There are two theories to explain the regulation size.

Overview

The term "homeostasis" is most often used in biology. Multicellular organisms to exist are necessary to maintain a constant internal environment. Many environmentalists believe that this principle also applies to the external environment. Homeostatic system should not only strive to survive, they also have to adapt to environmental changes and develop.

Properties of homeostasis:

§ The instability of the system: testing how best to adapt to it.

§ Aspiration for balance: all internal, structural and functional organization of the system contributes to the preservation of balance.

§ Unpredictability: the resultant effect of a particular action can often differ from the one that was expected.

There are different kinds of homeostasis:

Homeostasis of the ecological system– is the ability of the ecosystem to self-support and self-regulation. It is based on the principle of feedback, according to which the deviation value of some environmental factor from the norm causes a corresponding change in the processes of self-regulation in the ecosystem. As a result, the individual properties and combination of properties close to optimum, and its condition is stable and resistant.

Area, within which feedback mechanisms are able to maintain the stability of the system, in spite of the stresses, even in a modified form, called homeostatic plateau.

In the limits of the action of feedbacks ecosystem is stable due to the compensatory controller, and in conditions of anthropogenic pressure for ecosystem functioning, person must act as a compensatory controller: to plant trees, to clear the air, water, etc.

Support of homeostasis in ecosystem is possible only within certain limits.

Outside the scope of the of negative feedback takes effect positive feedback (we can see it on picture 1). The scope of the negative feedback can be visualized as a homeostatic plateau. It consists of steps, each step within the valid negative feedback. The transition from step to step can occur as a result of changes in the "probe." Thus, the increase or decrease in the amount of food resources translates homeostasis to another level.

Picture 1

Thus, homeostasis - is the most important condition for the existence of any ecosystem, however, between communities, its signs and laws are not the same.

Example:

In natural biogeocoenose, homeostasis is maintained that such a system is open, and it receives energy from the environment continuously.

Example:

Anthropogenic ecosystem cannot be considered as open. For example, in the ecosystem of artificial aeration facilities for wastewater treatment: a continuous flow of waste water, substances, contained here, accumulates in the aeration tank and the concentration of activated sludge is reduced and it is not enough for the sorption of pollutants. As a result, the balance is disturbed ecosystems, the quality of treatment is reduced and the system stops working. To maintain the system mode of operation, the man maintains himself this process.

So we can conclude, that total pledged homeostasis of anthropogenic ecosystem is impossible.

The homeostasis of populations. The regulation of populations:

Functions of homeostasis characteristic for populations of living organisms od all groups, however they are most fully studied in animals. For all diversity of population homeostasis mechanisms can be grouped into three functional categories:

§ Maintaining the spatial structure;

§ Maintaining the genetic structure;

§ Regulation of population size and density.

There are two theories to explain the regulation size.

1. Mortality in the population is due only to the influence of physical (weather, fire, pollution) or biological factors (predators) and affects the same proportion of individuals in the population, regardless of its size. Such factors, the effect of which is independent of the population, called factors, independent of density.

2. Mortality of individuals in the population is always dependent on the size of the latter. The number is greater, than the risk of death is the higher. In this case, the population affected by factors that depend on density. With a high population starts to feel a lack of resources, limited access to food, increasing the number of enemies, fill all available space for nesting, etc.

Among the regulatory factors includes, in particular, the relationship of organisms of predator - a victim.

Example:

For explaining, that is feedback in the ecology, we can consider the conditional simple ecosystem, consisting of two levels of graphics "deer - the wolf." In this system, predators feed on the victims. If the number of victims increases, the population of the predators increases too, if they eat only these victims. This demonstrates the positive feedback, which tends to bring the system out of balance.

Picture 2

So, regulatory factors never brought to the populations of null values ​​due to the fact that the strength of their action decreases as the number of populations.

The most stable is the large ecosystems and the most stable of them is the biosphere. This is explained by the fact that in large ecosystems self-regulating homeostasis created by the interaction of the cycling of matter and energy flows.

Date: 2015-12-11; view: 2349