The main biomes of the world. Major types of terrestrial biomes Temperate broadleaf forests

Aquatic biomes are habitats throughout the world, from tropical aquatic reefs and mangrove forests to arctic lakes. The aquatic biome occupies about 75% of the Earth's surface area, and is the largest of all biomes on the planet. Aquatic biomes provide a wide range of habitats, which in turn support staggering biodiversity.

The first life on our planet developed in ancient waters about 3.5 billion years ago. Although the specific aquatic habitats in which life originated remain unknown, scientists have suggested several potential locations: shallow tidal pools, hot springs, and deep-sea hydrothermal vents.

An aquatic biome is a three-dimensional habitat divided into distinct zones based on characteristics such as depth, tidal currents, water temperature, and proximity to continents. Besides, aquatic biomes can be divided into two main groups depending on the salinity of the water:

1. freshwater habitats;
2. marine habitats.

Other factors affecting the composition of the aquatic environment include the degree of light penetration under water. The top layer of water in which light penetrates enough to maintain is known as the photic zone. The water column in which there is too little light for photosynthesis is called the euphotic (or deep) zone.

The world's various aquatic habitats support a huge diversity of flora and fauna, including fish, invertebrates, amphibians, mammals, reptiles and birds. Some groups, such as echinoderms, coelenterates and fish, are exclusively aquatic inhabitants, with no terrestrial representatives.

Key Features

Below are the main characteristics of the aquatic biome:

• the largest of all biomes on the planet (about 75%);
• completely at the mercy of water;
• the first life originated in water;
• three-dimensional habitats, which are divided into zones depending on temperature, depth and distance from land, play a key role in shaping the world's climate.

Classification

> Aquatic biome

The aquatic biome is divided into the following habitats:

• Freshwater habitats are bodies of water with low salt content (less than 1%). Freshwater habitats are further divided into flowing bodies of water (such as rivers and streams) and standing bodies of water (such as lakes, ponds and wetlands). The biome of freshwater habitats is influenced by the soils of surrounding areas, local climate, structure and flow rate of water.
• Marine habitats are aquatic habitats with high salt content (more than 1%). Marine biomes include coral reefs, oceans, and seas. There are also mixed habitats where fresh and salt waters meet, which are home to mangroves. Marine habitats are often divided into five zones: 1) intertidal; 2) neritic; 3) pelagic; 4) abyssal; 5) benthal.

Animal world

Some of the animals that live in the aquatic biome are:

• Clown fish (Amphiprion) - sea ​​fish, living among the tentacles of sea anemones. Clownfish have a layer of mucus that protects them from the stinging cells of sea anemones. But other fish species (including those that feed on clownfish) do not have such protection. Thus, sea anemones protect them from predators. In turn, clownfish drive away fish that feed on sea anemones.
• Pharaoh cuttlefish (Sepia pharaonis)- a representative of the cephalopod class, inhabiting the coral reefs of the Red Sea and the Indian Ocean. The pharaoh cuttlefish has eight arms and two long tentacles. There is no outer shell, but there is an inner shell.
• Acropora staghorn, or staghorn coral (Acropora cervicornis)- a group of corals that includes about 400 species. Members of this group live on coral reefs around the world. Staghorn corals are fast-growing reef-building corals that form colonies various forms and sizes.
• Pygmy seahorse (Hippocampus zosterae)- a miniature species of seahorse that has a body length of about 2 cm. Pygmy seahorses live among aquatic vegetation on the bottom of the Gulf of Mexico and the waters around the archipelagoes of the Florida Keys, Bahamas and Bermuda. They use their long tails to cling to seaweed while they feed on tiny plankton drifting through the water.
• Great white shark (Carcharodon carcharias)- huge predatory fish, reaching more than 4.5 m in length. They are skilled hunters who have several hundred jagged, triangular teeth growing in several rows. Great white sharks live in warm coastal waters around the world.
• Loggerhead (Caretta Caretta)- a sea turtle that lives in the Atlantic, Pacific and Indian oceans, as well as the Mediterranean Sea. The loggerhead is an endangered species, largely due to fishing nets, in which turtles become entangled and die. This is the view sea ​​turtles Spends most of its life in water, venturing onto land only to lay eggs.
• Blue whale, or blue whale (Balaenoptera Musculus)- the largest animal that ever lived on Earth (maximum weight about 200 tons; length up to 33 m). The blue whale belongs to the suborder of baleen whales - group marine mammals, which have a set of plates in their mouths called “baleen” that filter tiny plankton from the water.

Question 1. How can we explain the differences in flora and fauna of different continents?
Differences in the flora and fauna of the continents are explained by:
1) geological history of the continents;
2) differences in climatic conditions;
3) isolation of continents from each other.

Question 2. What are the reasons for the identification of separate biogeographic regions on Earth?
Biome- a large biosystem consisting of several ecosystems (biogeocenoses) of one natural climatic zone and is characterized by some dominant type of vegetation or other landscape feature.
The following biomes exist on Earth: temperate forests (deciduous forests), steppes, deserts, coniferous forests (taiga), tundra, savannas, tropical rain forests.
The main factor determining the type of biome is climate, since the nature of the environment is created mainly by temperature, amount of precipitation, and the direction and strength of the winds. Taking into account the kinship of species inhabiting certain territories, the following biogeographic areas are currently distinguished:
1. Holarctic (North America with Greenland, Eurasia without India, Iceland, Korea, Japan and North Africa).
2. Paleotropical (sub-Saharan Africa, Madagascar, India and Indochina).
3. Australian (Australia, New Guinea, New Zealand, Oceania).
4. Neotropical (South and Central America).
5. Antarctic (Antarctica).

Question 3: Describe the major land biomes of different biogeographic regions.
Tundra of the Nearctic and Palearctic regions: low-growing vegetation - mosses, lichens, sedges, stunted shrubs. The main animals are deer, musk ox, lemming, arctic hare, arctic fox, wolf, white polar bear, white owl.
Coniferous forests of the Nearctic region: mostly dense forests of spruce, fir and other coniferous trees. The main animals are elk, deer, porcupine, vole, shrew, wolverine, lynx, woodpecker, and hazel grouse. Coniferous forests of the Palearctic region: the tree species that make up these forests are pine, fir, spruce. They belong to the same genera as the corresponding Nearctic trees, but are distinct species. The same applies to animals - elk, wolverine, lynx.
Deciduous forests of the Nearctic and Palearctic: broad-leaved forests consist of trees with a dense crown - oak, beech, maple; many colors. The main animals are mole, gopher, black squirrel, raccoon, opossum, chipmunk, red fox, black bear, songbirds.
Hard-leaved forests of the Nearctic: thickets of juniper and bushes with leathery leaves. fauna representatives come from neighboring biomes. Palaearctic Hardwood Forests: The Mediterranean region is very similar to the corresponding Nearctic biome, supporting animals from a variety of neighboring communities.
Nearctic steppes: various combinations of grass and shrub vegetation. Main animals - bison, antelope, wild rabbit, American badger, fox, koi<5т, степной тетерев, большое количество гремучих змей. Палеарктические степи: травы примерно такие же, как в Неарктике. Типичные животные - сайгак и антилопа; дикие ослы, лошадь и верблюд, а также суслик, хомяк, тушканчик, куница, шакал.
Neotropical steppe (pampa): the vegetation cover is a mixture of various grasses. Animal world- rhea, Pampas deer, guinea pig, tuco-tuco, pampas cat, South American fox, skunk, swallow, paired owl.
Rainforest of the eastern region: an abundance of hundreds of plant species forming impenetrable thickets; typical plants are creepers, bamboo, manila hemp, teak, banyan and ebony. Animals: primates are widely represented - gibbons, orangutans, small relatives of monkeys; Also characteristic are the Indian elephant, tapir, two kinds of rhinoceroses, tiger, sloth bear and bamboo bear, deer and antelope. Lots of pheasants, poisonous snakes and lizards.
The tropical forest of the neotropical region is unusually rich in lichens, orchids, and bromeliads. Characteristic are cabbage palm, tropical almonds, bamboo, and vines. Among the animals there are prehensile-tailed monkeys, prehensile-tailed bears, noses, sloths, pygmy deer, opossum mice, parrots, and hummingbirds.
The tropical forest of the Ethiopian region is poorer than other tropical forests. Plants - mahogany, many hewes, ferns, orchids and other epiphytes. Notable animals are the pygmy antelope, pygmy hippopotamus, gorilla, chimpanzee, and green monkey.
The Australian rainforest is either a typical continuous-canopy rainforest or a sparse eucalyptus forest. The forests are inhabited by tree kangaroo, koala, opossum, marsupial wolf, Tasmanian devil, platypus, flying dog, and lyrebird.
The Ethiopian savanna is mainly covered with grasses and shrubs, with acacias, baobab, spurge and palm trees. The fauna is represented by herbivores - zebra, eland, oryx, wildebeest, etc. Giraffe, elephant, lion, white and black two-horned rhinoceroses, warthog, cheetah, hyena dog, gopher, golden mole are also typical.
Australian savanna: mainly steppes and thickets of various shrubs and eucalyptus trees. Animals - giant red kangaroo, emu, bandicoot, marsupial rabbit, wombat, parrots.
Palaearctic deserts: scattered bushes of wormwood, finger grass, thickets of camel thorn and tamarisk. The fauna is represented by several species of herbivores, as well as hedgehogs, jerboas, bag rats and hamsters; of birds: eagles, falcons, owls.
Neotropical deserts: rare grasses, low shrubs, cacti, yucca. Among the animals - rhea, armadillo, vulture, fox, tuco-tuco.
Ethiopian deserts: the vegetation consists mainly of grasses and rare shrubs; date palms grow in oases. In the south, spurge and plants with tuberous roots are found. The most common animals are gazelle, porcupine, jerboa, eagle, and lizards.
Australian deserts: vegetation - native forms of quinoa, acacia and various eucalyptus trees. Animals include marsupial mole, kangaroo mouse, jerboa marsupial rat, parakeets.

Question 4. Find the territories mentioned in the paragraph on the geographical map; note their climatic conditions.
1. The Nearctic region includes the territory of all of North America, Newfoundland, and Greenland. In the north, snow and ice give way to tundra. Further south follows an array of coniferous and temperate forests in the east, prairies in the central part and a mixture of mountains, deserts and coniferous forests in the west.
2. The Palearctic region includes all of Eurasia. In the north strip eternal ice, tundra and coniferous forests. In the temperate zone there are broad-leaved forests, the richest in the Asian part. The central regions of Asia are arid and treeless.
3. The eastern region includes India and Indochina, as well as the islands of Ceylon, Java, Sumatra, Taiwan, Borneo. The islands are completely covered with tropical forests, most of the mainland is mountains with varied vegetation, and in the west of India there are dry steppes.
4. The Neotropical region includes South and Central America, the tropical part of Mexico, and the islands of the Caribbean archipelago. Because this area has been isolated for a long time, its flora and fauna differ sharply from those of other areas.
5. Ethiopian region. It includes almost all of Africa, about. Madagascar and the southern part of the Arabian Peninsula. In the central part1 of Africa there are savannas and steppes, West Africa and the mountainous part of the east are covered with tropical forests.
6. The Australian region includes Australia, New Zealand, New Guinea and the Pacific Islands. The central part of Australia is represented by desert, bordered by steppes, savannas with a rare patch of tropical forest. The islands have varied biomes, from tropical New Guinea to comparatively cold New Zealand.

What are biogeocenoses like? Everyone knows that a biogeocenosis, the producers of which are represented mainly by trees, is called a forest. Biogeocenoses located in an arid climate, dominated by grasses, are called steppe in Eurasia, prairie in North America, pampa in South America, and veld in South Africa. In order to understand the diversity of biogeocenoses, a certain classification is needed. There are quite a few such classifications, and the one that is probably used most often in the international scientific community will be used here. The unit of this classification is the biome.

A biome is a large type of biogeocenosis, characterized by a similar type of vegetation and occupying certain regions of the planet. Biomes are regulated by macroclimate and, first of all, by the amount of precipitation and temperature (Fig. 3.4.1).

Rice. 3.4.1. Distribution of some terrestrial biomes depending on rainfall and temperature

Biomes have a certain integrity. For example, between the zones of deciduous forests and steppes there is a forest-steppe zone, where the forest and steppe biomes “meet”. Under the existing climate in the forest-steppe territory, both types of biogeocenoses can be stable. Forest requires more water than steppe, but forest soil retains it more efficiently than steppe soil. Where a forest already exists, enough moisture is retained in the soil for the forest to exist. Where the steppe is located, there is not enough water for forest development. When the humidity or temperature of the climate changes, a gradual movement of the forest-steppe boundary occurs. The arid forest is replaced by the steppe, the moist steppe is overgrown with forest. However, there remains a wide band where two types of ecosystems alternate mosaically. Near-water areas, ravines, and lowlands turn out to be forested, while areas with sandy soil and well-warmed slopes become steppe. The characteristic type of vegetation depends on and influences the soil and climate, and also determines almost the entire composition of the community developing in a particular place.

How to reflect relationships different types communities relative to each other? There are two main methods - ordination(i.e. arrangement in some space in a certain order) and classification(i.e. distribution into groups separated from each other - classes or taxa). Ordination emphasizes the continuity of changes in properties, while classification emphasizes the discreteness of discontinuities. An example of community ordination is shown in Fig. 3.4.1., an example of a multi-level hierarchical classification of data is given below.

The main biomes on Earth are as follows.

Terrestrial biomes

Tundra. A biome of cold, humid climate, which is characterized by negative average annual temperatures, precipitation of about 200-300 mm per year and, most often, the presence of a layer of permafrost. There are arctic tundra, located in high latitudes, and alpine tundra, located in the highlands. Vegetation - low-growing perennials: lichens, mosses, grasses and shrubs.

Taiga. A cold-climate forest biome with long, snowy winters and precipitation exceeding evaporation. The main forest-forming species are conifers; the species diversity of trees is low (1-2 dominant species).

Deciduous forest. Temperate forest. Develops in regions with moderately warm summers and relatively mild winters with frosts. Characterized by a uniform distribution of precipitation, the absence of droughts, and an excess of precipitation over evaporation. In autumn, as the length of daylight hours shortens, leaves fall. Deciduous forests are relatively rich in species and are characterized by a complex vertical structure (the presence of several tiers).

Steppe. An area of ​​herbaceous vegetation in a semi-arid temperate zone. The most numerous grasses are grasses and sedges, many of which form a dense turf. Potential evaporation exceeds precipitation. Characteristic soils rich in organic matter are steppe chernozems. Synonyms: prairie, pampa, veld.

Savannah. Tropical grass-wood communities developing in areas with a stable alternation of dry and wet seasons. Individual trees or clumps of shrubs are scattered between open grassy areas.

Desert. A fairly diverse group of biomes located in areas with extremely arid climates or, in the case of the arctic or alpine desert, extremely low temperatures. Sandy, rocky, clayey, saline, icy and other deserts are known. Typically (with the exception of ice deserts, which develop in very cold conditions) either the average annual precipitation is less than 25 mm, or conditions provide very rapid evaporation of moisture.

Chaparral. Hard-leaved shrubland in a Mediterranean climate with mild, rainy winters and dry summers. It is characterized by a significant accumulation of dry wood, leading to periodic fires.

Seasonal rainforest. Distributed in areas with a hot climate and abundant rainfall, in which precipitation is unevenly distributed throughout the year, with a dry season. Extremely rich in species.

Evergreen rain forest. The richest biome, located in regions with high rainfall (>2000) and almost constant temperature (around 26°C). These forests contain 4/5 of all plant species on Earth; woody vegetation predominates.

Freshwater biomes

Lentic (standing) waters. Puddles, oxbow lakes, natural and artificial ponds, lakes and reservoirs. Living conditions are determined primarily by depth (and illumination) and the amount of nutrients. The exchange of nutrients and gases between the surface and depth is often difficult.

Lotic (flowing) waters. Streams, streams and rivers. Conditions are very dependent on the speed of the current. Capable of moving significant quantities of water and other inorganic and organic substances, they are closely connected with surrounding terrestrial systems.

Swamps. Reservoirs with a large amount of organic matter, the destruction of which is slowed down due to a lack of oxygen in the water; mainly characteristic of temperate and moderately cold climates.

Marine biomes

Pelagial. Open ocean and the depths of the sea far from the coasts. Producers (primarily phytoplankton) are concentrated in a relatively thin near-surface layer of water, where light penetrates. Characterized by the continuous descent of nutrients from the surface into depth.

continental shelf. Coastal zone seas and oceans, reaching a depth of approximately 200 m. Rich in species and diverse marine communities. The most diverse aquatic ecosystems are characteristic of coral reefs, which also belong to the continental shelf. “Hot spots” of biodiversity are also characteristic of great depths - for example, where volcanic gases escape into sea water (“black smokers” and other phenomena).

Upwelling zones. Relatively small areas of the ocean where deep waters enriched with nutrients rise to the surface. They have an exceptional impact on the productivity of the entire ocean as a whole.

Estuaries. Zones of mixing of river and sea waters that form in the seas opposite the mouths of large rivers. They are characterized by a significant amount of organic matter carried into the sea by rivers and constant fluctuations in salinity.

Biome- this is a natural zone or area with certain climatic conditions. conditions and the corresponding set of dominant (in forest biomes - trees, in the tundra - perennial grasses) species of plants and animals that make up the geographical unity. The term "biome" is used for large combinations of ecosystems. The decisive factor in identifying biomes is the characteristics of the vegetation of a particular region. Moving from the north to the equator, we can distinguish 9 main types of land biomes.

1) Tundra(it begins where the forests end and extends north to the eternal ice. The peculiarity of this biome is low annual precipitation, low temperature, short growing season, sparse vegetation, deer, white hare, few predators (arctic fox).

2) Taiga(northern coniferous forest biome) - spruce, fir, pine, birch, aspen; moose, deer; many predators (wolves, lynxes, wolverines). The development cycle of a predator depends on the development cycle of its prey.

3) Temperate deciduous forests(there is a lot of moisture, hot summers give way to cold winters; oak, beech, maple; wild boar, wolf, bear, woodpecker, blackbird, fertile soils (plowed) - forest vegetation was formed here under human influence.

4) Temperate steppes(a sea of ​​herbaceous vegetation; little precipitation for the existence of plants; the soil of the steppes is rich in humus (organic matter), since by the end of summer the grasses die and quickly decompose; cows, horses, sheep).

5) Mediterranean type vegetation(mild rainy winter, dry summer; trees and shrubs of the eucalyptus genus; fires play an important role (favor the growth of grasses and shrubs, create a natural barrier against the invasion of desert vegetation).

6) Deserts(desert landscape - stones, sand with sparse vegetation, stones, rocks; cacti, milkweed; desert animals survive by eating water-storing plants; jerboa, camel).

7) Tropical savannas and grasslands(two seasons - dry and wet), few trees, tall grass with rare trees from the baobab genera, tree-like spurges; Features of the development of grasses are wind pollination and vegetative growth. Reproduction, resumption of growth despite damage; herds, flocks - zebras, giraffes, elephants, ostriches).

8) Tropical or thorny woodland(sparse deciduous forests, thorny bushes; baobabs; uneven distribution of precipitation.

9) Rainforests(a variety of trees and animals (warm and humid all the time); possums, hornbills, birds of paradise, lemurs; the vast majority of the animal world is insects.

Cycle of substances in the biosphere.

Biosphere- the complex outer shell of the Earth, which contains the entire totality of living organisms and that part of the planet’s substance that is in the process of continuous exchange with these organisms. Available two main cycles of substances: large - geological and small - biogeochemical. Thus, the large cycle is caused by the interaction of solar (exogenous) energy with the deep (endogenous) energy of the Earth. It redistributes substances between the biosphere and the deeper horizons of our planet. By the Great Gyre The water cycle between the hydrosphere, atmosphere and lithosphere, which is driven by the energy of the Sun, is also called.

Water cycle in the biosphere

Plants use hydrogen in water during photosynthesis to build organic compounds, releasing molecular oxygen. In the respiration processes of all living beings, during the oxidation of organic compounds, water is formed again. In the history of life everything free water The hydrosphere has repeatedly gone through cycles of decomposition and new formation in the living matter of the planet. About 500,000 km 3 of water is involved in the water cycle on Earth annually.

Oxygen cycle in the biosphere

The Earth owes its unique atmosphere with a high content of free oxygen to the process of photosynthesis. The formation of ozone in high layers of the atmosphere is closely related to the oxygen cycle. Oxygen is released from water molecules and is essentially a byproduct of photosynthetic activity in plants. Abiotically, oxygen arises in the upper layers of the atmosphere due to the photodissociation of water vapor, but this source constitutes only thousandths of a percent of that supplied by photosynthesis.

The released oxygen is intensively consumed in the respiration processes of all aerobic organisms and in the oxidation of various mineral compounds. These processes occur in the atmosphere, soil, water, silt and rocks. It has been shown that a significant portion of the oxygen bound in sedimentary rocks is of photosynthetic origin. The exchange fund O in the atmosphere makes up no more than 5% of the total photosynthetic production. Many anaerobic bacteria also oxidize organic matter through the process of anaerobic respiration, using sulfates or nitrates.

Carbon cycle.

Carbon is an essential chemical element of organic substances of all classes. Green plants play a huge role in the carbon cycle. During the process of photosynthesis, carbon dioxide from the atmosphere and hydrosphere is assimilated by terrestrial and aquatic plants, as well as cyanobacteria, and converted into carbohydrates. In the process of respiration of all living organisms, the reverse process occurs: carbon in organic compounds is converted into carbon dioxide. As a result, many tens of billions of tons of carbon are involved in the cycle every year. Thus, two fundamental biological process-photosynthesis and respiration - determine the circulation of carbon in the biosphere.

The carbon cycle is not completely closed. Carbon can leave it for quite a long time in the form of deposits of coal, limestone, peat, sapropels, humus, etc.

Humans disrupt the regulated carbon cycle through intensive economic activity.

Nitrogen cycle.

The supply of nitrogen (N 2) in the atmosphere is huge (78% of its volume). In this case, plants cannot absorb free nitrogen, but only in a bound form, mainly in the form of NH 4 + or NO 3 –. Free nitrogen from the atmosphere is fixed by nitrogen-fixing bacteria and converted into forms available to plants. In plants, nitrogen is fixed in organic matter (in proteins, nucleic acids, etc.) and transmitted through food chains. After the death of living organisms, decomposers mineralize organic substances and convert them into ammonium compounds, nitrates, nitrites, as well as free nitrogen, which returns to the atmosphere.

Phosphorus cycle.

The bulk of phosphorus is contained in rocks formed in past geological eras. Phosphorus is included in the biogeochemical cycle as a result of rock weathering processes. In terrestrial ecosystems, plants extract phosphorus from the soil (mainly in the form of PO 4 3–) and incorporate it into organic compounds (proteins, nucleic acids, phospholipids, etc.) or leave it in inorganic form. Phosphorus is then transferred through food chains. After living organisms die and with their excretions, phosphorus returns to the soil.

Sulfur cycle.

The main reserve fund of sulfur is in sediments and soil, but unlike phosphorus there is a reserve fund in the atmosphere. The main role in the involvement of sulfur in the biogeochemical cycle belongs to microorganisms. Some of them are reducing agents, others are oxidizing agents.

In terrestrial ecosystems, sulfur enters plants from the soil mainly in the form of sulfates. In living organisms, sulfur is contained in proteins, in the form of ions, etc. After the death of living organisms, part of the sulfur is reduced in the soil by microorganisms to H 2 S, the other part is oxidized to sulfates and is again included in the cycle. The resulting hydrogen sulfide evaporates into the atmosphere, where it is oxidized and returned to the soil with precipitation.

13. The main stages of the evolution of the biosphere.

He studies the main stages of the evolution of living things. paleontology - the science of fossil organisms. For the period from 5 billion years ago to the present, the following geological eras are known: Katarchean, Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic.

Archean era begins with the appearance of the first living cells. The first living cells were called prokaryotes, that is, cells that do not have membrane-bound nuclei. These were the simplest organisms capable of rapid reproduction. They lived without oxygen and could not synthesize organic matter from inorganic. They easily adapted to the environment and ate it. Next, according to scientists, the nutrient medium for these cells is depleted and they change and begin to exist at the expense of solar energy and themselves produce the substances they need for life. This process is called "Photosynthesis". It is the main factor in the evolution of the biosphere. From this moment the formation of the Earth's atmosphere begins, and oxygen becomes the main condition for the existence of living organisms. The ozone layer is gradually formed, and the oxygen content in the air reaches the usual 21% today. This is how evolution continues for about 2 billion years.

And in the Proterozoic, that is, 1.8 billion years ago, living organisms with cells in which the nucleus is clearly expressed appear. After another 800 million years, these organisms, called eukaryotes, divided into plant and animal cells. Plants continued the function of photosynthesis, and animals began to “learn” to move.

900 million years ago the era of sexual reproduction began. This leads to species diversity and better adaptability to conditions environment. Evolutionary process accelerates.

About 100 million years pass and, according to scientists, the first multicellular organisms appear. I wonder how unicellular organisms differed before this? Multicellular organisms develop organs and tissues.

The Paleozoic era is coming and its first stage is the Cambrian. During the Cambrian period, almost all animals appeared, including those that exist today. These are: mollusks, crustaceans, echinoderms, sponges, archaeocyaths, brachiopods and trilobites.

500 million years ago large carnivores and small vertebrates appeared. After another 90 million years, they begin to populate the land. Living organisms that can exist on land and in water are called lungfish. From them came amphibians and land animals. These are ancient reptiles, similar to modern lizards. The first insects appear. Another 110 million years pass, and insects have learned to fly. In the Paleozoic era, especially during the Devonian and Carboniferous periods, the level of plant life significantly exceeded the existing level. The forests were thickets of tree-like lycophytes, giant horsetails and various ferns.

Fauna follows the path of improving seeds. The owners of land during this period are reptiles, which move further and further from water. Swimming, flying and moving on land appear. They are carnivores and herbivores.

Mesozoic. 230 million years ago. Evolution continues. Plants develop roots, stems, and leaves. A system is formed that provides the plant with water and nutrients. Reproduction methods are also changing. Spores and seeds become most suitable for these purposes on land. Unprocessed deposits begin organic waste. Along with coal deposits, additional oxygen begins to be released.

195 million years ago - the first birds and mammals. These are: pteranodon, plesiosaur, mesosaur, brontosaurus, triceratops and others.

Cenozoic. 67 million years ago. The world of mammals, birds, insects and plants is vast. In the previous period, significant cold snaps occurred, which made some changes in the process of plant reproduction. Angiosperms received benefits.

8 million years ago – the period of formation of modern creatures and primates.

Although the process of evolution took almost 4 billion years, precellular living organisms still exist today. These are viruses and phages. That is, some precellular evolved into humans, while others remained as they were.

Today the fauna numbers about 1.2 million species, and the flora about 0.5 million.

Characteristics of the main land biomes

• 1. Biome. Vegetation. Flora. Fauna. Animal world

Biome - this is a set of communities of a zone or subzone.

Vegetation - a set of plant communities (phytocenoses) inhabiting a certain territory. The distribution of vegetation is determined mainly by general climatic conditions and is subject to the laws of latitudinal zonation on the plains and altitudinal zonation in the mountains. At the same time, certain features of azonality and intrazonality are observed in the geographical distribution of vegetation. The main classification units of vegetation are: “vegetation type”, “formation” and “association”. The most important ecological groups of plants - trees, shrubs, shrubs, subshrubs and herbs.

Trees- perennial plants with a lignified main stem (trunk), which persists throughout life (from tens to hundreds of years), and branches that form the crown. The height of modern trees ranges from 2 to 100 m, sometimes more. Trees belong mainly to conifers and dicotyledons. Life form - phanerophytes.

Shrubs - perennial woody plants 0.6 - 6 m high, which do not have a main trunk in adulthood. The lifespan of most shrubs is 10 - 20 years. Shrubs are widespread along the forest borders (shrub steppe, forest-tundra). In forests they usually form undergrowth. Are important currants, gooseberries and others. Life form - phanerophytes.

Subshrubs - perennial plants in which renewal buds persist for several years, and the upper parts of the shoot are replaced annually. The height of most subshrubs is no more than 80 cm. Subshrubs grow mainly in arid areas. Their typical representatives are teresken, types of wormwood, astragalus, solyanka etc. Life form - chamephytes.

Shrubs - low-growing perennial plants with woody shoots; height 5-60 cm, live 5-10 years. Distributed in the tundra ( species of willow, many heathers), in coniferous forests, in sphagnum bogs ( cranberry, cassandra, wild rosemary), in the highlands, etc. Life form - chamephytes.

Subshrubs - perennial small shrubs, for example thyme.

Herbs - annual and perennial plants, which are characterized by the absence of erect above-ground stems that survive an unfavorable season. All herbs have renewal buds at the soil level or in the soil (on rhizomes, tubers, bulbs).

Flora should be distinguished from vegetation, that is, a set of systematic units (species, genera, families) in a given territory.

Flora can be defined as a historically established set of species of plants, fungi and microorganisms that inhabit any territory or inhabited it in past geological eras.

Fauna - a set of animal species living in a certain territory. The fauna is formed in the process of evolution from animals of different origins: autochthons (that arose here), allochthons (that arose elsewhere, but moved here long ago), immigrants (that came here relatively recently). The term “fauna” is also applicable to a set of animals of any systematic category (for example, bird fauna - avifauna, fish fauna - ichthyofauna, etc.).

Animal world - a collection of individuals of various animal species characteristic of a given territory.

Under the influence of climatic factors, the zonal features of biomes developed. Despite the similarity of climates of different meridional sectors of the same zone, communities of different sectors differ in the set of plant and animal species included in their composition. All this leads to differences in the structure and dynamics of biomes (4,5,16,23,35,40,46,52)

2. Zonal, intrazonal and extrazonal communities

biome community forest

Any biome has its own specific set of communities. At the same time, in every biome there are 1) zonal communities, 2) intrazonal communities, 3) extrazonal communities.

1 . Zo nal communities occupy plains (well-drained extensive plains or watersheds) on soils of medium mechanical composition (sandy loam and loam) in any natural zone. As a rule, zonal communities occupy the largest spaces within a zone.

2 . In trazonal communities do not form “their own” zone anywhere, but are found in non-zonal conditions of several neighboring or even all natural areas.

In ecology, the following intrazonal communities are distinguished:

1) intrazonal communities, characteristic of the non-zonal conditions of several neighboring zones,

2) azonal, characteristic of non-zonal conditions of all land zones.

However, there is no real difference between these categories. Large biocenotic categories and types of vegetation (for example, meadows, swamps) exist in all or almost all natural zones. The distribution of smaller categories (eg formation class) will be limited to only a few zones. These are, for example, sphagnum, green moss and papyrus swamps, tall grass and steppe meadows, etc. Intrazonal vegetation and animal populations bear the imprint of the zone with which they are genetically and ecologically connected. That is why in zones that are further apart they are less similar than in neighboring ones.

3 . Ek strazonal communities They form zonal communities outside a given zone, but, going beyond the boundaries of “their” zone, they are confined to non-zonal conditions. For example, broad-leaved forests, which form a special independent zone, are not found in the steppe on watersheds, but descend along the slopes of river valleys and into steppe ravines. In steppe ravines they form so-called canyon forests. Likewise, north of steppe zone steppe islands may find themselves tied to southern-facing slopes, as is the case in Yakutia and the Magadan region. Finally, along the western slope of the Urals there is a huge forest-steppe island located in the subzone mixed forests. It has all the features of a forest-steppe: the presence of birch groves, areas of steppes with John's feather grass, thickets of steppe shrubs ( steppe cherry, steppe myndAla etc.). This forest-steppe is associated with the emergence of gypsum and anhydrite on the daytime surface, creating favorable conditions for forest-steppe vegetation and animal populations. In all of these cases we are talking about extrazonal communities.

Thus, within any biome there are zonal communities (on flats in zonal conditions), as well as intrazonal and extrazonal communities (in non-zonal conditions). The combination of these three types of communities forms its own unique type of biome.

3. Cold (polar) deserts

Cold polar deserts formed in cold conditions arctic climate in the Northern Hemisphere or in the Antarctic climate in the Southern Hemisphere. In polar deserts, vegetation does not form a continuous cover. Often up to 70% of the earth's surface is occupied by gravelly, rocky, and sometimes cracked into polygonal soil. The snow here is shallow and is blown away by strong winds, often of a hurricane nature. Often only isolated tufts or cushions of plants huddle among rocky and gravelly placers; and only in lower areas do patches of denser vegetation appear green. Plants develop especially well where birds abundantly fertilize the soil with excrement (for example, in places of nesting aggregations, the so-called bird colonies).

Within the polar deserts there are few birds not associated with the sea ( snow bunting, Lapland plantain etc.). Colonial species predominate everywhere. This biome is characterized by bird colonies, leading ecological role in which they play auks (guillemot, auk, puffin), gulls (glaucous gull, kittiwake, silverAndflock, small polar etc.), eider(Northern Hemisphere) and penguins, glaucous gulls, white plovers(Southern Hemisphere). As a rule, bird colonies are confined either to cliffs or to areas of soft ground in which some birds dig holes. Penguins, for example, breed their young on polar ice and snow.

Some species of mammals penetrate into polar deserts lemmings (Ob, ungulate), but their numbers are still not very large. Plants predominate mosses and lichens; there are also some flowering plants (for example , blueberry squat, polar poppy etc.). In pollination of these plants they take active participation insects first and foremost bumblebees, as well as dipterans (flies, mosquitoes etc.).

Diptera - This is a order of insects in which only the front pair of wings is developed.

IN arctic desert The phytomass reserve is about 2.5 - 50 c/ha, and its annual production is less than 10 c/ha.

4. Tundra

Tundra characterized by extremely harsh conditions for plant growth and animal habitats. The growing season is short and lasts from 2 to 2.5 months. At this time, the summer Sun does not descend or only briefly descends below the horizon and the polar day sets in. That is why long-day plants dominate the tundra.

There is little precipitation - 200 - 300 mm per year. Strong winds, especially severe in winter time, blow away the already shallow snow cover into relief depressions. Even in summer, night temperatures often drop below 0 0 C. Frosts are possible at almost any time summer day. The average temperature in July does not exceed 10 0 C. Permafrost is located at an insignificant depth. Under peaty soils, the level of permafrost does not fall deeper than 40 - 50 cm. In the more northern regions of the tundra, it merges with the seasonal permafrost of the soil, forming a continuous layer. Soils of light mechanical composition thaw in summer to a depth of about one meter or more. In depressions where a lot of snow accumulates, permafrost may be very deep or absent altogether.

The relief of the tundra is not flat or level. Here we can distinguish elevated flat areas, usually called blocks, and interblock depressions with a diameter of tens of meters. In some areas of the tundra these low areas are called alasami. The surface of the blocks and interblock depressions is also not completely flat.

Based on the nature of the relief, tundras are divided into the following types:

1) lumpy tundra , which are characterized by mounds 1 - 1.5 m high and 1 - 3 m wide or manes 3 - 10 m long, alternating with flat hollows;

2) coarse tundra are characterized by the height of the hillocks from 3 to 4 m with a diameter of 10 - 15 m. The distance between the hillocks ranges from 5 to 20 - 30 m. Large hilly tundras are developed in the southernmost subzones of the tundra. The formation of mounds is associated with the freezing of water in the upper layers of peat, which increases the volume of these layers. Since the increase in volume is uneven, protrusion of the upper layers of peat occurs, leading to the formation and gradual growth of mounds.

3) spotted tundra developed in the more northern subzones of the tundra and are formed in the winter as a result of the outpouring of quicksand on the day surface, which leads to the formation of bare spots between which they huddle rare plants. Spotted tundras can also form under the influence of strong winds and frosts without outpouring of quicksand: in the winter period of the year, the soil cracks into polygonal units, soil particles accumulate in the cracks between them, on which plants settle in the warm season.

Tundra vegetation is characterized by the absence of trees and the predominance of lichens and mosses. Of the lichens, bushy ones from the genera are abundant cladonia, centraria, stereocaulon etc. These lichens give a small annual increase. For example, annual growth forest cladonia ranges from 3.7 to 4.7 mm, Cladonia slender- 4.8 - 5.2 mm, Cetraria glomerulosa - 5.0 - 6.3 mm, Cetraria snowy- 2.4 - 5.2 mm, stereocaulona easter- 4.8 mm. This is why reindeer cannot graze in the same place for a long time and are forced to move in search of food. The reindeer can use the visited pastures only after many years, when its main food plants - lichens - have grown.

All types of tundras are characterized by green mosses. Sphagnum mosses are found only in more southern areas of the tundra.

The vegetation cover of the tundra is very poor. There are few annuals due to the short growing season and low temperatures in the summer. Only where the vegetation cover is disturbed under the influence of human activity, or where there are emissions from the burrows of animals that inhabit the tundra, annuals can develop in significant quantities.

Of the perennials, there are many winter-green forms, which is also due to the need to make fuller use of the short growing season. In the tundra there are many shrubs with low woody trunks and branches creeping along the surface of the soil, pressed to the earth's surface, as well as herbaceous plants that form dense turf. Cushion-shaped forms are extremely widespread, which save heat and protect plants from low temperatures. Often plants have a trellis, elongated shape. Of the winter-green shrubs, we should highlight partridge grass, cassiopeia, lingonberry, crowberry; from shrubs with falling leaves - blueberries, dwarf birch, dwarf willow. Some dwarf willows have only a few leaves on short, squat trunks.

In the tundra there are almost no plants with underground storage organs (tubers, bulbs, succulent rhizomes) due to low temperatures and deep freezing of the soil.

Tundra is treeless. Ecologists believe that the main reason for the treelessness of the tundra lies in the objective contradiction that exists between the flow of water into the roots of trees and its evaporation by branches raised above the snow surface. This contradiction is especially pronounced in the spring, when the roots cannot yet absorb moisture from the frozen soil, and evaporation by the branches is very intense. This hypothesis is confirmed by the fact that along river valleys, where permafrost runs deep and the winds that increase evaporation are not so strong, trees penetrate far to the north.

According to the characteristics of the vegetation cover The tundra is divided into the following three subzones:

1) arctic tundra : spotted tundra is widespread, there are no closed shrub communities, green mosses predominate, sphagnum mosses are absent;

2) typical tundra: shrub communities dominate, lichen communities are widespread, green mosses dominate, sphagnum mosses are present, forming small peat bogs;

3) southern tundra: Sphagnum peat bogs are well developed, and forest communities are formed along river valleys.

In the tundra, winter and summer seasons are distinguished more clearly than in any other zone. The seasonal migrations of animals are pronounced here. A striking example of migration is the migration of birds that leave the tundra for the winter and return here again in the spring.

Seasonal migrations are also typical reindeer. So, reindeer for the summer they move to sea ​​coasts in more northern regions tundra, where winds to some extent reduce the intensity of midge attacks ( horseflies, mosquitoes, midges, gadflies), tormenting animals with their constant bites. In winter, deer go to more southern areas, where the snow is not so dense and it is easier for them to “hoof” it to get food. Nomadic herds of reindeer are constantly accompanied by tundra partridge which, as a result, gets the opportunity to use soil areas dug up by deer to search for food. Reindeer migration routes can be very long.

It should be noted that animals, on the one hand, are influenced by environmental conditions, on the other, with their life activities they have a powerful impact on the formation of various natural complexes. A striking example of how animals transform the environment is the life activity of lemmings.

Lemmings - a group of mammals of the vole subfamily. The body length is up to 15 cm, the tail - up to 2 cm. About 20 species of lemmings are known, living in the forests and tundras of Eurasia and North America. Lemmings are the main food of the arctic fox. They can be carriers of pathogens of a number of viral diseases. In some years they breed in large numbers and undertake long migrations.

The amount of food consumed by a lemming is 40 - 50 kg of plant mass per year. A lemming eats 1.5 times more per day than it weighs. The burrowing activity of lemmings has a huge impact environmental impact for life on the tundra. The number of lemming holes ranges from 400 to 10,000 per 1 hectare, which significantly increases soil aeration. Lemmings “throw out” up to 400 kg of soil per 1 hectare onto the daytime surface. On these emissions, plant species such as daisy heartwood, semolina, fescue, Arctic fireweed, rush grass etc. The lush vegetation on these outbursts creates the impression of miniature oases.

Mass reproductions of lemmings, which occur once every three years, are associated with the rhythms of nature.

One more a shining example The impact of animals on the habitat is the digging activity of gophers. Long-tailed ground squirrel, for example, promotes the establishment of forb-meadow communities on well-drained soils and emissions.

Geese and other waterfowl also contribute to changes in vegetation in the tundra: after plucking grass, patches of bare soil form. Subsequently, increased aeration leads to the development of first sedge-cotton grass, and then sedge-moss tundras.

In the tundra, self-pollination of plants and pollination by wind are widespread; entomophily is poorly developed. Insects rarely visit flowers. For example, in tundra conditions, perhaps only bumblebees are the only pollinator of plants with irregular flowers - astragalus, ostroglodochnik, mytnik.

Many flowers of tundra plants have a very short lifespan. Yes, y cloudberries covering vast expanses of tundra, the individual life of a flower does not exceed two days. Considering that during this time there are frosts, rains and hurricane winds that prevent insects from flying, then the chances of pollination with the help of insects drop. Many insects huddle in flowers not in search of nectar, but seek refuge here from unfavorable weather conditions. This means that they can sit in one flower for a long time, and then fly to a flower of another species, which also reduces the plants’ chances of being pollinated by insects.

Soil inhabitants in the tundra are few in number and concentrated in the upper soil horizons (mainly in the peat horizon). With depth number soil inhabitants decreases quickly because the soil is saturated with moisture or frozen.

Many northern birds are characterized by large sizes clutches and correspondingly larger broods compared to individuals of the same species living in more southern zones. This can be associated with the abundance of insects that serve as food for birds. The growth of young animals in the tundra is faster than in the south.

Many people incorrectly believe that with a long daylight period, birds feed their young for a longer time. However, it should be noted that even where the day is around the clock, birds still sleep for a significant part of the astronomical night. In all types of tundra there are few reptiles and amphibians due to permafrost.

Phytomass in the Arctic tundras is very small and amounts to about 50 c/ha; in shrub tundras it increases to 280 - 500 c/ha.

5. Forest-tundra

Forest-tundra - a natural zone of the Northern Hemisphere, transitional between the temperate forest zone and the tundra zone. In the natural landscapes of the forest-tundra zone, a complex complex of open forests, tundras, swamps and meadows is observed.

Sometimes ecologists consider the forest-tundra to be a transitional zone and often consider it as a tundra subzone. However this special zone, whose biocenoses differ from both tundra and forest.

The forest-tundra is characterized by woodlands . Birds nesting among the bushes appear here in significant numbers, for example, bluethroat. In the forest-tundra, the amount of seed food increases, which leads to an increase in the number and diversity of mice. Permafrost goes deeper. K rarely standing trees nests of corvids and small ones are confined to birds of prey. Forest-tundra has a special set of living conditions both in comparison with the tundra and in comparison with the forest. It is characterized by such types of trees as berefor, spruce(in the west), larch(in the east).

6. Temperate coniferous forests (taiga)

Taiga - type of vegetation with a predominance of coniferous forests. Taiga forests are common in the temperate zone of Eurasia and North America. In the forest stand of the taiga, the main role is played by spruce, pine, larch, fir; the undergrowth is poor, the herbaceous-shrub layer is monotonous ( blueberries, lingonberries, sorrel, green mosses).

Taiga communities are characteristic only of the temperate zone of the Northern Hemisphere. They are absent in the southern hemisphere.

Taiga forests can be formed either by dark coniferous species - spruce, fir, Siberian cedar pine (Siberian cedar), or light coniferous - larch, as well as pine(mainly on soils of light mechanical composition and sand).

In the taiga, the warmest month has a temperature from +10 0 C to +19 0 C, and the coldest month - from -9 0 C to - 52 0 C. The cold pole of the Northern Hemisphere lies within this zone. The duration of the period with average monthly temperatures above 10 0 C is short. There are 1 - 4 such months. The growing season is quite short. Based on ecological features and floristic composition, communities of dark-coniferous and light-coniferous taiga forests are distinguished.

Dark coniferous forest communities (spruce, fir, cedar) are quite simple in structure: the number of tiers is usually 2-3. The following tiers are presented here:

tree layer;

herbaceous or herbaceous-shrub layer;

moss layer.

In dead cover forests there is only one (tree) layer, and there are no grass (herb-shrub) or moss layers. The shrubs are sporadic and do not form a distinct layer. All dead cover forests are characterized by significant shading. In this regard, herbs and shrubs reproduce more often by vegetative means than by seed, forming clumps.

Forest litter in dark coniferous forests decomposes very slowly. Winter green plants are widely represented ( lingonberry, wintergreen). Lighting, in contrast to deciduous forests, is the same throughout the growing season. Therefore, there are practically no plants that time the development of flowers to the early spring months. The corollas of the flowers of the plants of the lower tier have white or pale colored tones, clearly visible against the dark green background of the moss and in the twilight of the dark coniferous forest. In an untouched dark coniferous forest, air currents are very weak and there are practically no winds. Therefore, the seeds of a number of plants of the lower tier have negligible weight, which allows them to be transported from place to place even by very weak air currents. These are, for example, seeds Wintergreen unicolor(seed weight - 0,000,004 g) and Goodyear orchids(seed weight - 0,000,002 g).

How can an embryo developing from seeds of such insignificant weight feed itself? It turns out that the development of plant embryos with such tiny seeds requires the participation of fungi, i.e. development of mycorrhiza.

Mycorrhiza (from Greek mykes- mushroom and rhiza- root, i.e. mushroom root) - mutually beneficial cohabitation (symbiosis) of the mycelium of a fungus with the root of a higher plant, for example, boletus with aspen, boletus with birch). Mitz e liy (mycelium) - the vegetative body of fungi, consisting of the finest branching threads - hyphae.

The hyphae of the fungus, which are extremely abundant in dark coniferous forests, grow together with the embryos developing from such seeds and supply them with the necessary nutrients, and then, when the embryo grows and becomes stronger, it, in turn, provides the fungus with the products of photosynthesis - carbohydrates. The phenomenon of mycorrhiza (symbiosis of a higher plant and a fungus) is very widely developed in forests in general, and is especially common in dark coniferous taiga forests.

Mycorrhiza (fungal root) is formed not only by flowering plants, but also by many trees. The fruiting bodies of many fungi that form mycorrhizae are edible for humans and animals. These are, for example, porcini mushroom, russula, boletus, growing under pine and larch, boletus And boletus, associated with small-leaved trees developing in the place of cleared dark coniferous forests, etc.

Animals that eat the juicy pulp of the fruits of taiga plants play a major role in seed dispersal. It should be noted that the consumption of such juicy fruits by animals is a condition for a number of plant species for high germination of their seeds. U blueberries And lingonberries For example, the high acidity of berry juice prevents the development of seeds in an untouched berry. If the berry is crushed by the paws of an animal or digested in its stomach, then the surviving seeds germinate quite well. High germination and good development of seeds are also facilitated by excrement released from the intestines with the seeds. In this case, excrement serves as fertilizer for developing seedlings. Blackbirds, for example, they successfully spread seeds mountain ash and many other wild berries, and bears- seeds raspberries, rowan, viburnum, currant etc.

A typical method of seed dispersal for dark coniferous forests is being carried away by ants. Some types of taiga plants have seeds equipped with special fleshy appendages (caruncles), making them attractive to the inhabitants of the dark coniferous forest.

In the dark coniferous taiga there is often a moss cover; it is very moisture-absorbing and, when wet, becomes thermally conductive. Therefore, the soils of dark coniferous forests can freeze very much in winter. The species composition of the forest stand, as well as the herb-shrub layer, is especially poor in the taiga of Europe and Western Siberia, richer in Eastern Siberia and the Far East, and is relatively rich in North America, where there are several species of the same genera of dark coniferous species as in Eurasia ( spruce, fir). In addition, North America is widely represented hemlock and pseudo-hemlock, absent in Eurasia. In the grass-shrub layer of the North American taiga there are many forms close to Eurasian - oxalis, weekday etc.

Dark coniferous taiga, like other types of forest, has a number of features that determine the nature of the animal population. In the taiga, as in other forests, there are few herd land animals. Meet wild boars, they come in winter reindeer And wolves. This is due to the fact that the presence of trees makes it difficult for animals to visually alert each other to impending danger. Among birds of prey, they are especially characteristic hawks who have adapted well to living conditions in the taiga. Hawks have relatively short wings and long tail. This facilitates their rapid maneuvering among tree branches and a sudden attack on the prey.

There is relatively little in the taiga forest diggers, because the presence of numerous shelters in the form of hollows, fallen trunks, and depressions in the earth's surface eliminates the need for animals to dig complex systems of burrows.

The differences in the winter and summer composition of the animal population in the dark coniferous taiga are less sharp than in the tundra and forest-tundra. Many herbivorous species in winter feed not on herbs and shrubs, but on twig food: for example, elk, hare etc.

The animal population as a whole is relatively poor in both quality and quantity. A number of species that live primarily in trees feed on the earth's surface. These are, for example, forest pipit, blackbirds and a number of other birds. Others, on the contrary, nest on the soil surface and feed mainly in the crowns of coniferous trees: black grouse, hazel grouse, capercaillie.

In coniferous forests they acquire great value seed feeds, in particular coniferous seeds. They produce high yields not annually, but once every 3-5 years. Therefore, the number of consumers of these feeds ( squirrel, chipmunk, mouse-like rodents) does not remain at the same level, but has its own rhythms associated with productive years. As a rule, the next year after a high seed harvest, there is a sharp increase in the number of individuals of those animal species that feed on these seeds. During years of starvation, many inhabitants (for example, squirrel) migrate to the west, during which they swim across large rivers (Yenisei, Ob, Kama, etc.) and thus expand their habitats.

In addition to seed feed, berry and twig feed, as well as pine needles and wood, are of great importance for taiga animals.

For some animals, pine needles are an indispensable food; for example for gypsy moth, causing real devastation of forests over large areas.

In the dark coniferous taiga they are very numerous primary(attacking healthy trees) and secondary(attacking weakened trees) wood pests - longhorned beetles and their larvae, bark beetles etc.

Many species of mammals and birds whose food is associated with trees are well adapted to climbing and often live in trees. These are squirrels And chipmunks from mammals, nuthatches, pikas, woodpeckers from birds. Insects that feed on seeds and wood of coniferous trees play an important role in the diet of birds and other animals that climb trees and nest in hollows. Good at climbing trees lynx, somewhat worse - brown bear.

From terrestrial mammals The following are the most characteristic features of the taiga: elk from ungulates, bank voles from rodents, shrews from insectivores.

A number of forest inhabitants connect tree communities with herbaceous ones. So, herons They nest in trees in the forest, and feed along the banks of rivers, lakes or in meadows.

The amplitude of fluctuations in the number of rodents in taiga forests is not as significant as in the tundra, which is associated with a less severe climate and with the protective role of taiga massifs, in which the direct impact of climate on animals is somewhat mitigated.

Communities of light coniferous forests (pine, larch) in Europe are represented mainly pine treeTonovena and are confined primarily to soils of light mechanical composition. In Siberia and North America, primary light-coniferous forests can also be associated with soils of a heavier texture. Here they play a big role various types larches, and in North America, pine trees. In North America, pine trees reach their exceptional diversity.

An important feature of light-coniferous forests is a sparse tree stand, associated with the increased photophilia of larches and pines. Therefore, in the soil cover of light coniferous forests they acquire a significant ecological role. lichens and a highly developed shrub layer formed rhododendrons, broomAndcom, viburnum, rose hips, currants etc. In North America, in light coniferous forests they are often found bebark fir, pseudotuga and a number of other breeds.

Biomass within the taiga varies noticeably depending on the type of forest, increasing from the forests of the northern taiga to the forests of the southern one. In the pine forests of the northern taiga it is 800 - 1000 c/ha, in the middle taiga - 2600 c/ha, in the southern taiga - about 2800 c/ha. In the spruce forests of the southern taiga, the biomass reaches 3,330 c/ha.

7. Broadleaf forests

Broadleaf forests temperate zones grow in a milder climate than coniferous forests. Unlike conifers, with the exception of larches, broad-leaved trees shed their leaves for the winter season. In early spring, it is very light in deciduous forests, since the trees are not yet covered with leaves. Illumination is the main factor in the formation of tiers.

In broad-leaved forests, abundant fallen leaves cover the soil surface with a thick, loose layer. Under such bedding, the moss cover develops very poorly. Loose litter protects the soil from a sharp drop in temperature and, therefore, winter freezing of the soil is either completely absent or very slight.

In this regard, a number of species of herbaceous plants begin to develop in winter as the thickness of the snow cover decreases and the temperature of the air and the earth's surface increases.

In broad-leaved forests, a group of spring ephemeroids appears, which, having finished flowering in early spring, then either vegetate or lose their above-ground organs ( oak anemone, goose onion etc.). The buds of these plants often develop in the fall; with the buds, the plants go under the snow, and in early spring, while still under the snow, flowers begin to develop.

Anemone (anemone) - a genus of rhizomatous herbs (occasionally subshrubs) of the Ranunculaceae family. In total, about 150 species are known, growing throughout the globe. Many types of anemone are early spring plants (for example, oak anemone).

Thick litter allows a variety of invertebrates to overwinter. Therefore, the soil fauna of deciduous forests is richer than that of coniferous forests. Common animals in deciduous forests include: mole, feeding on earthworms, insect larvae and other invertebrates.

The layered structure of broad-leaved forests is more complex than the structure of taiga forests. They usually contain one ( dead-blooded butches) up to 3 - 5 tiers ( oak forests). The moss cover in deciduous forests is poorly developed due to the thick litter. All single-story broad-leaved forests are dead cover.

Most of the herbaceous plants of the broad-leaved forest belong to oak forest broad grass. Plants of this ecological group have wide and delicate leaf blades and are shade-loving.

In the broad-leaved forests of Eurasia there are many seed-eaters, among which the various species of mice are especially diverse: wood mouse, yellow-throated mouse, Asian mouse etc. In North American forests, mice are replaced hamsters, having the appearance of mice, as well as representatives primitive jerboas who are good at climbing trees. Like all mice, they feed not only on plant foods (mainly seeds), but also on small invertebrates.

Broad-leaved forests do not form a continuous strip spanning the Northern Hemisphere. Significant tracts of broad-leaved forests are found in Western Europe, in the foothills of the Kuznetsk Alatau, where they form a continuous island of linden forests, in the Far East, etc. Significant areas of broad-leaved forests are also found in North America.

Broad-leaved forests are heterogeneous in floristic composition. Thus, in western Europe, in areas of mild climate, there are broad-leaved forests with dominance real chestnut and with an admixture beech. Further to the east, very shady beech forests with a single layer of trees dominate. Further east, without crossing the Urals, oak forests predominate.

In the northeastern part of North America there are forests dominated by American beech And Sakharmaple. They are less shady than European beech forests. In autumn, the foliage of North American broadleaf forests turns various shades of red and yellow flowers. There are several types of vines in these forests - ampelopsis, known as "wild grapes".

Maple - genus of trees and shrubs of the maple family. In total, about 150 species are known, growing in North and Central America, Eurasia and North Africa. Maples grow in deciduous and mixed forests. Norway maple, Tatarian maple, field maple, sycamore and other species are used in protective afforestation and landscaping purposes. Maple wood is used to make furniture, musical instruments, etc.

Oak forests in North America occupy the more continental areas of the Atlantic states. Several species are found in North American oak forests oak, many types maple, lapina (hickory), tulip derevo from the magnolia family, abundant creepers.

Hickory (Karia) ) - genus of tree family nut. The height of some species reaches 65 m. In total, about 20 species are known, growing in North America and East Asia(China). In many countries, some types of hickory are cultivated as ornamental plants and are used in protective afforestation. Nuts pecan and other hickories are edible and contain up to 70% edible oil.

The broad-leaved forests of the Far East are especially rich in species. There are many types of broad-leaved tree species: oak, walnut, maple, as well as representatives of genera absent from European broadleaf forests, e.g. Maakia, Aralia and others. The rich undergrowth includes honeysuckle, lilac, rhododendron, privet, mock orange etc. Lianas ( actinidia etc.) and other epiphytes.

Aralia - genus of plant family Araliaceae. There are trees, shrubs and tall perennial grasses. Only about 35 species are known to grow in the tropics and subtropics of the Northern Hemisphere. Many species are cultivated as ornamental plants.

In the Southern Hemisphere (Patagonia, Tierra del Fuego), broad-leaved forests are formed southern beech. The understory of these forests contains many evergreen forms, such as barberry.

The biomass of broad-leaved forests is about 5,000 c/ha.

8 . Forest-steppe

Forest-steppe is a natural zone of temperate and subtropical zones, in the natural landscapes of which steppe and forest areas alternate.

The forest-steppe zone is quite unique and is characterized by a combination of small forests with vast steppe grassy or shrubby areas. In Eurasia, the forest areas of this zone are represented by small oak forests, as well as birch and aspen groves. The combination of forest and herbaceous or shrub formations favors the existence of a number of species that are not particularly characteristic of both the steppe and the forest.

Typical examples of forest-steppe species are rooks, for which the pegs serve as nesting places, and the steppe areas serve as feeding places, as well as numerous falcons (falcon, merlin), cuckoos and other types.

9. Steppe

Steppes - vast areas of the temperate zone occupied by more or less xerophilic vegetation. The steppe zone is represented in Eurasia typical steppes , in North America - prairies , in South America - pampas , in New Zealand - by communities Tussokov .

From the point of view of the living conditions of the animal population of the steppe, they are characterized by the following main features:

good overview of the area;

abundance of plant foods;

relatively dry summer period;

existence of a summer period of rest (semi-rest).

In the steppes they dominate everywhere cereals, the stems of which are crowded into turf. In New Zealand such turfs are called tussocks. Tussoks can be very tall, their leaves are quite succulent, which is explained by the mild and humid climate.

In addition to cereals (monocots), dicotyledonous plants, which make up the ecological group, are also widely represented in the steppes "forbs" .

The following two stand out groups of steppe forbs:

1) northern colorful forbs;

2) southern colorless forbs.

Northern colorful forbs are characterized by bright flowers or inflorescences; and for southern colorless forbs - pubescent stems, narrow leaves, finely dissected and dim flowers.

The steppes are characterized by annual ephemerals and perennial ephemeroids, which retain tubers, bulbs and underground rhizomes after the above-ground parts die.

Ephemera - annual plants, the full development cycle of which occurs in a very short time (several weeks). Ephemera are characteristic of steppes, semi-deserts and deserts. Typical representatives of ephemera are dimorphic quinoa, desert alyssum, sickle-shaped hornwort, some types cereals And legumes.

Ephemeroids - perennial plants, the above-ground organs of which live for several weeks, then die, and the underground organs (bulbs, tubers) persist for several years. Ephemeroids are characteristic of steppes, semi-deserts and deserts. Typical examples of ephemeroids are the following: swollen sedge, prOSiberian fishing line, May lily of the valley, oak anemone, bulbous bluegrass, corydalis, tulips, sedges etc.

Various shrubs are found in the steppe zone: spirea, caragana, steppe cherry, steppe almond, some types juniper. The fruits of many shrubs are readily eaten by animals.

Animals of the steppe are characterized by a burrowing lifestyle, which is the result of an arid climate and the lack of reliable natural shelters. There are many diggers and burrowers in the steppe: mole rats, ground squirrels, marmots, voles, hamsters, prairie dogs. Animals that do not make burrows often lead a herd lifestyle and play an important role in the life of steppe biocenoses (for example, saiga). Without moderate grazing, in which animals break up accumulations of dead grass on the soil surface with their hooves, typical steppe plants degrade and are replaced by various annual and biennial weed species - thistle, sow thistle and others.

Overgrazing also leads to the degradation of steppe vegetation and the replacement of large-grass grasses ( feather grass) small-turf grasses ( fescue, thin-legged etc.), and with further strengthening - to the emergence of the so-called push , in which steppe perennials almost disappear and dominate bulbous bluegrass , which reproduces mainly vegetatively, as well as annuals. In addition, with overgrazing, desertification of the steppes occurs and less xerophilic plants are replaced by wormwood and other species characteristic of deserts and semi-deserts.

An important ecological factor in the development of steppe biomes is fires, as a result of which most of the above-ground parts of grasses die. The height of the flame in steppe fires can reach two to three meters. However, after a fire, the soil is enriched with valuable nutrients and the grass grows back quickly. The biomass of steppe vegetation is approximately 2,500 c/ha, which is significantly lower than the biomass of temperate broad-leaved forests.

10. Semi-deserts

Semi-deserts are natural zones of the temperate, subtropical and tropical zones with a predominance of semi-deserts. Semi-deserts are dominated by areas with sparse vegetation cover, which is dominated by grasses and wormwood (in Eurasia) or communities of perennial grasses and shrubs (on other continents).

The main feature of semi-desert biomes is that they are characterized by a complexity of vegetation cover that is significantly different from both the steppes and all other natural zones. Of the cereal communities, the semi-desert is most characterized by phytocenoses dominated by the Sarepta feather grass. The semi-desert provides optimal conditions for the existence of many species of animals, for example, the small ground squirrel, the black ground squirrel, etc.

11. Deserts

Desert - a type of vegetation with very sparse vegetation cover in conditions of extreme aridity and continental climate. Typical desert plants are ephedra, saxaul, solyanka, cacti, kendyr.

Ephedra - genus of evergreen plants of the ephedra family. About 45 species are known, growing in temperate and subtropical zones of the Northern Hemisphere. Contain alkaloids (ephedrine, etc.).

Saxaul - a genus of woody or shrubby plants of the family gonoeaceae. The height of some species reaches 12 m. In total, about 10 species are known, growing in the semi-deserts and deserts of Asia. Wood is used for fuel; green branches are food for camels and sheep. Saxaul is a good sand fixer.

There are many ephemerals and ephemeroids in deserts. Desert fauna presented antelopes, toatred deer, jerboas, gophers, gerbils, lizards, diverse insects etc.

Kulan - an odd-toed animal of the equine genus. Length about 2 m. Lives in deserts and semi-deserts of the Front, Middle and Central Asia. The number of kulan individuals is sharply declining. In some countries, the kulan is protected.

Jerboas (jerboa ) - family of mammals of the rodent order. Body length 5.5 - 25 cm; the tail is longer than the body. Only about 30 species are known to live in open landscapes of the Northern Hemisphere.

There are many different types of deserts around the globe. Deserts can vary in temperature and thermal regimes. Some of them (temperate deserts) are characterized by hot summers and often frosty winters, while others (tropical deserts) are characterized by year-round high temperatures.

All types of deserts are characterized by extremely insufficient moisture. Annual precipitation in deserts usually does not exceed 200 mm. The nature of the precipitation regime is different. In Mediterranean-type deserts, winter precipitation predominates, while in continental-type deserts a significant proportion of precipitation occurs in summer. However, in any case, potential evaporation is many times higher than the annual precipitation and amounts to 900-1500 mm per year.

The main soils of temperate deserts are gray soils and light brown soils, which, as a rule, are rich in easily soluble salts. Due to the fact that the vegetation cover of deserts is very sparse, the nature of the soils becomes fundamentally important when characterizing deserts. Therefore, deserts, unlike other communities, are usually divided not according to the nature of the vegetation cover, but according to the dominant soils. In this regard, the following four types of deserts are distinguished:

1) clayey;

2) salty (salt marsh);

3) sandy;

4) rocky.

Desert plants are highly adapted to survive in arid conditions. Everywhere in deserts they predominate subshrubs, which are often dormant in summer. The ways in which plants adapt to living in dry conditions are very diverse.

Among the inhabitants of deserts, especially tropical deserts, there are many succulents, including woody forms (for example, saxauls with scaly succulent leaves, etc.).

There are also shrubs devoid or almost devoid of foliage ( Eremospartons, CalligonatWe etc.). In deserts, plants are widely represented that dry out during periods of lack of rain and then come to life again. Lots of pubescent plants.

Ephemerals take advantage of the period when deserts are more humid. In continental deserts with little winter precipitation, ephemerals develop after rare heavy summer rains. In Mediterranean-type deserts, in which a certain amount of snow accumulates by spring, ephemerals (ephemeroids) develop mainly in early spring.

In deserts, the vegetation cover never closes with its above-ground parts. Sandy desert plants are characterized by the following features:

The ability to produce adventitious roots when filling the bases of trunks with sand,

The ability of root systems not to die when they are exposed as a result of sand blowing,

Leaflessness of perennial plants,

The presence of long (sometimes up to 18 m) roots reaching the groundwater level.

The fruits of sandy desert plants are enclosed in membranous vesicles or have a system of branched hairs that increase their volatility and prevent them from being buried in the sand. Among the inhabitants of sandy deserts there are many cereals And sedge.

Desert animals have also adapted to living in conditions of insufficient moisture. The burrowing lifestyle is a characteristic feature of desert inhabitants. They climb into holes during the hot part of the day, when life on the soil surface practically freezes. beetles, tarantulas, scorpions, woodlice, lizards, snakes and many other animals. The insignificant protective role of vegetation and its low nutritional value are essential features of the living conditions of animals in deserts. Only fast-moving animals like antelope from mammals and sandgrouse of birds, overcome unfavorable conditions for them in obtaining food due to the ability to fast movement and live in large herds or flocks. The remaining species either form small groups, or live in pairs or alone.

The conditions for the existence of animals in sandy deserts are unique. The looseness of the substrate necessitates an increase in the relative surface of the paws of animals, which is achieved both in mammals and in some insects running on the substrate by the development of hairs and bristles on the paws. The development of these adaptations in mammals is important not so much when running on sand as when digging holes, since it prevents the rapid shedding of sand particles and the collapse of the walls of the dug hole. Animals usually begin digging burrows in more compacted areas directly at the base of plant stems.

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