Introduction

Today, grassy plains occupy a quarter of the entire land. They have many different names: steppes - in Asia, llanos - in the Orinoco basin, veld - in Central Africa, savanna - in the eastern part of the African continent. All these areas are very fertile. Individual plants live up to several years, and when they die, they turn into humus. Hiding among the tall grasses leguminous plants, vetch, daisies and small flowers.

The name "grass" combines a wide variety of plants. This family is perhaps the largest in the entire plant kingdom, it includes more than ten thousand species. Herbs are the product of a long evolution; they are able to survive fires, droughts, floods, so they only need an abundance of sunlight. Their flowers, small and inconspicuous, are collected in small inflorescences at the top of the stem and are pollinated by the wind without requiring the services of birds, bats or insects.

Savannah is a community of tall grasses and woodlands with low to medium sized, fire-resistant trees. It is the result of the interaction of two factors, namely soil and rainfall.

The significance of the savanna lies in the conservation of rare species of animals and plants. Therefore, the study of the African savannas is relevant.

The object of study is the African savannas

The subject of the research is the study natural features African savannas.

The purpose of this course work is a comprehensive study of the types of African savannas.

The main tasks of the work are the following:

1.Consider the geographical location of the African savannas.

2.Explore the flora and fauna of the savannas.

.Consider the features of different types of African savannas.

.Consider modern environmental problems and ways to solve them in the savannas.

Chapter I. general characteristics African savannah

.1 Geographic location and climatic features African savannah

Savannah is a zonal type of landscape in tropical and subequatorial belts, where the change of the wet and dry seasons of the year is clearly expressed, while high temperatures oh air (15-32°C). As you move away from the equator, the period of the wet season decreases from 8-9 months to 2-3, and precipitation - from 2000 to 250 mm per year. The exuberant development of plants during the rainy season is replaced by droughts of the dry period with a slowdown in tree growth and grass burnout. As a result, a combination of tropical and subtropical drought-resistant xerophytic vegetation is characteristic. Some plants are able to store moisture in the trunks (baobab, bottle tree). The grasses are dominated by tall grasses up to 3-5 m, among them are sparsely growing shrubs and single trees, the occurrence of which increases towards the equator as the wet season lengthens to light forests.

Vast expanses of these amazing natural communities are found in Africa, although there are savannahs in South America, Australia, and India. The savannah is the most widespread and most characteristic landscape in Africa. The savannah zone surrounds the Central African rain forest with a wide belt. a tropical forest. In the north, the tropical forest is bordered by the Guinean-Sudanese savannas, stretching in a strip 400-500 km wide for almost 5000 km from the Atlantic to indian ocean, interrupted only by the valley of the White Nile. From the Tana River, savannas in a belt up to 200 km wide descend south to the valley of the Zambezi River. Then the savannah belt turns to the west and, now narrowing, now expanding, extends for 2500 km from the shores of the Indian Ocean to the Atlantic coast.

The forests in the frontier strip are gradually thinned out, their composition becomes poorer, patches of savannas appear among the massifs of continuous forest. Gradually, the tropical rainforest is limited only to river valleys, and on the watersheds they are replaced by forests shedding leaves for the dry season, or savannahs. Vegetation change occurs as a result of a shortening of the wet period and the appearance of a dry season, which becomes longer and longer as one moves away from the equator.

The savannah zone from northern Kenya to the sea coast of Angola is the largest plant community on our planet in terms of area, occupying at least 800 thousand km 2. If we add another 250,000 km2 of the Guinean-Sudanese savannah, it turns out that more than a million square kilometers of the Earth's surface is occupied by a special natural complex - the African savannah.

A distinctive feature of the savannas is the alternation of dry and wet seasons, which take about half a year, replacing each other. The fact is that for the subtropical and tropical latitudes, where the savannahs are located, the change of two different air masses is characteristic - humid equatorial and dry tropical. Monsoon winds, bringing seasonal rains, significantly affect the climate of the savannahs. Since these landscapes are located between the very humid natural zones of the equatorial forests and the very dry zones of the deserts, they are constantly influenced by both. But moisture is not long enough present in the savannahs for multi-tiered forests to grow there, and dry "winter periods" of 2-3 months do not allow the savannah to turn into a harsh desert.

The annual rhythm of life in the savannas is associated with climatic conditions. During the wet period, the riot of grassy vegetation reaches its maximum - the entire space occupied by savannahs turns into a living carpet of herbs. The picture is violated only by thickly low trees - acacias and baobabs in Africa, fan palms of Ravenal in Madagascar, cacti in South America, and in Australia - bottle trees and eucalyptus trees. The soils of the savannas are fertile. During the rainy period, when the equatorial air mass dominates, both the earth and the plants receive enough moisture to feed the numerous animals that live here.

But now the monsoon leaves, and dry tropical air takes its place. Now the time for testing begins. Grasses grown to human height are dried up, trampled down by numerous animals moving from place to place in search of water. Grasses and shrubs are very susceptible to fire, which often burns large areas. This is also “helped” by the indigenous people who make a living by hunting: by specially setting fire to the grass, they drive their prey in the direction they need. People did this for many centuries and greatly contributed to the fact that the vegetation of the savannas acquired modern features: an abundance of fire-resistant trees with thick bark, like baobabs, a wide distribution of plants with a powerful root system.

The dense and high grass cover provides abundant food for the largest animals, such as elephants, giraffes, rhinos, hippos, zebras, antelopes, which in turn attract such large predators as lions, hyenas and others. The largest birds live in the savannas - the ostrich in Africa and the South American condor.

Thus, the Savannahs in Africa occupy 40% of the continent. The savannas frame the forested areas of Equatorial Africa and extend through the Sudan, East and South Africa beyond the southern tropic. Depending on the duration of the rainy season and the annual amount of precipitation, tall grass, typical (dry) and desert savannas are distinguished in them.

In savannah areas:

the duration of the rainy period ranges from 8-9 months at the equatorial borders of the zones to 2-3 months at the outer borders;

the water content of rivers fluctuates sharply; in the rainy season, there is a significant solid runoff, slope and planar runoff.

parallel to the decrease in annual precipitation, the vegetation cover changes from tall grass savannas and savanna forests on red soils to desert savannas, xerophilic light forests and shrubs on brown-red and red-brown soils.

savannah africa climatic geographic

1.2 Flora of the savannas

An abundance of tall grasses gilded by the sun, rare trees and shrubs, found more or less depending on the area - such is the savanna that occupies most of sub-Saharan Africa.

The savannah zones are quite extensive, therefore, on their southern and northern borders, the vegetation is somewhat different. The savannahs bordering the desert zone in the north of the zone in Africa are rich in drought-resistant short grasses, spurges, aloes and acacias with highly branched roots. To the south, they are replaced by moisture-loving plants, and along the banks of the rivers, gallery forests with evergreen shrubs and lianas, similar to humid equatorial forests, enter the savanna zone. In the rift valley of East Africa, the largest lakes of the mainland are located - Victoria, Nyasa, Rudolf and Albert lakes, Tanganyika. Savannahs on their banks alternate with wetlands where papyrus and reeds grow.

The African savannas are home to many famous nature reserves and national parks. One of the most famous is the Serengeti, located in Tanzania. Part of its territory is occupied by the crater highlands - a well-known plateau with ancient craters of extinct volcanoes, one of which, Ngorongoro, has an area of ​​​​about 800 thousand hectares.

The vegetation of the savannah corresponds to the hot, with long dry periods, the climate that prevails in tropical places. Because the savannah is common in different parts world, including in South America and Australia. But the most vast territories it ranks, of course, in Africa, where it is represented in all its diversity.

The general appearance of the savannas is different, which depends, on the one hand, on the height of the vegetation cover, and on the other hand, on the relative amount of grasses, other perennial grasses, semi-shrubs, shrubs and trees. The herbaceous cover is sometimes very low, even pressed to the ground.

A special form of savannas is the so-called llanos, where trees are either completely absent or are found in a limited number, with the exception of only damp places where palm trees (Mauritia flexuosa, Corypha inermis) and other plants form entire forests (however, these forests do not belong to savannahs). ); in llanos there are sometimes single specimens of Rhopala (trees from the Proteaceae family) and other trees; sometimes the cereals in them form a cover as tall as a man; Compositae, leguminous, labiate, etc. grow between cereals. Many llanos in the rainy season are flooded by the floods of the Orinoco River.

The vegetation of the savannas is generally adapted to a dry continental climate and to periodic droughts, which occur in many savannas for whole months. Cereals and other grasses rarely form creeping shoots, but usually grow in tufts. The leaves of cereals are narrow, dry, hard, hairy or covered with a waxy coating. In grasses and sedges, young leaves remain rolled up into a tube. In trees, the leaves are small, hairy, shiny (“lacquered”) or covered with a waxy coating. The vegetation of the savannas generally has a pronounced xerophytic character. Many species contain large quantities of essential oils, especially those of the Verbena, Labiaceae, and Myrtle families of the Flaming Continent. The growth of some perennial grasses, semi-shrubs (and shrubs) is especially peculiar, namely, that the main part of them, located in the ground (probably, the stem and roots), grows strongly into an irregular tuberous woody body, from which then numerous, mostly unbranched or weakly branched, offspring. In the dry season, the vegetation of the savannas freezes; savannahs turn yellow, and dried plants are often subjected to fires, due to which the bark of trees is usually scorched. With the onset of rains, the savannahs come to life, covered with fresh greenery and dotted with numerous different flowers.

In the south, on the border with the equatorial tropical forests, a transitional zone begins - the forest savannah. There are not very many herbs, the trees grow densely, but they are small. Then comes the sparsely forested savannah - vast expanses overgrown with tall grasses, with groves or separately standing trees. Baobab dominates here, as well as palm, spurge and different kinds acacias. Gradually, trees and shrubs become more and more rare, and grasses, especially giant cereals, thicken.

And finally, near the deserts (Sahara, Kalahari), the savannah gives way to the withered steppe, where only tufts of dry grass and stunted thorny bushes grow.

.3 Savannah wildlife

The fauna of the savannah is a unique phenomenon. In no corner of the Earth in the memory of mankind has there been such an abundance of large animals as in the African savannas. As early as the beginning of the XX century. countless herds of herbivores roamed the expanses of the savannas, moving from one pasture to another or in search of watering places. They were accompanied by numerous predators - lions, leopards, hyenas, cheetahs. Carrion eaters followed the predators - vultures, jackals.

The seasonally dry tropical regions of Africa, from light deciduous forests and light forests to low-growing spiny forests and the sparse Sahelian savannah, differ from evergreen forests, first of all, by the presence of a well-defined dry period unfavorable for animals. This determines the clear seasonal rhythm of most forms, synchronous with the rhythm of moisture and vegetation vegetation.

During the dry season, most animals stop breeding. Some groups, mainly invertebrates and amphibians, take shelter during drought and hibernate. Others store food (ants, rodents), migrate (locusts, butterflies, birds, elephants and ungulates, predatory beasts) or they concentrate on small areas - stations of experience (surroundings of water bodies, drying up channels with closely spaced groundwater, etc.).

Animals appear in large numbers, constructing solid shelters. Strong cone-shaped termite mounds are striking, which are more than 2 m high. The walls of these structures seem to be made of cement or baked clay, and they can hardly be broken through with a crowbar or a pickaxe. The above-ground dome protects the numerous chambers and passages below from both drying out in the hot season and rainfall during the wet season. Termite passages in depth reach aquifers of the soil; during a drought, a favorable moisture regime is maintained in the termite mound. Here the soil is enriched with nitrogen and ash elements of plant nutrition. Therefore, trees often regenerate on destroyed and near residential termite mounds. Of vertebrates, a number of rodents and even predators build burrows, ground and tree nests. The abundance of bulbs, rhizomes and seeds of grasses and trees allows them to harvest these feeds for future use.

The tiered structure of the animal population, characteristic of evergreen forests, in seasonally dry forests, light forests, and especially in savannahs, is somewhat simplified due to a decrease in the proportion of tree forms and an increase in those living on the surface and in the grass layer. However, the significant heterogeneity of vegetation, caused by a mosaic of tree, shrub and herbaceous phytocenoses, causes a corresponding heterogeneity of the animal population. But the latter is dynamic. Most animals are alternately associated with one or another plant group. Moreover, movements are not only on the scale of seasons, but even within a day. They cover not only herds of large animals and flocks of birds, but also small animals: mollusks, insects, amphibians and reptiles.

In the savannas, with their huge food resources, there are many herbivores, especially antelopes, of which there are more than 40 species. Until now, in some places there are herds of the largest wildebeests with a large mane, a powerful tail and horns bent down; Kudu antelopes with beautiful helical horns, elands, etc. are also common. There are also dwarf antelopes, reaching a little more than half a meter in length.

Remarkable are the animals of the African savannas and semi-deserts saved from extinction - giraffes, they have been preserved mainly in national parks. The long neck helps them to get and gnaw young shoots and leaves from trees, and the ability to run fast is the only means of protection from pursuers.

In many areas, especially in the east of the continent and south of the equator, African wild zebra horses are common in the savannas and steppes. They are hunted mainly for their strong and beautiful hides. In some places, domesticated zebras are replacing horses, as they are not susceptible to tsetse bites.

Until now, African elephants have been preserved - the most remarkable representatives of the fauna of the Ethiopian region. They have long been exterminated for their valuable tusks, and in many areas they have completely disappeared. Elephant hunting is currently prohibited throughout Africa, but this ban is often violated by ivory poachers. Now elephants are found in the least populated mountainous areas, in particular in the Ethiopian highlands.

In addition, they live in the national parks of East and South Africa, where their population is even increasing. But still, the existence of the African elephant as a biological species in recent decades turned out to be under a real threat, which can only be prevented by active joint activities of national and international organizations. Among the endangered animals are rhinos that lived in the eastern and southern parts of the mainland. African rhinos have two horns and are represented by two species - black and white rhinoceros. The latter is the largest of modern species and reaches a length of 4 m. Now it is preserved only in protected areas.

Hippos are much more widespread, living along the banks of rivers and lakes in different parts of Africa. These animals, as well as wild pigs, are exterminated for their edible meat and also for their skin.

Herbivores serve as food for numerous predators. In the savannahs and semi-deserts of Africa, lions are found, represented by two varieties: the Barbary, living north of the equator, and the Senegal, common in the southern part of the mainland. Lions prefer open spaces and almost never enter forests. Hyenas, jackals, leopards, cheetahs, caracals, servals are common. There are several members of the civet family. In the plain and mountain steppes and savannahs there are many monkeys belonging to the group of baboons: real Raigo baboons, geladas, mandrills. Of the thin-bodied monkeys, the Gverets are characteristic. Many of their species live only in a cool mountain climate, as they do not tolerate the high temperatures of the lowlands.

Among rodents, mice and several types of squirrels should be noted.

Birds are numerous in the savannas: African ostriches, guinea fowls, marabou, weavers, a very interesting secretary bird that feeds on snakes. Lapwings, herons, pelicans nest near water bodies.

There are no less reptiles than in the northern deserts, often they are represented by the same genera and even species. Many different lizards and snakes, land turtles. Some types of chameleons are also characteristic. There are crocodiles in the rivers.

The great mobility of animals makes the savannah highly productive. Wild ungulates are almost constantly on the move, they never overgraze the way livestock do. Regular migrations, i.e., movements, of herbivorous animals of the African savanna, covering hundreds of kilometers, allow the vegetation to fully recover in a relatively short time. It is not surprising that in last years the idea arose and strengthened that a reasonable, scientifically based exploitation of wild ungulates promises greater prospects than traditional pastoralism, primitive and unproductive. Now these questions are being intensively developed in a number of African countries.

Thus, the fauna of the savannah has been developing for a long time as a single independent whole. Therefore, the degree of adaptation of the entire complex of animals to each other and each individual species to specific conditions is very high. Such adaptations include, first of all, a strict division according to the method of feeding and the composition of the main feed. The vegetation cover of the savannah can only feed a huge number of animals because some species use grass, others use young shoots of shrubs, others use bark, and others use buds and buds. Moreover, different types of animals take the same shoots from different heights. Elephants and giraffes, for example, feed at the height of the tree crown, the giraffe gazelle and the large kudu reach the shoots located one and a half to two meters from the ground, and the black rhinoceros, as a rule, breaks the shoots near the ground. The same division is observed in purely herbivorous animals: what the wildebeest likes does not attract the zebra at all, and the zebra, in turn, nibbles grass with pleasure, past which the gazelles pass indifferently.

Chapter II. Features of the types of African savannas

.1 Tall grass wet savannas

Tall grass savannas are various combinations of grassy vegetation with forest islands or individual tree specimens. The soils that form beneath these landscapes are referred to as red or ferralitic soils of seasonal rainforests and tall grass savannahs.

Tall grass savannas are wet. They grow very tall cereals, including elephant grass, which reaches 3 m in height. Among these savannahs are scattered arrays of park forests, gallery forests stretch along the riverbeds.

Tall grass savannas occupy an area where the annual precipitation is 800-1200 mm, and the dry season lasts 3-4 months, they have a dense cover of tall grasses (elephant grass up to 5 m), groves and massifs of mixed or deciduous forests on watersheds, gallery evergreen ground moisture forests in the valleys. They can be called a transition zone from forest vegetation to a typical savannah. Among the continuous cover of high (up to 2-3 m) grasses, trees (as a rule, deciduous species) rise. The tall grass savannah is characterized by baobabs, acacias, and terminalia. Red lateritic soils are most common here.

There is an opinion that the wide distribution of moist tall-grass savannahs, replacing deciduous-evergreen forests, is associated with human activity, which burned vegetation during the dry season. The disappearance of the dense tree layer contributed to the appearance of countless herds of ungulates, as a result of which the renewal of tree vegetation became impossible.

The Sahelian savannas and, to a lesser extent, the spiny forests of Somalia and the Kalahari are faunistically depleted. Many of the animals that are close or common with the forest disappear here.

2.2 Typical grass savannas

From the border of the hylae, the zone of cereal savannah begins. Typical (or dry) savannas are replaced by tall grasses in areas where the rainy season lasts no more than 6 months. The grasses in such savannahs are still very dense, but not very tall (up to 1 m). Grassy spaces alternate with light forests or individual groups of trees, among which numerous acacias and giant baobabs, or monkey bread trees, are especially typical.

Typical grass savannahs are developed in areas with an annual rainfall of 750-1000 mm and a dry period of 3 to 5 months. In typical savannahs, a continuous grass cover is not higher than 1 m (species of bearded vulture, temedy, etc.), from tree species characteristic palm trees (fan, hyphena), baobabs, acacias, in East and South Africa - euphorbia. Most of the wet and typical savannas are of secondary origin. In Africa, north of the equator, the savannahs extend in a wide strip from the Atlantic coast to the Ethiopian highlands, while south of the equator they occupy the north of Angola. The height of wild-growing cereals reaches 1-1.5 m, and they are mainly represented by hyperrhenium and bearded vultures.

A typical grass savanna is an area entirely covered with tall grasses, with a predominance of grasses, with sparsely standing individual trees, shrubs or groups of trees. Most plants have a hydrophytic character due to the fact that during the rainy season the air humidity in the savannas resembles a tropical forest. However, plants of a xerophytic character also appear, adapting to the transfer of a dry triode. Unlike hydrophytes, they have smaller leaves and other adaptations to reduce evaporation.

During the dry period, grasses burn out, some types of trees drop their leaves, although others lose it only shortly before the new one appears; savanna becomes yellow; dried grass is annually burned to fertilize the soil. The damage that these fires of vegetation bring is very great, since it violates normal cycle winter dormancy of plants, but at the same time it also causes their vital activity: after a fire, young grass quickly appears. When the rainy season comes, cereals and other herbs grow amazingly quickly, and the trees are covered with leaves. In the grass savanna, the grass cover reaches heights of 2-3 m. , and in low places 5 m .

Of the cereals here are typical: elephant grass, species of Andropogon, etc., with long, wide, hairy leaves of a xerophytic appearance. Of the trees, the oil palm 8-12 m should be noted. heights, pandanus, butter tree, Bauhinia reticulata is an evergreen tree with broad leaves. Baobab and various types of doum palm are often found. Along the river valleys stretch several kilometers wide gallery forests resembling giley, with many palm trees.

Cereal savannas are gradually replaced by acacia. They are characterized by a continuous cover of grasses of lower height - from 1 to 1.5 m. ; of the trees they are dominated by various types of acacias with a dense umbrella-shaped crown, for example, species: Acacia albida, A. arabica, A. giraffae, etc. In addition to acacias, one of the characteristic trees in such savannas is the baobab, or monkey breadfruit, reaching 4 min diameter and 25 m height, containing a significant amount of water loose fleshy trunk.

In the cereal savanna, where the rainy season lasts 8-9 months, cereals grow 2-3 m high, and sometimes up to 5 m: elephant grass (Pennisetum purpureum), bearded vulture with long hairy leaves, etc. Among solid sea cereals rise individual trees: baobabs (Adansonia digitata), doom palms (Hyphaene thebaica), oil palms.

To the north of the equator, the cereal savannahs reach approximately 12°N. In the southern hemisphere, the zone of savannas and light forests is much wider, especially off the coast of the Indian Ocean, where it extends in places to the tropic. The difference in moisture conditions in the northern and southern parts of the zone suggests that mesophilic deciduous forests grew in the more humid northern regions, while xerophytic light forests with a predominance of representatives of the legume family (Brachystegia, Isoberlinia) occupied only the southern regions of their modern distribution. To the south of the equator, this plant formation was called the "miombo" woodlands. The expansion of its range can be explained by resistance to fires, high speed renewal. In eastern South Africa, woodlands occur in combination with other types of vegetation well south of the tropic.

Under grass savannahs and light forests, special types of soils are formed - red soils under savannahs and red-brown soils under forests.

In drier areas, where the rainless period lasts from five to three months, dry spiny semi-savannahs predominate. Most of the year the trees and shrubs in these areas stand without leaves; low grasses (Aristida, Panicum) often do not form a continuous cover; among cereals grow low up to 4 m heights, thorny trees (Acacia, Terminalia, etc.)

This community is also called the steppe by many researchers. This term is widely used in the literature devoted to the vegetation of Africa, but does not quite correspond to the understanding of our term "steppe".

Dry thorny semi-savannahs are replaced with the distance from the acacia savannahs to the so-called thorny-shrub savannah. It reaches 18-19 ° S. sh., occupying most of the Kalahari.

2.3 Desert savannas

In areas with a wet period of 2-3 months. typical savannahs turn into thickets of thorny bushes and hard grasses with sparse turf. As the wet period is reduced to 3-5 months. and a general decrease in precipitation, the grass cover becomes more sparse and stunted, various acacias predominate in the composition of tree species, low, with a peculiar flat crown. Such plant communities, called desert savannas, form a relatively narrow band in the northern hemisphere north of the typical savannas. This strip expands from west to east in the direction of decreasing annual precipitation.

In the deserted savannas, scanty rains are rare and occur only for 2-3 months. The strip of these savannas, stretching from the coast of Mauritania to Somalia, expands to the east of the African continent, and this natural zone also covers the Kalahari basin. The vegetation here is represented by turf grasses, as well as thorny shrubs and low leafless trees. In typical and deserted savannas, tropical red-brown soils are developed, not rich in humus, but with powerful alluvial horizons. In places of development of basic rocks and lava covers - in the southeast of Sudan, in Mozambique, Tanzania and the Shari River basin - significant areas are occupied by black tropical soils related to chernozems.

Under such conditions, instead of a continuous herbaceous cover, only turf grasses and leafless and thorny shrubs remain. The belt of semi-deserts or deserted savannahs on the Sudanese plains is called "sahel", which in Arabic means "shore" or "edge". This is really the outskirts of green Africa, beyond which the Sahara begins.

In the east of the mainland, desert savannahs occupy especially large areas, covering the Somali peninsula and extending to the equator and south of it.

Deserted savannas are typical for areas with an annual rainfall of no more than 500 mm and a dry period of 5 to 8 months. Deserted savannahs have a sparse grass cover, thickets of thorny bushes (mainly acacias) are widespread in them.

Despite a number common features, savannahs are distinguished by considerable diversity, which makes it very difficult to separate them. There is a point of view that most of the savannahs of Africa arose on the site of exterminated forests and only deserted savannahs can be considered natural.

Chapter III. Ecological problems of African savannas

.1 Human role in the savannah ecosystem

Among biocenoses of dry land, the steppes produce the largest biomass of animals per unit of surface, therefore, from time immemorial, they have attracted a person who lived mainly by hunting. This upright primate was created by nature itself to live in the steppes, and it was here that in the struggle for food and shelter, escaping from enemies, he turned into a rational being. However, improving, man increasingly complicated his weapons and invented new methods of hunting herbivores and predatory animals, which played a fatal role for many of them.

Whether ancient man was already involved in the extermination of a number of animal species is a moot point. There are various, very conflicting opinions on this matter. Some scientists believe that many inhabitants of the African savannahs and steppes were already destroyed in the early Paleolithic, characterized by the use of a hand ax (the so-called Acheulean culture). According to supporters of this opinion, the same thing happened in North America, when about 40 thousand years ago man first entered this continent through the Bering Bridge. At the end of the Ice Age, 26 genera of African and 35 genera of North American large mammals disappeared from the face of the Earth.

Proponents of the opposite point of view insist that ancient man, with his still extremely imperfect weapons, cannot be considered guilty of their destruction. Mammals that went extinct at the end of the Ice Age were most likely victims of global climate change that affected the vegetation that served them as food or their prey.

It has been established that when, much later, well-armed people appeared in Madagascar, whose animal world did not know natural enemies, this led to very sad consequences. In Madagascar, in a relatively short period of time, at least 14 species of large lemurs, 4 species of giant ostriches were exterminated, and, in all likelihood, the aardvark and pygmy hippopotamus befell the same fate.

However, only when a white man applied firearms, this led to a catastrophic imbalance between him and the world of large animals. By now, in all corners of the Earth, man has almost completely destroyed the large animals of the savannas, turning the once endless grassy plains into arable land or pastures for livestock.

The destruction of the original vegetation led to the disappearance of many small and medium-sized animals. Only in national parks and other protected areas are the remains of a unique community of living creatures that have been formed over millions of years. The man-hunter destroyed his steppe ancestral home and many animals generated by the amazing savannah ecosystem.

A hundred years ago, Africa was represented as a continent of untouched nature. However, even then nature was significantly changed. economic activity person. At the beginning of the 21st century, the environmental problems that arose during the predatory campaigns of European colonialists escalated.

Evergreen forests have been cut down for centuries for redwoods. They were also uprooted and burned for fields and pastures. Burning of plants in slash-and-burn agriculture leads to a violation of the natural vegetation cover and deterioration of the soil. Its rapid depletion forced to leave cultivated land after 2-3 years. Now almost 70% of Africa's forests have been destroyed, and their remains continue to disappear rapidly. In place of forests, plantations of cocoa, oil palm, bananas, and peanuts arose. Deforestation leads to many negative consequences: an increase in the number of floods, increased droughts, the occurrence of landslides, and a decrease in soil fertility. Reproduction of forests is very slow.

The nature of the savannas has also been significantly changed. Huge areas are plowed up there, pastures. Due to overgrazing of cattle, sheep and camels, cutting down trees and shrubs, the savannas are increasingly turning into deserts. Especially negative consequences of such use of land in the north, where the savannah turns into desert. The expansion of desert areas is called desertification.

Aerospace images taken from artificial Earth satellites have convincingly shown that in the last half century alone, the Sahara has moved south by 200 km. and increased its area by thousands of square kilometers.

Protective forest belts are planted on the border with deserts, cattle grazing is limited in areas with a sparse vegetation cover, and arid regions are irrigated. Great changes in natural complexes occurred as a result of mining.

Long colonial past and irrational use natural resources led to a serious imbalance between the components of natural complexes. Therefore, in many countries of Africa, the problems of nature protection have become acute.

3.2 Economic role of savannas

Savannas play a very important role in human economic life. According to climatic and soil conditions, the savannas are favorable for tropical agriculture. At present, significant areas of savannas have been cleared and plowed up. Significant areas are plowed up here, cereals, cotton, peanuts, jute, sugar cane and others are grown. Animal husbandry is developed in drier places. Some species of trees growing in savannahs are used by humans for their own purposes. So, teak wood gives solid valuable wood that does not rot in water.

At present, it can be said with full confidence that a significant part of the wet and dry savannahs of Africa arose as a result of human activities on the spot. mixed forests, almost disappeared deciduous forests and light forests. Since man learned how to make fire, he began to use it for hunting, and later for clearing thickets for arable land and pastures. For millennia, farmers and pastoralists set fire to the savannah before the start of the rainy season to fertilize the soil with ash. Arable land, which quickly lost fertility, was abandoned after several years of use, and new areas were prepared for crops. In pasture areas, vegetation suffered not only from burning, but also from trampling, especially if the number of livestock exceeded the fodder "capacity" of pasture lands. The fire destroyed most of the trees. For the most part, only a few tree species that have adapted to fires, the so-called "fire-loving" ones, have survived, the trunk of which is protected by thick bark, which is charred only from the surface.

Plants that reproduce by root shoots or have seeds with a thick shell have also survived. Among the fire-lovers are thick-bodied giant baobabs, the shea tree, or karite, called the oil tree, since its fruits give edible oil, etc.

The fencing of private properties, the construction of roads, steppe fires, the opening of large areas and the expansion of cattle breeding aggravated the plight of wild animals. Finally, the Europeans, unsuccessfully trying to fight the tsetse fly, staged a grand slaughter, and more than 300 thousand elephants, giraffes, buffaloes, zebras, wildebeest and other antelopes were shot from rifles and machine guns from vehicles. Many animals also died from the plague brought with cattle.

3.3 Conservation action to protect the African Savannahs

The fauna of the African savannah is of great cultural and aesthetic importance. Untouched corners with pristine rich fauna literally attract hundreds of thousands of tourists. Each African reserve is a source of joy for many, many people. Now you can drive hundreds of kilometers across the savannas and not meet a single large animal.

Once virgin forests are being developed by man and gradually uprooted to clear land, or cut down for the purpose of harvesting building materials. Further, the soil, which is no longer strengthened by plant roots and protected by tree crowns, is washed away during tropical rains, and the natural landscape, rich in the recent past, becomes impoverished, transforming into a barren desert.

Often the interests of the wild inhabitants of Africa run counter to the needs of the local population, which makes the protection of wildlife in Africa complicated. In addition, environmental protection measures are also more expensive, and not every country's government can afford to finance them.

However, some African states are concerned about the state of wild flora and fauna on their territory, so nature protection is given increased attention. Wild animals are protected in the national parks of such countries, water bodies are to be cleaned for fish breeding, and comprehensive measures are being taken to restore forests.

New governments independent states Africa, throwing off the yoke of colonialism, strengthened and expanded the network of such reserves - the last refuges for wild animals. Only there can one still admire the view of the primeval savannah. For this purpose, protected areas are being established - nature reserves and national parks. They protect the components of natural complexes (plants, animals, rocks etc.) and research work is underway. Reserves have a strict environmental regime, and tourists who are required to comply with established rules can visit national parks.

In Africa, protected areas are large areas. They are arranged in various natural complexes - in the mountains, on the plains, in humid evergreen forests, savannahs, deserts, on volcanoes. Serengeti, Kruger, Rwenzori national parks are world-wide.

National natural Park Serengeti- One of the largest and most famous in the world. Translated from the Maasai language, its name means boundless plain. The park is located in East Africa. It is called the African paradise for animals. Herds of thousands of large ungulates (various species of antelopes, zebras) and predators (lions, cheetahs, hyenas) live in its expanses, which have been preserved in an untouched state as they have been since time immemorial.

national park Kruger- One of the oldest on the mainland. It originated in southern Africa as early as 1898. Buffaloes, elephants, rhinoceros, lions, leopards, cheetahs, giraffes, zebras, various antelopes, marabou, secretary birds reign supreme in this region of the savannah. Each type of animal has thousands of individuals. By their diversity, the park is often compared to Noah's Ark.

Ngorongoro National Parklocated in the crater of an extinct volcano. Buffaloes, rhinos, antelopes, giraffes, hippos, and various birds are protected there.

At Rwenzori parkchimpanzees and gorillas are protected.

The creation of reserves and national parks contributes to the conservation of rare plants, unique wildlife and individual natural complexes of Africa. Thanks to protective measures, the number of many species of animals that were on the verge of extinction has been restored. The world's largest diversity of species makes Africa a real paradise for ecotourists.

Conclusion

The African savannas are the Africa of our imagination. Huge expanses of the earth, unusually amazing fauna, the greatest herds on the planet. And everything seems to exist here outside of time.

Savannah is incredibly changeable, fickle. A dense forest may appear in this place in a few years. But there may be another development of events: all the trees will disappear, only grass will remain.

Savannah life is subject to the weather, which is very capricious here. Every year there is a dry, hot season. But no year is like the previous one.

The significance of the savannas is enormous. This is, first of all, biological value communities as habitats for many species of animals and plants, including those that are endangered. Also, savannahs, after the forest zone, give the highest yield of plant products.

It's sad, but once Live nature Africa was even more diverse. Currently, unfortunately, part of the species of wild flora and fauna is completely destroyed, and some more are under the threat of extermination.

A great misfortune for the inhabitants of the African savannahs are hunters who harass commercial species of animals under the root. But the advance of civilization on the original natural habitats of representatives of the wild fauna of Africa has become no less a problem. The traditional routes of migration of wild animals are blocked by roads, and new human settlements appear in places of wild thickets.

Now humanity understands the need to protect nature on Earth - it can be hoped that in the near future the wildlife of Africa will not only not suffer even more from human activity, but will also, to some extent, restore its impoverished flora and fauna, returning to it its former splendor and diversity. .

List of sources

1. Boris Znachnov Radio Africa / Around the World No. 4, 2008 S. 84-92

Boris Zhukov Eden at the bottom of the boiler / Vokrug Sveta No. 11, 2010 P. 96-101

Vlasova T.V. Physical geography of continents and oceans: a textbook for students. higher ped. textbook institutions / T.V. Vlasova, M.A. Arshinova, T.A. Kovalev. - M.: Publishing Center "Academy", 2007. - 487p.

Vladimir Korachantsev. Moscow. Armada-press, Africa-land of paradoxes (Green series 2001. Around the world), 2001- 413s.

Gusarov V.I. Aggravation environmental issues Africa /Kraєznavstvo. Geography. Tourism №29-32, 2007 pp. 7-11

Kryazhimskaya N.B. Planet Earth. Equatorial and subequatorial belt M., 2001 - 368 p.

Mikhailov N.I. Physical-geographical zoning. M.: Publishing House of Moscow State University, 1985.

Nikolai Balandinsky The Pearl of Tanzania / Around the World No. 12, 2008 p118-129

Yurkivsky V. M. The land of the world: Dovid. - K .: Libid, 1999.

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Biologists managed to observe an interesting ecological war. On one side fought the largest land animals of the planet - African elephants, on the other - ants. And the insects won this battle. There is a saying among biologists: “Before your eyes, an animal from the Red Book is eating a plant from the Red Book. What are you going to do?" This joke is quite vital: in wild nature conflicts of interest are not uncommon. One multiplied species causes damage to another species and the entire ecosystem. For residents middle lane the most painful example is beavers, which, if there are too many of them, not only fell individual trees, but also swamp the forest and completely change the landscape. The African savannah has its own problems: landscapes suffer from African elephants, which, thanks to protection, have greatly bred. The African elephant is the largest land mammal, each individual requires vegetation from an area of ​​\u200b\u200babout 5 km² to feed. learn a lot of interesting things http://twitter.com/malno2003 right now. Very interesting and informative. They eat branches and leaves from trees, peel off the bark, trample grass and destroy shrubs. In the past, elephants were able to migrate over long distances, and during their absence, damaged vegetation had time to recover. Now these animals are concentrated in national parks in a limited area. Therefore, they greatly change the landscape of the savannah, in some places turning it into a treeless plain. At the "table and house" ants work to protect species in nature symbiosis Close and prolonged coexistence of different species. Rakhnovidnosti: mutualism (mutually beneficial relationship), parasitism (relationships that are beneficial to one, but harmful to another), commensalism (relationships that are useful to one, but useless to another). However, African trees found defenders - small ants of four species (Crematogaster mimosae, C. nigriceps, C. sjostedti, and Tetraponera penzigi). They enter into symbiosis with trees - mainly with the acacia Acacia drepanolobium. Insects receive food (nectar) from the tree and shelter in the form of swellings at the base of the thorns. And the benefits of insects for trees become clear gradually. As installed in the field and laboratory experiments Todd Palmer of the Mpala Research Center in Kenya and Jacob Goheen of the University of Florida, ants prevent elephants from eating trees and thereby preserve the local ecosystem. So the symbiosis of acacias with ants can be attributed to mutualism - mutually beneficial relationship . “It's like the story of David and Goliath,” comments Todd Palmer. “Tiny ants weighing about 5 mg stand up to huge animals a billion times their size, protect trees and have a big impact on the ecosystem in which they live.” In the Laikipia region, in Kenya, where biologists worked, they noticed that elephants eat all types of trees in the savannah, except for those that live in symbiosis with ants. The best hair products on this site. Be the most beautiful. Acacia A. drepanolobium dominates in areas with clay soil, while in areas with sandy soil, trees of different species alternate. Scientists set up a long-term experiment: they fenced off areas of the savannah on both soils with high fences, blocking access to large animals. In six years, the population density of elephants in Laikipia has increased by 2.5 times. The biologists assessed changes in the savanna tree cover throughout the area and in the fenced areas. On sandy soil in the Elephant Free Zone, tree cover increased by 6%, while it decreased by 8.8% in the control plots. On the clay soil, where the “ant” acacia dominated, the fenced and control areas did not differ - the elephants did not touch either one or the other. acacias of another species, A. mellifera, living without ants. They then removed the ants from some of the branches of A. drepanolobium and moved them to the branches of A. mellifera. Six elephants were offered a choice of two types of acacia with and without ants. It turned out that elephants willingly eat any kind of acacia without insects, and seasoning from ants makes any species inedible for them. The experiment was repeated in nature. Ants were smoked out of their shelters with the smoke of burning grass, after which the liberated trees were fenced off from crawling insects. And we looked at the condition of the plots after 6 and 12 months. Deprived of defenders, the trees began to eat elephants. Some trees were deprived of ants not completely, but by 30% and 60%, and the degree of their nibbling was proportional to the number of remaining symbionts. The number of ants on a tree was estimated by the number of insects climbing the trunk per minute. Ants in the trunk - very unpleasant It turned out that the “Achilles heel” of an elephant is its trunk, which makes the giant vulnerable to insects. Although the outside of the trunk is covered with rough skin, inside it is very delicate and sensitive, its inner surface has a lot of nerve endings. Ants crawl into the trunk and bite, and this is very unpleasant and painful for the elephant. Unlike elephants, giraffes are more tolerant of ants - they lick insects from their snouts. long tongue. Therefore, giraffes calmly eat "ant acacias." But since giraffes are not comparable in size to elephants, they do not cause as much damage to the savannah. Come in here. Rent luxury apartments in Odessa. Center. Expensive. You'll like it. You will not regret. I recommend Ants stabilize the landscapeThe activity of ants affects the entire ecosystem. The savannah is a stable community of grasses and trees, but the animals that live in it shift the balance either one way or the other. A decrease in the number of elephants can transform the savannah into a continuous forest. Conversely, an increase in the number of elephants turns the savannah into an open steppe. Ants in this case serve as a stabilizer, softening the influence of large animals on vegetation. And the predominance of almost exclusively acacia forests in most of the Kenyan savanna is their merit. An article about the war of ants with elephants was published in the journal Current Biology.

All the constituent parts of the animal and plant world are closely interconnected and enter into complex relationships. Some are beneficial to the participants or generally vital, such as lichens (the result of a symbiosis of fungus and algae), others are indifferent, and still others are harmful. Based on this, it is customary to distinguish three types of relationships between organisms - this is neutralism, antibiosis and symbiosis. The first, in fact, is nothing special. These are such relations between populations living in the same territory, in which they do not influence each other, do not interact. But antibiosis and symbiosis - examples of which are very common, are important components of natural selection and participate in the divergence of species. Let's dwell on them in more detail.

Symbiosis: what is it?

It is a fairly common form of mutually beneficial cohabitation of organisms, in which the existence of one partner is impossible without the other. The most famous case is the symbiosis of a fungus and algae (lichens). Moreover, the first receives the products of photosynthesis synthesized by the second. And the algae extracts mineral salts and water from the hyphae of the fungus. Life alone is not possible.

Commensalism

Commensalism is actually a one-sided use by one species of another, without having a harmful effect on it. It can be carried out in several forms, but the main two are:

All others are to some extent modifications of these two forms. For example, entoykia, in which one species lives in the body of another. This is observed in karapus fish, which use the cloaca of holothurians (a species of echinoderms) as a dwelling, but feed outside it on various small crustaceans. Or epibiosis (some species live on the surface of others). In particular, barnacles feel good on humpback whales, absolutely not disturbing them.

Cooperation: description and examples

Cooperation is a form of relationship in which organisms can live separately, but sometimes come together for a common benefit. It turns out that this is an optional symbiosis. Examples:

Mutual cooperation and living together in an animal environment is not uncommon. Here are just a few of the more interesting examples.

Symbiotic relationships between plants

Plant symbiosis is very common, and if you look closely at the world around us, you can see it with the naked eye.

Symbiosis (examples) of animals and plants

The examples are very numerous, and many relationships between different elements of the plant and animal world are still poorly understood.

What is antibiosis?

Symbiosis, examples of which are found at almost every step, including in human life, as part of natural selection is an important component of evolution as a whole.

On the New Territory of the Zoo there is a corner of the African savanna, the most amazing place on Earth, where several species of large ungulates can be seen simultaneously from one point. They get along great there. giraffes, a variety of antelopes, zebras and African ostrich. In nature, each species, without competing with another, feeds in a certain plant layer: antelopes eat young succulent shoots, zebras' favorite food is cereal inflorescences, and giraffes graze at a height of 2-6 meters, eating parts of plants that are inaccessible to other animals.

In search of pastures with fresh grass and watering places, the inhabitants of the savannas make seasonal migrations. The migration of many thousands of herds of ungulates is a truly majestic spectacle, which can still be observed in the African savanna to this day.

In a large clearing, you can simultaneously see a giraffe, a zebra, and an African ostrich. Like any neighbors, they communicate, play, and sometimes quarrel with each other. The young giraffe, a female, arrived at the zoo from Africa at the end of 2004, she is accustomed to and completely trusts people, despite the fact that she was born in nature and suffered a tiring journey. Food is placed in special baskets suspended at a height of 3 m, but the animal is happy to “cut” those trees from below that it can reach.

Giraffe- the tallest land animal on Earth, the growth of large males reaches a 6-meter mark, in addition, these creatures have a long, up to 40 cm, tongue, which, moreover, is extremely flexible and mobile. In nature, with such a tongue, they pluck young shoots of acacias, deftly bypassing the sharp thorns of these plants. In the zoo, giraffes are fed hay, willow branches, vegetables and fruits.

Zebra Grevy, living in the African meadow - the largest and most elegant of all existing species zebras These animals are threatened with extinction in nature. Despite the strictest ban, poaching continues on them, the main reason for which is an unusually beautiful skin. Scientists are still looking for an explanation for the color of zebras, but perhaps the English writer R. Kipling said it best of all: “Having spent a long time half in the shade, half in the light under the changeable pattern of shadows falling from tree branches, the giraffe became spotted, and the zebra striped ... and the leopard ran around and wondered what happened to his breakfast and lunch ... "

In the summer of 2009 our zebras had a baby. This is the first birth of Grevy's zebra at the Moscow Zoo. In 2011, another zebra was born. Children in zebras, like in horses, are born fully formed, after a few minutes they stand on their legs, take their first steps and begin to suck milk. By the end of the first day, they are already trying to play, funny bouncing and kicking with all four legs. They spent their happy childhood in the African meadow with their mother, and when they grew up, they left for other zoos.

black antelope- one of the largest and most spectacular African antelopes - invariably attracts attention with a contrasting head color and long saber-shaped horns. Despite the formidable appearance, the horns are only a tournament weapon for males. In the mating season, the sound of clashing horns is heard over the savannah, the strongest bend the heads of their rivals to the ground and win the right to leave descendants.
The appearance of the wildebeest is not consistent with the image of the antelope that lives in our imagination: a slender graceful animal with a graceful head and huge expressive eyes. This antelope has bull horns and a nose, a horse's tail and a unique beard that grows up and down. In addition, from such a large animal you absolutely do not expect to hear an almost "bird" whistle. Both appearance and voice give the beast a formidable and comical look at the same time. The zoo contains the most rare view of these antelopes is the white-tailed wildebeest.

African ostrich - the largest bird in the world. Males reach a height of 270 cm and a weight of 150 kg! By the way, males and females are very easy to distinguish not only in size, but also in color. The elegant black outfit of the male is decorated with lush white feathers. The grayish-brown plumage of females looks much more modest. These giants cannot fly, but they run excellently, reaching speeds of up to 70 km / h. An ostrich has only two toes on its feet, and one of them is noticeably larger. When the bird runs, it “rises on tiptoe” and pushes off the ground only with powerful inner fingers.

Since August 2009, a family has been living in a separate enclosure to the left of the entrance to the pavilion meerkat. In summer, these animals can be seen in the outdoor enclosure, in winter - inside the pavilion.
These cute and funny animals in nature live in South Africa, in harsh conditions the Kalahari and Namib deserts. People have nicknamed them "sentinels of the desert" for their characteristic high stance on their hind legs and for the vigilance they show in guarding territory and defending themselves from enemies. These small predators feed mainly on insects and other invertebrates, including dangerous ones such as scorpions, which are eaten by meerkats along with a venom gland. They also hunt small snakes, and drive large ones out of their territory. Therefore, local residents are always happy to see meerkats near their homes, and sometimes even start them at home, since these animals are easily tamed. However, do not rush to get a meerkat as a pet, these animals feel good only in a family of their own kind. Single meerkats, both in captivity and at home, live poorly and not for long.

The aviary to the right of the entrance was specially converted for pygmy hippopotamus. This wonderful animal came to the zoo in the summer of 2017. The pygmy hippopotamus is not at all a reduced copy of the large one, although it certainly looks very much like its much larger counterpart. The appearance of the "baby" is not so heavy, the back line is slightly inclined forward, the legs and neck are relatively longer, and the head is smaller and neater. The eyes and nostrils do not protrude as high above the head as in an ordinary hippo, due to which the muzzle looks very charming. The body length of hippos is about 1.5 meters, and their weight is 250 kg. For comparison: the body weight of an ordinary hippopotamus can reach 3500 kg. At home, in Africa, pygmy hippos are endangered, there are no more than one thousand of them left. Fortunately, they are kept and bred in many zoos around the world, and there is hope that these wonderful animals will not disappear from the face of the Earth. Unfortunately, you can see the pygmy hippopotamus in the enclosure only in summer, its winter enclosure is not on display.

Since October 2009, tiny antelopes have been kept in the pavilion dik-dik. This is the smallest antelope in the world, their weight is no more than 5 kg. Dik-diks are charming graceful creatures, their gray-speckled fur seems to be sprinkled with salt, a red crest on their heads between the horns, beautiful white “glasses” around their huge eyes. Thin legs end in hooves. Males have sharp horns.

Dik-diks live in the African bush, in the thickets thorny bushes, laying tunnels-paths in them. These paths are so narrow that only such a small creature as a dik-dik can fit there. In case of danger, they disappear into the bushes literally before our eyes. So small and defenseless antelopes survive surrounded by large African predators. Thorny bushes are not only their home and safe haven - the leaves of the bushes are their main food. The diet of dik diks is similar to that of giraffes, but giraffes eat leaves high in the trees, and pygmy antelopes near the ground.

You can see dik-diks in one of the inner enclosures. In the zoo, they lead a lifestyle typical of most representatives of the African fauna - they are active in the morning, sleep in nest houses made of branches during the day, and have a period of little activity in the evening. The main food in the zoo is twigs, grass, oats, carrots. In the aviary for antelopes, several houses made of branches were equipped. Employees jokingly call dik-dik - rustling in the blackthorn.

Abstract on ecology was prepared by Natalia Morozova

10th grade school №1328

In nature, every living organism does not live in isolation. It is surrounded by many other representatives of wildlife. And they all interact with each other. Interactions between organisms, as well as their influence on living conditions, are a combination of biotic factors.

Biotic factors are a set of influences of the vital activity of some organisms on others.

Among them are usually distinguished:

1. Influence of animal organisms (zoogenic factors)

2. Influence of plant organisms (phytogenic factors)

3. Human influence (anthropogenic factors)

The action of biotic factors can be considered as their action on the environment, on individual organisms inhabiting this environment, or the action of these factors on entire communities.

Types of interactions.

Heterotypic reactions are relationships between individuals of different species. The influence that two species living together have on each other can be neutral, favorable or unfavorable. Hence, the types of relationships can be as follows:

Neutralism - both types are independent and do not have any influence on each other.

Competition - each of the species has an adverse effect on the other. Species compete for food, shelter, egg-laying sites, etc. Both species are called competitive.

Mutualism is a symbiotic relationship where both cohabiting species benefit each other.

Collaboration - both species form a community. It is not mandatory, since each species can exist separately, in isolation, but living in a community benefits both of them.

Commensalism (literally, “eating together at the same table”) is a relationship of species in which one of the partners benefits without harming the other.

Ammensalism is a type of interspecies relationship in which, in a shared habitat, one species suppresses the existence of another species without experiencing opposition.

Predation is a type of relationship in which representatives of one species eat (destroy) representatives of another, that is, organisms of one species serve as food for another.

Protocooperation (literally: primary cooperation) is a simple type of symbiotic relationship. In this form, the coexistence is beneficial for both species, but not necessarily for them, i.e. is not an indispensable condition for the survival of species (populations).

With commensalism, as useful-neutral relationships, the following are distinguished:

Eating together is the consumption of different substances or parts of the same food.

Freeloading is the consumption of the host's leftover food.

Lodging - the use by some species of others (their bodies or their dwellings) as a shelter or dwelling.

It should be remembered that the types of relationships of a particular pair may vary depending on external conditions or life stages of interacting organisms. In addition, in nature, it is not a couple that is involved in relationships, but a much larger number. Interspecific relations in nature are infinitely diverse.

Neutralism.

If two species do not influence each other, then neutralism takes place.

With neutralism, individuals are not directly related to each other. Both species live in the same territory without coming into contact, so their cohabitation does not entail both positive and negative consequences for them, but depends on the state of the communities as a whole. So, moose and squirrels (or woodpeckers and blackbirds) living in the same forest practically do not contact. Neutralism-type relationships are developed in species-rich communities.

True neutralism in nature is very rare, since indirect interactions are possible between all species, the effect of which we do not see due to the incompleteness of our knowledge.

Competition.

Competition is very widespread in nature. It occurs where ecological resources are in short supply, and rivalry inevitably arises between species. At the same time, each species experiences oppression, which negatively affects the growth and survival of organisms, and the number of their populations.

Competitive relations are one of the most important types of natural biotic interactions. There are intraspecific and interspecific competition (competition, struggle) for food, space and other resources. One of the manifestations of intraspecific competition is territoriality. Big influence the outcome of competition is influenced by external factors and properties of populations of competing species. The outcome of competition is of great interest not only to ecologists who study the processes of formation of the composition of natural communities, but also to evolutionists who study the mechanisms of natural selection. For a species under competitive pressure, this means that its population density, as well as the role it plays in the natural community, will decrease or be regulated by competition. Competitive relations play an important role in the distribution of organisms, in the formation of the species composition of natural communities and in increasing their stability.

Competition weakens in areas with a sparse population provided by a small number of species: for example, in arctic and desert areas there is almost no competition.

Intraspecific competition. Territoriality.

Intraspecific competition is the struggle for the same resources between individuals of the same species. This is an important factor in the self-regulation of populations.

In some organisms, under the influence of intraspecific competition for living space, an interesting type of behavior has formed - territoriality. It is characteristic of many birds, some fish, and other animals.

Intraspecific competition is manifested in territorial behavior, when, for example, an animal defends its nesting site or a certain area in its vicinity. So, during the breeding season of birds, the male protects a certain territory, to which, apart from his female, he does not allow a single individual of his species. The same picture can be observed in many fish (for example, stickleback)

The defense of a territory is not necessarily accompanied by an active struggle. Loud singing and threatening postures usually enough to drive out a competitor. However, if one of the partner-parents dies, it is quickly replaced by a bird from among the individuals that have not yet settled. Thus, territorial behavior can be considered a regulator that prevents both overpopulation and underpopulation.

In some species, intraspecific regulation begins long before serious competition is detected. Thus, the high density of animals is a factor of oppression that reduces the rate of reproduction of this population even with an abundance of food resources.

Intraspecific competition is an important regulator that controls population growth. Due to this competition, a certain relationship arises between the density of the population and the rate of processes of extinction (mortality) or reproduction (birth rate) of individuals. This, in turn, leads to the emergence of a certain relationship between the number of parental pairs and the number of offspring they produce. Such relationships act as regulators of population fluctuations.

Also, a manifestation of intraspecific competition is the existence of a social hierarchy in animals, which is characterized by the appearance of dominant and subordinate individuals in the population. For example, in the May beetle, three-year-old larvae suppress one- and two-year-old larvae. This is the reason why the emergence of adult beetles is observed only once every three years, while in other insects (for example, Agriotes seed beetles) the duration of the larval stage is also three years, and the emergence of adults occurs annually due to the lack of competition between larvae.

Competition between individuals of the same species for food becomes more intense as population density increases. In some cases, intraspecific competition can lead to differentiation of the species, to its breakup into several populations occupying different territories. So, about the savanna bunting (Passerculus sandwichensis), one ecological subspecies is located on dry hills, the other - on coastal salt marshes. Competition is often the reason for the migration of a part of a population of individuals from one geographical area to another. This explains the flights of various granivorous birds, the so-called narrow stenophages of the taiga - nutcrackers, waxwings, raiding Western Europe when there is not enough food in the areas of their usual distribution.

Interspecies competition.

Interspecific competition is the active search by two or more species of the same food resources of the habitat. Competitive relationships, as a rule, arise between species with similar ecological requirements. Competition between species is extremely widespread in nature and affects almost all of them, since it is rare that a species does not experience at least a little pressure from individuals of other species. When living together, each of them is at a disadvantage due to the fact that the presence of another species reduces the possibility of mastering the food resources, shelters and other livelihoods available in the habitat. Ecology considers interspecific competition in a specific, narrower sense - only as mutually negative relations of species occupying a similar ecological niche.

Competitive relationships can be very diverse: from direct physical struggle to almost peaceful coexistence. And at the same time, if two species with the same ecological needs find themselves in the same community, then one competitor will definitely crowd out the other. For example: in Europe, in human settlements, the gray rat completely replaced another species of the same genus - the black rat, which now lives in the steppe and desert regions. gray rat bigger, more aggressive, better swimmer, so she managed to win. In Russia, on the contrary, the relatively small red cockroach - the Prussian completely replaced the larger black cockroach only because it was able to better adapt to the specific conditions of human habitation. In Australia, the common bee, introduced from Europe, has supplanted the small, stingless native bee.

Interspecific competition can be demonstrated in simple laboratory experiments. So, in the studies of the Russian scientist G.F. Gause, cultures of two types of ciliates - shoes with a similar nature of nutrition were placed separately and together in vessels with hay infusion. Each species, placed separately, successfully multiplied, reaching the optimal number. However, when living together, the number of one of the species gradually decreased, and its individuals disappeared from the infusion, while the ciliates of the second species survived. It was concluded that long-term coexistence of species with close ecological requirements is impossible. As it turned out, after a while only individuals of one species remain alive, surviving in the struggle for food, as its population grew and multiplied faster. This conclusion is called the rule of competitive exclusion.

But the outcome of competition depends not only on the properties of the interacting species, but also on the conditions in which the competition takes place. Depending on the conditions prevailing in a particular habitat, the winner of the competition may be either one or another species, which in a given ecological situation has at least slight advantages over the other, and, consequently, greater adaptability to environmental conditions.

The researchers investigated the effect of temperature and humidity on the outcome of interspecific competition between two flour beetle species. Vessels with flour, kept at a certain combination of heat and moisture, placed several individuals of both species. Here, the beetles began to multiply, but after a while, individuals of only one species remained. It is noteworthy that at high rates of heat and moisture, one species won, and at low rates, another.

In some cases, this leads to the coexistence of competing species. After all, heat and humidity, like other environmental factors, are by no means evenly distributed in nature. Even within a small area (forest, field or other habitat), you can find zones that differ in microclimate. In this variety of conditions, each species develops the place where it is guaranteed to survive.

Thus, only those competing species coexist in the community that have adapted to at least slightly differ in ecological requirements. So, in the African savannas, ungulates use pasture food in different ways: zebras cut off the tops of grasses, wildebeests eat plants of certain species, gazelles pluck only the lower grasses, and topi antelopes feed on tall stems.

In our country, insectivorous birds feeding on trees avoid competition with each other due to the different nature of the search for prey on different parts of the tree.

Competition is one of the reasons why two species that differ slightly in the specifics of nutrition, behavior, lifestyle, etc., rarely cohabit in the same community. Here the competition is in the nature of direct hostility. The fiercest competition, with unforeseen consequences, occurs when man introduces species of animals into communities without regard for already established relationships.

More often, competition manifests itself indirectly, is of an insignificant nature, since different species perceive the same environmental factors differently. The more diverse the possibilities of organisms, the less intense the competition will be.

The value of competition as an environmental factor.

As already mentioned, competitive relations play an extremely important role in the formation of the species composition and regulation of the number of species in the community.

Ecologists know that organisms that lead a similar way of life, have a similar structure, do not live in the same places. And if they live nearby, they use different resources and are active in different time. Their ecological niches seem to diverge in time and space.

discrepancy ecological niches when related species live together, the example of two species of sea fish-eating birds - great and long-nosed cormorants, which usually feed in the same waters and nest in the neighborhood - illustrates well. Scientists were able to find out that the composition of the food of these birds varies significantly: the long-nosed cormorant catches fish swimming in the upper layers of the water, while the great cormorant catches it mainly at the bottom, where flounders, flounders, bottom-dwelling invertebrates, such as shrimp, predominate.

Competition has a huge impact on the distribution of closely related species, although often only indirect evidence indicates this. Species with very similar needs usually live in different geographic areas or different habitats in the same area, or avoid competition in some other way, for example, due to differences in food or differences in daily, or even seasonal, activity.

The ecological action of natural selection seems to be aimed at eliminating or preventing a prolonged confrontation between species with a similar way of life. The ecological separation of closely related species is fixed in the course of evolution. In Central Europe, for example, there are five closely related species of tits, whose isolation from each other is due to differences in habitat, sometimes feeding grounds, and size of prey. Ecological differences are reflected in a number of small details. external structure, in particular in changes in the length and thickness of the beak. Changes in the structure of organisms that accompany the processes of divergence of their ecological niches suggest that interspecific competition is one of the critical factors evolutionary transformations. If interspecific competition is weakly expressed, then under the influence of intraspecific competition, populations of a given species expand the boundaries of their habitat.

Thus, interspecific competition can play an important role in shaping the appearance of a natural community. Generating and consolidating the diversity of organisms, it helps to increase the stability of communities, more efficient use of available resources.

Symbiosis.

In the animal kingdom, termites provide an example of the most perfect symbiosis, the digestive tract of which serves as a haven for flagella or bacteria. Thanks to the symbiosis, the termites are able to digest the wood, and the micro-organisms have a shelter outside of which they cannot exist.

It should be noted that the complex of relations of the symbiosis type contains a wide variety of transitions - from more or less indifferent relations to those where both members of cohabitation ensure mutual existence. “Although there is thus no proof that any animal performs an action exceptionally beneficial to another species,” wrote Charles Darwin in On the Origin of Species, “yet each seeks to profit from the instincts of others.”

Mutualism.

Commensalism.

Relationships in which one of the partners benefits without harming the other, as noted earlier, are called commensalism. The manifestations of commensalism are diverse, therefore, a number of options are distinguished in it:

"Freeloading" is the consumption of the host's leftover food. Such, for example, are the relationships between lions and hyenas, which pick up the remains of uneaten food, or sharks with sticky fish (see appendix fig. 6.5.)

“Companionship” is the consumption of different substances or parts of the same food. For example: the relationship between different types of soil saprophyte bacteria that process various organic substances from decayed plant residues, and higher plants, which consume the resulting mineral salts.

"Housing" is the use by some species of others (their bodies or their dwellings) as shelter or dwelling. This type of relationship is widespread in plants.

A clear example of commensalism is provided by some barnacles that attach themselves to the skin of a whale. At the same time, they get the advantage - faster movement, and the whale does not cause almost any inconvenience.

In general, the partners do not have any common interests, and each perfectly exists on its own. However, such alliances make it easier for one of the participants to move or get food, seek shelter, etc. Sometimes such alliances can be completely fictitious. So, in the shells of mollusks and shells of crustaceans, various types of bryozoans are sometimes found. This union is completely accidental, since bryozoans are able to attach themselves to any hard surface, and yet many sedentary animals benefit from attaching to a living creature. The owner carries them from place to place. Often, when moving, the flow of water makes it easier for them to get food.

Commensalism is especially common among marine animals. The relationship that connects some fish with sharks is well known. Pilot fish, feeding on leftovers from the "table" of the shark, constantly scurry about in small shoals at its nose. Another example are animals whose burrow serves as a refuge for various "guests" who feed on scraps from the owner's table. In the burrows of mammals, nests of birds and dwellings of social insects (see appendix to Fig. 6.6.), commensal insects are represented by a large number of species (for example, in the burrows of the alpine marmot, up to 110 species of beetles).

Among the commensals, foleoxenes are distinguished, which are found in burrows and nests by chance; foleophiles found in these shelters more often than in environment, and foleobists who spend their whole lives in them.

Relations such as commensalism play an important role in nature, as they contribute to a closer cohabitation of species, a more complete development of the environment and the use of food resources.

Living organisms as a living environment.

Tick-borne encephalitis is a disease that affects the central nervous system person. It is caused by a virus, the carrier and custodian of which are ixodid ticks. Favorite habitats for ticks southern part taiga forests throughout the European and Asian parts of Russia.

Polyphages - attacking a large number of species. These include many predatory mammals and insects.

The principle of coincidence.

Predation.

Predation is a type of relationship between organisms in which representatives of one species kill and eat representatives of another. Predation is one of the forms of food relations.

Predation is often called any eating of some organisms by others. Consequently, herbivory can also be attributed to one of the forms of predation. In nature, predatory relationships are widespread. Not only the fate of an individual predator or its prey depends on their outcome, but also some important properties of such large ecological objects as biotic communities and ecosystems.

A typical predator (wolf, lynx, mink) is characterized by hunting behavior. But besides predators - hunters exist large group predators - gatherers, the way of feeding which consists in a simple search and collection of prey. Such, for example, are many insectivorous birds that gather food on the ground, in grass or on trees. Predation is a widespread form of biotic relationship.

The significance of predation can only be understood by considering this phenomenon at the population level. Long-term communication between predator and prey populations creates their interdependence, which acts like a regulator, preventing too sharp fluctuations in numbers or preventing the accumulation of weakened or sick individuals in populations. In some cases, predation can significantly reduce the negative consequences of interspecific competition and increase the stability and diversity of species in communities.

Predators and humans.

For a person, the problem of predation can become very important in cases where he competes with predators for a particular type of resource, whether it be populations of domestic or wild animals.

For a long time, many countries were the scene of a merciless struggle between man and predators. The main incentive for this struggle was the reward received by the hunter for the killed predator. However, it was not possible to achieve complete destruction of predators: it turned out that as the number of these animals decreased, the work of hunters became unprofitable. The hunter was forced to switch to another, more profitable type of prey. Interestingly, in this case, it behaved in the same way as a natural predator, when the density of the prey population decreases and the energy cost of the prey does not cover the costs of its search, tracking and capture.

Sometimes a person also encounters the opposite difficulty: an insufficient number of predators. A very high number of rodents or insect pests in a given area may be due to the absence or small number of predators. Man seeks to use predators in pest control. Sometimes it brings nice results. An example of this is ladybug Rhodolia, the resettlement of which from Australia helped to destroy the worm (insect pest), which at the end of the last century posed a serious threat to citrus plantations in some parts of North America.

Relationships: predator - prey.

Human interest in the problem of predation is also due to the fact that often he himself behaves like a typical predator. In order to obtain raw materials, he exploits populations of wild animals, which often leads to their complete destruction.

Long-term contact between a natural predator and its prey does not have such catastrophic consequences, despite the fact that predators themselves kill the individuals they feed on.

It has been established that during the long-term coexistence of interacting animal species, their changes proceed in concert, so that the evolution of one species partially depends on the evolution of another. Such consistency in the processes of joint development of organisms of different species is called coevolution.

Many ecologists are of the opinion that when interacting species undergo a joint evolutionary development, the negative effects of one of them on the other become weaker.

As the prey gains experience in avoiding enemies, predators develop more effective devices for catching it. In other words, in the evolution of the connection between predator and prey, the prey acts in such a way as to free itself from the actions of the predator, and the predator - in order to constantly maintain its influence on the prey. This leads to the emergence of a variety of adaptations in predators and prey.

One may recall the complex social hunting behavior of wolves or lions; long sticky tongues and accurate aiming of some fish, toads and lizards; bent poisonous teeth of vipers with a device for injecting poison; spiders and their trapping webs; deep sea fish- angler; snakes - boas that strangle their prey (see appendix fig. 6.3)

The victims also historically developed protective properties in the form of anatomical, morphological, physiological, biochemical features. For example, body outgrowths, spikes, spines, shells, protective coloration, poisonous glands, the ability to quickly hide, burrow into loose soil, build shelters inaccessible to predators, and resort to signaling danger. As a result of such mutual adaptations, certain groups of organisms are formed in the form of specialized predators and specialized prey. Thus, the main food of the lynx (Felix Lynx) is hares, and the wolf (Canis Lupus) is a typical polyphagous predator.

It has been noticed that in the actions of many predators there is something that can be called prudence. A predator, for example, does not benefit from the complete destruction of all prey individuals, and, as a rule, this does not happen in nature.

Predation is a laborious process that requires a lot of energy. For example, a group of two lionesses and eight cubs travels several kilometers overnight, even if the youngest cubs are only a month old. At the same time, cubs experience the same hardships that adult animals undergo. Many of them die, including from hunger.

During the hunt, predators are often exposed to dangers no less than their victims. Sometimes predators die from collisions with other predators in the course of the struggle for prey.

But the main enemy of a predator is time. Only the fastest and strong predators are capable of chasing a prey at a great distance, successfully catching it, spending the minimum time on this. The less nimble ones cannot compete and are doomed to starvation.

The value of predation in nature.

Is the effect of a predator only negative? This question could be answered unequivocally "yes", if we take into account only the fate of a particular animal caught in the teeth of a predator. Ecologists, however, are much more interested in the fate of populations than of individual organisms.

Predators destroy that part of the population that, for one reason or another, turns out to be weaker in competition for suitable territories.

The predator, killing the weaker ones, acts like a breeder who selects the seeds that give the best shoots. The influence of a predator leads to the fact that the renewal of the prey population occurs faster, because rapid growth leads to an earlier participation of individuals in reproduction. At the same time, the victims' consumption of their food is increasing. Thus, the impact of predators increases the flow of energy in the ecosystem.

Predators selectively destroy animals with a low ability to get their own food, that is, slow, frail, sick individuals. The strong and resilient survive. This applies to the entire living world: predators improve (qualitatively) prey populations. The mink renders the same service to the muskrat, birds of prey to rodents, and wolves to deer.

Predation is one of the leading factors determining the regulation of the number of organisms.

Of course, in agricultural areas it is necessary to control the number of predators, since the latter can harm livestock. However, in areas inaccessible to hunting, predators must be conserved for the benefit of both prey populations and plant communities interacting with them.

Bibliography

A. Stepanovskikh "General Ecology"

E.A. Kriksunov, V.V. Pasechnik "Ecology