A comparative description of one of the natural ecosystems. Agrocenosis

Potato bed and garden fruit trees? All of these are agrocenoses. In our article we will get acquainted with the main characteristics of this concept.

Communities of organisms

Under natural conditions, different types of living beings do not live separately. As a result, different communities are formed. One of them is biocenosis. Its structure includes populations of various species living in an area with homogeneous conditions. The basis of such a community is the phytocenosis.

But living organisms are connected not only to each other. also have a certain influence on them. Therefore, ecologists call another structure - biogeocenosis. This is a territory with approximately the same conditions, in which populations of different species are united with each other and the physical environment through the circulation of substances and energy.

Agrocenosis is also a community of organisms, but it is significantly different from all the others. What is the difference? Let's figure it out.

Biogeocenosis and agrocenosis

An agrocenosis is a community of organisms created by humans. It may include plants, animals, fungi and microorganisms. The purpose of its creation is to obtain agricultural products. But most often an artificial agrocenosis is called a field, a vegetable garden, a garden or a garden bed.

Biogeocenosis is a natural, self-developing structure.

The characteristics of agrocenosis also include the almost complete absence of self-regulation. All processes in this community are controlled by humans. When its activity ceases, the agrocenosis ceases to exist.

Biogeocenosis uses only solar energy for its development. There are additional reserves in the agrocenosis. This is the energy that humans contribute when irrigating, plowing land, using fertilizers, special feed, and chemicals to control weeds and rodents.

Signs of agrocenosis

Agrocenoses are characterized by low species diversity. Since these communities are created for the purpose of obtaining certain agricultural products, they include one or two representatives of the organic world. As a result, the number of other species inhabiting the area decreases.

Agrocenosis is a weakly stable structure. Its development occurs only under human influence in artificially recreated conditions. Therefore, the ability to withstand fluctuations in the intensity of factors environment without sudden changes structure and functions of agrocenosis is almost impossible.

Trophic connections

Any natural community is characterized by the presence of food chains. Agrocenosis is no exception. Its trophic networks are very weakly branched. This is due to depleted species diversity.

In biogeocenosis there is a continuous circulation of substances and energy. For example, plant products are consumed by other organisms and then returned to natural system in a modified form. This could be water, carbon dioxide or mineral elements.

This does not happen in agrocenosis chains. Having received a harvest, a person simply withdraws it from circulation. In this case, trophic connections are broken. To compensate for such losses, it is necessary to systematically apply fertilizers.

Development conditions

To increase the yield and productivity of agrocenoses, people use artificial selection. During this process, a person selects individuals with the most useful qualities capable of producing viable and fertile offspring. This type of selection acts faster and more efficiently than natural selection.

On the other hand, this leads to an inability for self-regulation and self-renewal. If a person stops his activities, the agrocenosis is destroyed. This won't happen right away. So, perennial herbaceous cultivated plants will last about 4 years, and trees - several dozen.

To maintain the development of agrocenoses, people must constantly prevent succession processes. This term means the destruction or replacement of some natural communities by others. For example, if you do not delete weeds, they will first become the dominant species. Over time, they will completely replace the culture. The fact is that weeds have a number of adaptations that help them successfully survive unfavorable conditions. This is the presence of underground - rhizomes, bulbs, a large number of seeds, a variety of methods of propagation and vegetative propagation.

The importance of agrocenoses

Thanks to agrocenoses, people receive agricultural products, which they use as food and the basis for the food industry. The advantage of artificial communities is their controllability and unlimited ability to increase productivity. But human activity also leads to negative consequences. Plowing of land, deforestation and other manifestations of irrational environmental management lead to an imbalance. Therefore, when creating agrocenoses, it is necessary to take into account the connections between wild and cultivated species.

So, agrocenosis is an artificial biogeocenosis. Man creates it to receive various types products. To do this, he selects productive varieties of plants, animal breeds, types of fungi or strains of microorganisms. The main characteristics of agrocenosis include: poorly branched, lack of circulation of substances and energy, insignificant species diversity and constant human control.

- this is the interaction of living and inanimate nature, which consists of living organisms and their habitat. An ecological system is a large-scale balance and connection that allows the maintenance of a population of species of living things. Nowadays, there are natural and anthropogenic ecosystems. The differences between them are that the first is created by the forces of nature, and the second with the help of humans.

The meaning of agrocenosis

Agrocenosis is an ecosystem created by human hands for the purpose of producing crops, animals and mushrooms. An agrocenosis is also called an agroecosystem. Examples of agrocenosis are:

apple and other orchards;
corn and sunflower fields;
cow and sheep pastures;
vineyards;
vegetable gardens

Man, due to the satisfaction of his needs and the increase in population in Lately forced to change and destroy natural ecosystems. In order to rationalize and increase the volume of agricultural crops, people create agroecosystems. Nowadays, 10% of all available land is occupied by land for growing crops, and 20% is pasture.

The difference between natural ecosystems and agrocenosis

The main differences between agrocenosis and natural ecosystems are:

artificially created crops cannot compete in the fight against wild species and;
agroecosystems are not adapted to self-healing, and are completely dependent on humans and without him they quickly weaken and die;
a large number of one species in the agroecosystem contributes to the large-scale development of viruses, bacteria and harmful insects;
There is a much greater diversity of species in nature than in human-grown crops.

Artificially created agricultural plots must be under full human control. A disadvantage of agrocenosis is the frequent increase in populations of pests and fungi, which not only harm the crop, but can also worsen the condition of the environment. The population size of a crop in an agrocenosis increases only through the use of:

weed and pest control;
dryland irrigation;
drying waterlogged soil;
replacement of crop varieties;
fertilizers with organic and mineral substances.

In the process of creating an agroecosystem, man built completely artificial stages of development. Soil reclamation is very popular - an extensive set of measures aimed at improving natural conditions in order to get the maximum high level harvest. Only the right one scientific approach, monitoring soil condition, moisture level and mineral fertilizers are able to increase the productivity of agrocenosis in comparison with the natural ecosystem.

Negative consequences of agrocenosis

It is important for humanity to maintain a balance of agro- and natural ecosystems. People create agroecosystems to increase food supply and use them for food processing. However, the creation of artificial agroecosystems requires additional territories, so people often plow the land and thereby destroy existing natural ecosystems. This upsets the balance of wild and cultural species animals and plants.

The second negative role is played by pesticides, which are often used to control pests in agroecosystems. These chemicals Through water, air and insect pests they enter natural ecosystems and pollute them. In addition, excessive use of fertilizers for agroecosystems also causes groundwater problems.

Agricultural ecosystems (agroecosystems)

the main objective created agricultural systems – rational use those biological resources, who are directly involved in the sphere of human activity - sources food products, technological raw materials, medicines. This also includes species specially cultivated by humans that are objects of agricultural production: fish farming, fur farming, special cultivation of forest crops, as well as species used for industrial technologies.

Agroecosystems are created by humans to obtain high yields - pure production of autotrophs. Summarizing everything that has already been said above about agroecosystems, we emphasize the following their main differences from natural ones (Table 10.2):

1. The diversity of species in them is sharply reduced: a decrease in the species of cultivated plants also reduces the species diversity of the animal population of the biocenosis; the species diversity of animals bred by humans is negligible compared to nature; cultivated pastures (with underseeding of grasses) are similar in species diversity to agricultural fields.

2. Species of plants and animals cultivated by humans “evolve” due to artificial selection and are uncompetitive in the fight against wild species without human support.

3. Agroecosystems receive additional energy subsidized by humans, in addition to solar energy.

4. Pure products (harvest) are removed from the ecosystem and do not enter the food chain of the biocenosis, and its partial use by pests, losses during harvesting, which can also end up in natural trophic chains, are suppressed in every possible way by humans.

5. Ecosystems of fields, gardens, pastures, vegetable gardens and other agrocenoses are simplified systems supported by humans in the early stages of succession, and they are just as unstable and incapable of self-regulation as natural pioneer communities, and therefore cannot exist without human support.

Table 10.2

Natural ecosystems	Agroecosystems
Primary natural elementary units of the biosphere, formed during evolution	Secondary artificial elementary units of the biosphere transformed by humans
Complex systems with a significant number of animal and plant species in which populations of several species dominate. They are characterized by a stable dynamic balance achieved by self-regulation	Simplified systems with dominant populations of one plant or animal species. They are stable and characterized by the variability of the structure of their biomass
Productivity is determined by the adaptive characteristics of organisms participating in the cycle of substances	Productivity is determined by the level economic activity and depends on economic and technical capabilities
Primary products are used by animals and participate in the cycle of substances. “Consumption” occurs almost simultaneously with “production”	The crop is harvested to satisfy human needs and feed livestock. Living matter accumulates for some time without being consumed. The highest productivity develops only for a short time

In agrocenoses, an excessive increase in individual species, called an “ecological explosion” by Charles Elton, occurs much more often. For example, “ecological explosions” are known from history: in the last century, the late blight fungus destroyed potatoes in France and caused famine, and the Colorado potato beetle spread in America to Atlantic Ocean and at the beginning of the 20th century . penetrated Western Europe, in the 40s. - V European part Russia. In the difficult post-war times, this beetle literally “cleared” our fields, since we were not prepared for its invasion.

To prevent such phenomena from occurring, it is necessary to artificially regulate the number of pests with the rapid suppression of those that are just trying to get out of control. At the same time, human opinion often does not coincide with nature’s “opinion” about the excessive numbers of a particular pest. Thus, from the standpoint of natural selection, stabilization of the codling moth population at some level does not harm the existence of the apple tree as a species, but humans need much more high-quality fruits for nutrition. Therefore, in agricultural practice, he uses such means to suppress the number of pests and in such quantities that they have an effect many times stronger than natural abiotic and biotic regulators.

Simplification of the natural environment of man, from an ecological point of view, is very dangerous. Therefore, it is impossible to turn the entire landscape into an agricultural one; it is necessary to preserve and increase its diversity, leaving untouched protected areas that could be a source of species for communities recovering in succession.

Practical work No. 4

Topic: “Comparative description of natural systems and agroecosystems.”

1.. Target: consolidate knowledge about the structure of ecosystems, learn to write a description of natural and artificial ecosystems, explain the differences between them and their significance;

2. Execution order:

3.1. Practicing terms and concepts.

3.2. Doing work, solving tasks.

3.3. Performing a test task.

3. Report outline:

4.1. Topic and purpose of the lesson.

4.2. Answers to assignments.

4.3. Test task answers.

Equipment : textbook, tables

Progress.

Exercise 1. Study the description of the natural ecosystem and divide the forest inhabitants into 3 groups (producers, consumers, decomposers). Make 3 food chains characteristic of this ecosystem.

The biocenosis of deciduous forest is characterized not only by species diversity, but also by a complex structure. Plants living in the forest differ but in their height ground units. In this regard, several species are distinguished in plant communities"floors"or tiers. The first tier - woody - consists of the mostlight-loving species - oak, linden. The second tier includes less light-loving and shorter trees - pear, maple, apple tree. The third tier consists of shrubs of hazel, euonymus, viburnum, etc. The fourth tier is herbaceous. Plant roots are also distributed on the same floors. Tiering land plants and their roots allows better use of sunlight and mineral reserves of the soil. In the herbaceous layer, the vegetation cover changes during the season. One group of grasses, called ephemerals, are light-loving. These are lungwort, corydalis, anemone; they start growing in early spring when there is no foliage on the trees and the soil surface is brightly lit. In a short period of time, these herbs manage to form flowers, produce fruits and accumulate reserves. nutrients. In summer, in these places, under the cover of blossoming trees, shade-tolerant plants. In addition to plants, the forest is inhabited by: in the soil - bacteria, fungi, algae, protozoa, round and ringed worms, insect larvae and adult insects. Spiders weave their webs in the grass and shrub layers. Higher in crowns hardwood Caterpillars of moths, silkworms, leaf rollers, adult forms of leaf beetles, and beetles are abundant. The terrestrial layers are inhabited by numerous vertebrates - amphibians, reptiles, various birds, among mammals - rodents (voles, mice), lagomorphs, ungulates (elk, deer), predators - fox, wolf. IN upper layers moles are found in the soil.

Task 2. Study the agrocenosis of a wheat field and divide the forest inhabitants into 3 groups (producers, consumers, decomposers). Make 3 food chains characteristic of a given agroecosystem.

Its vegetation consists, in addition to the wheat itself, of various weeds: white pigweed, field thistle, yellow sweet clover, field bindweed, and creeping wheatgrass. In addition to voles and other rodents, granivores and predator birds, foxes, wagtail, earthworms, ground beetles, pest bug, aphids, insect larvae, ladybug, rider. The soil is inhabited by earthworms, beetles, bacteria and fungi, which decompose and mineralize the straw and roots of wheat left after the harvest.

Task 3. Assess the driving forces shaping natural and agroecosystems. Enter the following statements into the table:

has a minimal effect on the ecosystem,

does not affect the ecosystem,

action is aimed at achieving maximum productivity.

does not affect the ecosystem

Artificial selection

minimal effect on the ecosystem

action aimed at achieving maximum productivity

Task 4. Rate some quantitative characteristics ecosystems (more less)

The correct answer is in bold!!!

Control questions(testing):

1. The main source of energy for agroecosystems is
A) mineral fertilizers
B) sun rays
C) organic fertilizers? D) soil water

2. Why a field sown with cultivated plants cannot be considered a natural ecosystem
A) there are no power circuits
B) there is no circulation of substances
C) in addition to solar energy, additional energy is used
D) plants are not arranged in tiers in space

3. What are the similarities between a sugar beet plantation and a meadow ecosystem?
A) have an open cycle of substances
B) they are characterized by a short length of power circuits C) they lack secondary consumers (predators)
D) have food chains and networks

4. Agrocenosis is considered an artificial ecosystem, since it
A) exists only due to the energy of sunlight
B) cannot exist without additional energy
B) consists of producers, consumers and decomposers
D) does not include consumers and decomposers

5. Plays a major role in increasing the productivity of agroecosystems
A) exceeding the seed sowing norm
B) introduction of crop rotation in the fields
B) growing plants of one type
D) increase in the area of agrocenosis

6. Agrocenoses are characterized
A) dominance of monoculture
B) reducing the number of pests
C) the diversity of the species of organisms included in them
D) a decrease in the competitiveness of cultivated plants

7. When insect pests are destroyed by pesticides, their mass reproduction is sometimes observed, since
A) the number of birds of prey increases
B) the growth of agricultural plants accelerates
C) their natural enemies are destroyed
D) the number of cultivated plants decreases

8. The agroecosystem, in comparison with the natural ecosystem, is less stable, since
A) it consists of a wide variety of species
B) there is a closed cycle of matter and energy in it
C) producers in it absorb the energy of the Sun
D) it has short food chains

Conclusion: It is necessary not only to create artificial ecosystems, but also to preserve natural ones. Careful protection of these ecosystems is required, because everything that nature has created is much better than artificial ecosystems. driving forces in natural and agroecosystems, are the main factors that support and help the development of these ecosystems.

Nature is multifaceted and beautiful. We can say that this is a whole system, including both living and inanimate nature. There are many other different systems within it, inferior in scale to it. But not all of them are completely created by nature. Humans contribute to some of them. The anthropogenic factor can radically change the natural landscape and its orientation.

Agroecosystem - arose as a result of anthropogenic activity. People can plow the land and plant trees, but no matter what we do, we have always been and will be surrounded by nature. This is something of its peculiarity. How do agroecosystems differ from natural ecosystems? This is worth looking into.

generally

In general, an ecological system is any collection of organic and inorganic components in which the circulation of substances exists.

Whether natural or man-made, it is still an ecological system. But still, how do agroecosystems differ from natural ecosystems? First things first.

Natural ecosystem

A natural system, or, as it is also called, biogeocenosis, is a set of organic and inorganic components on an area of the earth’s surface with homogeneous natural phenomena: the atmosphere, rocks, hydrological conditions, soils, plants, animals and the world of microorganisms.

The natural system has its own structure, which includes the following components. Producers, or, as they are also called, autotrophs, are all those plants capable of producing organic matter, that is, capable of photosynthesis. Consumers are those who eat plants. It is worth noting that they are of the first order. In addition, there are consumers of other orders. And finally, another group is the group of decomposers. This usually includes various types of bacteria and fungi.

Structure of the natural ecosystem

In any ecosystem there are food chains, food webs and trophic levels. A food chain is a sequential transfer of energy. A food web refers to all the chains connected to each other. Trophic levels are the places that organisms occupy in food chains. Producers belong to the very first level, consumers of the first order belong to the second, consumers of the second order belong to the third, and so on.

The saprophytic chain, or in other words detrital, begins with dead remains and ends with some type of animal. There is an omnivorous food chain. Pasture grazing) in any case begins with photosynthetic organisms.

This is all that concerns biogeocenosis. How do agroecosystems differ from natural ecosystems?

Agroecosystem

An agroecosystem is an ecosystem created by man. This includes gardens, arable land, vineyards, and parks.

Like the previous one, the agroecosystem includes the following blocks: producers, consumers, decomposers. The first include cultivated plants, weeds, plants of pastures, gardens and forest belts. Consumers are all farm animals and humans. A decomposer block is a complex of soil organisms.

Types of agroecosystems

The creation of anthropogenic landscapes includes several types:

agricultural landscapes: arable lands, pastures, irrigated lands, gardens and others;
forest: forest parks, shelterbelts;
water: ponds, reservoirs, canals;
urban: cities, towns;
industrial: mines, quarries.

There is another classification of agroecosystems.

Types of agroecosystems

Depending on the level of economic use, systems are divided into:

agrosphere (global ecosystem),
agricultural landscape,
agroecosystem,
agrocenosis.

Depending on the energy feature natural areas division occurs into:

tropical;
subtropical;
moderate;
arctic types.

The first is characterized by a high supply of heat, continuous vegetation and the predominance of perennial crops. The second is two growing seasons, namely summer and winter. The third type has only one growing season, as well as a long dormant period. As for the fourth type, cultivation of crops here is very difficult due to low temperatures, as well as cold spells for a long time.

Variety of signs

All cultivated plants must have certain properties. Firstly, high ecological plasticity, that is, the ability to produce crops in wide range fluctuations in climatic conditions.

Secondly, the heterogeneity of populations, that is, each of them must contain plants that differ in characteristics such as flowering time, resistance to drought, and frost resistance.

Thirdly, early maturity - the ability for rapid development, which will outstrip the development of weeds.

Fourthly, resistance to fungal and other diseases.

Fifthly, resistance to harmful insects.

Comparative and agroecosystems

In addition, as mentioned above, these ecosystems differ greatly in a number of other characteristics. Unlike natural ones, in an agroecosystem the main consumer is the person himself. It is he who strives to maximize the production of primary (crop) and secondary (livestock) products. The second consumer is farm animals.

The second difference is that the agroecosystem is shaped and regulated by humans. Many people ask why an agroecosystem is less sustainable than an ecosystem. The thing is that they have a weakly expressed ability for self-regulation and self-renewal. They exist only for a short time without human intervention.

The next difference is selection. The stability of the natural ecosystem is ensured by natural selection. In an agroecosystem it is artificial, provided by humans and aimed at obtaining the maximum possible production. The energy received by the agricultural system includes the sun and everything that humans provide: irrigation, fertilizers, and so on.

Natural biogeocenosis feeds only on natural energy. Typically, plants grown by humans include several species, while the natural ecosystem is extremely diverse.

The different nutritional balance is another difference. Plant products in a natural ecosystem are used in many food chains, but nevertheless still return to the system. This results in a cycle of substances.

How do agroecosystems differ from natural ecosystems?

Natural and agroecosystems differ from each other in many ways: plants, consumption, vitality, resistance to pests and diseases, species diversity, type of selection and many other characteristics.

An ecosystem created by man has both advantages and disadvantages. The natural system, in turn, cannot have any disadvantages. Everything about it is beautiful and harmonious.