 1000 atmospheres)
Temperature	Significant (varies within very wide limits (from -80 to +100 °C and more)	Less than the value for the inhabitants of the air (varies much less, usually from -2 to +40°C)
Oxygen	Non-essential (mostly in excess)	Essential (often in short supply)
Weighted substances	Unimportant; not used for food (mainly minerals)	Important (food source, especially organic matter)
Dissolved substances in environment	To some extent (only relevant in soil solutions)	Important (certain quantities required)

The impact of the above factors is inextricably linked with the movement of air masses - wind. In the process of evolution, living organisms of the land-air environment have developed characteristic anatomical, morphological, physiological, behavioral and other adaptations. For example, organs have appeared that provide direct absorption of atmospheric oxygen during respiration (the lungs and trachea of animals, the stomata of plants). Skeletal formations (animal skeleton, mechanical and supporting tissues of plants) have received strong development, which support the body in conditions of low environmental density. Adaptations have been developed to protect against unfavorable factors, such as the periodicity and rhythm of life cycles, the complex structure of the integument, mechanisms of thermoregulation, etc. A close connection with the soil has formed (animal limbs, plant roots), the mobility of animals in search of food has developed, and air currents have appeared. seeds, fruits and pollen of plants, flying animals.

Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment of life.

Low air density determines its low lifting force and insignificant controversy. All inhabitants of the air are closely connected with the surface of the earth, which serves them for attachment and support. The density of the air does not provide high resistance to the body when moving along the surface of the earth, but it makes it difficult to move vertically. For most organisms, staying in the air is associated only with settling or searching for prey.

The low lifting force of air determines the maximum mass and size of terrestrial organisms. The largest animals on the surface of the earth are smaller than the giants of the aquatic environment. Large mammals (the size and mass of a modern whale) could not live on land, as they would be crushed by their own weight. Giant Mesozoic dinosaurs led a semi-aquatic lifestyle. Another example: tall, erect redwood plants (Sequoja sempervirens), reaching 100 m, have powerful supporting wood, while in the thalli of the giant brown algae Macrocystis, growing up to 50 m, the mechanical elements are only very weakly isolated in the core part of the thallus.

Low air density creates little resistance to movement. The ecological benefits of this property of the air environment were used by many land animals during evolution, acquiring the ability to fly. 75% of all species of land animals are capable of active flight. These are mostly insects and birds, but there are also mammals and reptiles. Land animals fly mainly with the help of muscular efforts. Some animals can glide using air currents.

Due to the mobility of air, which exists in the lower layers of the atmosphere, vertical and horizontal movement of air masses, passive flight of certain types of organisms is possible, developed anemochory - dispersal by air currents. Organisms passively transported by air currents are collectively called aeroplankton, by analogy with planktonic inhabitants of the aquatic environment. For passive flight along N.M. Chernova, A.M. Bylova (1988) organisms have special adaptations - small body size, an increase in its area due to outgrowths, strong dismemberment, a large relative surface of the wings, the use of a web, etc.

Anemochorous seeds and fruits of plants also have very small sizes (for example, fireweed seeds) or various wing-shaped (maple Acer pseudoplatanum) and parachute-shaped (dandelion Taraxacum officinale) appendages

Wind-pollinated plants have a number of adaptations that improve the aerodynamic properties of pollen. Their floral integument is usually reduced and the anthers are not protected from the wind in any way.

In the distribution of plants, animals and microorganisms main role vertical conventional air flows and weak winds play a role. Storms and hurricanes also have a significant environmental impact on terrestrial organisms. Quite often, strong winds, especially blowing in one direction, bend tree branches and trunks to the leeward side and cause the formation of flag-shaped crowns.

In areas where strong winds constantly blow, the species composition of small flying animals is usually poor, since they are not able to resist powerful air currents. Thus, a honey bee flies only when the wind force is up to 7 - 8 m/s, and aphids fly only when the wind is very weak, not exceeding 2.2 m/s. Animals in these places develop dense integuments that protect the body from cooling and loss of moisture. On oceanic islands with constant strong winds, birds and especially insects predominate, having lost the ability to fly, they lack wings, since those who are able to rise into the air are blown out to sea by the wind and die.

The wind causes a change in the intensity of transpiration in plants and is especially pronounced during dry winds, which dry out the air and can lead to the death of plants. The main ecological role of horizontal air movements (winds) is indirect and consists in strengthening or weakening the impact on terrestrial organisms of such important environmental factors as temperature and humidity. Winds increase the release of moisture and heat from animals and plants.

When there is wind, heat is easier to bear and frost is more difficult, and desiccation and cooling of organisms occurs faster.

Terrestrial organisms exist in conditions of relatively low pressure, which is caused by low air density. In general, terrestrial organisms are more stenobatic than aquatic ones, because normal pressure fluctuations in their environment amount to fractions of the atmosphere, and for those that rise to high altitudes, for example, birds, do not exceed 1/3 of normal.

Gas composition of air, as already discussed earlier, in the ground layer of the atmosphere it is quite homogeneous (oxygen - 20.9%, nitrogen - 78.1%, m.g. gases - 1%, carbon dioxide - 0.03% by volume) due to its high diffusion ability and constant mixing by convection and wind currents. At the same time, various impurities of gaseous, droplet-liquid, dust (solid) particles entering the atmosphere from local sources often have significant environmental significance.

Oxygen, due to its constantly high content in the air, is not a factor limiting life in the terrestrial environment. The high oxygen content contributed to an increase in metabolism in terrestrial organisms, and animal homeothermy arose on the basis of the high efficiency of oxidative processes. Only in places, under specific conditions, is a temporary oxygen deficiency created, for example, in decomposing plant debris, grain reserves, flour, etc.

In certain areas of the surface air layer, the carbon dioxide content can vary within fairly significant limits. Thus, in the absence of wind in large industrial centers and cities, its concentration can increase tenfold.

There are regular daily changes in the content of carbon dioxide in the ground layers, determined by the rhythm of plant photosynthesis (Fig. 5.17).

Rice. 5.17. Daily changes in the vertical profile

CO 2 concentrations in forest air (from W. Larcher, 1978)

Using the example of daily changes in the vertical profile of CO 2 concentration in forest air, it is shown that during the day, at the level of tree crowns, carbon dioxide is spent on photosynthesis, and in the absence of wind, a zone poor in CO 2 (305 ppm) is formed here, into which CO comes from the atmosphere and soil (soil respiration). At night, a stable air stratification is established with an increased concentration of CO 2 in the soil layer. Seasonal fluctuations in carbon dioxide are associated with changes in the respiration rate of living organisms, mostly soil microorganisms.

In high concentrations, carbon dioxide is toxic, but such concentrations are rare in nature. Low CO 2 content inhibits the process of photosynthesis. To increase the rate of photosynthesis in the practice of greenhouse and greenhouse farming (in closed ground conditions), the concentration of carbon dioxide is often artificially increased.

For most inhabitants of the terrestrial environment, air nitrogen is an inert gas, but microorganisms such as nodule bacteria, azotobacteria, and clostridia have the ability to bind it and involve it in the biological cycle.

The main modern source of physical and chemical pollution The atmosphere is anthropogenic: industrial and transport enterprises, soil erosion, etc. Thus, sulfur dioxide is toxic to plants in concentrations from one fifty-thousandth to one millionth of the volume of air. Lichens die when there are traces of sulfur dioxide in the environment. Therefore, plants that are particularly sensitive to SO 2 are often used as indicators of its content in the air. Common spruce and pine, maple, linden, and birch are sensitive to smoke.

Light mode. The amount of radiation reaching the Earth's surface is determined by the geographic latitude of the area, the length of the day, the transparency of the atmosphere and the angle of incidence of the sun's rays. Under different weather conditions, 42 - 70% of the solar constant reaches the Earth's surface. Passing through the atmosphere, solar radiation undergoes a number of changes not only in quantity, but also in composition. Short-wave radiation is absorbed by the ozone shield and oxygen in the air. Infrared rays are absorbed in the atmosphere by water vapor and carbon dioxide. The rest reaches the Earth's surface in the form of direct or diffuse radiation.

The combination of direct and diffuse solar radiation makes up from 7 to 7„ of the total radiation, while on cloudy days the diffuse radiation is 100%. At high latitudes, diffuse radiation predominates, while in the tropics, direct radiation predominates. Scattered radiation contains up to 80% of yellow-red rays at noon, direct radiation - from 30 to 40%. On clear sunny days, solar radiation reaching the Earth's surface consists of 45% visible light (380 - 720 nm) and 45% infrared radiation. Only 10% comes from ultraviolet radiation. The radiation regime is significantly influenced by atmospheric dust. Due to its pollution, in some cities the illumination may be 15% or less of the illumination outside the city.

Illumination on the Earth's surface varies widely. It all depends on the height of the Sun above the horizon or the angle of incidence of the sun’s rays, the length of the day and weather conditions, and the transparency of the atmosphere (Fig. 5.18).

Rice. 5.18. Distribution of solar radiation depending on

height of the Sun above the horizon (A 1 - high, A 2 - low)

Depending on the season and time of day, the light intensity also fluctuates. In certain regions of the Earth, the quality of light is also unequal, for example, the ratio of long-wave (red) and short-wave (blue and ultraviolet) rays. Short-wave rays are known to be absorbed and scattered by the atmosphere more than long-wave rays. In mountainous areas there is therefore always more short-wave solar radiation.

Trees, shrubs, and plant crops shade the area and create a special microclimate, weakening radiation (Fig. 5.19).

Rice. 5.19. Radiation attenuation:

A - in a rare pine forest; B - in corn crops Of the incoming photosynthetically active radiation, 6-12% is reflected (R) from the surface of the planting

Thus, in different habitats, not only the intensity of radiation differs, but also its spectral composition, the duration of illumination of plants, the spatial and temporal distribution of light of different intensities, etc. Accordingly, the adaptations of organisms to life in a terrestrial environment under one or another light regime are also varied. . As we noted earlier, in relation to light there are three main groups of plants: light-loving(heliophytes), shade-loving(sciophytes) and shade-tolerant. Light-loving and shade-loving plants differ in the position of their ecological optimum.

In light-loving plants it is located in the area of full sunlight. Strong shading has a depressing effect on them. These are plants of open areas of land or well-lit steppe and meadow grasses (the upper tier of the grass stand), rock lichens, early spring herbaceous plants of deciduous forests, most cultivated plants of open ground and weeds, etc. Shade-loving plants have an optimum in the area of low light and cannot tolerate strong light. These are mainly the lower shaded layers of complex plant communities, where shading is the result of the “interception” of light by taller plants and co-inhabitants. This includes many indoor and greenhouse plants. For the most part they come from the herbaceous cover or epiphytic flora of tropical forests.

The ecological curve of the relationship to light in shade-tolerant plants is somewhat asymmetrical, since they grow and develop better in full light, but adapt well to low light. They are a common and highly flexible group of plants in terrestrial environments.

Plants in the terrestrial-air environment have developed adaptations to various light conditions: anatomical-morphological, physiological, etc.

A clear example of anatomical and morphological adaptations is a change in external appearance in different light conditions, for example, the unequal size of leaf blades in plants related in systematic position, but living in different lighting (meadow bell - Campanula patula and forest - C. trachelium, field violet - Viola arvensis, growing in fields, meadows, forest edges, and forest violets - V. mirabilis), fig. 5.20.

Rice. 5.20. Distribution of leaf sizes depending on conditions

plant habitats: from wet to dry and from shaded to sunny

Note. The shaded area corresponds to conditions prevailing in nature

Under conditions of excess and lack of light, the spatial arrangement of leaf blades in plants varies significantly. In heliophyte plants, the leaves are oriented to reduce the influx of radiation during the most “dangerous” daytime hours. The leaf blades are located vertically or at a large angle to the horizontal plane, so during the day the leaves receive mostly sliding rays (Fig. 5.21).

This is especially pronounced in many steppe plants. An interesting adaptation to the weakening of the received radiation is in the so-called “compass” plants (wild lettuce - Lactuca serriola, etc.). The leaves of wild lettuce are located in the same plane, oriented from north to south, and at noon the arrival of radiation to the leaf surface is minimal.

In shade-tolerant plants, the leaves are arranged so as to receive the maximum amount of incident radiation.

Rice. 5.21. Receipt of direct (S) and diffuse (D) solar radiation to plants with horizontal (A), vertical (B) and differently oriented (C) leaves (according to I. A. Shulgin, 1967)

1,2 - leaves with different angles of inclination; S 1, S 2 - direct radiation reaching them; Stot - its total intake to the plant

Often, shade-tolerant plants are capable of protective movements: changing the position of leaf blades when exposed to strong light. Areas of grass cover with folded oxalis leaves coincide relatively precisely with the location of large sun flares. A number of adaptive features can be noted in the structure of the leaf as the main receiver of solar radiation. For example, in many heliophytes, the leaf surface helps to reflect sunlight (shiny - in laurel, covered with a light hairy coating - in cactus, euphorbia) or weaken their effect (thick cuticle, dense pubescence). The internal structure of the leaf is characterized by the powerful development of palisade tissue and the presence of a large number of small and light chloroplasts (Fig. 5.22).

One of the protective reactions of chloroplasts to excess light is their ability to change orientation and move within the cell, which is clearly expressed in light plants.

In bright light, chloroplasts occupy a wall position in the cell and become an “edge” towards the direction of the rays. In low light, they are distributed diffusely in the cell or accumulate in its lower part.

Rice. 5.22. Different sizes of chloroplasts in shade-tolerant plants

(A) and light-loving (B) plants:

1 - yew; 2- larch; 3 - hoof; 4 - spring clearweed (According to T.K. Goryshina, E.G. Spring, 1978)

Physiological adaptations plants to the light conditions of the ground-air environment cover various vital functions. It has been established that in light-loving plants, growth processes react more sensitively to a lack of light compared to shady plants. As a result, there is an increased elongation of stems, which helps plants break through to the light and into the upper tiers of plant communities.

The main physiological adaptations to light lie in the area of photosynthesis. In general terms, the change in photosynthesis depending on light intensity is expressed by the “photosynthesis light curve.” Its following parameters are of ecological importance (Fig. 5.23).

1. The point of intersection of the curve with the ordinate axis (Fig. 5.23, A) corresponds to the magnitude and direction of gas exchange in plants in complete darkness: photosynthesis is absent, respiration takes place (not absorption, but release of CO 2), therefore point a lies below the x-axis.

2. The point of intersection of the light curve with the abscissa axis (Fig. 5.23, b) characterizes the “compensation point,” i.e., the light intensity at which photosynthesis (CO 2 absorption) balances respiration (CO 2 release).

3. The intensity of photosynthesis with increasing light increases only up to a certain limit, then remains constant - the light curve of photosynthesis reaches a “saturation plateau”.

Rice. 5.23. Photosynthesis light curves:

A - general diagram; B - curves for light-loving (1) and shade-tolerant (2) plants

In Fig. 5.23 the inflection area is conventionally designated by a smooth curve, the break of which corresponds to a point V. The projection of point c onto the x-axis (point d) characterizes the “saturated” light intensity, i.e., the value above which light no longer increases the intensity of photosynthesis. Projection onto the ordinate axis (point d) corresponds to the highest intensity of photosynthesis for a given species in a given ground-air environment.

4. An important characteristic of the light curve is the angle of inclination (a) to the abscissa, which reflects the degree of increase in photosynthesis with increasing radiation (in the region of relatively low light intensity).

Plants exhibit seasonal dynamics in their response to light. Thus, in the hairy sedge (Carex pilosa), in early spring in the forest, the newly emerged leaves have a plateau of light saturation of photosynthesis at 20 - 25 thousand lux; with summer shading in these same species, the curves of the dependence of photosynthesis on light become corresponding to the “shadow” parameters, t That is, the leaves acquire the ability to use weak light more efficiently, and these same leaves, after overwintering under the canopy of a leafless spring forest, again display the “light” features of photosynthesis.

A unique form of physiological adaptation during a sharp lack of light is the loss of the plant’s ability to photosynthesize and the transition to heterotrophic nutrition with ready-made organic substances. Sometimes such a transition became irreversible due to the loss of chlorophyll by plants, for example, shady orchids spruce forests(Goodyera repens, Weottia nidus avis), whirligig (Monotropa hypopitys). They live off dead organic matter obtained from trees and other plants. This method of nutrition is called saprophytic, and plants are called saprophytes.

For the vast majority of terrestrial animals with day and night activity, vision is one of the methods of orientation and is important for searching for prey. Many animal species also have color vision. In this regard, animals, especially victims, developed adaptive features. These include protective, camouflage and warning coloring, protective similarity, mimicry, etc. The appearance of brightly colored flowers of higher plants is also associated with the characteristics of the visual apparatus of pollinators and, ultimately, with the light regime of the environment.

Water mode. Moisture deficiency is one of the most significant features of the land-air environment of life. The evolution of terrestrial organisms took place through adaptation to obtaining and preserving moisture. The humidity regimes of the environment on land are varied - from complete and constant saturation of the air with water vapor, where several thousand millimeters of precipitation falls per year (regions of equatorial and monsoon-tropical climates) to their almost complete absence in the dry air of deserts. Thus, in tropical deserts the average annual precipitation is less than 100 mm per year, and at the same time, rain does not fall every year.

The annual amount of precipitation does not always make it possible to assess the water supply of organisms, since the same amount can characterize a desert climate (in the subtropics) and a very humid one (in the Arctic). An important role is played by the ratio of precipitation and evaporation (total annual evaporation from the free water surface), which also varies in different regions of the globe. Areas where this value exceeds the annual precipitation amount are called arid(dry, arid). Here, for example, plants experience lack of moisture during most of the growing season. Areas in which plants are provided with moisture are called humid, or wet. Transition zones are often identified - semi-arid(semiarid).

The dependence of vegetation on average annual precipitation and temperature is shown in Fig. 5.24.

Rice. 5.24. Dependence of vegetation on the average annual

precipitation and temperature:

1 - tropical forest; 2 - deciduous forest; 3 - steppe;

4 - desert; 5 - coniferous forest; 6 - arctic and mountain tundra

The water supply of terrestrial organisms depends on the precipitation regime, the presence of reservoirs, soil moisture reserves, the proximity of groundwater, etc. This has contributed to the development of many adaptations in terrestrial organisms to various water supply regimes.

In Fig. Figure 5.25 from left to right shows the transition from lower algae living in water with cells without vacuoles to primary poikilohydric terrestrial algae, the formation of vacuoles in aquatic green and charophytes, the transition from thallophytes with vacuoles to homoyohydric cormophytes (the distribution of mosses - hydrophytes is still limited to habitats with high air humidity , in dry habitats mosses become secondary poikilohydric); among ferns and angiosperms (but not among gymnosperms) there are also secondary poikilohydric forms. Most leafy plants are homoyohydric due to the presence of cuticular protection against transpiration and strong vacuolation of their cells. It should be noted that xerophilicity of animals and plants is characteristic only of the ground-air environment.

Rice. 5.25. Adaptation of plant water metabolism to terrestrial

way of life (from V. Larcher, 1978)

Precipitation (rain, hail, snow), in addition to providing water and creating moisture reserves, often plays another environmental role. For example, during heavy rains, the soil does not have time to absorb moisture, the water quickly flows in strong streams and often carries weakly rooted plants, small animals and fertile soil into lakes and rivers. In floodplains, rain can cause floods and thus have adverse effects on the plants and animals living there. In periodically flooded places, unique floodplain fauna and flora are formed.

Hail also has a negative effect on plants and animals. Agricultural crops in individual fields are sometimes completely destroyed by this natural disaster.

The ecological role of snow cover is diverse. For plants whose renewal buds are located in the soil or near its surface, and for many small animals, snow plays the role of a heat-insulating cover, protecting them from low winter temperatures. When frosts are above -14°C under a 20 cm layer of snow, the soil temperature does not fall below 0.2°C. Deep snow cover protects the green parts of plants from freezing, such as Veronica officinalis, hoofed grass, etc., which go under the snow without shedding their leaves. Small land animals lead an active lifestyle in winter, creating numerous galleries of passages under the snow and in its thickness. In the presence of fortified food, rodents (wood and yellow-throated mice, a number of voles, water rats, etc.) can breed there in snowy winters. During severe frosts, hazel grouse, partridges, and black grouse hide under the snow.

Winter snow cover often prevents large animals from obtaining food and moving, especially when an ice crust forms on the surface. Thus, moose (Alces alces) freely overcome a layer of snow up to 50 cm deep, but this is inaccessible to smaller animals. Often during snowy winters, the death of roe deer and wild boars is observed.

Large amounts of snow also have a negative impact on plants. In addition to mechanical damage in the form of snow chips or snow blowers, a thick layer of snow can lead to damping off of plants, and when the snow melts, especially in a long spring, to soaking of plants.

Plants and animals suffer from low temperatures and strong winds in winters with little snow. Thus, in years when there is little snow, mouse-like rodents, moles and other small animals die. At the same time, in latitudes where precipitation falls in the form of snow in winter, plants and animals have historically adapted to life in snow or on its surface, developing various anatomical, morphological, physiological, behavioral and other characteristics. For example, in some animals the supporting surface of their legs increases in winter by overgrowing them with coarse hair (Fig. 5.26), feathers, and horny scutes.

Others migrate or fall into an inactive state - sleep, hibernation, diapause. A number of animals switch to feeding on certain types of feed.

The whiteness of the snow cover reveals dark animals. The seasonal change in color in the ptarmigan and tundra partridge, ermine (Fig. 5.27), mountain hare, weasel, and arctic fox is undoubtedly associated with selection for camouflage to match the background color.

Precipitation, in addition to its direct impact on organisms, determines one or another air humidity, which, as already noted, plays an important role in the life of plants and animals, as it affects the intensity of their water metabolism. Evaporation from the surface of the body of animals and transpiration in plants are more intense, the less the air is saturated with water vapor.

Absorption by the above-ground parts of droplet-liquid moisture falling in the form of rain, as well as vaporous moisture from the air, in higher plants is found in epiphytes of tropical forests, which absorb moisture over the entire surface of the leaves and aerial roots. The branches of some shrubs and trees, for example saxauls - Halaxylon persicum, H. aphyllum, can absorb vaporous moisture from the air. In higher spore plants and especially lower plants, the absorption of moisture by above-ground parts is a common method of water nutrition (mosses, lichens, etc.). With a lack of moisture, mosses and lichens are able to survive for a long time in a state close to air-dry, falling into suspended animation. But as soon as it rains, these plants quickly absorb moisture with all ground parts, acquire softness, restore turgor, and resume the processes of photosynthesis and growth.

In plants in highly humid terrestrial habitats, there is often a need to remove excess moisture. As a rule, this happens when the soil is well warmed up and the roots actively absorb water, and there is no transpiration (in the morning or during fog, when the air humidity is 100%).

Excess moisture is removed by guttation - this is the release of water through special excretory cells located along the edge or at the tip of the leaf (Fig. 5.28).

Rice. 5.28. Types of guttation in different plants

(according to A.M. Grodzinsky, 1965):

1 - for cereals, 2 - for strawberries, 3 - for tulips, 4 - for milkweeds,

5 - in Bellevalia Sarmatian, 6 - in clover

Not only hygrophytes, but also many mesophytes are capable of guttation. For example, in the Ukrainian steppes, guttation was found in more than half of all plant species. Many meadow grasses humidify so much that they wet the soil surface. This is how animals and plants adapt to the seasonal distribution of precipitation, its quantity and nature. This determines the composition of plants and animals, the timing of certain phases in their development cycle.

Humidity is also affected by the condensation of water vapor, which often occurs in the surface layer of air when the temperature changes. Dew appears when the temperature drops in the evening. Often dew falls in such quantities that it abundantly wets plants, flows into the soil, increases air humidity and creates favorable conditions for living organisms, especially when there is little other precipitation. Plants contribute to the deposition of dew. Cooling at night, they condense water vapor on themselves. The humidity regime is significantly affected by fogs, thick clouds and other natural phenomena.

When quantitatively characterizing the plant habitat based on the water factor, indicators are used that reflect the content and distribution of moisture not only in the air, but also in the soil. Soil water, or soil moisture, is one of the main sources of moisture for plants. Water in the soil is in a fragmented state, interspersed with pores of different sizes and shapes, has a large interface with the soil, and contains a number of cations and anions. Hence, soil moisture is heterogeneous in physical and chemical properties. Not all the water contained in the soil can be used by plants. Based on its physical state, mobility, availability and importance for plants, soil water is divided into gravitational, hygroscopic and capillary.

The soil also contains vaporous moisture, which occupies all water-free pores. This is almost always (except in desert soils) saturated water vapor. When the temperature drops below 0°C, soil moisture turns into ice (initially free water, and with further cooling - part of the bound water).

The total amount of water that can be held by soil (determined by adding excess water and then waiting until it stops dripping out) is called field moisture capacity.

Consequently, the total amount of water in the soil cannot characterize the degree of moisture supply to plants. To determine it, it is necessary to subtract the wilting coefficient from the total amount of water. However, physically accessible soil water is not always physiologically available to plants due to low soil temperature, lack of oxygen in soil water and soil air, soil acidity, and high concentration of mineral salts dissolved in soil water. The discrepancy between the absorption of water by the roots and its release by the leaves leads to wilting of plants. The development of not only the above-ground parts, but also the root system of plants depends on the amount of physiologically available water. In plants growing on dry soils, the root system, as a rule, is more branched and more powerful than on wet soils (Fig. 5.29).

Rice. 5.29. Root system winter wheat

(according to V.G. Khrzhanovsky et al., 1994):

1 - at large quantities precipitation; 2 - at average;

3 - at low

One of the sources of soil moisture is groundwater. When their level is low, capillary water does not reach the soil and does not affect its water regime. Moistening the soil due to precipitation alone causes strong fluctuations in its humidity, which often negatively affects plants. It has a harmful effect and is too high level groundwater, because this leads to waterlogging of the soil, depletion of oxygen and enrichment in mineral salts. Constant soil moisture, regardless of the vagaries of the weather, ensures an optimal groundwater level.

Temperature regime. A distinctive feature of the land-air environment is the large range of temperature fluctuations. In most land areas, daily and annual temperature ranges are tens of degrees. Changes in air temperature are especially significant in deserts and subpolar continental regions. For example, the seasonal temperature range in deserts Central Asia 68-77°C, and daily 25-38°C. In the vicinity of Yakutsk, the average January temperature is 43°C, the average July temperature is +19°C, and the annual range is from -64 to +35°C. In Trans-Urals annual course air temperatures are sharp and combined with great variability in temperatures of the winter and spring months in different years. The coldest month is January, the average air temperature ranges from -16 to -19°C, in some years it drops to -50°C, the warmest month is July with temperatures from 17.2 to 19.5°C. Maximum positive temperatures are 38-41°C.

Temperature fluctuations at the soil surface are even more significant.

Terrestrial plants occupy a zone adjacent to the soil surface, i.e., to the “interface”, on which the transition of incident rays from one medium to another or in another way - from transparent to opaque. A special thermal regime is created on this surface: during the day there is strong heating due to the absorption of heat rays, at night there is strong cooling due to radiation. From here, the ground layer of air experiences the sharpest daily temperature fluctuations, which are most pronounced over bare soil.

The thermal regime of plant habitats, for example, is characterized based on temperature measurements directly in the vegetation cover. In herbaceous communities, measurements are taken inside and on the surface of the grass stand, and in forests, where there is a certain vertical temperature gradient, at a number of points at different heights.

Resistance to temperature changes in the environment in terrestrial organisms varies and depends on the specific habitat where their life takes place. Thus, terrestrial leafy plants for the most part grow in a wide temperature range, that is, they are eurythermic. Their life span in the active state extends, as a rule, from 5 to 55°C, while these plants are productive between 5 and 40°C. Plants of continental regions, which are characterized by a clear diurnal temperature variation, develop best when the night is 10-15 ° C colder than the day. This applies to most plants in the temperate zone - with a temperature difference of 5-10 ° C, and tropical plants with an even smaller amplitude - about 3 ° C (Fig. 5.30).

Rice. 5.30. Areas of optimal temperatures for growth and

development of various plants (after Went, 1957)

In poikilothermic organisms, with increasing temperature (T), the duration of development (t) decreases more and more rapidly. The development rate Vt can be expressed by the formula Vt = 100/t.

To reach a certain stage of development (for example, in insects - from an egg), i.e. pupation, the imaginal stage, always requires a certain amount of temperature. The product of effective temperature (temperature above the zero point of development, i.e. T-To) by the duration of development (t) gives a species-specific thermal constant development c=t(T-To). Using this equation, you can calculate the time of onset of a certain stage of development, for example, of a plant pest, at which its control is effective.

Plants, as poikilothermic organisms, do not have their own stable body temperature. Their temperature is determined by the thermal balance, i.e., the ratio of energy absorption and release. These values depend on many properties of both the environment (the size of the radiation arrival, the temperature of the surrounding air and its movement) and the plants themselves (color and other optical properties plants, size and arrangement of leaves, etc.). The primary role is played by the cooling effect of transpiration, which prevents severe overheating of plants in hot habitats. As a result of the above reasons, the temperature of plants usually differs (often quite significantly) from the ambient temperature. There are three possible situations here: the plant temperature is higher than the ambient temperature, lower than it, equal to or very close to it. The excess of plant temperature over air temperature occurs not only in highly heated, but also in colder habitats. This is facilitated by the dark color or other optical properties of plants, which increase the absorption of solar radiation, as well as anatomical and morphological features that help reduce transpiration. Arctic plants can warm up quite noticeably (Fig. 5.31).

Another example is the dwarf willow - Salix arctica in Alaska, whose leaves are 2-11 °C warmer than the air during the day and even at night during the polar “24-hour day” - by 1-3 °C.

For early spring ephemeroids, the so-called “snowdrops,” heating of the leaves provides the opportunity for fairly intense photosynthesis on sunny but still cold spring days. For cold habitats or those associated with seasonal temperature fluctuations, an increase in plant temperature is ecologically very important, since physiological processes thereby become independent, to a certain extent, from the surrounding thermal background.

Rice. 5.31. Temperature distribution in a rosette plant of the Arctic tundra (Novosieversia glacialis) on a sunny June morning at an air temperature of 11.7 ° C (according to B. A. Tikhomirov, 1963)

On the right is the intensity of life processes in the biosphere: 1 - the coldest layer of air; 2 - upper limit of shoot growth; 3, 4, 5 - zone of greatest activity of life processes and maximum accumulation of organic matter; 6 - permafrost level and lower rooting limit; 7 - area of lowest soil temperatures

A decrease in the temperature of plants compared to the surrounding air is most often observed in highly illuminated and heated areas of the terrestrial sphere (desert, steppe), where the leaf surface of plants is greatly reduced, and increased transpiration helps remove excess heat and prevents overheating. In general terms, we can say that in hot habitats the temperature of the above-ground parts of plants is lower, and in cold habitats it is higher than the air temperature. The coincidence of plant temperature with the ambient air temperature is less common - in conditions that exclude a strong influx of radiation and intense transpiration, for example, in herbaceous plants under the canopy of forests, and in open areas - in cloudy weather or during rain.

In general, terrestrial organisms are more eurythermic than aquatic ones.

In the ground-air environment, living conditions are complicated by the existence weather changes. Weather is the continuously changing state of the atmosphere at the earth's surface, up to approximately an altitude of 20 km (the boundary of the troposphere). Weather variability is manifested in the constant variation of the combination of environmental factors such as temperature and humidity, cloudiness, precipitation, wind strength and direction, etc. (Fig. 5.32).

Rice. 5.32. Atmospheric fronts over the territory of Russia

Weather changes, along with their regular alternation in the annual cycle, are characterized by non-periodic fluctuations, which significantly complicate the conditions for the existence of terrestrial organisms. In Fig. Figure 5.33 uses the example of the codling moth caterpillar Carpocapsa pomonella to show the dependence of mortality on temperature and relative humidity.

Rice. 5.33. Mortality of codling moth caterpillars Carpocapsa

pomonella depending on temperature and humidity (according to R. Dazho, 1975)

It follows from this that equal mortality curves have a concentric shape and that the optimal zone is limited by relative humidity of 55 and 95% and temperature of 21 and 28 ° C.

Light, temperature and air humidity usually determine not the maximum, but the average degree of opening of stomata in plants, since the coincidence of all conditions promoting their opening rarely happens.

The long-term weather regime characterizes climate of the area. The concept of climate includes not only the average values of meteorological phenomena, but also their annual and daily variations, deviations from them, and their frequency. The climate is determined by the geographical conditions of the area.

The main climatic factors are temperature and humidity, measured by precipitation and water vapor saturation in the air. Thus, in countries remote from the sea, there is a gradual transition from a humid climate through a semiarid intermediate zone with occasional or periodic dry periods to an arid territory, which is characterized by prolonged drought, salinization of soil and water (Fig. 5.34).

Rice. 5.34. Scheme of changes in climate, vegetation and soils along the profile through the main landscapes of the European part of Russia from northwest to southeast to the Caspian lowland (according to V.N. Sukachev, 1934)

Note: where the precipitation curve intersects the ascending evapotranspiration line, the boundary between humid (left) and arid (right) climates is located. The humus horizon is shown in black, the illuvial horizon is shown in shading.

Each habitat is characterized by a certain ecological climate, i.e., the climate of the ground layer of air, or ecoclimate.

Vegetation has a great influence on climatic factors. Thus, under the forest canopy, air humidity is always higher, and temperature fluctuations are less than in the clearings. The light regime of these places is also different. Different plant associations form their own regime of light, temperature, humidity, i.e. phytoclimate.

Ecoclimate or phytoclimate data are not always sufficient to fully characterize the climatic conditions of a particular habitat. Local elements environments (relief, exposure, vegetation, etc.) very often change the regime of light, temperature, humidity, air movement in a particular area in such a way that it can differ significantly from the climatic conditions of the area. Local climate modifications that develop in the surface layer of air are called microclimate. For example, the living conditions surrounding insect larvae living under the bark of a tree are different than in the forest where the tree grows. The temperature of the southern side of the trunk can be 10 - 15°C higher than the temperature of its northern side. Burrows, tree hollows, and caves inhabited by animals have a stable microclimate. There are no clear differences between ecoclimate and microclimate. It is believed that ecoclimate is the climate of large areas, and microclimate is the climate of individual small areas. Microclimate influences living organisms of a particular territory or locality (Fig. 5.35).

Rice. 5.35. The influence of microclimate on vegetation in the tundra

(according to Yu. I. Chernov, 1979):

at the top is a well-warmed slope of southern exposure;

below - a horizontal section of the plakor (the floristic composition in both sections is the same)

The presence of many microclimates in one area ensures the coexistence of species with different requirements for the external environment.

Geographical zonality and zonality. The distribution of living organisms on Earth is closely related to geographic zones and zones. The belts have a latitudinal extension, which, naturally, is primarily due to radiation boundaries and the nature of atmospheric circulation. On the surface of the globe there are 13 geographical zones, which are distributed on continents and oceans (Fig. 5.36).

Rice. 5.36. The ratio of land areas occupied by different

physical-geographical zones, in% (according to N.F. Reimers, 1990)

These are like arctic, antarctic, subarctic, subantarctic, north and south moderate, north and south subarctic, north and south tropical, north and south subequatorial And equatorial. Inside the belts there are geographical zones, where, along with radiation conditions, the moisture of the earth's surface and the ratio of heat and moisture characteristic of a given zone are taken into account. Unlike the ocean, where the supply of moisture is complete, on the continents the ratio of heat and moisture can have significant differences. From here, geographic zones extend to continents and oceans, and geographic zones extend only to continents. Distinguish latitudinal And meridial or longitudinal natural areas. The former stretch from west to east, the latter - from north to south. In the longitudinal direction, latitudinal zones are divided into subzones, and in the latitude - on provinces.

The founder of the doctrine of natural zonality is V.V. Dokuchaev (1846-1903), who substantiated zonality as a universal law of nature. All phenomena within the biosphere are subject to this law. The main reasons for zonation are the shape of the Earth and its position relative to the sun. In addition to latitude, the distribution of heat on Earth is influenced by the nature of the relief and the height of the area above sea level, the ratio of land and sea, sea currents, etc.

Subsequently, the radiation foundations for the formation of zonality of the globe were developed by A. A. Grigoriev and M. I. Budyko. To establish a quantitative characteristic of the relationship between heat and moisture for various geographical zones, they determined some coefficients. The ratio of heat and moisture is expressed by the ratio of the surface radiation balance to the latent heat of evaporation and the amount of precipitation (radiation dryness index). A law was established, called the law of periodic geographical zoning (A. A. Grigorieva - M. I. Budyko), which states: that with the change of geographical zones, similar geographical(landscape, natural) zones and some of their general properties are repeated periodically.

Each zone is confined to a certain range of indicator values: a special nature of geomorphological processes, a special type of climate, vegetation, soil and animal life. In the territory former USSR The following geographical zones were noted: icy, tundra, forest-tundra, taiga, mixed forests. Russian plain, monsoon mixed forests Far East, forest-steppes, steppes, semi-deserts, temperate deserts, deserts subtropical zone, Mediterranean and humid subtropics.

One of important conditions the variability of organisms and their zonal distribution on earth is variability chemical composition environment. In this regard, the teaching of A.P. Vinogradov about biogeochemical provinces, which are determined by the zonality of the chemical composition of soils, as well as the climatic, phytogeographical and geochemical zonality of the biosphere. Biogeochemical provinces are areas on the Earth's surface that differ in content (in soils, waters, etc.) chemical compounds, which are associated with certain biological reactions on the part of the local flora and fauna.

Along with horizontal zoning in the terrestrial environment, high-rise or vertical zonality.

The vegetation of mountainous countries is richer than on the adjacent plains, and is characterized by an increased distribution of endemic forms. Thus, according to O. E. Agakhanyants (1986), the flora of the Caucasus includes 6,350 species, of which 25% are endemic. The flora of the mountains of Central Asia is estimated at 5,500 species, of which 25-30% are endemic, while on the adjacent plains of the southern deserts there are 200 plant species.

When climbing into the mountains, the same change of zones is repeated as from the equator to the poles. At the foot there are usually deserts, then steppes, deciduous forests, coniferous forests, tundra and, finally, ice. However, there is still no complete analogy. As you climb the mountains, the air temperature decreases (the average air temperature gradient is 0.6 °C per 100 m), evaporation decreases, ultraviolet radiation and illumination increase, etc. All this forces plants to adapt to dry or wet conditions. The dominant plants here are cushion-shaped life forms and perennials, which have developed adaptation to strong ultraviolet radiation and reduced transpiration.

Peculiar and animal world high mountain areas. Low air pressure, significant solar radiation, sharp fluctuations in day and night temperatures, and changes in air humidity with altitude contributed to the development of specific physiological adaptations in the body of mountain animals. For example, in animals the relative volume of the heart increases, the content of hemoglobin in the blood increases, which allows more intensive absorption of oxygen from the air. Rocky soil complicates or almost eliminates the burrowing activity of animals. Many small animals (small rodents, pikas, lizards, etc.) find refuge in rock crevices and caves. Among the birds typical for mountainous regions are mountain turkeys (sulars), mountain finches, larks, and large birds - bearded vultures, vultures, and condors. Large mammals in the mountains are inhabited by rams, goats (including snowbucks), chamois, yaks, etc. Predators are represented by species such as wolves, foxes, bears, lynxes, snow leopards (irbis), etc.

Lecture 3 HABITAT AND THEIR CHARACTERISTICS (2 hours)

1.Aquatic habitat

2. Ground-air habitat

3. Soil as a habitat

4.Organism as a habitat

In progress 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

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) - 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 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).

Benthos(benthos – depth) – bottom hydrobionts. 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 zones, 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).

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 an altitude gradient than on land.

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 (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 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 (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. comes homothermy. 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 (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.

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.

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 rapid development small organisms in the summer, and in temperate and northern latitudes - also in the winter, after the establishment of ice cover and covering it 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). 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). For deep-sea algae, strongly dissected leaves are typical, the leaf blades are thin and translucent. 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.

Heterophylly: egg capsules, water lilies, arrow leaf, chilim (water chestnut).

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.

The characteristic properties of the aquatic environment, different from land, are high density, mobility, acidity, and the ability to dissolve gases and salts. For all these conditions, hydrobionts have historically developed appropriate adaptations.

2. Ground-air habitat

In the course of evolution, this environment was developed later than the aquatic environment. Its peculiarity is that it is gaseous, therefore it is characterized by low humidity, density and pressure, and high oxygen content. In the course of evolution, living organisms have developed the necessary anatomical, morphological, physiological, behavioral and other adaptations.

Animals in the ground-air environment move on the soil or through the air (birds, insects), and plants take root in the soil. In this regard, animals developed lungs and trachea, and plants developed a stomatal apparatus, i.e. organs with which the land inhabitants of the planet absorb oxygen directly from the air. Skeletal organs have developed strongly, ensuring autonomy of movement on land and supporting the body with all its organs in conditions of insignificant environmental density, thousands of times less than water. Environmental factors in the ground-air environment they differ from other habitats by high light intensity, significant fluctuations in temperature and air humidity, the correlation of all factors with geographic location, changing seasons and time of day. Their effects on organisms are inextricably linked with air movement and position relative to the seas and oceans and are very different from the effects in the aquatic environment (Table 1).

Habitat conditions for air and water organisms

(according to D.F. Mordukhai-Boltovsky, 1974)

air environment

aquatic environment

Humidity	Very important (often in short supply)	Does not have (always in excess)
Density	Minor (except for soil)	Large compared to its role for the inhabitants of the air
Pressure	Almost none	Large (can reach 1000 atmospheres)
Temperature	Significant (varies within very wide limits - from -80 to +1ОО°С and more)	Less than the value for the inhabitants of the air (varies much less, usually from -2 to +40°C)
Oxygen	Non-essential (mostly in excess)	Essential (often in short supply)
Suspended solids	Unimportant; not used for food (mainly minerals)	Important (food source, especially organic matter)
Dissolved substances in the environment	To some extent (only relevant in soil solutions)	Important (certain quantities required)

Land animals and plants have developed their own, no less original adaptations to unfavorable environmental factors: the complex structure of the body and its integument, the periodicity and rhythm of life cycles, thermoregulation mechanisms, etc. Targeted mobility of animals in search of food has developed, wind-borne spores, seeds and pollen, as well as plants and animals whose life is entirely connected with the air. An exceptionally close functional, resource and mechanical relationship with the soil has been formed.

Many of the adaptations were discussed above as examples in characterizing abiotic environmental factors. Therefore, there is no point in repeating ourselves now, since we will return to them in practical classes.