Wednesday -- it is a part of nature that surrounds living organisms and has a direct or indirect effect on them. From the environment, organisms receive everything necessary for life and excrete metabolic products into it. The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements may be partially or completely indifferent to the body, others are necessary, and still others have a negative effect.
living conditions, or the conditions of existence, is a set of elements of the environment necessary for the organism, with which it is in inseparable unity and without which it cannot exist.
Organisms' adaptations to their environment are called adaptation. The ability to adapt is one of the main properties of life in general, which ensures the possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels - from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. All adaptations of organisms to existence in various conditions have developed historically. As a result, groupings of plants and animals specific to each geographical area were formed.
Separate properties or elements of the environment that affect organisms are called environmental factors .
The variety of environmental factors is divided into two large groups: abiotic and biotic.
Abiotic factors -- This is a complex of conditions of the inorganic environment that affect the body.
Biotic factors -- it is a set of influences of the vital activity of some organisms on others. In some cases, anthropogenic factors are singled out as an independent group of factors along with abiotic and biotic ones, thereby emphasizing the extraordinary effect of the anthropogenic factor.
The influence of environmental factors is determined primarily by their impact on the metabolism of organisms. Hence, all environmental factors according to their action can be divided into direct and indirectly acting. Both can have significant impacts on the life of individual organisms and on the entire community. Environmental factors can act either in the form of a direct one, or in the form of an indirect one. Each environmental factor is characterized by certain quantitative indicators, such as strength and range of action.
For different types of plants and animals, the conditions in which they feel especially good are not the same. For example, some plants prefer very moist soil, while others prefer relatively dry soil. Some require intense heat, others tolerate colder environments better, etc. biosphere organism water substance
The intensity of the environmental factor, the most favorable for the life of the organism, is called the optimum, and giving the worst effect - the pessimum. , i.e., the conditions under which the vital activity of the organism is maximally inhibited, but it can still exist.
Environment? this is everything that surrounds the body and directly or indirectly affects its state and functioning (development, growth, survival, reproduction, etc.). The environment that provides the possibility of the existence of organisms on Earth is very diverse. Four qualitatively different environments of life can be distinguished on our planet: water, land-air, soil and a living organism.
Water environment
Water serves as a habitat for many organisms. From water, they receive all the substances necessary for life: food, water, gases. Therefore, no matter how high the diversity of aquatic organisms, they must all be adapted to the main features of life in the aquatic environment. These features are determined by the physical and chemical properties of water.
In the water column there is constantly a large number of small representatives of plants and animals leading life in suspension. Their ability to soar is provided not only by the physical properties of water, which has a buoyant force, but also by special adaptations of the organisms themselves. For example, numerous outgrowths and appendages that significantly increase the surface of the body relative to its mass and, therefore, increase friction against the surrounding fluid.
Animals are adapted to movement in the aquatic environment in different ways. Active swimmers (fish, dolphins, etc.) have a characteristic streamlined body shape and limbs in the form of fins. Their fast swimming is also facilitated by the peculiarities of the structure of the outer integument and the presence of a special lubricant? mucus that reduces friction with water.
In some aquatic beetles, the exhaust air released from the spiracles is retained between the body and the elytra due to hairs that are not wetted by water. With the help of such a device, an aquatic insect quickly rises to the surface of the water, where it releases air into the atmosphere. Many protozoa move with the help of oscillating cilia (ciliates) or flagella (euglena).
Water has a very high heat capacity, i.e., the ability to accumulate and retain heat. For this reason, there are no sharp temperature fluctuations in water, which often occur on land. Can the waters of the polar seas be very cold? close to freezing. However, the constancy of temperature allowed the development of a number of adaptations that ensure life even in these conditions.
One of the most important properties of water is the ability to dissolve other substances that can be used by aquatic organisms for respiration and nutrition.
Breathing requires oxygen. Therefore, the saturation of water with it is of great importance.
The amount of oxygen dissolved in water decreases with increasing temperature. Moreover, oxygen dissolves worse in sea water than in fresh water. For this reason, the waters of the open sea of the tropical zone are poor in living organisms. Conversely, in polar waters, where there is more oxygen, is there an abundance of plankton? small crustaceans that feed on representatives of a rich fauna, including fish and large cetaceans.
Respiration of aquatic organisms can be performed by the entire surface of the body or by special organs? gills. For successful breathing, it is necessary that there is a constant renewal of water near the body. This is achieved by various kinds of movements. For many organisms it is necessary to maintain a constant flow of water. This can be provided by the movement of the animal itself or by special devices, such as oscillating cilia or tentacles, which produce a whirlpool near the mouth, driving food particles into it.
The saline composition of water is very important for life, Ca 2+ ions are of particular importance for organisms. Mollusks and crustaceans need calcium to build their shells or shells. The concentration of salts in water can vary greatly. Water is considered fresh if it contains less than 0.5 g per liter of dissolved salts. Sea water is characterized by constant salinity and contains an average of 35 g of salts per liter.
Ground-air environment
The ground-air environment, mastered later in the course of the evolution of the aquatic environment, is more complex and diverse. It is characterized by a higher level of organization of the living.
The most important factor in the life of organisms living here is the properties and composition of the surrounding air masses. The density of air is much lower than the density of water, so do terrestrial organisms have highly developed supporting tissues? internal and external skeleton. The forms of movement are extremely diverse: running, jumping, crawling, flying, etc. Birds and many insects move through the air. Air currents carry plant seeds, spores, microorganisms.
Air masses are characterized by a huge volume and are constantly in motion. Air temperature can change very quickly and over large spaces. Therefore, organisms living on land have numerous adaptations to withstand or avoid sudden changes in temperature. The most remarkable adaptation is the development of warm-bloodedness, which arose precisely in the ground-air environment.
In general, the air-land environment is more diverse than the water; living conditions here vary greatly in time and space. These changes are noticeable even at a distance of several tens of meters, for example, at the border of a forest and a field, at different heights in the mountains, even on different slopes of small hills. At the same time, pressure drops are less pronounced here, but often there is a lack of moisture. Therefore, terrestrial inhabitants have developed adaptations associated with providing the body with water, especially in arid conditions. In plants, this is a powerful root system, a waterproof layer on the surface of leaves and stems, and the ability to regulate the evaporation of water through stomata. In animals, in addition to the structural features of the external integument, these are also behavioral features that contribute to maintaining the water balance, for example, migration to watering places or avoidance of drying conditions.
Of great importance for the life of terrestrial organisms is the composition of the air (79% nitrogen, 21% oxygen and 0.03% carbon dioxide), which provides the chemical basis of life. Thus, a decrease in the specific amount of oxygen in the air, depending on the elevation of the terrain, determines the upper limit of animal life. Humans, for example, have never formed permanent settlements above 6,000 meters above sea level.
Carbon dioxide (carbon dioxide) is the most important raw material source for photosynthesis. Air nitrogen is necessary for the synthesis of proteins and nucleic acids.
The soil
Soil as a habitat? the top layer of land, formed by mineral particles processed by the activities of soil inhabitants. This is an important and very complex component of the biosphere, closely related to its other parts. Soil life is extraordinarily rich. Some organisms spend their whole life in the soil, others - part of their life. Soil plays an important role in plant life.
Living conditions in the soil are largely determined by climatic factors, the most important of which is temperature.
Organism bodies
Environmental problems of resource management
Sources, composition and extent of atmospheric pollution
Sources of air pollution
The influence of some atmospheric pollutants on the human body and plants
Specific air pollutants
Greenhouse effect
Destruction of the ozone screen (ozone holes)
acid rain
Atmospheric protection
Anthropogenic impacts on the hydrosphere and its protection
Main sources of pollution of surface and ground waters
Major water pollutants
Ecological consequences of hydrosphere pollution
Depletion of the hydrosphere and its ecological consequences
The state of water resources in the Omsk region
Main soil types
Anthropogenic impact on the soil
Soil pollution
Secondary salinization and waterlogging
desertification
Agriculture as one of the environmental impact factors
Anthropogenic impacts on rocks, their massifs and subsoil
The main environmental consequences of subsoil development for the lithosphere
Protection of soils, mountain ranges and subsoil
Anthropogenic impacts on biotic communities and their protection
The value of the forest in nature and human life
Brief description of the vegetation cover of the Omsk region
Vegetation degradation
Plant protection
reserves
Reserves
National parks
natural parks
Dendrological parks and botanical gardens
Red Book
Ecology, rational use and protection of natural resources of wild medicinal plants
Sources of contamination of medicinal plants
Rational use and protection of natural resources of wild medicinal plants
Fundamentals of environmental law
Environmental certification
Environmental audit
Environmental assessment
Environmental control
Legal liability for environmental offenses
Economic mechanism of environmental protection
Environmental monitoring
Regulation of environmental quality
FORMATION OF ECOLOGY AS A SCIENCE
Methods of ecological research.
Assessment of the state of species in ecosystems
Spatial structure of ecosystems
Spatial structure of biogeocenoses
Consortative connections in ecosystems
mutually beneficial relationship
Useful-neutral relationship
mutually harmful relationship
Anthropogenic ecosystems
The living matter of the planet
Basic properties of the biosphere
Anthropogenic cycle
Basic ideas about the evolution of the biosphere
The concept of the noosphere according to V. I. Vernadsky
Modern problems of the biosphere
Autotrophic and heterotrophic organisms (ecological classification of living organisms by type of nutrition)
Life environments on planet Earth
Some general patterns of environmental factors
The concept of nature management. Natural resources.
Environment and conditions for the existence of organisms
Environment and conditions of existence of organisms.
Wednesday- everything that surrounds the body and directly or indirectly affects its vital activity, development, growth, survival, reproduction, etc.
The environment of each organism is composed of sets of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements are necessary for the body, others are indifferent to it, and others have a harmful effect.
Conditions of existence, or living conditions- a set of elements of the environment necessary for the organism, with which it is in inseparable unity and without which it cannot exist.
Organisms' adaptations to their environment are called adaptation. The ability to adapt is one of the main properties of life in general, providing the possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels - from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. All adaptations of organisms to existence in various conditions have developed historically. As a result, groupings of plants and animals specific to each geographical area were formed.
Separate properties or elements of the environment that affect organisms are called environmental factors(Table 3.1).
Table 3.1
Different approaches to the classification of environmental factors
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ENVIRONMENTAL FACTORS |
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ABIOTIC |
BIOTIC |
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Light, temperature, moisture, wind, air, pressure, currents, day length, etc. The mechanical composition of the soil, its permeability, moisture capacity |
The influence of plants on other members of the biocenosis The influence of animals on other members of the biocenosis Anthropogenic factors arising from human activities |
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BY TIME |
BY PERIODICITY |
IN ORDER |
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Evolutionary Historical |
Periodic Non-periodic |
Primary Secondary |
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BY ORIGIN |
ACCORDING TO THE ENVIRONMENT | ||||||||
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Space Abiotic (abiogenic) biogenic Biotic Biological Natural-anthropogenic Anthropogenic (including man-made, environmental pollution, including disturbance |
Atmospheric Water (humidity) Geomorphological edaphic Physiological Genetic population Biocenotic ecosystem biospheric | ||||||||
Environmental factors are usually divided into three main groups: abiotic, biotic and anthropic.
abiotic factors - a complex of conditions of the inorganic and organic environment that affect the body. Abiotic factors are divided into chemical (chemical composition of air, ocean, soil, etc.) and physical (temperature, pressure, wind, humidity, light, radiation regime, etc.).
Antropical factors - a set of impacts of human activity on the organic world. Already by the fact of his existence, a person has an impact on the environment (due to breathing, approximately 1.1 1012 kg CO2, etc.) and immeasurably more by industrial activity to an ever-increasing degree.
The impact on the body of abiotic factors can be direct and indirect (indirect). So, for example, the temperature of the environment determines the rate of physiological processes in the body and, accordingly, its development (direct influence); at the same time, influencing the development of plants that are food for animals, it has an indirect effect on the latter.
The effect of environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness, etc.). All organisms in the process of evolution have developed adaptations to the perception of factors within certain quantitative limits. Moreover, for each organism there is a set of factors that are most favorable for it.
The more the dose of factors deviates from the optimal value for a given type (increase or decrease), the more its vital activity is inhibited. The boundaries beyond which the existence of an organism is impossible are called lower and upper limit of endurance (tolerance).
The intensity of the environmental factor that is most favorable for the organism (its life activity) is called optimum, and giving the worst effect - pessimism.
Organisms can adapt over time to changing factors. The property of species to adapt to changing ranges of environmental factors is called ecological plasticity(environmental valence). The wider the range of fluctuations of the ecological factor within which a given species can exist, the greater its ecological plasticity, the wider the range of its tolerance (endurance).
Ecologically non-plastic (hardy) species are called stenobiont(from Greek. stenos- narrow), more plastic (hardy) - eurybiontic(from Greek. euros- wide). Species of organisms that have developed for a long time under relatively stable conditions lose their ecological plasticity and acquire stenobiont features; species that existed under conditions of significant changes in environmental factors become eurybiont.
The attitude of organisms to fluctuations of one or another environmental factor is expressed by adding prefixes steno- and evry- (steno- and eurythermal, steno- and eurythotic, etc.).
Historically adapting to abiotic environmental factors and entering into biotic relationships with each other, plants, animals and microorganisms are distributed over various environments and form diverse biogeocenoses, eventually merging into biosphere Earth.
Biogeocenosis- territorially (spatially) isolated integral elementary unit of the biosphere, all components of which are closely connected with each other.
All environmental factors act on the body simultaneously and in interaction. Such a combination is called constellation. Therefore, the optimum and limits of the organism's endurance in relation to one factor depend on others. Moreover, if the intensity of at least one factor goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable other conditions are. This factor is called limiting. A special case of the principle of limiting factors is the minimum rule formulated by Liebig (a German chemist) to characterize the yield of agricultural crops: the substance that is at a minimum (in the soil, in the air) controls the yield and determines the size and stability of the latter.
Habitat and conditions of existence of organisms. Environmental factors
From the concept of ʼʼhabitatʼʼ one should distinguish the concept of ʼʼexistence conditionsʼʼ - a set of vital environmental factors without which living organisms cannot exist (light, heat, moisture, air, soil). Unlike them, other environmental factors, although they have a significant impact on organisms, are not vital for them (for example, wind, natural and artificial ionizing radiation, atmospheric electricity, etc.).
environmental factors. Elements of the environment that cause adaptive reactions (adaptations) in living organisms and their communities are called environmental factors.
According to the origin and nature of the action, environmental factors are divided into abiotic (elements of inorganic or inanimate nature), biotic (forms of the impact of living beings on each other) and anthropogenic (all forms of human activity that affect wildlife).
Abiotic factors are divided into physical, or climatic (light, air and water temperature, air and soil humidity, wind), edaphic, or soil-ground (mechanical composition of soils, their chemical and physical properties), topographic, or orographic (landscape features ), chemical (water salinity, gas composition of water and air, soil and water pH, etc.).
Anthropogenic (anthropic) factors are all forms of activity of human society that change nature as the habitat of living organisms or directly affect their life. The allocation of anthropogenic factors into a separate group is due to the fact that at present the fate of the Earth's vegetation cover and all currently existing species of organisms is practically in the hands of human society.
One and the same environmental factor has a different meaning in the life of cohabiting organisms. For example, the salt regime of the soil plays a primary role in the mineral nutrition of plants, but is indifferent to most land animals. The intensity of illumination and the spectral composition of light are extremely important in the life of phototrophic plants, while in the life of heterotrophic organisms (fungi and aquatic animals), light does not have a noticeable effect on their vital activity.
Environmental factors act on organisms in different ways. Οʜᴎ can act as stimuli causing adaptive changes in physiological functions; as limiters, predetermining the impossibility of the existence of certain organisms in given conditions; as modifiers that determine morphological and anatomical changes in organisms.
The reaction of organisms to the influence of abiotic factors. The impact of environmental factors on a living organism is very diverse. Some factors have a stronger influence, others are weaker; some affect all aspects of life, others - on a certain life process. Nevertheless, in the nature of their impact on the body and in the responses of living beings, a number of general patterns can be identified that fit into some general scheme of the action of the environmental factor on the vital activity of the organism (Fig. 14.1).
On fig. 14.1 the intensity (or ʼʼdoseʼʼ) of the factor (for example, temperature, illumination, salt concentration in soil solution, pH or soil moisture, etc.) is plotted along the abscissa axis, and the body's response to the impact of an environmental factor in its quantitative expression is plotted along the ordinate axis (for example, the intensity of photosynthesis, respiration, growth rate, productivity, number of individuals per unit area, etc.), i.e., the degree of the factor’s beneficence.
The range of action of the ecological factor is limited by the corresponding extreme threshold values (minimum and maximum points), at which the existence of an organism is still possible. These points are called the lower and upper limits of endurance (tolerance) of living beings in relation to a particular environmental factor.
Rice. 14.1. Scheme of the effect of the environmental factor on the vital activity of organisms: 1, 2. 3 - points of minimum, optimum and maximum, respectively; I, II, III zones of pessimum, norm and optimum, respectively.
Point 2 on the abscissa axis, corresponding to the best indicators of the vital activity of the organism, means the most favorable value of the influencing factor for the organism - this is the optimum point. For most organisms, it is often difficult to determine the optimal value of the factor with sufficient accuracy; therefore, it is customary to speak of an optimum zone. The extreme sections of the curve, expressing the state of oppression of organisms with a sharp deficiency or excess of the factor, are called areas of pessimum or stress. The sublethal values of the factor lie near the critical points, and the lethal values lie outside the survival zone.
Such a regularity of the reaction of organisms to the impact of environmental factors allows us to consider it as a fundamental biological principle: for each species of plants and animals there is an optimum, a zone of normal life, pessimal zones and limits of endurance in relation to each environmental factor.
Different types of living organisms differ markedly from each other both in the position of the optimum and in the limits of endurance. For example, polar foxes in the tundra can tolerate fluctuations in air temperature in the range of about 80°C (from +30 to -55°C), some warm-water crustaceans withstand water temperature changes in the range of no more than 6°C (from 23 to 29°C) , the filamentous cyanobacterium oscillatoria, living on the island of Java in water with a temperature of 64 ° C, dies at 68 ° C after 5-10 minutes. In the same way, some meadow grasses prefer soils with a rather narrow range of acidity - at pH = 3.5-4.5 (for example, common heather, white-backed protruding, small sorrel serve as indicators of acidic soils), others grow well with a wide range of pH - from strongly acidic to alkaline (for example, Scotch pine). In this regard, organisms whose existence requires strictly defined, relatively constant environmental conditions are called stenobiont (Greek stenos - narrow, bion - living), and those that live in a wide range of environmental variability are called eurybiont (Greek eurys - wide). At the same time, organisms of the same species can have a narrow amplitude with respect to one factor and a wide amplitude with respect to another (for example, adaptability to a narrow temperature range and a wide range of water salinity). At the same time, the same dose of the factor should be optimal for one species, pessimal for another, and go beyond the limits of endurance for the third.
The ability of organisms to adapt to a certain range of variability of environmental factors is called ecological plasticity. This feature is one of the most important properties of all living things: by regulating their vital activity in accordance with changes in environmental conditions, organisms acquire the ability to survive and leave offspring. This means that eurybiont organisms are ecologically the most plastic, which ensures their wide distribution, while stenobiont organisms, on the contrary, are characterized by weak ecological plasticity and, as a result, usually have limited distribution areas.
Interaction of environmental factors. limiting factor.
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Environmental factors affect a living organism jointly and simultaneously. At the same time, the effect of one factor depends on the strength and combination of other factors acting simultaneously. This pattern is called the interaction of factors. For example, heat or frost is easier to bear in dry rather than moist air. The rate of water evaporation by plant leaves (transpiration) is much higher if the air temperature is high and the weather is windy.
In some cases, the lack of one factor is partially compensated by the strengthening of another. The phenomenon of partial interchangeability of the action of environmental factors is commonly called the effect of compensation. For example, the wilting of plants can be stopped both by increasing the amount of moisture in the soil and by lowering the air temperature, which reduces transpiration; in deserts, the lack of precipitation is to a certain extent compensated for by increased relative humidity at night; in the Arctic, long daylight hours in summer compensate for the lack of heat.
At the same time, none of the environmental factors necessary for the body should be completely replaced by another. The absence of light makes plant life impossible, despite the most favorable combination of other conditions. For this reason, if the value of at least one of the vital environmental factors approaches a critical value or goes beyond its limits (below the minimum or above the maximum), then, despite the optimal combination of other conditions, individuals are threatened with death. Such factors are called limiting (limiting).
The nature of the limiting factors must be different. For example, the oppression of herbaceous plants under the canopy of beech forests, where, with optimal thermal conditions, high carbon dioxide content, rich soils, the possibilities for the development of grasses are limited by a lack of light. This result can only be changed by influencing the limiting factor.
Environmental limiting factors determine the geographic range of a species. Thus, the movement of a species to the north can be limited by a lack of heat, and to areas of deserts and dry steppes - by a lack of moisture or too high temperatures. Biotic relations can also serve as a factor limiting the distribution of organisms, for example, the occupation of the territory by a stronger competitor or the lack of pollinators for flowering plants.
The identification of limiting factors and the elimination of their action, i.e., the optimization of the habitat of living organisms, is an important practical goal in increasing crop yields and the productivity of domestic animals.
Populations. Structure and properties of populations
Indicators of the structure of populations. As the first necessary biological system, the population has a certain structure and properties. The structure of a population is reflected by such indicators as the number and distribution of individuals in space, the ratio of groups by sex and age, their morphological, behavioral and other features.
Number - the total number of individuals in the population. This value is characterized by a wide range of variability, but it should not be below certain limits. Reducing the number compared to these limits can lead to the extinction of the population. It is believed "that if the population is less than a few hundred individuals, then any random causes (fire, flood, drought, heavy snowfalls, severe frosts, etc.) can reduce it so much that the remaining individuals cannot meet and leave offspring. Fertility will cease to cover the natural loss, and the remaining individuals will die out within a relatively short time.
Density is the number of individuals per unit area or volume. With an increase in the population density, as a rule, increases; it remains the same only in the case of its resettlement and expansion of its range. In some animals, population density is regulated by complex behavioral and physiological mechanisms.
The spatial structure of the population is characterized by the peculiarities of the distribution of individuals in the occupied territory. It is determined by the properties of the habitat and the biological characteristics of the species. Along with random and uniform distribution in nature, group distribution is most common. A group of animals, making joint efforts, can more easily defend themselves from predators, search for and obtain food. Life in families, herds, colonies, harems also leads to group distribution of individuals. The spatial structure can change over time; it depends on the season of the year, on the population size, age and sex structure, etc.
The sex structure reflects a certain ratio of males and females in a population. The genetic mechanism of sex determination ensures the splitting of offspring by sex in a ratio of 1: 1. Due to the different viability of male and female individuals, this primary sex ratio at fertilization often differs markedly from the secondary one (at birth - in mammals) and even more so from the tertiary, characteristic for mature individuals. For example, in human populations, the secondary sex ratio is 100 girls/106 boys; by the age of 16-18, this ratio levels off and becomes equal to 1:1, by the age of 50 - 100 women / 85 men, and by the age of 80, the sex ratio becomes 2:1 (100 women / 50 men).
The change in the sexual structure of a population is reflected in its role in the ecosystem, since males and females of many species differ from each other in the nature of nutrition, rhythm of life, behavior, etc.
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So, females of some species of mosquitoes, ticks and midges are blood-sucking, while males feed on plant sap or nectar. The predominance of the proportion of females over males ensures a more intensive growth of the population.
The age structure reflects the ratio of different age groups in populations, depending on life expectancy, the time of puberty, the number of offspring in a litter, the number of offspring per season, etc.
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If any age group decreases or increases, this affects the total population. For example, the mass extermination of large sexually mature individuals as a result of fishing leads to a sharp decrease in the population size due to its weak replenishment with young individuals. For this reason, the presence in the population of a large number of individuals of younger age groups indicates its well-being. If the population is dominated by old individuals, it can be said with certainty that this population ends its existence.
The ecological structure indicates the attitude of various groups of organisms to environmental conditions. For example, individuals of one plant population differ in a number of characteristics: in size, number of shoots, flowers, fruits, seeds, etc. At the same time, different individuals of the same population bloom at the same time, which contributes to their more complete pollination (with simultaneous and short-term flowering insects may not have time to pollinate all the flowers). Such a population has a lower risk of being left without seeds, for example, in the case of short-term frosts (only part of the flowers will freeze).
Population dynamics. Theoretically, any population is capable of unlimited growth in numbers, if it is not limited by environmental factors (limited resources, diseases, predators, etc.). In such a hypothetical case, the rate of population growth will depend only on the magnitude of the biotic potential inherent in each particular species. Biotic potential reflects the theoretically possible number of offspring from one pair (or one individual) for a certain period of time, for example, for the entire life cycle or for a year.
In different species, the magnitude of the biotic potential differs sharply. For example, in large mammals, even under the most favorable conditions, the number can increase only 1.05-1.1 times per year. In many insects and crustaceans (aphids, daphnia), the number increases by 10 10 -10 30 times per year, and even more in bacteria. Moreover, in these cases, under ideal conditions, the size of any population over a certain time will grow exponentially (Fig. 14.2). An increase in numbers at a constant rate is called exponential growth. The curve that reflects such a population growth on the graph quickly increases the steepness and goes to infinity.
Rice. 14.2. Exponential (theoretical) (a) and logistic (real) (b) population growth curves.
Under natural conditions, exponential population growth is extremely rare. For example, it has been noted in a rabbit population introduced to Australia, where it had unlimited food and space resources without the deterrent effect of predators. This type of growth is also observed during outbreaks of locusts, gypsy moths and other insects. At the same time, periods of exponential growth are usually short-lived.
With an increase in population density, there is usually a slowdown in population growth, as the population is placed in conditions with limited resources. For example, animals at a high population density may not have enough food, and plants begin to shade each other or they lack moisture. The type of population growth with limited resources, characterized by a decrease in speed as population density increases, is commonly called logistic (see Fig. 14.2).
The general changes in population size are determined by such processes as fertility, mortality and migration of individuals.
Fertility characterizes the frequency of the appearance of new individuals in a population. The average birth rate of each species has historically been defined as an adaptation to replenish population decline. Distinguish between absolute and specific fertility.
Absolute fertility - the number of individuals born (hatched, budded, etc.) in a population per unit of time. Specific birth rate - the number of individuals born in a population per unit of time per individual. The specific birth rate makes it possible to compare the birth rate in populations with different sizes.
The higher the birth rate, the greater the proportion of individuals participating in reproduction, the higher the fecundity, the more often reproductive cycles follow each other. Usually, the birth rate in each population is balanced by its characteristic mortality.
The number of populations is also significantly affected by the migration of individuals.
Migrations are the regular movements of animals between significantly different, spatially disparate habitats. Such migrations are caused by a change in the conditions of existence in habitats or a change in the requirements of the animal to these conditions at different stages of development. The mass movement of individuals between populations can change their structure and basic properties (prevent the death of a population that is on the verge of extinction, or, on the contrary, lead it to a sharp reduction). For example, the mass eviction of settled animals (squirrels, nutcrackers, lemmings, etc.) with a sudden deterioration in conditions (droughts, fires, floods, etc.), overpopulation often ends in their mass death.
Migrations (daily, seasonal) allow organisms to use optimal environmental conditions in places where their permanent residence is impossible. Οʜᴎ lead to the development of new biotopes, the expansion of the common range of the species, to the exchange of individuals between populations, increase the unity and overall stability of the species, and contribute to success in the struggle for existence.
In the absence of migration, the change in the population size depends on the ratio of the birth rate and death rate.
If the birth rate is higher than the death rate, then the population will increase, and, on the contrary, it will decrease if the death rate exceeds the birth rate. Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, the number of populations under natural conditions is constantly changing as environmental conditions change. The amplitude and period of these fluctuations depend on the degree of environmental variability, as well as on the biological characteristics of a particular species.
Behavioral factors play an important role in the regulation of population abundance and density. For example, in populations of many rodents, an increase in the concentration of the adrenaline hormone in the blood, observed at a high population density, causes aggressiveness, various hormonal disorders (in females, embryo resorption may occur). As a result, the number of rodents is decreasing.
Another form of behavior - the protection of an individual site (territoriality) - is also aimed at regulating the population. Often, almost the entire territory occupied by a population is divided into individual areas, which are designated in various ways (the secret of odorous glands, scratches on trees, the singing of male birds, urine, etc.). Marking and protection of sites that do not allow the reproduction of ʼʼalienʼʼ individuals on them leads to the rational use of the territory. In this case, the excess part of the population does not reproduce or is forced to move out of the occupied space.
There are a number of other historically established mechanisms that retard the growth of populations and thus ensure their stability. These include chemical interactions of individuals (for example, tadpoles release substances into the water that retard the growth of other tadpoles); changes in physiology and behavior with increasing density, which leads to the manifestation of mass migration instincts; the spread of diseases (the probability of transmission of infections increases with an increase in population density), etc.
Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, due to a variety of mechanisms, the range of all daily, seasonal and annual changes in the number and density of populations, as a rule, is less than theoretically possible, corresponding to the realization of the entire biotic potential. Overpopulation is always unfavorable for any species, as it can lead to a rapid undermining of environmental resources, lack of food, shelters, space, which will inevitably lead to a general weakening of populations.
Habitat and conditions of existence of organisms. Environmental factors - concept and types. Classification and features of the category "Habitat and conditions for the existence of organisms. Environmental factors" 2017, 2018.
Environmental factors is a set of environmental conditions that affect living organisms. Distinguish inanimate factors- abiotic (climatic, edaphic, orographic, hydrographic, chemical, pyrogenic), wildlife factors— biotic (phytogenic and zoogenic) and anthropogenic factors (impact of human activity). Limiting factors include any factors that limit the growth and development of organisms. The adaptation of an organism to its environment is called adaptation. The appearance of an organism, reflecting its adaptability to environmental conditions, is called a life form.
The concept of environmental environmental factors, their classification
Separate components of the habitat that affect living organisms, to which they react with adaptive reactions (adaptations), are called environmental factors, or ecological factors. In other words, the complex of environmental conditions that affect the life of organisms is called ecological factors of the environment.
All environmental factors are divided into groups:
1. include components and phenomena of inanimate nature that directly or indirectly affect living organisms. Among the many abiotic factors, the main role is played by:
- climatic(solar radiation, light and light regime, temperature, humidity, precipitation, wind, atmospheric pressure, etc.);
- edaphic(mechanical structure and chemical composition of the soil, moisture capacity, water, air and thermal conditions of the soil, acidity, humidity, gas composition, groundwater level, etc.);
- orographic(relief, slope exposure, slope steepness, elevation difference, height above sea level);
- hydrographic(transparency of water, fluidity, flow, temperature, acidity, gas composition, content of mineral and organic substances, etc.);
- chemical(gas composition of the atmosphere, salt composition of water);
- pyrogenic(effect of fire).
2. - a set of relationships between living organisms, as well as their mutual influences on the environment. The action of biotic factors can be not only direct, but also indirect, expressed in the adjustment of abiotic factors (for example, changes in the composition of the soil, microclimate under the forest canopy, etc.). Biotic factors include:
- phytogenic(the influence of plants on each other and on the environment);
- zoogenic(the influence of animals on each other and on the environment).
3. reflect the intense impact of a person (directly) or human activity (indirectly) on the environment and living organisms. These factors include all forms of human activity and human society that lead to a change in nature as a habitat and other species and directly affect their lives. Each living organism is influenced by inanimate nature, organisms of other species, including humans, and in turn affects each of these components.
The influence of anthropogenic factors in nature can be both conscious and accidental, or unconscious. Man, plowing up virgin and fallow lands, creates agricultural land, breeds highly productive and disease-resistant forms, settles some species and destroys others. These impacts (conscious) are often negative in nature, for example, the rash resettlement of many animals, plants, microorganisms, the predatory destruction of a number of species, environmental pollution, etc.
Biotic factors of the environment are manifested through the relationship of organisms that are part of the same community. In nature, many species are closely interrelated, their relationships with each other as components of the environment can be extremely complex. As for the connections between the community and the surrounding inorganic environment, they are always bilateral, mutual. Thus, the nature of the forest depends on the corresponding type of soil, but the soil itself is largely formed under the influence of the forest. Similarly, the temperature, humidity and light in the forest are determined by the vegetation, but the formed climatic conditions in turn affect the community of organisms living in the forest.
The impact of environmental factors on the body
The impact of the environment is perceived by organisms through environmental factors called ecological. It should be noted that the environmental factor is only a changing element of the environment, causing in organisms, when it changes again, response adaptive ecological and physiological reactions, which are hereditarily fixed in the process of evolution. They are divided into abiotic, biotic and anthropogenic (Fig. 1).
They name the whole set of factors of the inorganic environment that affect the life and distribution of animals and plants. Among them are distinguished: physical, chemical and edaphic.
Physical factors - those whose source is a physical state or phenomenon (mechanical, wave, etc.). For example, temperature.
Chemical Factors- those that come from the chemical composition of the environment. For example, water salinity, oxygen content, etc.
Edaphic (or soil) factors are a combination of chemical, physical and mechanical properties of soils and rocks that affect both the organisms for which they are the habitat and the root system of plants. For example, the influence of nutrients, moisture, soil structure, humus content, etc. on the growth and development of plants.
Rice. 1. Scheme of the impact of the habitat (environment) on the body
- factors of human activity affecting the natural environment (and hydrospheres, soil erosion, deforestation, etc.).
Limiting (limiting) environmental factors called such factors that limit the development of organisms due to a lack or excess of nutrients compared to the need (optimal content).
So, when growing plants at different temperatures, the point at which maximum growth is observed will be optimum. The entire range of temperatures, from minimum to maximum, at which growth is still possible, is called range of stability (endurance), or tolerance. Its limiting points, i.e. maximum and minimum habitable temperatures, - stability limits. Between the optimum zone and the limits of stability, as the latter is approached, the plant experiences increasing stress, i.e. we are talking about stress zones, or zones of oppression, within the stability range (Fig. 2). As the distance from the optimum goes down and up on the scale, not only does stress increase, but when the limits of the organism's resistance are reached, its death occurs.
Rice. 2. Dependence of the action of the environmental factor on its intensity
Thus, for each species of plants or animals, there are optimum, stress zones and limits of stability (or endurance) in relation to each environmental factor. When the value of the factor is close to the limits of endurance, the organism can usually exist only for a short time. In a narrower range of conditions, long-term existence and growth of individuals is possible. In an even narrower range, reproduction occurs, and the species can exist indefinitely. Usually, somewhere in the middle part of the stability range, there are conditions that are most favorable for life, growth and reproduction. These conditions are called optimal, in which individuals of a given species are the most adapted, i.e. leaving the largest number of offspring. In practice, it is difficult to identify such conditions, so the optimum is usually determined by individual indicators of vital activity (growth rate, survival rate, etc.).
Adaptation is the adaptation of the organism to the conditions of the environment.
The ability to adapt is one of the basic properties of life in general, providing the possibility of its existence, the ability of organisms to survive and reproduce. Adaptations are manifested at different levels - from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. All adaptations of organisms to existence in various conditions have developed historically. As a result, groupings of plants and animals specific to each geographical area were formed.
Adaptations can be morphological, when the structure of an organism changes up to the formation of a new species, and physiological, when changes occur in the functioning of the body. Morphological adaptations closely adjoin the adaptive coloration of animals, the ability to change it depending on the illumination (flounder, chameleon, etc.).
Widely known examples of physiological adaptation are hibernation of animals, seasonal flights of birds.
Very important for organisms are behavioral adaptations. For example, instinctive behavior determines the action of insects and lower vertebrates: fish, amphibians, reptiles, birds, etc. Such behavior is genetically programmed and inherited (innate behavior). This includes: the method of building a nest in birds, mating, raising offspring, etc.
There is also an acquired command received by the individual in the course of his life. Education(or learning) - the main mode of transmission of acquired behavior from one generation to another.
The ability of an individual to control his cognitive abilities in order to survive unexpected environmental changes is intellect. The role of learning and intelligence in behavior increases with the improvement of the nervous system - an increase in the cerebral cortex. For man, this is the determining mechanism of evolution. The ability of species to adapt to a particular range of environmental factors is denoted by the concept ecological mysticism of the species.
The combined effect of environmental factors on the body
Environmental factors usually act not one by one, but in a complex way. The effect of any one factor depends on the strength of the influence of others. The combination of different factors has a significant impact on the optimal conditions for the life of the organism (see Fig. 2). The action of one factor does not replace the action of another. However, under the complex influence of the environment, one can often observe the “substitution effect”, which manifests itself in the similarity of the results of the influence of different factors. Thus, light cannot be replaced by an excess of heat or an abundance of carbon dioxide, but by acting on changes in temperature, it is possible to suspend, for example, the photosynthesis of plants.
In the complex influence of the environment, the impact of various factors for organisms is unequal. They can be divided into main, accompanying and secondary. The leading factors are different for different organisms, even if they live in the same place. The role of the leading factor at different stages of the life of the organism can be either one or the other elements of the environment. For example, in the life of many cultivated plants, such as cereals, temperature is the leading factor during germination, soil moisture during heading and flowering, and the amount of nutrients and air humidity during ripening. The role of the leading factor may change at different times of the year.
The leading factor may not be the same in the same species living in different physical and geographical conditions.
The concept of leading factors should not be confused with the concept of. A factor whose level in qualitative or quantitative terms (lack or excess) turns out to be close to the endurance limits of a given organism, is called limiting. The action of the limiting factor will also manifest itself in the case when other environmental factors are favorable or even optimal. Both leading and secondary environmental factors can act as limiting ones.
The concept of limiting factors was introduced in 1840 by the chemist 10. Liebig. Studying the influence of the content of various chemical elements in the soil on plant growth, he formulated the principle: “The minimum substance controls the crop and determines the magnitude and stability of the latter in time.” This principle is known as Liebig's Law of the Minimum.
The limiting factor can be not only a lack, as Liebig pointed out, but also an excess of such factors as, for example, heat, light and water. As noted earlier, organisms are characterized by ecological minimum and maximum. The range between these two values is usually called the limits of stability, or tolerance.
In general, the complexity of the influence of environmental factors on the body is reflected in the law of tolerance by W. Shelford: the absence or impossibility of prosperity is determined by the lack or, conversely, the excess of any of a number of factors, the level of which may be close to the limits tolerated by the given organism (1913). These two limits are called tolerance limits.
Numerous studies have been carried out on the "ecology of tolerance", thanks to which the limits of the existence of many plants and animals have become known. One such example is the effect of an air pollutant on the human body (Fig. 3).
Rice. 3. Effect of air pollutant on the human body. Max - maximum vital activity; Dop - allowable vital activity; Opt - optimal (not affecting vital activity) concentration of a harmful substance; MPC - the maximum allowable concentration of a substance that does not significantly change vital activity; Years - lethal concentration
The concentration of the influencing factor (harmful substance) in fig. 5.2 is marked with the symbol C. At concentration values C = C years, a person will die, but irreversible changes in his body will occur at much lower values C = C pdc. Therefore, the range of tolerance is limited precisely by the value C pdc = C lim. Hence, C MPC must be determined experimentally for each polluting or any harmful chemical compound and not allowed to exceed its C plc in a particular habitat (living environment).
In environmental protection, it is important upper limits of organism resistance to harmful substances.
Thus, the actual concentration of the pollutant C actual should not exceed C MPC (C actual ≤ C MPC = C lim).
The value of the concept of limiting factors (Clim) lies in the fact that it gives the ecologist a starting point in the study of complex situations. If an organism is characterized by a wide range of tolerance to a factor that is relatively constant, and it is present in the environment in moderate amounts, then this factor is unlikely to be limiting. On the contrary, if it is known that one or another organism has a narrow range of tolerance to some variable factor, then this factor deserves careful study, since it can be limiting.
Habitat - a part of nature (a set of specific abiotic and biotic conditions) that directly surrounds living organisms Habitat -
part of nature (a set of specific
abiotic and biotic conditions),
directly surrounding living organisms
and having a direct or indirect effect on
their condition, growth, development, reproduction,
survival, etc.
main habitats: aquatic, terrestrial
(air), soil and the body of another organism,
used by parasites and semi-parasites.
From the concept of "habitat" it is necessary to distinguish the concept
"conditions of existence" set of vital
necessary environmental factors, without which living organisms cannot
exist (light, heat, moisture, air, soil).
Environmental factors are elements of the environment that cause adaptive reactions in living organisms and their communities (adaptation).
Environmental factors - elements of the environmentenvironments that cause living organisms and their
communities adaptive reactions (adaptations)
According to the origin and nature of the action, environmental factors are divided into abiotic
(elements of inorganic, or inanimate, nature), biotic (forms of exposure of living beings to each other
each other) and anthropogenic (all forms of human activity that affect wildlife).
Abiotic factors are divided into physical, or climatic (light, air and water temperature, humidity
air and soil, wind), edaphic, or soil-ground (mechanical composition of soils, their chemical and
physical properties), topographic, or orographic (landscape features),
chemical (water salinity, gas composition of water and air, soil and water pH, etc.).
Biotic factors are various forms of influence of some organisms on the vital activity of others. At
in this case, some organisms can serve as food for others (for example, plants for animals, prey for a predator), be
habitat (for example, a host for a parasite), to promote reproduction and dispersal (for example, birds and
insect pollinators for flowering plants), exert mechanical, chemical and other effects.
Anthropogenic (anthropic) factors are all forms of activity of human society,
changing nature as the habitat of living organisms or directly affecting their life. Selection
anthropogenic factors into a separate group due to the fact that at present the fate of the vegetation cover
The earth and all currently existing species of organisms is practically in the hands of human society.
Despite this diversity, the effect of environmental factors on the body in the responses of living beings can reveal a number of common laws.
Despite this diversity, the effect of ecologicalfactors on the body in the responses of living
creatures, a number of general patterns can be identified:
a) ecological plasticity (or ecological valency) - a property
organisms to adapt to a particular range of environmental factors;
b) the law of the limiting factor or the law of the minimum. If all conditions
turn out to be favorable, with the exception of one, which acquires
crucial for life (deficiency or redundancy), it is called
the law of the limiting factor;
c) the law of tolerance - the range of endurance of environmental factors;
d) laws of optimum (favorable effects of survival) of minimum and
maximum - the transferred values of the factor are critical points,
limiting the degree of tolerance for survival.
Optimum - the intensity of the environmental factor, the most favorable for the organism. Pessimum - the conditions under which the body is tested
Optimum -intensity
ecological
factor, most
favorable to
organism.
Pessimum -
conditions, when
which organism
experiencing
oppression.
Factors of the aquatic environment.
To the factors of the aquatic environmentrelate
physiochemical properties
waters that are applied
deep imprint on
structure and
vitality
the organisms that inhabit it.
10. Relief factors (orographic factors).
According to the shape of the relief, they distinguish:macroreliefs (mountains, lowlands, valleys),
mesoreliefs (hills, ravines),
microreliefs (small depressions, ejecta of earth digging
animals).
11. Types of impact of environmental factors on organisms.
Types of environmental impactfactors on organisms.
Environmental factors affect living organisms in various ways.
They may be:
stimuli that promote the emergence of adaptive
(adaptive) physiological and biochemical changes (hibernation,
photoperiodism);
limiters that change the geographic distribution of organisms due to
the impossibility of existence in these conditions;
modifiers that cause morphological and anatomical changes
organisms;
signals indicating changes in other environmental factors.
12.
Elements of the environment that affect a living organism are called environmental factors.The life of any organism depends on a certain state of the surrounding substances and processes.
These conditions are divided into:
1. Abiotic environmental factors, which are divided into:
climatic; soil-ground.
Climatic include: the energy coming from the Sun and the periodic change in time of day and year
illumination (photoperiodism). The visible spectrum of sunlight illuminates us, infrared - warms, and
ultraviolet - feeds, participating in photosynthesis and in small doses - heals.
2. Humidity of atmospheric air and amount of precipitation.
3. The gas composition of the atmosphere, normally consisting of a mixture of nitrogen 78.09%, oxygen 20.05%, carbon dioxide
0.03% and other gases, including ozone in the upper layers. Nitrogen is involved in the creation of proteins that form body mass
living organisms into which it enters as a result of the activity of microorganisms capable of
arrange from the air and transfer to the soil and plants. Oxygen is found in proteins, fats and carbohydrates
providing the oxidation of nutrients in cells, which is the source of energy for living organisms.
Carbon dioxide, participating in plant photosynthesis, is a regulator of solar and terrestrial response.
radiation of heat rays. Ozone is an "umbrella" that blocks ultraviolet rays for a long time.
waves less than 0.3 m/km are fatal to life.
13.
4. Temperature5. Wind and atmospheric pressure
Soil and ground include:
Soils of varying fertility, formed as a result of climate interaction,
plants, animals and microorganisms. Soil is a habitat for many microorganisms and
plant roots. It has its own ecological features.
In the soil are of paramount importance:
"structure;" chemical composition; humidity. But light or temperature fluctuations
practically do not play a role, except for the upper layers. The inhabitants of the soil environment are called
edaphobionts or geobionts. Water, varying in degree of transparency, acidity and
the presence of dissolved gases, especially oxygen.
Biotic factors - a set of influences of the vital activity of some organisms on
others. Exposure occurs both within species through sex and age relationships,
joint hunting and protection from enemies, or fighting for food and territory, and between species.
14. Combined action of environmental factors
Environmental factors act not individually, but as a whole complex.The action of one factor is not replaced by the action of another. "Effect
substitution” is manifested in the similarity of the results.
According to the impact factors are divided: leading and background.
Synergy - the joint action of environmental factors Rule
interactions of environmental factors: Some factors may enhance or
mitigate the effect of other factors.
limiting factors. A factor whose level in quality or
quantitatively (lack or excess) is close to
the limits of the organism's endurance.
