Temperature is the most important environmental factor. Temperature has a huge impact on many aspects of the life of organisms, their geography of distribution, reproduction and other biological properties of organisms, which depend mainly on temperature. Range, i.e. The temperature limits in which life can exist range from approximately -200°C to +100°C, and bacteria have sometimes been found to exist in hot springs at temperatures of 250°C. In reality, most organisms can survive in an even narrower range of temperatures.

Some types of microorganisms, mainly bacteria and algae, are able to live and reproduce in hot springs at temperatures close to the boiling point. The upper temperature limit for hot spring bacteria is about 90°C. Temperature variability is very important from an environmental point of view.

Any species is able to live only within a certain temperature range, the so-called maximum and minimum lethal temperatures. Beyond these critical temperature extremes, cold or heat, death of the organism occurs. Somewhere between them there is an optimal temperature at which the vital activity of all organisms, living matter as a whole, is active.

Based on the tolerance of organisms to temperature conditions, they are divided into eurythermic and stenothermic, i.e. able to tolerate temperature fluctuations within wide or narrow limits. For example, lichens and many bacteria can live at different temperatures, or orchids and other heat-loving plants of tropical zones are stenothermic.

Some animals are able to maintain a constant body temperature, regardless of the ambient temperature. Such organisms are called homeothermic. In other animals, body temperature varies depending on the ambient temperature. They are called poikilothermic. Depending on the method of adaptation of organisms to temperature conditions, they are divided into two ecological groups: cryophylls - organisms adapted to cold, to low temperatures; thermophiles - or heat-loving.

Allen's rule- an ecogeographical rule established by D. Allen in 1877. According to this rule, among related forms of homeothermic (warm-blooded) animals leading a similar lifestyle, those that live in colder climates have relatively smaller protruding body parts: ears, legs, tails, etc.

Reducing the protruding parts of the body leads to a decrease in the relative surface of the body and helps to save heat.

An example of this rule are representatives of the Canine family from various regions. The smallest (relative to body length) ears and less elongated muzzle in this family are found in the Arctic fox (area: Arctic), and the largest ears and narrow, elongated muzzle are found in the fennec fox (area: Sahara).

This rule also applies to human populations: the shortest (relative to body size) nose, arms and legs are characteristic of the Eskimo-Aleut peoples (Eskimos, Inuit), and the longest arms and legs are for the Furs and Tutsis.

Bergman's rule- an ecogeographical rule formulated in 1847 by the German biologist Karl Bergmann. The rule states that among similar forms of homeothermic (warm-blooded) animals, the largest are those that live in colder climates - in high latitudes or in the mountains. If there are closely related species (for example, species of the same genus) that do not differ significantly in their feeding patterns and lifestyle, then larger species are also found in more severe (cold) climates.

The rule is based on the assumption that the total heat production in endothermic species depends on the volume of the body, and the rate of heat transfer depends on its surface area. As the size of organisms increases, the volume of the body grows faster than its surface. This rule was first tested experimentally on dogs of different sizes. It turned out that heat production in small dogs is higher per unit mass, but regardless of size it remains almost constant per unit surface area.

Indeed, Bergmann's rule is often fulfilled both within the same species and among closely related species. For example, the Amur form of the tiger from the Far East is larger than the Sumatran form from Indonesia. Northern wolf subspecies are on average larger than southern ones. Among closely related species of the bear genus, the largest ones live in northern latitudes (the polar bear, brown bears from Kodiak Island), and the smallest species (for example, the spectacled bear) live in areas with a warm climate.

At the same time, this rule was often criticized; it was noted that it cannot be of a general nature, since the size of mammals and birds is influenced by many other factors besides temperature. In addition, adaptations to harsh climates at the population and species level often occur not through changes in body size, but through changes in the size of internal organs (increasing the size of the heart and lungs) or through biochemical adaptations. Taking into account this criticism, it is necessary to emphasize that Bergman’s rule is statistical in nature and manifests its effect clearly, all other things being equal.

Indeed, there are many exceptions to this rule. Thus, the smallest race of woolly mammoth is known from the polar island of Wrangel; many forest wolf subspecies are larger than tundra wolves (for example, the extinct subspecies from the Kenai Peninsula; it is assumed that their large size could give these wolves an advantage when hunting large moose inhabiting the peninsula). The Far Eastern subspecies of leopard living on the Amur is significantly smaller than the African one. In the examples given, the compared forms differ in lifestyle (island and continental populations; tundra subspecies, feeding on smaller prey, and forest subspecies, feeding on larger prey).

In relation to humans, the rule is applicable to a certain extent (for example, pygmy tribes apparently appeared repeatedly and independently in different areas with a tropical climate); however, differences in local diets and customs, migration, and genetic drift between populations place limits on the applicability of this rule.

Gloger's rule is that among related forms (different races or subspecies of the same species, related species) of homeothermic (warm-blooded) animals, those that live in warm and humid climates are brighter colored than those that live in cold and dry climate. Established in 1833 by Konstantin Gloger (Gloger C. W. L.; 1803-1863), a Polish and German ornithologist.

For example, most desert bird species are duller in color than their relatives from subtropical and tropical forests. Gloger's rule can be explained both by considerations of camouflage and by the influence of climatic conditions on the synthesis of pigments. To a certain extent, Gloger's rule also applies to hypokilothermic (cold-blooded) animals, in particular insects.

Humidity as an environmental factor

Initially, all organisms were aquatic. Having conquered land, they did not lose their dependence on water. Water is an integral part of all living organisms. Humidity is the amount of water vapor in the air. Without moisture or water there is no life.

Humidity is a parameter characterizing the content of water vapor in the air. Absolute humidity is the amount of water vapor in the air and depends on temperature and pressure. This amount is called relative humidity (i.e., the ratio of the amount of water vapor in the air to the saturated amount of vapor under certain conditions of temperature and pressure.)

In nature there is a daily rhythm of humidity. Humidity fluctuates vertically and horizontally. This factor, along with light and temperature, plays a large role in regulating the activity of organisms and their distribution. Humidity also modifies the effect of temperature.

An important environmental factor is air drying. Especially for terrestrial organisms, the drying effect of air is of great importance. Animals adapt by moving to protected places and leading an active lifestyle at night.

Plants absorb water from the soil and almost all (97-99%) evaporates through the leaves. This process is called transpiration. Evaporation cools the leaves. Thanks to evaporation, ions are transported through the soil to the roots, ions are transported between cells, etc.

A certain amount of moisture is absolutely necessary for terrestrial organisms. Many of them require a relative humidity of 100% for normal functioning, and on the contrary, an organism in normal condition cannot live for a long time in absolutely dry air, because it constantly loses water. Water is an essential part of living matter. Therefore, the loss of water in a certain amount leads to death.

Plants in dry climates adapt through morphological changes and reduction of vegetative organs, especially leaves.

Land animals also adapt. Many of them drink water, others absorb it through the body in liquid or vapor form. For example, most amphibians, some insects and mites. Most desert animals never drink; they satisfy their needs from water supplied with food. Other animals obtain water through the process of fat oxidation.

Water is absolutely necessary for living organisms. Therefore, organisms spread throughout their habitat depending on their needs: aquatic organisms live constantly in water; hydrophytes can only live in very humid environments.

From the point of view of ecological valency, hydrophytes and hygrophytes belong to the group of stenogyrs. Humidity greatly affects the vital functions of organisms, for example, 70% relative humidity was very favorable for field maturation and fertility of female migratory locusts. When propagated successfully, they cause enormous economic damage to crops in many countries.

For ecological assessment of the distribution of organisms, the indicator of climate aridity is used. Dryness serves as a selective factor for the ecological classification of organisms.

Thus, depending on the humidity characteristics of the local climate, species of organisms are distributed into ecological groups:

1. Hydatophytes are aquatic plants.

2. Hydrophytes are terrestrial-aquatic plants.

3. Hygrophytes - terrestrial plants living in conditions of high humidity.

4. Mesophytes are plants that grow with average moisture

5. Xerophytes are plants that grow with insufficient moisture. They, in turn, are divided into: succulents - succulent plants (cacti); sclerophytes are plants with narrow and small leaves, and rolled into tubes. They are also divided into euxerophytes and stypaxerophytes. Euxerophytes are steppe plants. Stypaxerophytes are a group of narrow-leaved turf grasses (feather grass, fescue, tonkonogo, etc.). In turn, mesophytes are also divided into mesohygrophytes, mesoxerophytes, etc.

Although inferior in importance to temperature, humidity is nevertheless one of the main environmental factors. For most of the history of living nature, the organic world was represented exclusively by aquatic organisms. An integral part of the vast majority of living beings is water, and almost all of them require an aquatic environment to reproduce or fuse gametes. Land animals are forced to create an artificial aquatic environment in their bodies for fertilization, and this leads to the latter becoming internal.

Humidity is the amount of water vapor in the air. It can be expressed in grams per cubic meter.

Light as an environmental factor. The role of light in the life of organisms

Light is one of the forms of energy. According to the first law of thermodynamics, or the law of conservation of energy, energy can change from one form to another. According to this law, organisms are a thermodynamic system constantly exchanging energy and matter with the environment. Organisms on the surface of the Earth are exposed to a flow of energy, mainly solar energy, as well as long-wave thermal radiation from cosmic bodies.

Both of these factors determine the climatic conditions of the environment (temperature, rate of water evaporation, movement of air and water). Sunlight with an energy of 2 cal falls on the biosphere from space. by 1 cm 2 in 1 min. This is the so-called solar constant. This light, passing through the atmosphere, is weakened and no more than 67% of its energy can reach the Earth’s surface on a clear noon, i.e. 1.34 cal. per cm 2 in 1 min. Passing through cloud cover, water and vegetation, sunlight is further weakened, and the distribution of energy in it across different parts of the spectrum changes significantly.

The degree to which sunlight and cosmic radiation are attenuated depends on the wavelength (frequency) of the light. Ultraviolet radiation with a wavelength of less than 0.3 microns almost does not pass through the ozone layer (at an altitude of about 25 km). Such radiation is dangerous for a living organism, in particular for protoplasm.

In living nature, light is the only source of energy; all plants, except bacteria, photosynthesize, i.e. synthesize organic substances from inorganic substances (i.e. from water, mineral salts and CO-In living nature, light is the only source of energy, all plants except bacteria 2 - using radiant energy in the process of assimilation). All organisms depend for nutrition on terrestrial photosynthetic organisms, i.e. chlorophyll-bearing plants.

Light as an environmental factor is divided into ultraviolet with a wavelength of 0.40 - 0.75 microns and infrared with a wavelength greater than these magnitudes.

The action of these factors depends on the properties of the organisms. Each type of organism is adapted to a particular wavelength of light. Some types of organisms have adapted to ultraviolet radiation, while others have adapted to infrared radiation.

Some organisms are able to distinguish between wavelengths. They have special light-perceiving systems and color vision, which are of great importance in their life. Many insects are sensitive to short-wave radiation, which humans cannot perceive. Moths perceive ultraviolet rays well. Bees and birds accurately determine their location and navigate the terrain even at night.

Organisms also react strongly to light intensity. Based on these characteristics, plants are divided into three ecological groups:

1. Light-loving, sun-loving or heliophytes - which are able to develop normally only under the sun's rays.

2. Shade-loving plants, or sciophytes, are plants of the lower tiers of forests and deep-sea plants, for example, lilies of the valley and others.

As light intensity decreases, photosynthesis also slows down. All living organisms have threshold sensitivity to light intensity, as well as to other environmental factors. Different organisms have different threshold sensitivity to environmental factors. For example, intense light inhibits the development of Drosophila flies, even causing their death. Cockroaches and other insects do not like light. In most photosynthetic plants, at low light intensity, protein synthesis is inhibited, and in animals, biosynthesis processes are inhibited.

3. Shade-tolerant or facultative heliophytes. Plants that grow well in both shade and light. In animals, these properties of organisms are called light-loving (photophiles), shade-loving (photophobes), euryphobic - stenophobic.

Environmental valence

the degree of adaptability of a living organism to changes in environmental conditions. E.v. represents a species property. It is expressed quantitatively by the range of environmental changes within which a given species maintains normal life activity. E.v. can be considered both in relation to the reaction of a species to individual environmental factors, and in relation to a complex of factors.

In the first case, species that tolerate wide changes in the strength of the influencing factor are designated by a term consisting of the name of this factor with the prefix “eury” (eurythermal - in relation to the influence of temperature, euryhaline - in relation to salinity, eurybatherous - in relation to depth, etc.); species adapted only to small changes in this factor are designated by a similar term with the prefix “steno” (stenothermic, stenohaline, etc.). Species with broad E. v. in relation to a complex of factors, they are called eurybionts (See Eurybionts) in contrast to stenobionts (See Stenobionts), which have low adaptability. Since eurybionticity makes it possible to populate a variety of habitats, and stenobionticity sharply narrows the range of habitats suitable for the species, these two groups are often called eury- or stenotopic, respectively.

Eurybionts, animal and plant organisms capable of existing under significant changes in environmental conditions. For example, the inhabitants of the marine littoral zone endure regular drying during low tide, strong heating in summer, and cooling and sometimes freezing in winter (eurythermal animals); The inhabitants of river estuaries can withstand it. fluctuations in water salinity (euryhaline animals); a number of animals exist in a wide range of hydrostatic pressure (eurybates). Many terrestrial inhabitants of temperate latitudes are able to withstand large seasonal temperature fluctuations.

The eurybiontism of the species is increased by the ability to tolerate unfavorable conditions in a state of anabiosis (many bacteria, spores and seeds of many plants, adult perennial plants of cold and temperate latitudes, wintering buds of freshwater sponges and bryozoans, eggs of branchial crustaceans, adult tardigrades and some rotifers, etc.) or hibernation (some mammals).

CHETVERIKOV'S RULE, As a rule, according to Krom, in nature all types of living organisms are represented not by individual isolated individuals, but in the form of aggregates of numbers (sometimes very large) of individuals-populations. Bred by S. S. Chetverikov (1903).

View- this is a historically established set of populations of individuals, similar in morpho-physiological properties, capable of freely interbreeding with each other and producing fertile offspring, occupying a certain area. Each species of living organisms can be described by a set of characteristic features and properties, which are called characteristics of the species. Characteristics of a species by which one species can be distinguished from another are called species criteria.

The most commonly used are seven general criteria of the form:

1. Specific type of organization: a set of characteristic features that make it possible to distinguish individuals of a given species from individuals of another.

2. Geographical certainty: the existence of individuals of a species in a specific place on the globe; range - the area where individuals of a given species live.

3. Ecological certainty: individuals of a species live in a specific range of values ​​of physical environmental factors, such as temperature, humidity, pressure, etc.

4. Differentiation: a species consists of smaller groups of individuals.

5. Discreteness: individuals of a given species are separated from individuals of another by a gap - hiatus. Hiatus is determined by the action of isolating mechanisms, such as discrepancies in the timing of reproduction, the use of specific behavioral reactions, sterility of hybrids, etc.

6. Reproducibility: reproduction of individuals can be carried out asexually (the degree of variability is low) and sexually (the degree of variability is high, since each organism combines the characteristics of the father and mother).

7. A certain level of numbers: numbers undergo periodic (waves of life) and non-periodic changes.

Individuals of any species are distributed extremely unevenly in space. For example, stinging nettle, within its range, is found only in moist, shady places with fertile soil, forming thickets in the floodplains of rivers, streams, around lakes, along the edges of swamps, in mixed forests and thickets of shrubs. Colonies of the European mole, clearly visible on the mounds of earth, are found on forest edges, meadows and fields. Suitable for life
Although habitats are often found within the range, they do not cover the entire range, and therefore individuals of this species are not found in other parts of it. There is no point in looking for nettles in a pine forest or a mole in a swamp.

Thus, the uneven distribution of a species in space is expressed in the form of “islands of density”, “condensations”. Areas with a relatively high distribution of this species alternate with areas with low abundance. Such “density centers” of the population of each species are called populations. A population is a collection of individuals of a given species, inhabiting a certain space (part of its range) for a long time (a large number of generations), and isolated from other similar populations.

Free crossing (panmixia) practically takes place within the population. In other words, a population is a group of individuals freely joining together, living for a long time in a certain territory, and relatively isolated from other similar groups. A species, therefore, is a collection of populations, and a population is a structural unit of a species.

Difference between a population and a species:

1) individuals of different populations interbreed freely with each other,

2) individuals of different populations differ little from each other,

3) there is no gap between two neighboring populations, that is, there is a gradual transition between them.

The process of speciation. Let us assume that a given species occupies a certain habitat determined by its feeding pattern. As a result of divergence between individuals, the range increases. The new habitat will contain areas with different food plants, physical and chemical properties, etc. Individuals that find themselves in different parts of the habitat form populations. In the future, as a result of the ever-increasing differences between individuals of populations, it will become increasingly clear that individuals of one population differ in some way from individuals of another population. A process of population divergence is taking place. Mutations accumulate in each of them.

Representatives of any species in the local part of the range form a local population. The totality of local populations associated with areas of the habitat that are homogeneous in terms of living conditions constitutes an ecological population. So, if a species lives in a meadow and forest, then they speak of its gum and meadow populations. Populations within a species' range that are associated with specific geographic boundaries are called geographic populations.
Population sizes and boundaries can change dramatically. During outbreaks of mass reproduction, the species spreads very widely and giant populations arise.

A set of geographical populations with stable characteristics, the ability to interbreed and produce fertile offspring is called a subspecies. Darwin said that the formation of new species occurs through varieties (subspecies).

However, it should be remembered that in nature often some element is missing.
Mutations occurring in individuals of each subspecies cannot by themselves lead to the formation of new species. The reason lies in the fact that this mutation will wander throughout the population, since individuals of the subspecies, as we know, are not reproductively isolated. If a mutation is beneficial, it increases the heterozygosity of the population; if it is harmful, it will simply be rejected by selection.

As a result of the constantly occurring mutation process and free crossing, mutations accumulate in populations. According to the theory of I. I. Shmalhausen, a reserve of hereditary variability is created, i.e., the vast majority of mutations that arise are recessive and do not manifest themselves phenotypically. Once a high concentration of mutations in the heterozygous state is reached, crossing of individuals carrying recessive genes becomes possible. In this case, homozygous individuals appear in which the mutations already manifest themselves phenotypically. In these cases, mutations are already under the control of natural selection.
But this is not yet decisive for the process of speciation, because natural populations are open and foreign genes from neighboring populations are constantly introduced into them.

There is a gene flow sufficient to maintain a high similarity of gene pools (the totality of all genotypes) of all local populations. It is estimated that the replenishment of the gene pool due to foreign genes in a population consisting of 200 individuals, each of which has 100,000 loci, is 100 times greater than due to mutations. As a consequence, no population can change dramatically as long as it is subject to the normalizing influence of gene flow. The resistance of a population to changes in its genetic composition under the influence of selection is called genetic homeostasis.

As a result of genetic homeostasis in a population, the formation of a new species is very difficult. One more condition must be met! Namely, it is necessary to isolate the gene pool of the daughter population from the maternal gene pool. Isolation can come in two forms: spatial and temporal. Spatial isolation occurs due to various geographical barriers, such as deserts, forests, rivers, dunes, and floodplains. Most often, spatial isolation occurs due to a sharp reduction in the continuous range and its disintegration into separate pockets or niches.

Often a population becomes isolated as a result of migration. In this case, an isolate population arises. However, since the number of individuals in an isolate population is usually small, there is a danger of inbreeding - degeneration associated with inbreeding. Speciation based on spatial isolation is called geographic.

The temporary form of isolation includes changes in the timing of reproduction and shifts in the entire life cycle. Speciation based on temporary isolation is called ecological.
The decisive thing in both cases is the creation of a new, incompatible with the old, genetic system. Evolution is realized through speciation, which is why they say that a species is an elementary evolutionary system. A population is an elementary evolutionary unit!

Statistical and dynamic characteristics of populations.

Species of organisms enter the biocenosis not as individuals, but as populations or parts thereof. A population is a part of a species (consists of individuals of the same species), occupying a relatively homogeneous space and capable of self-regulation and maintaining a certain number. Each species within the occupied territory breaks up into populations. If we consider the impact of environmental factors on an individual organism, then at a certain level of the factor (for example, temperature), the individual under study will either survive or die. The picture changes when studying the effect of the same factor on a group of organisms of the same species.

Some individuals will die or reduce their vital activity at one specific temperature, others - at a lower temperature, and others - at a higher temperature. Therefore, we can give another definition of a population: all living organisms, in order to survive and produce offspring, must, under dynamic environmental conditions factors exist in the form of groups, or populations, i.e. a collection of cohabiting individuals with similar heredity. The most important feature of a population is the total territory it occupies. But within a population there may be groups that are more or less isolated for various reasons.

Therefore, it is difficult to give an exhaustive definition of the population due to the blurred boundaries between individual groups of individuals. Each species consists of one or more populations, and a population is thus the form of existence of a species, its smallest evolving unit. For populations of various species, there are acceptable limits for the reduction in the number of individuals, beyond which the existence of the population becomes impossible. There are no exact data on critical values ​​of population numbers in the literature. The given values ​​are contradictory. However, the fact remains undoubted that the smaller the individuals, the higher the critical values ​​of their numbers. For microorganisms this is millions of individuals, for insects - tens and hundreds of thousands, and for large mammals - several dozen.

The number should not decrease below the limits beyond which the probability of meeting sexual partners sharply decreases. The critical number also depends on other factors. For example, for some organisms a group lifestyle (colonies, flocks, herds) is specific. Groups within a population are relatively isolated. There may be cases when the population as a whole is still quite large, and the number of individual groups is reduced below critical limits.

For example, a colony (group) of a Peruvian cormorant should have a population of at least 10 thousand individuals, and a herd of reindeer - 300 - 400 heads. To understand the mechanisms of functioning and solve issues of using populations, information about their structure is of great importance. There are gender, age, territorial and other types of structure. In theoretical and applied terms, the most important data is on the age structure - the ratio of individuals (often combined into groups) of different ages.

Animals are divided into the following age groups:

Juvenile group (children) senile group (senile group, not involved in reproduction)

Adult group (individuals engaged in reproduction).

Typically, normal populations are characterized by the greatest viability, in which all ages are represented relatively evenly. In a regressive (endangered) population, senile individuals predominate, which indicates the presence of negative factors that disrupt reproductive functions. Urgent measures are required to identify and eliminate the causes of this condition. Invading (invasive) populations are represented mainly by young individuals. Their vitality usually does not cause concern, but there is a high probability of outbreaks of excessively high numbers of individuals, since trophic and other connections have not been formed in such populations.

It is especially dangerous if it is a population of species that were previously absent from the area. In this case, populations usually find and occupy a free ecological niche and realize their reproduction potential, intensively increasing their numbers. If the population is in a normal or close to normal state, a person can remove from it the number of individuals (in animals) or biomass (in plants), which increases over the period of time between withdrawals. First of all, individuals of post-productive age (who have completed reproduction) should be removed. If the goal is to obtain a certain product, then age, gender and other characteristics of populations are adjusted taking into account the task.

The exploitation of populations of plant communities (for example, for timber production) is usually timed to coincide with the period of age-related slowdown in growth (product accumulation). This period usually coincides with the maximum accumulation of woody mass per unit area. The population is also characterized by a certain sex ratio, and the ratio of males and females is not equal to 1:1. There are known cases of a sharp predominance of one sex or another, alternation of generations with the absence of males. Each population can also have a complex spatial structure (divided into more or less large hierarchical groups - from geographical to elementary (micropopulations).

Thus, if the mortality rate does not depend on the age of individuals, then the survival curve is a decreasing line (see figure, type I). That is, the death of individuals occurs evenly in this type, the mortality rate remains constant throughout life. Such a survival curve is characteristic of species whose development occurs without metamorphosis with sufficient stability of the born offspring. This type is usually called the hydra type - it is characterized by a survival curve approaching a straight line. In species for which the role of external factors in mortality is small, the survival curve is characterized by a slight decrease until a certain age, after which there is a sharp drop as a result of natural (physiological) mortality.

Type II in the picture. The nature of the survival curve close to this type is characteristic of humans (although the human survival curve is somewhat flatter and, thus, is something between types I and II). This type is called the Drosophila type: it is what fruit flies exhibit in laboratory conditions (not eaten by predators). Many species are characterized by high mortality in the early stages of ontogenesis. In such species, the survival curve is characterized by a sharp drop in the younger ages. Individuals that survive the “critical” age exhibit low mortality and live to older ages. The type is called the oyster type. Type III in the picture. The study of survival curves is of great interest to the ecologist. It allows us to judge at what age a particular species is most vulnerable. If the effects of causes that can change fertility or mortality occur at the most vulnerable stage, then their influence on the subsequent development of the population will be greatest. This pattern must be taken into account when organizing hunting or pest control.

Age and sex structures of populations.

Any population is characterized by a certain organization. The distribution of individuals over the territory, the ratio of groups of individuals by sex, age, morphological, physiological, behavioral and genetic characteristics reflect the corresponding population structure : spatial, gender, age, etc. The structure is formed, on the one hand, on the basis of the general biological properties of the species, and on the other, under the influence of abiotic environmental factors and populations of other species.

The population structure is thus adaptive in nature. Different populations of the same species have both similar and distinctive features that characterize the specific environmental conditions in their habitats.

In general, in addition to the adaptive capabilities of individual individuals, in certain territories adaptive features of group adaptation of the population as a supra-individual system are formed, which indicates that the adaptive features of the population are much higher than those of the individuals composing it.

Age composition- is important for the existence of a population. The average lifespan of organisms and the ratio of numbers (or biomass) of individuals of different ages are characterized by the age structure of the population. The formation of the age structure occurs as a result of the combined action of the processes of reproduction and mortality.

In any population, 3 age ecological groups are conventionally distinguished:

Pre-reproductive;

Reproductive;

Post-reproductive.

The pre-reproductive group includes individuals that are not yet capable of reproduction. Reproductive - individuals capable of reproduction. Post-reproductive - individuals who have lost the ability to reproduce. The duration of these periods varies greatly depending on the type of organism.

Under favorable conditions, the population contains all age groups and maintains a more or less stable age composition. In rapidly growing populations, young individuals predominate, while in declining populations, older individuals are no longer able to reproduce intensively. Such populations are unproductive and not stable enough.

There are types with simple age structure populations that consist of individuals of almost the same age.

For example, all annual plants of one population are in the seedling stage in the spring, then bloom almost simultaneously, and produce seeds in the fall.

In species with complex age structure populations have several generations living at the same time.

For example, the life history of elephants includes young, mature and aging animals.

Populations that include many generations (of different age groups) are more stable and less susceptible to the influence of factors affecting reproduction or mortality in a particular year. Extreme conditions can lead to the death of the most vulnerable age groups, but the most resilient survive and give rise to new generations.

For example, a person is considered as a biological species with a complex age structure. The stability of the species' populations was demonstrated, for example, during the Second World War.

To study the age structures of populations, graphic techniques are used, for example, population age pyramids, widely used in demographic studies (Fig. 3.9).

Fig.3.9. Population age pyramids.

A - mass reproduction, B - stable population, C - declining population

The stability of species populations largely depends on sexual structure , i.e. ratios of individuals of different sexes. Sexual groups within populations are formed on the basis of differences in morphology (shape and structure of the body) and ecology of the different sexes.

For example, in some insects, males have wings, but females do not, males of some mammals have horns, but females do not, male birds have bright plumage, while females have camouflage.

Ecological differences are reflected in food preferences (females of many mosquitoes suck blood, while males feed on nectar).

The genetic mechanism ensures an approximately equal ratio of individuals of both sexes at birth. However, the initial ratio is soon disrupted as a result of physiological, behavioral and environmental differences between males and females, causing uneven mortality.

Analysis of the age and sex structure of populations makes it possible to predict its numbers for a number of coming generations and years. This is important when assessing the possibilities of fishing, shooting animals, saving crops from locust attacks, and in other cases.

Temperature of the human environment

Some peoples live in very extreme conditions and unusual places that are not entirely convenient for life. For example, some of the coldest settlements are the village of Oymyakon and the city of Verkhnoyansk in Yakutia, Russia. Temperatures here in winter are average

is minus 45 degrees Celsius.

The coldest larger city is also located in Siberia - Yakutsk with a population of about 270 thousand people. The temperature there in winter is also about minus 45 degrees, but in summer it can rise to 30 degrees!

The highest average annual temperature was observed in the abandoned city of Dallol, Ethiopia. In the 1960s, an average temperature of + 34 C0 was recorded here. Among large cities, Bangkok, the capital of Thailand, is considered the hottest, where the average temperature in March-May is also about 34 degrees.

The most extreme temperatures where people work are found in gold mines in South Africa. The temperature at about 3 kilometers underground is plus 65 degrees Celsius. Measures are taken to cool the mines, such as using ice or insulating wall coverings, so miners can work without overheating.

The importance of temperature lies, first of all, in its direct influence on the speed and nature of metabolic reactions in organisms. The biological properties of living organisms, their cells and cellular structures, as well as proteins determine the possibility of their life activity in the temperature range from 0 to 50°C, however, the general temperature range of active life on the planet is much wider and is limited to the following limits (Table 2).

Table 2. Temperature range of active life on the planet, C0

The vital activity of most organisms, their activity depends mainly on heat coming from outside, and body temperature depends on the values ​​of ambient temperature and energy balance (the ratio of absorption and release of radiant energy).

For each organism or group of individuals there is an optimal temperature zone, within which activity is especially pronounced.

Temperature factor over a large area of ​​the Earth

The temperature factor over a large area of ​​the Earth is subject to pronounced daily and seasonal fluctuations, which in turn determines the corresponding rhythm of biological phenomena in nature. Depending on the provision of thermal energy in symmetrical areas of both hemispheres of the globe, starting from the equator, the following climatic zones are distinguished:

1. Tropical zone. The minimum average annual temperature exceeds 16 °C; on the coolest days it does not fall below 0 °C. Temperature fluctuations over time are insignificant, the amplitude does not exceed 5 °. Vegetation is year-round.

2. Subtropical zone. The average temperature of the coldest month is not lower than 4 °C, and the warmest month is above 20 °C. Sub-zero temperatures are rare. There is no stable snow cover in winter. The growing season continues. 9--11 months

3. Temperate zone. The summer growing season and the winter dormant period of plants are well defined. In the main part of the zone there is stable snow cover. Frosts are typical in spring and autumn. Sometimes this zone is divided into two: moderately warm and moderately cold, which are characterized by four seasons.

4. Cold zone. The average annual temperature is below 0 °C, frosts are possible even during a short (2-3 months) growing season. The annual temperature fluctuation is very large.

The pattern of vertical distribution of vegetation, soils, and fauna in mountainous areas is also mainly determined by the temperature factor. In the mountains of the Caucasus, India, and Africa, four or five plant belts can be distinguished, the sequence of which from bottom to top corresponds to the sequence of latitudinal zones from the equator to the pole at the same altitude.

The importance of temperature lies primarily in its direct influence on the speed and nature of metabolic reactions in organisms.

The biological properties of living organisms, their cells and cellular structures, as well as proteins determine the possibility of their life activity in the temperature range from 0 to 50 ° C, however, the general temperature range of active life on the planet is much wider and is limited to the following limits (Table 42).

Among the organisms that can exist at very high temperatures, we should mention, first of all, bacteria and some thermophilic algae that inhabit water from sources with a temperature of 85-87 ° C. Successfully tolerate very high temperatures (65-

80 °C) crustose lichens, seeds and vegetative organs of desert plants (saxaul, camel thorn, tulips), located in the upper layer of hot soil. There are many species of animals and plants that can withstand high subzero temperatures. Polar waters with temperatures from 0 to -2° are inhabited by various representatives of the flora and fauna - microalgae, invertebrates, fish, the life cycle of which constantly occurs in such temperature conditions.

Significantly greater adaptive capabilities exist in organisms for regularly recurring seasonal periods of lower temperatures in the winter season. Many plants and animals With appropriate preparation, they successfully tolerate extremely low temperatures on our planet from -68 to -70 ° C (Yakutia, Antarctica) in a state of deep rest or suspended animation. In laboratory experiments, seeds, pollen, plant spores, nematodes, rotifers, cysts of protozoa and other organisms, sperm after dehydration or placement in solutions of special protective substances - cryoprotectors- tolerate temperatures close to absolute zero.

Currently, progress has been made in the practical use of substances with cryoprotective properties (glycerin, polyethylene oxide, dimethyl sulfoxide, sucrose, mannitol, etc.) in biology, agriculture, and medicine. Cryoprotectant solutions provide long-term storage of canned blood, sperm for artificial insemination of farm animals, and some organs and tissues for transplantation; protection of plants from winter frosts, early spring frosts, etc. These problems fall within the competence of cryobiology And cryomedicine and are being addressed by many scientific institutions.

The vital functions of most organisms, their activity depends mainly on heat coming from outside, and body temperature - on the values ​​of ambient temperature and energy balance (the ratio of absorption and release of radiant energy). Such organisms are called poikilothermic(ectothermic). Poikilothermy (cold-bloodedness) is characteristic of all microorganisms, plants, invertebrates and a significant part of chordates.

In representatives of the two highest classes of vertebrates - birds and mammals - heat generated as a product of biochemical reactions serves as a significant source of increasing their body temperature and maintaining it at a constant level, regardless of the temperature of the environment. Such organisms are called homeothermic(endothermic). Due to this property, many animal species are able to live and reproduce at temperatures below zero (reindeer, polar bear, pinnipeds, penguins). The maintenance and preservation of high body temperature in warm-blooded organisms is carried out thanks to active metabolism and good thermal insulation created by thick hair, dense plumage or a thick layer of subcutaneous fat.

A special case of homeothermy is heterothermy- different levels of body temperature depending on the functional activity of the body. Heterothermy is characteristic of animals that fall into hibernation or temporary torpor during unfavorable periods of the year. At the same time, their high body temperature is noticeably reduced due to slow metabolism (gophers, hedgehogs, bats, swift chicks, etc.).

The limits of endurance of large values ​​of the temperature factor are different for both poikilothermic and homeothermic organisms. Eurythermic species are able to tolerate temperature fluctuations over a wide range.

Stenothermic organisms live in conditions of narrow temperature limits, being divided into heat-loving stenothermic species (orchids, tea bush, coffee, corals, jellyfish, etc.) and cold-loving ones (elfin cedar, pre-glacial and tundra vegetation, fish of the polar basins, abyssal animals - the areas of greatest ocean depths, etc.).

For each organism or group of individuals there is an optimal temperature zone, within which activity is especially pronounced. Above this zone is a zone of temporary thermal torpor, and even higher is a zone of prolonged inactivity or summer hibernation, bordering on a zone of high lethal temperature. When the latter decreases below the optimum, there is a zone of cold torpor, hibernation and lethal low temperature.

The distribution of individuals in the population, depending on changes in the temperature factor throughout the territory, generally obeys the same pattern. The optimal temperature zone corresponds to the highest population density, and on both sides of it there is a decrease in density up to the boundary of the range, where it is lowest.

The temperature factor over a large area of ​​the Earth is subject to pronounced daily and seasonal fluctuations, which in turn determines the corresponding rhythm of biological phenomena in nature. Depending on the provision of thermal energy in symmetrical areas of both hemispheres of the globe, starting from the equator, the following climatic zones are distinguished:

1. Tropical zone. The minimum average annual temperature exceeds 16 °C; on the coolest days it does not fall below 0 °C. Temperature fluctuations over time are insignificant, the amplitude does not exceed 5 °. Vegetation is year-round.

2. Subtropical zone. The average temperature of the coldest month is not lower than 4 °C, and the warmest month is above 20 °C. Sub-zero temperatures are rare. There is no stable snow cover in winter. The growing season continues. 9-11 months

3. Temperate zone. The summer growing season and the winter dormant period of plants are well defined. In the main part of the zone there is stable snow cover. Frosts are typical in spring and autumn. Sometimes this zone is divided into two: moderately warm and moderately cold, which are characterized by four seasons.

4. Cold zone. The average annual temperature is below 0 °C, frosts are possible even during a short (2-3 months) growing season. The annual temperature fluctuation is very large.

Pattern vertical placement vegetation, soil, and fauna in mountainous areas is also mainly determined by the temperature factor. In the mountains of the Caucasus, India, and Africa, four or five plant belts can be distinguished, the sequence of which from bottom to top corresponds to the sequence of latitudinal zones from the equator to the pole at the same altitude.

Temperature is one of the most important abiotic factors that operates always and everywhere. It is temperature that determines the rate of biochemical reactions and affects most physical processes.
Although the optimal temperature regime for most species is between +15 and +30 °C, there are organisms that can withstand very high or low temperatures. For example, some bacteria and algae live in hot springs at temperatures of +85-87 °C. The resting stages of development of organisms - cysts, insect pupae, bacterial spores, plant seeds - withstand temperature changes well.
All invertebrates and most vertebrates are cold-blooded organisms that are unable to maintain a constant body temperature. Their temperature depends on the thermal regime of the environment. Therefore, in the cold season, the activity of such animals is greatly reduced. Birds and mammals are warm-blooded animals; they have an almost constant body temperature, independent of the ambient temperature. Maintaining a high body temperature in warm-blooded organisms is ensured by a high level of metabolism, perfect thermoregulation and good thermal insulation.
Since temperature is subject to daily and seasonal fluctuations, organisms are forced to adapt to such changes. In the cold season, mammals develop thicker and longer fur, fat actively accumulates in the subcutaneous fatty tissue, which provides thermal insulation, and in birds the mass of feathers increases in winter. Some animals have developed behavioral adaptations to the seasonal decrease in temperature: migration, flight, digging holes and searching for shelters. In deserts, where daytime soil temperatures can reach +60-70 °C, animals bury themselves in the sand or hide in holes. In plants during the hot season, evaporation from the surface of leaves increases.
Humidity. Water is necessary for life for all living organisms. Moreover, if loss of moisture is especially dangerous for terrestrial animals and plants, then for organisms living in water, on the contrary, excess water in the body can upset the salt balance. Therefore, aquatic organisms develop various adaptations for removing excess water, for example, contractile vacuoles in the ciliate slipper.
For terrestrial living organisms, humidity is one of the most important factors
which determines their distribution. Throughout life, water is inevitably lost by the body, so its reserves must be constantly replenished. Depending on environmental conditions, organisms have developed various adaptations to supply themselves with water and conserve moisture. Such drought-resistant plants as camel thorn, saxaul, and desert wormwood have a very deep root system (Fig. 67). Other desert and semi-desert plants have narrow, hard leaves covered with a waxy coating, which significantly reduces water loss through evaporation. Some succulent plants (cacti, euphorbia) have highly developed water-storing tissue, and their leaves are transformed into spines or scales (Fig. 68). Interesting are the adaptations of some steppe plants that manage to grow and bloom in a short wet spring period. They survive the dry season in the form of seeds, bulbs, and tubers.
Animals that live in low humidity conditions also have certain adaptations. Many of them never drink and use only the liquid that is in their food. The dense chitinous cover of terrestrial arthropods prevents the evaporation of moisture. In the process of evolution, having switched to a terrestrial existence, reptiles completely lost their skin glands. A number of animals (insects, camels, marmots) use metabolic water, which is formed during the breakdown of fat, for their life. In arachnids, in the course of adaptation to saving moisture, the metabolism has changed - dehydrated metabolic products (almost dry crystals of uric acid) are released.

Rice. 67. Root system of camel thorn
Adaptive behavioral features are of great importance for animals in arid regions - searching for shelter, nocturnal lifestyle. When the air is very dry, many desert animals hide in holes and tightly close the entrance to them. The air in a closed room is quickly saturated with water vapor, which prevents further loss of moisture by the body. During periods of drought, many rodents, turtles, snakes, and some insects hibernate.
Light. The main source of energy for living organisms is sunlight. Its biological effect depends on the intensity, duration of action, spectral composition, daily and seasonal frequency.

Rice. 68. Cacti are plants with highly developed water-storing tissue

The ultraviolet part of the spectrum contributes to the formation of vitamin D in animals. These rays are perceived by the visual organs of insects, and in plants, ultraviolet provides the synthesis of pigments and vitamins. The visible part of the spectrum is most significant for organisms. Thanks to illumination, animals orient themselves in space, and photosynthesis occurs in plants. Infrared rays are a source of thermal energy, which is very important for cold-blooded organisms.
Depending on the requirements for lighting conditions, plants are divided into light-loving, shade-tolerant and shade-loving. Light-loving plants are inhabitants of open areas; they do not tolerate even slight shading (for example, steppe plants, white acacia). In diffused light, most ferns and mosses grow in shaded places, and the record holder for living in dark conditions is seaweed.
An important factor in the life of plants and animals is the length of daylight and the change of seasons. For many organisms, changes in day length serve as a signal for changes in physiological activity. This phenomenon
called photoperiodism. In the process of evolution, animals and plants have developed certain biological rhythms - daily and seasonal. The length of the day determines the timing of flowering and ripening of fruits in plants, the migration of birds, the change of fur in mammals, the beginning of the mating season, preparation for hibernation, etc. The lifestyle of nocturnal and daytime animals is significantly different. Plants' flowers open and close at certain times.
Many biochemical and physiological processes in the human body have a rhythmic nature. More than a hundred different parameters are known that change with a 24-hour rhythm (body temperature, blood pressure, hormone secretion, etc.). The study of human biorhythms is very important for organizing an optimal work and rest regime, developing measures for the prevention and treatment of various diseases.
The distribution of certain species is determined not only by light, humidity and temperature, but also by other abiotic environmental parameters. For example, only certain types of plants that can withstand high soil salinity can live in the coastal strip of the ocean, and the wind affects the settlement and migration of spiders and flying insects.
Questions for review and assignments What adaptations to changes in environmental temperature do plants and animals have? Tell us about the adaptations of living organisms to a lack of water. Through what part of the solar radiation spectrum do photosynthesis occur in plants? Tell us what you know about the biological rhythms of living organisms.
Think! Do it! What climate conditions and soil are typical for your region? Why do you think, with constant directed changes in abiotic environmental conditions, the adaptation of living organisms to these changes cannot be endless? Why do poultry farms and greenhouses use additional artificial lighting to increase the length of daylight hours? Solve the problem of placing indoor plants depending on the ecological characteristics of the species.
Work with computer
Refer to the electronic application. Study the material and complete the assignments.

In this article we bring to your attention a variety of interesting facts about temperature. Perhaps every schoolchild knows that temperature is a fundamental concept in physics. In general, temperature plays a big role for all life forms on earth. It turns out that at very low or, on the contrary, very high temperatures, different things behave in a rather strange way. Highest temperature was created by human hands and amounted to 4 billion C 0 . It’s hard to believe, but scientists managed to reach such an unimaginable temperature level, which is 250 times higher than the core temperature of the Sun. This kind of record was achieved thanks to the RHIC ion collider, which is located at the Brookhaven Natural Laboratory (New York). The length of this RHIC collider is 4 kilometers. During the research, they tried to recreate the conditions of the Big Bang. To do this, they forced gold ions to collide with each other, creating a quark-gluon plasma.

Most extreme temperature in our Solar System. The Sun star is very hot. At the very center of the Sun, the temperature reaches approximately 15 million Kelvin, and the surface of the Sun itself is heated to 5700 Kelvin. By the way, the temperature of the Earth's core is approximately the same as on the surface of the Sun. Jupiter is considered the hottest planet in our solar system. Since the temperature of its core is five times higher than the temperature on the surface of the Sun.

The coldest temperature recorded on the Earth's satellite, the Moon. In some craters that are in the shade, the temperature reaches only 30 Kelvin - above absolute zero.

There are peoples who live in almost extreme conditions and the most unusual places that seem in no way suitable for life. So there is the coldest village on earth - Oymyakon and also the city of Verkhoyansk, which is in Yakutia (Russia). In this area in winter the average temperature drops to minus 45C 0 . This is perhaps the most extreme temperature of the human environment. The coldest city is also located in Siberia - Yakutsk (population 270 thousand). The winter temperature there reaches minus 45 C 0, but in the summer it can rise to 30 C 0.

The most extreme high temperatures were recorded in the Mponeng gold mines (South America). At a depth of 3 kilometers, the temperature reaches plus 65 C 0. And people work in such conditions. To somehow reduce this incredible heat, insulating wall coverings and ice are used.

Lowest temperature was achieved under artificial conditions - 100 pico Kelvin (0, 0000000001 K). Such results were achieved thanks to magnetic cooling. Something similar can be achieved with lasers. At such abnormally low temperatures, any material or substance behaves differently from its usual environment.

Temperature in space. What is she like? In outer space, temperatures remain above absolute zero due to radiation that remains from the Big Bang. For example, if you leave a thermometer in space for some time and away from radiation sources, it will show 2.73 Kelvin (minus 270 C 0). This temperature is considered the lowest natural temperature in the Universe. Although space is quite cold, as it is for us. But it turns out that astronauts face the most important problem - heat. The metal from which objects in orbit are made sometimes heats up to 260 C 0 . This happens due to the free rays of the Sun. And in order to reduce the temperature of the ship, it wrapped in a special material that reduces the temperature by half.

But, nevertheless, the temperature in space is falling. So research has shown that every 3 billion years our Universe cools by approximately 1 degree. The temperature on planet Earth is in no way related to the cosmic temperature. In addition, the Earth has been slowly warming up lately.

Is there a highest temperature? There is a concept of absolute zero, this is a temperature below which it is impossible to fall. But which is the highest, science cannot yet answer.

In fact, the highest is called the Planck temperature. It was in the Universe at the time of the Big Bang, so modern science says. And this temperature reached 10 ^32 Kelvin. In simple terms, this is billions of times higher and greater than the highest temperature ever achieved artificially. And today it remains the highest of all possible.