Ecological factors

Theme 2. Ecological Systems

Ecological factors

Environment (environment, exogenous environment) is the sum-total of abiotic and biotic conditions of animals, fungi and microorganisms habitation.

Natural environment is the sum-total of all natural conditions, bodies and phenomena with which an organism is in direct or indirect contact. There are air, water and soil kinds of environment.

Natural environment is the integral material system, which possesses a very difficult structure and is developing in accordance with inherent to it specific laws. It is in a state of dynamic equilibrium and reacts to any change of factors which support this equilibrium by alteration of all its structural links. Natural environment is all the living and the lifeless, which surrounds organisms and with which they are in contact with.

Natural environment is subdivided into:

1) actual natural environment («wild nature») means areas of nature, which are not disturbed by economic activity of man. The features of self-support and self-regulation without permanent correcting influence of man are characteristic for this environment. In other words, wild nature existed before the appearance of man, can exist without man now and will do without man in future.

2) quasinatural environment is all modifications of natural environment, artificially created by people. The absence of self-support system is characteristic for them, i.e. they gradually collapse without permanent regulative influence of man. The so-called «cultural landscapes», external space of settlements, green plantations belong to this type.

3) artenatural environment is the whole artificial world, created by man, which does not have material and energy analogues in nature, is alien to it as a system and is immediately beginning to collapse without continuous updating. Asphalt and concrete of modern cities and villages, internal space of places of life and work, technological equipment, transport, furniture, synthetic materials, etc. belong here.

4) social environment. As such social environment is studied by the science of sociology, however when dealing with ecological issues it is by all means necessary to take into account influencing natural environment by social strata.

The elements of an organism environment which render positive or negative influence on living organisms during even one of phases of their individual development are called ecological factors. Ecological factors are all constituent parts (elements) of natural environment, which influence the existence and development of organisms and to which living organisms react with reactions of adaptation (when there is no adaptation, death comes). Ecological factors affect an organism both directly and through intermediate links. There are three groups of ecological factors: abiotic, biotic, and anthropogenic.

Abiotic factors are conditioned by the influence of lifeless nature, i.e., by inorganic conditions – chemical and physical, such, as composition of air, water, soil, temperature, light, humidity, radiation, pressure etc.

Biotic factors are connected with the influence of organisms, i.e. these are forms of interaction between organisms, for example, an owner and a parasite. Biotic factors are subdivided into three following groups:

а) phytogenous represent the influence of plants which cohabitate. This cohabitation in its turn can be direct and indirect. Direct influence means mechanical contacts, symbiosis, parasitism. Indirect influence means phytogenous changes of organisms habitation environment.

б) zoogenic is influence of animals (eating up, trampling down, pollination, distribution of seeds and influencing the environment).

в) microbogenic and mycogenic mean the influence of microorganisms and fungi (parasitism, change of environment).

Anthropogenic factors are the factors arising up under the influence of man’s activity. Industrial and agricultural production influences the nature most of all.The result of such influence is the change of organisms habitation environment (ploughing up steppes, deforestation, contamination of environment etc.). Influence of this activity on nature can be both conscious and casual.

Presently 10 groups of ecological factors are differentiated (while their general quantity is about 60), the classification of which is as follows:

1) According to time - factors of time (evolutional, historical, operating);

2) According to periodicity – periodic (temperature, luminosity, tides, humidity of air, which depends upon temperature, vegetable food) and non-periodic which show up suddenly (floods, fires, earthquakes, volcanic explosions, parasites etc.);

3) Primary and secondary;

4) According to the origin (space, abiotic, biotic, natural and anthropogenic, technogenic, anthropogenic);

5) According to the place of origin (atmospheric, water, geomorphological, physiological, genetic, ecosystematic);

6) According to the character (informative, physical, chemical, energy, thermal, biogenic, complex, climatic);

7) According to the object of influence (individual, group, specific, social);

8) According to the degree of influence (lethal, extreme, limiting, disturbing, mutagenic);

9) According to the conditions of action – those which depend or do not depend on density;

10) According to the spectrum of influence (selective or general influence).

The most essential ecological factors, without which existence of living organisms is impossible, are light, temperature, water, food and (for the majority) oxygen.

The same ecological factors can be favorable for one group of organisms and unfavorable for the other. An important element is the reaction of organisms to the degree of influence of an ecological factor the negative action of which can arise in case of surplus or insufficient dose. Therefore there appeared concepts of favorable dose, or the area of factor optimum, and the area of pessimum (the factor dose at which organisms feel oppressed).

The range between the areas of optimum and pessimum is the criterion for determination of ecological valency, i.e., the ability of living organism to adapt to the changes in conditions of habitation environment. Quantitatively this ability is expressed by the range of the environment, within the boundaries of which this biological kind normally exists. Ecological valency of different kinds can considerably differentiate. For example, a reindeer endures fluctuations in air temperature from -55 to +25-30°C, and tropical corals perish even at the change of temperature for 5 – 6 °С.

In accordance with ecological valency organisms are subdivided into 2 types: a) with small adaptability to the changes of the environment (orchids, trout, Far-Eastern hazel-hen, deep-water fish); b) with great adaptability to the changes of environment (Colorado beetle, mice, rats, wolves, cockroaches, reed, couch-grass).

In nature ecological factors operate in complex, integrally.

The concept of limiting factors is also important. Limiting factors are such the level or the dose of which approaches the limit of an organism endurance, according to its concentration below or above the optimum. Most often limiting factors are temperature, light, biogenic matters, flows and pressure in the environment, fires etc. So, the strongest limiting factor for plants which grow on land is often the content of phosphorus in soil because of very slow turnover cycle of this element in nature.

Organisms with the wide range of tolerance to all ecological factors are most widespread. The highest tolerance is characteristic for bacteria and dark blue-green algae (seaweeds), which survive in the wide range of temperatures, radiation, saltness, рН.

Ecosystems

An ecosystem is a natural complex, formed by living organisms and the environment of their habitation which are connected between themselves by the exchange of matter and energy. The term «ecosystem» was introduced by an English scientist A. Tensli in 1935. He considered ecosystems as basic units of nature on the surface of Earth, although they do not have a certain volume and can cover space of any extent. An association and lifeless environment function in common as an ecological system (or ecosystem). The concept of ecosystem is a basic functional unit in ecology. An ecosystem is a single natural complex, which was formed for a long period by living organisms and the environment which they exist in, and where all components are closely connected by the exchange of matter and energy. The ecosystem is also characterized with such features as stability and distinctly functioning internal cycle of matter. There are microecosystems (the trunk of a rotten tree, a stump with mushrooms, a bog); mesoecosystems (a forest, a lake, a pond, a storage pool) and macroecosystems (a continent, an ocean). A global ecosystem of our planet is the biosphere which unites in itself all the ecosystems of lower levels.

Living components of ecosystems are the following:

а) producers are organisms, synthesizing organic substances from inorganic ones (green plants, photo- and chemosynthesizing microorganisms);

б) consumers are users of living organic matter (herbivorous and predatory animals, parasites);

в) decomposers are organisms, feeding on the dead organic matter (saprophytic microorganisms and invertebrates).

Lifeless components of ecosystems are atmosphere, mountain rock, soil, water.

The sum-total of living components of an ecosystem makes its biota.

The more components are included in the composition of an ecosystem, the more stable it is. As lifeless components are more or less stable, then stability of an ecosystem depends more on its living components. The reduction of biological diversity, thus, reduces stability of any ecosystem, and it can have irreversible consequences, first of all for man and quality of his life.

Ecosystems are characterized according to the following parameters: 1) specific or population composition and quantitative correlation of specific populations; 2) spatial distribution of separate elements; 3) the sum-total of all connections, above all – food chains.

Ecosystems are open thermodynamic functionally integral systems which exist due to the reception of energy and partly matter from the environment and which are self-developing and self-regulated.

Basic properties of ecosystems are the following capabilities:

to carry out the cycle of matter in the habitation environment;

to resist external influence;

to produce biological products.

Appropriate directed process of change of associations as a result of cooperation of living organisms between themselves and the abiotic environment surrounding them is called succession (from Latin successio which means succession, inheritance). The succession is completed with forming a new association which is adapted to the climatic conditions.

The sum-total of all factors of the environment (abiotic and biotic) within the limits of which the existence of a kind is possible is called an ecological niche. Ecological niche can not be empty.

In ecology there is also a term «geobiocenosis», suggested by a botanist V.N. Sukachev. This term designates the sum-total of plants, animals, microorganisms, soil, water and atmosphere on the homogeneous area of dry land. A geobiocenosis is the synonym of an ecosystem. An ecosystem is more general concept, than a geobiocenosis.

A biological kind (species) is the sum-total of organisms with similar morphological characteristics. These organisms can interbreed and have common gene pool (genefond). Kind has subkinds (subspecies) and populations. Population is the sum-total of individuals of one biological kind which is capable of reproductionduring unlimited time under conditions of the environment which is changing in definite parameters.

Energy of ecosystems. Life on Earth exists due to the Sun energy. Light is the only food resource on Earth, energy of which, in connection with carbon dioxide and water, creates the process of photosynthesis.

Principles of ecosystems functioning. V.I. Vernadskiy formulated the law of organism and environment unity: life develops as a result of permanent exchange of the matter and information on the base of the stream of energy in the combined unity of the environment and organisms which live in it. The form of the organism existence always corresponds to the conditions of its life.

There is the law of internal dynamic equilibrium of an ecosystem: if there is a change of some ecological factors, then necessarily all the other ecological components of the system, its dynamic qualities are changed either in this ecosystem or in the attended chain. Any biological system, being in the state of mobile (dynamic) equilibrium with the environment and developing evolutionally, increases affecting the environment. The influence grows until it will not be limited by external factors or some evolutional and ecological catastrophe. The environment is able to change considerably quicker than a species which lives in it and submits to genetic conservatism. This refers to man also. The environment of habitation quickly and sharply changes, and man as a biological creature cannot adapt to this at that rate, that’s why the possibility of the biocenosis destruction is created.

Homoeostasis is one of important ecological concepts. Homoeostasis is the state of internal dynamic equilibrium of the natural system (ecosystem), which is supported by regular renewal of its basic elements and material and energy composition, and also permanent functional self-regulation of components. Homoeostasis is characteristic and necessary for all natural systems. Proceeding from the cybernetic nature of ecosystems homoeostatic mechanism is a feed-back.

Large ecosystems are the most steady ones and the biosphere is the most stable among them, and young ecosystems are the most unsteady ones. This is explained by the fact that self-regulative homoeostasis in large ecosystems is created due to the interaction of cycles of matter and streams of energy.

Permissible influence and ecosystems stability. At present economic activity of man became comparable with processes in nature. Humankind cannot continue uncontrolledly contaminate the environment, but it cannot stop or decrease pace of his economic activity. The most acceptable way out is establishing rational relations with nature. Rational relations mean not only protection of nature, but the usage of natural resources without damage, guaranteeing their renewal. The definition of limits of permissible influence of man is closely connected with many aspects of ecology, first of all, with ecological rate setting, risk assessment, ecotoxicology. The notion ‘ecological rate setting’ refers to the system of regulation of influence on man and the environment, rate setting of the environment objects, territories. The notion of ‘ecological rate setting’ covers a number of the following aspects: nature management, protection of natural ecosystems and preservation of their ecological welfare, guaranteeing safe environment and people’s health. People’s health and ‘public health’ in general is the main priority of state policy in all countries.

In order to save natural ecosystems under conditions of economic activity it is necessary to know what size of anthropogenic influence will not result in dangerous effects and degradation. The determination of possible influence limits is necessary for decision of such practical tasks.

Any load for the ecological system, arising up due to some influence, which is able to destroy its natural (normal) state is defined as the ecological load. If the ecological load will not cause undesirable consequences, changes with organisms living on the Earth, first of all with man, and also will not result in worsening (weak or substantial) the environment quality, it can be considered possible.

The possible anthropogenic influencing the natural environment means the influence which does not affect the natural environment quality or which changes nature within possible limits, i.e. does not destroy an ecosystem and does not cause unfavorable consequences with major populations, first of all with man.

The concept of the possible influence for an ecosystem and the environment on the whole refers to the notion of the environment quality. The environment quality is the sum-total of indexes, characterizing the state of the environment.

Such indexes and parameters must be set for separate organisms, populations, associations, ecosystems and the biosphere on the whole. The establishment of these parameters takes into account two levels of harmful factors influence on natural systems:

The level of critical influence (starting with which the death or irreversible degradation of this system can take place);

The level of possible influence, which is substantially different from critical.

Possible influence can result in comparatively small changes of the natural environment quality, which do not affect normal development of ecosystems and separate populations, on ecological prosperity and stability of systems.

Ecological prosperity is such state of an ecosystem, which is characterized by normal reproduction of its basic links. Each higher level of organization has less stability to unfavorable influence than the preceding one. The catastrophe threatens an ecosystem then, when all buffer systems of lower levels of organization are worn out, and the buffer capacity of an ecosystem is outspent (exhausted).

The buffer capacity of ecosystems is the amount of contaminating substances, which an ecosystem can accept and which will not result in negative consequences.

The stability of an ecosystem is determined as the correlation between the amount of the system deviations from the normal state and the size of influence.

The size of possible influence depends upon what limits of characteristics fluctuation are considered possible. For developing rates of possible influence it is necessary to carry out the system of work for studying the character and regularity of distribution, accumulation, destruction, bioaccumulation, transformations of contaminating substances, their transformation in ecosystems, transition from one environment in the other one on local, regional and global scales. Rates of possible influence cannot be uniform for all types of ecosystems, and also for all climatic and geographic conditions.

Дата добавления: 2015-10-29