Lecture 7. The doctrine about biosphere and biosphere - noosphere concept

of Vernadsky. Ecosystem. Biocenosis, biotope,

biogeocenosis and ecosystem.

Plan

1. Biocenosis, biotope and biogeocenosis.

2. The structural organization of ecosystem

3. Food chain

4. Circulation of substances and a stream of energy in the ecosystem

5. An ecological pyramid. Types of ecological pyramids

6. Biological production (efficiency) of ecosystem

7. Cyclic changes of ecosystem.

8. Succession

Biocenosis is a group of communities of the different species living in the certain territory. Biotope is the certain territory with the abiotic factors of an inhabitancy (a climate, soil). Biogeocenosis is a totality of biocenosis and biotope.

2. The structure of ecosystem

From the point of view of trophic structure ecosystem is divided into two circles – autotrophic and heterotrophic (Odum, 1986).

1. The top autotrophic circle, or «a green belt» is a circle of plants or their parts containing a chlorophyll where fixing of light energy, use of simple inorganic compounds and accumulation of complex organic compounds prevail.

2) The bottom heterotrophic circle, or «a brown belt» is a circle of soil and the precipitation, decompositing substances, roots and etc. in which use, transformation and decomposition of complex compounds prevail.

From the biological point of view in structure of ecosystem there are following components (Odum, 1986):

1) inorganic substances;

2) organic compounds;

3) air, water and substrate medium;

4) producers;

5) macroconsumers;

6) microconsumers.

1. Producers are the autotrophic organisms, which are capable to produce organic substances from inorganic, using photosynthesis or chemosynthesis (plants and autotrophic bacteria).

2. Consumers (macroconsumers) are the heterotrophic organisms consuming organic substance of producers or others consumers (animals, heterotrophic plants, some microorganisms). There are consumers of the first order and the second order.

3. Reducers (microconsumers, destructors) are the heterotrophic organisms, eating fossils and decomposing them to mineral substances (saprotrophic bacteria and mushrooms).

As a rule, in any ecosystem it is possible to note three functional groups of organisms: producers, consumers and reducers. In ecosystems formed only by microorganisms, consumers are absent. Each group consists of set of the populations occupying ecosystem.

In ecosystem, food and power bonds proceed in a line: producers->consumers-> reducers.

3. Food chain

Eating each other, alive organisms form food chain. The food chain is a sequence of organisms, on which the energy having in food is transferred (from its initial source). Each part of chain is called a trophic level. The first trophic level is producers (autotrophic organisms, mainly green plants). The second trophic level is consumers of the first level (herbivorous animals). The third trophic level – consumers of the second level (the primary predators eating herbivorous animals). The fourth trophic level is consumers of the third level (the secondary predators, eating carnivore animals). Last trophic level is reducers (saprotrophicе bacteria and mushrooms). They carry out a mineralization - transformation of fossils into inorganic substances.

There are two types of food chain. Chain of выедания (or pasturable) - the food circuits beginning alive photosynthesizing organisms. Chain of decomposition is a food chain beginning with the died rests of plants, corpses and excrement of animals. Thus, the stream of energy passing through ecosystem, is broken as though into two basic directions. Energy to consumers comes in through living tissues of plants or through stocks of dead organic substance. Chain of выедания prevails in water ecosystem, chain of decomposition is in ecosystem of land.

4. Circulation of substances and the stream of energy in ecosystem

In ecosystem organic substances are synthesized by autotrophic from inorganic substances. Then they are consumed by heterotrophic. Allocated during ability to live or after destruction of organisms (both autotrophic and heterotrophic) organic substances are exposed to a mineralization i.e. transformation into inorganic substances. These inorganic substances can be again used by autotrophic to synthesize organic substances. So, biological circulation of substances is carried out.

At the same time, energy cannot circulate within the limits of ecosystem. The stream of energy (transfer of energy), having in food, in the ecosystem is unidirectional carried out from autotrophic to heterotrophic.

In picture the simplified scheme of energy stream at three trophic levels of the food chain is shown. Trophic levels are shown as tanks, which size corresponds to the energy having in their biomass (B), the size of channels connecting them is equal to size of streams of energy. The stream of solar energy (L} enters in an input in the system.

At the first trophic level green plants absorb about 50 % of the solar energy (L_А.) | But, during photosynthesis, its some part will be transformed to energy of chemical bonds of organic substances. It is total primary production (P_G ). The most part of not assimilated energy disperses in an environment in the form of thermal energy. The part of the formed organic substances is oxidized, and liberated energy is consumed for maintenance of all metabolic processes. These are so-called expenses for breath (R). This energy, finally, also disperses in the form of heat. The remained part of new-formed organic substances makes up a gain of plants biomass (DB) and it is called as pure primary production (Р_N). Only 1 % of the energy absorbed by a plant is transformed into pure initial production. Thus, Р_N = P_G - R.

The scheme of an energy stream in the food chain, showing three trophic levels:

1 is an entering energy on a trophic level; L is a solar energy, get on plants; L_A- the energy absorbed by plants (nearby 0,5 L); L_U is not used part of energy of a sunlight; A is an assimilation, i.e. energy (reserved) in organic substance; R is an expense for breath; P_G is a total primary production (nearby 0,05L_N); P_N is a pure primary production; P is a secondary production (consumers); N_U is an energy not used by consumers (accumulated or exported); N_A is an energy not assimilated by consumers (allocated with excrement). Numbers below is a order of size of energy losses at each transport.

Only part of pure primary production reaches the second trophic level. Its some part (N_U) is not used by consumers of the first level. It can be collected or be exported for limits of system. That part which consumers assimilated (have consumed) (A), is partially spent for breath (Л), it is partially allocated with excrement (N_A), and the rest collects in the form of secondary production (P).

Secondary production at each subsequent trophic level of consumers (_Р2, _Р3, etc.) composites about 10 % previous (though at a level of predators it can be above 20 %). As a result, the longer the food chain the less energy (collected in the organic substances) remains by its end. Therefore the number of trophic levels never meets too greater.

6. Biological production (efficiency) of ecosystem

The gain of a biomass in the ecosystem, created for a time unit, is called biological production (efficiency). There are primary and secondary productions of community.

Primary production is a biomass created by producers for a time unit. It is divided into total and pure productions. Total primary production (the general assimilation) is the general biomass created by plants during photosynthesis. Its part is discharged for maintenance of ability to live of plants (expenses for breath (40-70 %). The remained part makes up pure primary production (pure assimilation) which in the further is used by consumers and reducers, or it is collected in the ecosystem.

Secondary production is a biomass created by consumers for a time unit. It is various for each following trophic level.

The weight of organisms of the certain group (producers, consumers, reducers) or communities as a whole is called a biomass. Tropical rain woods posses the highest biomass and efficiency, and the lowest is desert and tundra (tab. 8).

If velocity of the plants growth (formation of the primary production) in the ecosystem is above rates of its processing by consumers and reducers it results in increase of producer biomass. If recycling of products decomposition in chain of decomposition is insufficient an accumulation of dead organic substance proceeds. It results in peatining bogs, in formation of a powerful wood laying, etc. In stable ecosystems the biomass remains constant as practically all production is spent in the food chains.

8. Сукцессии

Translational changes are changes in biocenosis, finally, resulting in change of this community by another. Succession is a consecutive change of biocenosis (ecosystem), expressed in change of specific structure and structure of community. Successions are desertification of steppes, overgrown of lakes and formation of bogs, etc.

Depending on the reasons caused change of biocenosis, сукцессии are divided into natural and anthropogenous, autogenious and allogenious.

Сукцессия of Siberian darkneedle forests (fir-cedar taiga) after devastating forest fire

Numbers in rectangular are vibrations in duration of passage of сукцессии phases (in brackets term their termination is specified). The biomass and biological efficiency are shown in unspecified scale. (Curves reflect the qualitative and quantitative parties of the process.) (Rejmers, 1990.)

Natural succession occurs under action of the natural reasons which have been not connected with activity of man. Anthropogenous succession is caused by activity of the person.

Лекция 7. Учение о биосфере и биосферно - ноосферная

концепция В.И.Вернадского. Экологические системы.

Биоценоз, биотоп, биогеоценоз и экосистема.

План

1. Биоценоз, биотоп, биогеоценоз.

2. Структурная организация (структура) экосистемы

3. Пищевые цепи и сети

4. Круговорот веществ и поток энергии в экосистеме

5. Экологическая пирамида. Типы экологических пирамид

6. Биологическая продукция (продуктивность) экосистемы

7. Циклические изменения экосистемы.

8. Сукцессии

Биоценоз — совокупность популяций разных ви­дов, обитающих на определенной территории. Биотоп — определенная территория со свойственными ей абиотичес­кими факторами среды обитания (климат, почва). Биогео­ценоз — совокупность биоценоза и биотопа.

2. Структурная организация (структура) экосистемы

С точки зрения трофической структуры экосистему можно разделить на два яруса — автотрофный и гетерот­рофный (по Ю. Одуму, 1986).

1. Верхний автотрофный ярус, или «зеленый пояс», включающий растения или их части, содержащие хлоро­филл, где преобладают фиксация энергии света, использо­вание простых неорганических соединений и накопление сложных органических соединений.

2) Нижний гетеротрофный ярус, или «коричневый пояс» почв и осадков, разлагающихся веществ, корней и т.д., в котором преобладают использование, трансформация и разложение сложных соединений.

С биологической точки зрения в составе экосистемы удобно выделить следующие компоненты (по Ю, Одуму, 1986):

1) неорганические вещества;

2) органические соединения;

3) воздушную, водную и субстратную среду;

4) продуцентов;

5) макроконсументов;

6) микроконсументов.

1. Продуценты — автотрофные организмы, способные производить органические вещества из неорганических, используя фотосинтез или хемосинтез (растения и авто­трофные бактерии).

2. Консументы (макроконсументы, фаготрофы) — гете­ротрофные организмы, потребляющие органическое веще­ство продуцентов или других консументов (животные, ге­теротрофные растения, некоторые микроорганизмы). Консументы бывают первого порядка (фитофаги, сапрофаги), второго порядка (зоофаги, некрофаги) и т.д.

3.Редуценты (микроконсументы, деструкторы, сапротрофы, осмотрофы) -- гетеротрофные организмы, питающи­еся органическими остатками и разлагающие их до мине­ральных веществ (сапротрофные бактерии и грибы).

Как правило, в любой экосистеме мож­но выделить три функциональные группы организмов: продуцентов, консументов и редуцентов. В экосистемах образованных только микроорганизмами, консументы отсутствуют. В каждую группу входит множество популяций, населяющих экосистему.

В экосистеме пищевые и энергетические связи идут в направлении: продуценты—> консументы —> редуценты.