Variant – 10

1. Types of communications and mutual relations between organisms

Alive organisms are definitely connected to each other.

Types of relations between organisms. Influence of one species on another can be positive, negative and neutral. Thus different combinations of types of influence are possible. There are neutralism, mutualism, commensalism, predatoriness, parasitism, a competition, amensalism.

Neutralism is a cohabitation of two species in one territory, not having for them neither positive, nor negative consequences. For example, squirrel and elks do not affect to each other.

Mutualism (biology), symbiotic interaction between different species that is mutually beneficial.

For example, there are herbivorous hoofed animals and cellulosedestructive bacteria.

Commensalism 

A symbiotic relationship in which one organism derives benefit while causing little or no harm to the other.

Amensalism 

Definition of Amensalism : between two species involves one impeding or restricting the success of the other without being affected positively or negatively by the presence of the other. It is a type of symbiosis. Usually this occurs when one organism exudes a chemical compound as part of its normal metabolism that is detrimental to another organism.

Parasitism. In this association one organism [the parasite] benefits and the other [the host] is adversely affected [weakened, sickened, damaged etc]. This description would also fit the relationship between a carnivore and its live prey and a herbivore and the plant it feeds on, especially if they are very specialized in the food they eat.

Symbiosis (from Ancient Greek σύν "together" and βίωσις "living") is close and often long-term interaction between two or more different biological species.

Symbiosis and evolution

While historically, symbiosis has received less attention than other interactions such as predation or competition, it is increasingly recognized as an important selective force behind evolution, with many species having a long history of interdependent co-evolution

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

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.

3. Producers. Consumers. Reducers.

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.