Parting 

Natural or agrarian has clear boundaries. Diversity of communities and ecosystems. Importance of abiotic components

"Introduction to General Biology and Ecology. Grade 9". A.A. Kamensky (gdz)

Characteristics of communities, ecosystems (biogeocenoses)

Question 1. Which of the communities and ecosystems that you know have more or less clear boundaries?
Community- a group of plants, or a group of animals, such as forest plants or pond animals. Biogeocenosis has relatively clear boundaries. Biogeocenosis- this is a complex of living beings (biocenosis) and an abiotic environment, which also includes the territory occupied by organisms. Biogeocenosis and ecosystem concepts are similar, but not identical. The concept of an ecosystem is broader than the concept of biogeocenosis. An ecosystem can be represented by a pond, a swamp, a puddle, an anthill, a mountain range, and, finally, the biosphere as a whole. Biogeocenosis is an ecosystem whose boundaries are defined by a plant community - phytocenosis (oak forests, steppes, coniferous forests, etc.), that is biogeocenosis is a special case ecosystems.
Particularly clear boundaries are characteristic of artificial cenoses - agrocenoses (rice check, rye field, forest belt, etc.).

Question 2. Can all bird populations inhabiting a forest area be considered a community?
Biocenosis- this is a complex of living beings inhabiting a forest area, i.e. the totality of populations of all plant, animal, fungi and microorganisms living in the territory of this forest area. The variety of bird species that inhabit the forest area is only a part of the animals that live in this forest area.

Question 3. What factors of inanimate nature affect the flora and fauna of the community?
The flora and fauna of the community is influenced by factors of inanimate nature: light, temperature, humidity, chemical composition of water and soil, atmosphere, etc.

The concept of community and ecosystem. A group of populations of different species inhabiting a certain area forms a community. The idea of ​​any landscape is primarily associated with its vegetation. Tundra, taiga, deciduous forests, meadows, steppes, deserts consist of various plant communities. Birch forests differ from oak forests not only in tree composition, but also in undergrowth and grass cover. Each plant community is inhabited by its own communities of animals, fungi and microorganisms.

All communities of plants, animals, microorganisms, fungi are in close connection with each other, creating an inextricable system of interacting organisms and their populations - a biocenosis, which is also called a community. Communities of any size and level can be distinguished. For example, in the steppe community there is a community of meadow steppes, and in it there are communities of plants, vertebrates and invertebrates, and microorganisms.

The environment and the community, as well as members of the community, exchange matter and energy with each other: living organisms receive matter and energy from the environment or from each other and return them back to the environment. Thanks to these exchange processes, organized in the form of a flow of energy and the circulation of substances, the community (biocenosis) and its environment are an inseparable unity, one complex system. Such a system is called an ecosystem or biogeocenosis (Fig. 102). Recently, the term "ecosystem" is used more often.

Rice. 102. Ecosystem of coniferous (above) and mixed forests

Functional groups of organisms in a community. Any community consists of a set of organisms that can be divided into three functional groups according to the type of nutrition. Green plants are autotrophs. They are able to accumulate solar energy in the process of photosynthesis and synthesize organic substances. Autotrophs are producers, i.e. producers of organic matter, the first functional group of biocenosis organisms.

Any community also includes heterotrophic organisms, which need ready-made organic substances for nutrition. There are two groups of heterotrophs: consumers, or consumers, and decomposers, i.e., destroyers. Animals are considered consumers. Herbivores eat plant foods, while carnivores eat animals. The decomposers include microorganisms - bacteria and microscopic fungi. Decomposers decompose animal excretions, the remains of dead plants, animals and microorganisms, and other organic substances. Destroyers feed on organic compounds formed during decomposition. In the process of nutrition, decomposers mineralize organic substances to water, carbon dioxide and mineral elements. Mineralization products are reused by producers.

Consequently, in the ecosystem, food and energy connections go in the directions

All three listed groups of organisms exist in any community. Each group includes many populations inhabiting the ecosystem. Only the joint work of all three groups ensures the functioning of the ecosystem.

Examples of ecosystems. Different ecosystems differ from each other both in the species composition of organisms and in the properties of their habitat. Consider a deciduous forest and a pond as examples.

Deciduous forests include beeches, oaks, hornbeams, lindens, maples, birches, aspens, mountain ash and other trees whose foliage falls in autumn. Several tiers of plants stand out in the forest: high and low woody, shrubs, grasses and moss ground cover. The plants of the upper tiers are more photophilous and better adapted to fluctuations in temperature and humidity than the plants of the lower tiers. Shrubs, grasses and mosses in the forest are shade-tolerant; in summer they exist in the twilight, which is formed after the trees have fully unfolded their leaves. On the surface of the soil lies a litter consisting of semi-decomposed remains of fallen leaves, twigs of trees and shrubs, and dead grasses (Fig. 103).

Rice. 103. Deciduous forest ecosystem

The fauna of deciduous forests is rich. There are many burrowing rodents (mice, voles), burrowing insectivores (shrews), predators (fox, badger, bear). There are mammals living on trees (lynx, squirrel, chipmunk). The group of large herbivores includes deer, elk, roe deer. Wild boars are widespread.

Birds nest in different tiers of the forest: on the ground, in bushes, on trunks or in hollows and on tops of trees. There are many insects that feed on leaves (for example, caterpillars) and wood (bark beetles). In the litter and upper soil horizons, in addition to insects, there is a huge number of other invertebrates (earthworms, mites, insect larvae), a lot of fungi and bacteria.

An example of an ecosystem where water serves as the living environment of organisms is the well-known ponds. Rooting or large floating plants (bulrush, cattail, water lilies) settle in the shallow water of the ponds. Throughout the entire water column to the depth of penetration of light, small floating plants are distributed, in the bulk of algae, called phytoplankton. When there is a lot of algae, the water turns green, as they say "blooms". Phytoplankton is rich in diatoms and green algae, as well as cyanobacteria.

Insect larvae, tadpoles, crustaceans, herbivorous fish and mollusks feed on living plants or plant debris, predatory insects and fish eat a variety of small animals, and large predatory fish prey on both herbivorous and predatory, but smaller fish.

Organisms that decompose organic matter (bacteria, flagella, fungi) are distributed throughout the pond, but they are especially numerous at the bottom, where the remains of dead plants and animals accumulate.

We see how dissimilar both in appearance and in the species composition of the populations of the ecosystems of the forest and the pond. The habitat of species is different: in the forest - air and soil; in a pond - air and water. However, the functional groups of living organisms are of the same type. Producers in the forest - trees, shrubs, herbs, mosses; in the pond - floating plants, algae and blue-greens. The composition of consumers in the forest includes animals, birds, insects and other invertebrates (the latter inhabit the soil and litter). In the pond, consumers include insects, various amphibians, crustaceans, herbivorous and predatory fish. Decomposers (fungi and bacteria) are represented in the forest by terrestrial forms, and in the pond by aquatic forms.

The same functional groups of organisms exist in all terrestrial (tundra, coniferous and deciduous forests, steppes, meadows, deserts) and aquatic (oceans, seas, lakes, rivers, ponds) ecosystems.

  1. Define community, biogeocenosis, producers, decomposers, consumers. Give examples of biogeocenoses (ecosystems) in your area.
  2. List the most important components of the ecosystem and reveal the role of each of them.
  3. How and why will the life of an oak forest change in those cases if there: a) the entire bush was cut down; b) chemically destroyed herbivorous insects?

The ecosystem includes all living organisms (plants, animals, fungi and microorganisms), which, to one degree or another, interact with each other and their inanimate environment (climate, soil, sunlight, air, atmosphere, water, etc.) .).

The ecosystem has no definite size. It can be as big as a desert or a lake, or as small as a tree or a puddle. Water, temperature, plants, animals, air, light and soil all interact together.

The essence of the ecosystem

In an ecosystem, each organism has its own place or role.

Consider the ecosystem of a small lake. In it, you can find all kinds of living organisms, from microscopic to animals and plants. They depend on things like water, sunlight, air, and even the amount of nutrients in the water. (Click to learn more about the five basic needs of living organisms).

Lake ecosystem diagram

Any time an "outsider" (a living being(s) or an external factor such as rising temperatures) is introduced into an ecosystem, catastrophic consequences can occur. This is because the new organism (or factor) is capable of distorting the natural balance of interaction and causing potential harm or destruction to the non-native ecosystem.

Generally, the biotic members of an ecosystem, together with their abiotic factors, depend on each other. This means the absence of one member or one abiotic factor can affect the entire ecological system.

If there is not enough light and water, or if the soil is low in nutrients, the plants may die. If the plants die, the animals that depend on them are also at risk. If animals that depend on plants die, other animals that depend on them will also die. The ecosystem in nature works the same way. All of its parts must function together to maintain balance!

Unfortunately, ecosystems can be destroyed by natural disasters such as fires, floods, hurricanes, and volcanic eruptions. Human activity also contributes to the destruction of many ecosystems and.

Main types of ecosystems

Ecological systems have indefinite dimensions. They are able to exist in a small space, for example, under a stone, a rotting tree stump or in a small lake, and also occupy large areas (like the entire rainforest). From a technical point of view, our planet can be called one huge ecosystem.

Diagram of a small rotting stump ecosystem

Types of ecosystems depending on the scale:

  • microecosystem- a small scale ecosystem like a pond, puddle, tree stump, etc.
  • mesoecosystem- an ecosystem, such as a forest or a large lake.
  • Biome. A very large ecosystem or collection of ecosystems with similar biotic and abiotic factors, such as an entire rainforest with millions of animals and trees, and many different water bodies.

Ecosystem boundaries are not marked with clear lines. They are often separated by geographical barriers such as deserts, mountains, oceans, lakes, and rivers. Since boundaries are not strictly fixed, ecosystems tend to merge with each other. This is why a lake can have many smaller ecosystems with their own unique characteristics. Scientists call this mixing "Ecoton".

Types of ecosystems by type of occurrence:

In addition to the above types of ecosystems, there is also a division into natural and artificial ecological systems. A natural ecosystem is created by nature (forest, lake, steppe, etc.), and an artificial one is created by man (garden, garden plot, park, field, etc.).

Ecosystem types

There are two main types of ecosystems: aquatic and terrestrial. Every other ecosystem in the world falls into one of these two categories.

Terrestrial ecosystems

Terrestrial ecosystems can be found anywhere in the world and are subdivided into:

forest ecosystems

These are ecosystems that have an abundance of vegetation or a large number of organisms living in a relatively small space. Thus, the density of living organisms in forest ecosystems is quite high. A small change in this ecosystem can affect its entire balance. Also, in such ecosystems you can find a huge number of representatives of the fauna. In addition, forest ecosystems are divided into:

  • Tropical evergreen forests or tropical rainforests: receiving an average rainfall of more than 2000 mm per year. They are characterized by dense vegetation dominated by tall trees located at different heights. These territories are a refuge for various species of animals.
  • Tropical deciduous forests: Along with a huge variety of tree species, shrubs are also found here. This type of forest is found in quite a few parts of the world and is home to a wide variety of flora and fauna.
  • : They have quite a few trees. It is dominated by evergreen trees that renew their foliage throughout the year.
  • Broad-leaved forests: They are located in humid temperate regions that have sufficient rainfall. During the winter months, the trees shed their leaves.
  • : Located directly in front, the taiga is defined by evergreen conifers, sub-zero temperatures for six months and acidic soils. In the warm season, you can meet a large number of migratory birds, insects and.

desert ecosystem

Desert ecosystems are located in desert regions and receive less than 250 mm of precipitation per year. They occupy about 17% of the entire land mass of the Earth. Due to the extremely high air temperature, poor access to and intense sunlight, and not as rich as in other ecosystems.

grassland ecosystem

Grasslands are located in the tropical and temperate regions of the world. The area of ​​the meadow mainly consists of grasses, with a small number of trees and shrubs. The meadows are inhabited by grazing animals, insectivores and herbivores. There are two main types of meadow ecosystems:

  • : Tropical grasslands that have a dry season and are characterized by singly growing trees. They provide food for a large number of herbivores, and are also a hunting ground for many predators.
  • Prairies (temperate grasslands): This is an area with a moderate grass cover, completely devoid of large shrubs and trees. In the prairies, forbs and tall grass are found, and arid climatic conditions are also observed.
  • Steppe meadows: Territories of dry grasslands, which are located near semi-arid deserts. The vegetation of these grasslands is shorter than in the savannas and prairies. Trees are rare, and usually found on the banks of rivers and streams.

mountain ecosystems

The highlands provide a diverse range of habitats where a large number of animals and plants can be found. At altitude, harsh climatic conditions usually prevail, in which only alpine plants can survive. Animals that live high in the mountains have thick fur coats to protect them from the cold. The lower slopes are usually covered with coniferous forests.

Aquatic ecosystems

Aquatic ecosystem - an ecosystem located in an aquatic environment (for example, rivers, lakes, seas and oceans). It includes aquatic flora, fauna, and water properties, and is divided into two types: marine and freshwater ecological systems.

marine ecosystems

They are the largest ecosystems that cover about 71% of the Earth's surface and contain 97% of the planet's water. Sea water contains a large amount of dissolved minerals and salts. The marine ecological system is divided into:

  • Oceanic (relatively shallow part of the ocean, which is located on the continental shelf);
  • Profundal zone (deep water area not penetrated by sunlight);
  • Bental region (area inhabited by benthic organisms);
  • intertidal zone (a place between low and high tides);
  • Estuaries;
  • Coral reefs;
  • Salt marshes;
  • Hydrothermal vents where chemosynthetic feeders.

Many types of organisms live in marine ecosystems, namely: brown algae, corals, cephalopods, echinoderms, dinoflagellates, sharks, etc.

Freshwater ecosystems

Unlike marine ecosystems, freshwater ecosystems cover only 0.8% of the Earth's surface and contain 0.009% of the world's total water supply. There are three main types of freshwater ecosystems:

  • Stagnant: Waters where there is no current, such as pools, lakes or ponds.
  • Flowing: Fast moving waters such as streams and rivers.
  • Wetlands: places where the soil is permanently or intermittently flooded.

Freshwater ecosystems are home to reptiles, amphibians and about 41% of the world's fish species. Fast-moving waters typically contain a higher concentration of dissolved oxygen, thereby supporting more biodiversity than stagnant pond or lake water.

Structure, components and factors of the ecosystem

An ecosystem is defined as a natural functional ecological unit consisting of living organisms (biocenosis) and their inanimate environment (abiotic or physico-chemical), which interact with each other and create a stable system. Pond, lake, desert, pasture, meadow, forest, etc. are common examples of ecosystems.

Each ecosystem consists of abiotic and biotic components:

Ecosystem structure

Abiotic components

Abiotic components are unrelated factors of life or the physical environment that influence the structure, distribution, behavior and interaction of living organisms.

Abiotic components are mainly represented by two types:

  • climatic factors which include rain, temperature, light, wind, humidity, etc.
  • Edaphic factors, including soil acidity, topography, mineralization, etc.

Importance of abiotic components

The atmosphere provides living organisms with carbon dioxide (for photosynthesis) and oxygen (for respiration). The processes of evaporation, transpiration and occur between the atmosphere and the surface of the Earth.

Solar radiation heats the atmosphere and evaporates water. Light is also essential for photosynthesis. provides plants with energy for growth and metabolism, as well as organic products to feed other life forms.

Most living tissue is made up of a high percentage of water, up to 90% or more. Few cells are able to survive if the water content falls below 10%, and most of them die when the water content is less than 30-50%.

Water is the medium through which mineral food products enter plants. It is also essential for photosynthesis. Plants and animals get water from the Earth's surface and soil. The main source of water is atmospheric precipitation.

Biotic Components

Living things, including plants, animals, and microorganisms (bacteria and fungi) present in an ecosystem are biotic components.

Based on their role in the ecological system, biotic components can be divided into three main groups:

  • Producers produce organic substances from inorganic substances using solar energy;
  • Consumers feed on ready-made organic substances produced by producers (herbivores, predators, etc.);
  • Reducers. Bacteria and fungi that destroy dead organic compounds of producers (plants) and consumers (animals) for nutrition, and emit simple substances (inorganic and organic) into the environment, formed as by-products of their metabolism.

These simple substances are re-produced as a result of cyclical exchange of substances between the biotic community and the abiotic environment of the ecosystem.

Ecosystem levels

To understand the layers of an ecosystem, consider the following figure:

Ecosystem Tier Diagram

Individual

An individual is any living being or organism. Individuals do not breed with individuals from other groups. Animals, unlike plants, are usually included in this concept, since some representatives of the flora can interbreed with other species.

In the diagram above, you can see that the goldfish interacts with the environment and will breed exclusively with members of its own species.

population

A population is a group of individuals of a given species that live in a particular geographic area at a given time. (An example is the goldfish and representatives of its species). Note that a population includes individuals of the same species that may have various genetic differences such as coat/eye/skin color and body size.

Community

The community includes all living organisms in a certain area at a given time. It may contain populations of living organisms of different species. In the diagram above, notice how goldfish, salmon, crabs, and jellyfish coexist in a particular environment. A large community usually includes biodiversity.

Ecosystem

An ecosystem includes communities of living organisms interacting with the environment. At this level, living organisms depend on other abiotic factors such as rocks, water, air, and temperature.

Biome

In simple terms, it is a collection of ecosystems that have similar characteristics with their abiotic factors adapted to the environment.

Biosphere

When we look at different biomes, each of which transitions into another, a huge community of people, animals and plants is formed, living in certain habitats. is the totality of all ecosystems present on Earth.

Food chain and energy in an ecosystem

All living beings must eat to get the energy they need to grow, move, and reproduce. But what do these living organisms eat? Plants get their energy from the sun, some animals eat plants and others eat animals. This ratio of feeding in an ecosystem is called the food chain. Food chains generally represent the sequence of who feeds on whom in a biological community.

The following are some of the living organisms that can fit in the food chain:

food chain diagram

The food chain is not the same as. The trophic web is a combination of many food chains and is a complex structure.

Energy transfer

Energy is transferred along food chains from one level to another. Part of the energy is used for growth, reproduction, movement and other needs, and is not available for the next level.

Shorter food chains store more energy than longer ones. The spent energy is absorbed by the environment.

Biological community ( biocenosis ) is a collection of individuals of various species living in a certain territory and interacting with each other. Examples of communities are coniferous forests, steppes, tropical rainforests, coral reefs, deserts. A biological community together with its environment is called an ecosystem ( biogeocenosis ).

The physical properties of the environment, especially the annual temperature and precipitation regime, influence the characteristics of the biological community and determine the appearance of either a forest, or a meadow, or a desert or a swamp. The biological community, in turn, can also change the physical characteristics of the environment. In terrestrial ecosystems, for example, wind speed, humidity, temperature and soil characteristics can be influenced by the plants and animals that live there.

Within the biogeocenosis, each species occupies its own ecological niche (a unique set of resources). Most often niches for species appear at a certain stage of succession. succession - the process of gradual transformation of the species composition, community structure and physical characteristics of the environment, which occurs after natural or anthropogenic disturbances in the ecosystem.

Some species can only be observed at certain stages of succession. For example, sun-loving butterflies and annuals are often found only in the early stages of succession, in the first months after the formation of a “bald spot” in an old forest. Shade-tolerant forest plants and birds nesting in the hollows of dead trees appear in the late stages of succession, i.e. in the old forest. Human economic activity often breaks the natural order of succession.

The composition of communities is also determined by competition and predators. Predators often significantly reduce the number of species - their prey - and may even displace some of them from their usual habitats. When predators are exterminated, the population of their prey can rise to a critical level or even exceed it. Then, after the exhaustion of the limiting resource, the destruction of the population may begin.

The community structure is also determined by symbiotic relationships (including mutualistic ones), in which species are in a mutually beneficial relationship. Mutualistic species achieve greater density when living together. Common examples of such mutualism are plants with fleshy fruits and birds that feed on these fruits and spread their seeds; fungi and algae, which together form lichens; plants that give shelter to ants, supplying them with nutrients; coral polyps and the algae that live in them.