The struggle for existence is the driving factor of evolution, the totality of relationships between animal individuals and flora with each other and with the outside world. Scientist Charles Darwin identified three forms of struggle for existence:
- The relationship of organisms with inanimate nature, or adaptation to abiotic factors external environment;
- interspecies struggle, which includes relationships between individuals belonging to different species;
- intraspecific struggle, including relationships between individuals of the same species.
Form 1. Relationship of organisms with inanimate nature
The relationship of organisms with inanimate nature can be shown in the following examples.
Plants of the North are more frost-resistant than southern forms, because specimens unable to tolerate low temperatures, became extinct and the offspring were preserved only from those of them that, as a result of mutational variability, acquired frost resistance. The herbaceous vegetation of the tundra has a short growing season, allowing the formation of seeds during the short summer. And this is a consequence of the fact that plants that did not have time to form seeds within short term northern summer, could not leave offspring. And here, in the struggle of life, those who, thanks to corresponding hereditary changes, had a shortened growing season, won the struggle of life.
Adaptation to droughts
The herbaceous vegetation of deserts has an even shorter growing season, allowing them to mature within a few days of the spring wet period.
Let's imagine a picture from the past... On the edge of the desert lived a plant with a relatively long growing season. Its seeds were carried by the wind towards the desert. They undoubtedly had individual differences, which affected the speed of emergence, intensity of growth and maturation, so not all of them could survive and leave offspring.
Some individual characteristics turned out to correspond to the conditions of existence, however, they also produced seeds that were also not of the same type. And again, selection preserved only those plants that were most adapted to specific living conditions. Moreover, the seeds of these plants fell even further into the desert. Among the plants grown from these seeds, selection again took place for the ability to survive in conditions of an even shorter growing season. This is how plant species with short period vegetation (ephemera).
In other plants - inhabitants of deserts - selection went in other directions, which ensured the appearance of new characters that made it possible to exist in these conditions. Growing in deserts Central Asia saxaul does not have true leaves. They have become pointed scales pressed against the stem, or even small tubercles on the stem, which prevent excessive evaporation of water. Thus, this trait is a consequence of selection, i.e. survival of those who lost less moisture.
Perhaps the mutation of plants with reduced leaves did not appear immediately, but the reduction of the evaporating surface in plants - the ancestors of saxaul - went through a number of stages (mutations). Selection preserved those who survived better; these turned out to be plants that evaporated less moisture.
An interesting example is given by Darwin regarding insects - inhabitants of small oceanic islands. They either fly beautifully or have no wings at all. Apparently, those carried by sudden gusts of wind were carried out to sea, only those that could withstand the wind or did not fly at all were preserved. Selection in this direction has led to the fact that on the island of Madeira, out of 550 species of beetles, 200 species are flightless.
Form 2. Interspecies wrestling
As a result of interspecific struggle, those adaptations appeared that are necessary for plants and animals in their complex relationships with each other. Thus, plants developed thorns, thorns, burning hairs, a bitter taste, etc.
One can imagine that ancient ancestor the rose hips had no thorns. The leaves and branches on the bushes of these plants were eaten by herbivores. But on some bushes the stems had a slight roughness. Such bushes were eaten less readily. In the end, those whose spikes grew larger and larger survived. Exactly the same process led in some cases to the formation of spines, in others to the appearance unpleasant odor or taste and various signs that prevent eating.
Among plants pollinated by insects, more seeds could form those that better “attract” pollinating insects. Bright color, aroma, abundant sweet nectar, flower structure, etc. played a role here. As a result, those varieties that were inferior to others in this respect ceased to be visited by insects and were ultimately doomed to extinction.
Origin of animal color
Insects, lizards and a number of other species hiding between the leaves of plants are green or brown in color; desert inhabitants are the color of sand. The coloring of animals that live in forests, such as the leopard, has spots that resemble highlights, while the tiger imitates the coloring and shadow of the stems of reeds or reeds. This coloring is called protective.
In predators, it was established due to the fact that its owners could sneak up on prey unnoticed, and in organisms that are prey, protective coloring is a consequence of the fact that the prey remained less noticeable to predators. How did she appear?
Camouflage helps to hide from predators. If you couldn't find it, scroll to the next picture.
Numerous mutations gave and give big variety forms that differ in color. In some cases it turned out to be close to the background environment, i.e. hid the animal, played a protective role. Those animals whose protective coloring was weakly expressed were either left without food or became victims themselves.
Sometimes animals are similar not only in color, but also in shape to some objects or other animals. This phenomenon is called mimicry. A moth butterfly caterpillar frozen on a tree branch is almost indistinguishable from a twig.
Symbiosis between species
Interspecific struggle reached particular intensity at various stages of evolution in cases where the improvement of one group of organisms necessitated the improvement of another, dependent group:
These are examples of the so-called conjugate evolution, which is a very important form of development, as it leads to long-term mutual improvement of many groups of animals and plants.
Form 3. Intraspecific struggle
The intraspecific struggle for existence is the most intense, complex and most acute, because individuals and populations of the same species require the same conditions to exist and leave offspring.
Intraspecific struggle can be for the female, for leadership in the flock, for more advantageous habitats Of the animals belonging to the same species and serving as food for a certain type of predator, the less adapted ones, for example, those with the least pronounced protective coloration, slower running, etc., become victims first of all. The same is observed in predators. The more adaptable person gets the prey more successfully: more dexterous, faster, more savvy, etc.
The more fit not only have an advantage in their own survival, but also in providing food for their offspring, and therefore in their survival. From the above examples it is clear that, for example, butterflies, hares, foxes belonging to the same population do not directly enter into struggle with each other, but indirectly, competition arises between them for the right to survive and, at the cost of the death of less adapted brethren, the more adapted survive.
The struggle between individuals and the herd instinct
But in a number of cases, direct competition occurs between individuals of the same population. In some species of animals, there is competition between males of the same population for a female (many species of spiders, wood grouse, black grouse, turukhtan, deer, elk). The stronger ones win. Intraspecific struggle should also include the division of the habitat into “ hunting areas", which are determined in songbirds by voice, in mammals most often by odorous secretions, etc.
Excessive population increases can cause food shortages. In such cases, fertility decreases in a number of species (for example, mouse-like rodents). Some birds (tits, storks, Siberian Cranes) kill part of their offspring, usually sick and weakened chicks. Exorbitant population growth leads to outbreaks of epidemics that reduce population sizes. But even at the same time, the fittest survive, for example, those who have innate immunity to these diseases.
Some animal species have evolved the ability to live in herds (deer and many other ungulates) or colonies (gulls), which provide better protection from predators. Predators can unite for a common hunt (wolves).
| comparison table forms of struggle for existence (with examples) | |
|---|---|
| Form | Description |
| Fight against the environment | Unique properties that allow you to survive in conditions unfavorable environment(droughts, frosts, aggressive environments) give advantages to the organism of one species over others. Example: animals change color in winter and hibernate; exterminated plants have high seed productivity and vegetative propagation is typical. |
| Interspecies fight | The struggle for survival between species located in the same territory and claiming the same resources. For example: plant thorns (rose hips), unpleasant/poisonous taste or smell allowed them to survive longer and produce offspring longer, compared to other species. Gray rats replaced black rats, being more aggressive and better swimmers. |
| Among individuals of the same species, the least adapted individuals were the first to be eaten by predators. It is more difficult for weaker individuals of predators to obtain food, and therefore to feed their offspring. For example: among antelopes, only healthy and strong individuals survive, the rest go to food. Among coniferous forest Some trees of the same age grow more, the roots go deeper, suppressing weaker trees. | |
It should be emphasized that all forms of the struggle for existence are closely intertwined. If there is no doubt that the streamlined shape of the fish’s body is due to living in water, then this shape was formed not as a result of the influence of the water itself, but as a result of competition with other animals of their own and other species. For some it provided the opportunity to overtake prey, for others - to elude the enemy.
The study of the struggle for existence, intraspecific and interspecific relationships is of great importance practical significance to develop measures to combat pests of agricultural and forestry, when breeding useful species, for fishing and hunting, etc. It is enough to recall the variety of forms of biotic connections, as the role of their study in rational human activity in ecological systems becomes clear.
Entitled struggle for existence C. Darwin introduced into biology a collective concept that unites various shapes relationships between the organism and the environment, which lead to the natural selection of organisms for reproduction, i.e., to the survival and leaving of offspring by the most adapted individuals. Darwin himself noted that this concept is introduced in a very expanded, “metaphorical” understanding. With the term “struggle,” Darwin, however, correctly emphasized the well-known activity of the organism in its relationship with the environment.
Charles Darwin initially substantiated the inevitability of the struggle for existence geometric progression reproduction, leading to the fact that there is not enough means of subsistence for everyone. Already from the above review of the forms of struggle it is quite clear that the importance of this factor was significantly exaggerated.
The most important forms of the struggle for existence turn out to be independent of the reproduction of the organism. The severity of the constitutional struggle has no connection with the number of individuals of a given species. The severity of direct interspecific struggle is even inversely related to the number of individuals of a given species (than larger number individuals of a given species, the less intense is the fight against a given number of predators).
Only indirect struggle, and namely active competition, intensifies in direct proportion to the number of competing individuals and, therefore, is directly determined by the progression of reproduction. However, it is precisely this form of struggle that we cannot attribute to being the main factor in progressive evolution, as will be seen from what follows. The reality of various forms of struggle for existence and great value This struggle in a natural setting is not discussed, and we therefore do not examine this issue in more detail.
Darwin identified three forms of struggle for existence:
- intraspecific
- interspecific
- fight against physical conditions environment
In addition, Darwin pointed out the existence of complex forms of relationships between living organisms.
Intraspecific struggle for existence
Intraspecific struggle for existence- This is a fight between individuals of the same species. This struggle is the most fierce and especially stubborn. It is accompanied by oppression and displacement of less adapted individuals of a given species. During this struggle, organisms of the same species constantly compete for living space, for food, for shelter, a sexual partner, and a place for reproduction. The intraspecific struggle for existence intensifies with an increase in population size and increased specialization of the species.
Interspecies struggle for existence
Each species of plants, animals, fungi, and bacteria in the ecosystem enters into certain relationships with other members of the biocenosis. Interspecies struggle for existence- this is a struggle between individuals various types.
Darwin, in a cleared and dug area measuring three by two feet, counted all the weed seedlings. There were 367 of them. After some time, when counting, it turned out that 295 seedlings were destroyed by slugs and insects. A particularly persistent struggle for existence exists between organisms that belong to closely related species: gray rat displaces the black cockroach, the missle thrush causes a decrease in the number of song thrush (in Scotland), in Russia the Prussian cockroach displaces the black cockroach, in Australia the imported honey bee displaces the small, stingless, native bee.
The relationships between species are complex, since all species are natural communities interconnected. The relationship can be antagonistic and symbiotic (plants cannot exist without cohabitation with certain types of fungi, bacteria and animals). Darwin described the dependence of clover yield on the number of cats in a given area. This is due to the fact that cats eat mice, which destroy bumblebee honeycombs and their nests. Bumblebees turned out to be the only full-fledged clover pollinators.
Ecologists in the 20th century identified wide range various relationships between organisms in communities: predation, antibiosis, amenalism, competition, various forms of symbiosis.
Control of abiotic conditions
Organisms for their existence and reproduction have a certain optimum range for all abiotic environmental factors - illumination, temperature, humidity, chemical composition air, water and soil environment. The exit of an environmental factor beyond the optimum zone, beyond the comfort zone, has a depressing and eliminating effect.
So, due to the low temperature on Darwin’s estate in the winter of 1854-1855. 4/5 birds died. Optimal temperature for the winter cutworm 22.5° C. At a temperature of 30° C, the fertility of this butterfly decreases by 10%. Fall armyworm caterpillars overwinter in the soil. In winters with little snow, they die even at relatively low temperatures. Abiotic factors act not only directly, but also indirectly. For example, by reducing the amount of food.
Fighting physical living conditions ( constitutional struggle) leads to the selection of the most resistant individuals to the complex of physical conditions in which organisms live. The struggle with physical conditions intensifies the intraspecific and interspecific struggle for existence.
Charles Darwin used the term struggle for existence in a broad and metaphorical sense, including in it the dependence of one creature on another and on environmental conditions, meaning by this not only the life of an individual, but also its success in leaving behind offspring. Knowing about the diversity of the struggle for existence, Darwin used several phrases for this phenomenon: struggle for life, struggle for existence, competition.
The struggle for existence is a complex and diverse relationship of individuals within a species, between species and with factors of inorganic nature. This is a set of interactions of organisms with each other and with environmental factors.
For Darwin, the struggle for existence is important not in itself, but because of the result to which it leads. "Thanks to this struggle, changes, no matter how insignificant and no matter what the cause, if they are of any use to the individuals of a given species in their infinite difficult relationships to other organic beings and the physical conditions of life, will contribute to the preservation of these individuals and will be inherited by their descendants. These descendants will, in turn, have a greater chance of survival." As a result of the struggle for existence, individuals most adapted to the conditions of a given biogeocenosis survive and reproduce. Less adapted ones die or are eliminated from reproduction. This is how nature selects individuals - natural selection.
struggle for existence
in biology - one of the main concepts in the theory of evolution of Charles Darwin, which he used to designate the relationships between organisms, as well as between organisms and abiotic conditions, leading to the death of the less adapted and the survival of the most adapted individuals, i.e. to natural selection. The complexity of the problem and the metaphorical nature of the term gave rise to it different interpretations and even the exclusion of this concept from evolutionary biology by some modern Darwinists. Attempts have been made to transfer the doctrine of the struggle for existence to human society(social Darwinism).
Struggle for existence
(biol.), metaphorical expression, proposed by Charles Darwin (1859) to determine the activity of an organism aimed at preserving life and ensuring the existence of offspring. Concept of B. for p. closely related to natural selection. In the very general view B. for s. stems from the discrepancy between the high ability of organisms to reproduce and the maximum dimensions of space, food reserves, water, etc., necessary for the normal existence of organisms of any kind. Thus, according to Darwin’s calculations, if all the cubs that were born survived and reproduced, a pair of elephants - one of the slowest reproducing mammals - would have left 19 million descendants in 750 years. One diatom with unhindered reproduction, it could cover the entire surface of the Earth with a film within a day and a half. However, this potential ability to reproduce is never fully realized in nature. Most of emerging individuals do not survive to adulthood and die in the process of direct or indirect B. for s. ≈ either under the influence of unfavorable climatic and other abiotic environmental factors (constitutional B. for s.), or in the fight against representatives of other species (interspecific B. for s.), or in the fight against individuals of their own species (intraspecific B. for s. ). Constitutional and interspecific B. for s. in themselves are only destructive factors. Only intraspecific struggle leads to the creation of new forms of organization. When describing the processes of intraspecific B. for p. The concept of competition is often used. The result of competition among heterogeneous individuals of a given species in the struggle for life and reproduction is selective elimination (destruction); general elimination, or random extermination, individual elimination (including direct elimination by physical factors, biological factors and indirect elimination by physiological factors; the latter comes down to the survival of less depleted individuals), family elimination and group elimination. In evolution special meaning has a combination of individual and group elimination. Elimination takes on a selective character only through competition, which can be intragroup (individual active and passive), interfamily and intergroup (I. I. Shmalgauzen).
Intraspecific B. for s. manifests itself in competition between individuals of a given species when they collide with any enemies and harmful influences, in competition in the use of food and other vital factors (light, water, etc.) and in competition in the means of more effectively protecting life and offspring. Interspecific B. for s. can occur directly between predator and prey, as well as between individuals of different, sometimes very distant species: herbivorous mammals and herbivorous insects (for example, locusts, grasshoppers) compete, “fight” for food.
In the concept of B. for s. includes, according to Darwin's definition, all forms of relationships between organisms, and not just competitive relations struggle in the narrow sense of the word. Since the time of Darwin, the greater importance of biotic conditions (i.e., the life activity of other creatures with which given organism connected by nutritional and any other relationships) than abiotic.
Vulgarizing B. for s. in nature and arbitrarily transferring its patterns to social life, some bourgeois sociologists and economists put forward the concept of social Darwinism, which was sharply criticized by F. Engels (see Anti-Dühring, 1966, pp. 64≈66). The methodological mistake of social Darwinists lies in the attempt to reduce social laws to the level of biological ones. Having shown, following B. Franklin and C. Linnaeus, the existence in nature of the desire to reproduce in geometric progression, Darwin actually refuted the main idea of the English economist T. R. Malthus (see Malthusianism) about the supposedly existing discrepancy between human reproduction (in geometric progression) and livelihood (in arithmetic progression), to which K. Marx specifically drew attention (see K. Marx and F. Engels, Works, 2nd ed., vol. 26, part 2, p. 127).
The concept of B. for s., put forward by Darwin, had vital importance, reflecting at the level of natural science of the 19th century. internal driving force evolution and served Darwin as one of the most important premises when creating the theory of development organic world. Comparing the presence of B. in nature with. with the observed diversity of individuals within any species, Darwin came to the conclusion that natural selection≈ main driving factor evolutionary process. Thus, the doctrine of evolution was placed on a materialistic natural-historical basis. Remaining a broad generalizing concept, B. for p. when specifically studied, it breaks down into a number of phenomena related to the study of biogeocenotic relationships at the level of populations, species, biocenoses, relationships between organisms and abiotic environmental factors, etc. In all cases, B. for s. leads to comparative assessment individuals of a certain population in the conditions of a specific biogeocenosis, to selective elimination and natural selection.
Lit.: Darwin Ch., The origin of species by means of natural selection or the preservation of favored breeds in the struggle for life. Soch., vol. 3, M.≈L., 1939; Shmalgauzen I.I., Problems of Darwinism, M., 1946; Story evolutionary teachings in biology, M.≈L., 1966.
A. V. Yablokov.
Wikipedia
Struggle for existence
Struggle for existence- one of the driving factors of evolution, along with natural selection and hereditary variability, a set of diverse and complex relationships that exist between organisms and environmental conditions. Also, the third chapter of Charles Darwin's book “The Origin of Species by Means of Natural Selection” is titled “The Struggle for Existence.”
1) What is the peculiarity of the intraspecific struggle for existence?
2) What is the result of the interspecies struggle for existence?
3) What is the evolutionary significance of the fight against unfavorable conditions environment?
STRUGGLE FOR EXISTENCE
Under the name of the struggle for existence, Charles Darwin introduced into biology a collective concept that unites various forms of interaction of an organism with the environment, which lead to the natural selection of organisms. The main reason for the struggle for existence is the insufficient adaptation of individual individuals to use environmental resources, such as food, water and light. The scientist identified three forms of struggle for existence: intraspecific, interspecific and struggle with the physical conditions of the environment.
Intraspecific struggle for existence is the struggle between individuals of the same species. This struggle is the most fierce and especially persistent. It is accompanied by oppression and displacement of less adapted individuals of a given species. For example, this is how competition occurs between pines in pine forest for the light or by males in the fight for a female. In the process of struggle, organisms of the same species constantly compete for living space, food, shelter, and a place for reproduction. The intraspecific struggle for existence intensifies with an increase in population size and increased specialization of the species.
The relationships between species are complex, since all species in natural communities are interconnected. The relationship can be antagonistic or symbiotic. Thus, plants cannot exist without cohabitation with certain types of fungi, bacteria and animals.
The fight against unfavorable environmental conditions manifests itself in various negative impacts inanimate nature on organisms. Thus, plants growing in deserts are affected by a lack of moisture, nutrients in the soil and heat air.
For evolution, the significance of various forms of struggle for existence is unequal. Interspecies struggle for existence leads to the improvement of some species over others. As a result of such a struggle, the winning species are preserved, and the losing ones die out. The intraspecific struggle for existence causes an increase in the diversity of intraspecific characteristics in individuals and reduces the intensity of competition for the same environmental resources.
Explanation.
The correct answer must contain the following elements:
1) Fight between individuals of the same species.
2) Decrease in the number of one of the two species.
Replacement of one species by another.
3) The fight against unfavorable environmental conditions leads to the selection of individuals that are most resistant to a given set of physical conditions.
Under the name of the struggle for existence, Charles Darwin introduced into biology a collective concept that unites various forms of relationships between an organism and its environment, which lead to the natural selection of organisms for reproduction, that is, to the survival and leaving of offspring by the most adapted individuals. C. Darwin initially justified the inevitability of the struggle for existence by the geometric progression of reproduction, leading to the fact that there are not enough means of life for everyone. However, the significance of this factor is clearly exaggerated.
The most important forms of the struggle for existence turn out to be independent of organism's reproduction rate. The severity of the constitutional struggle has nothing to do with in number individuals of this species. The severity of direct interspecies struggle is even in inverse relationship with the number individuals of a given species (the greater the number of individuals of a given species, the less intense the fight against a given number of predators).
Only indirect struggle, and namely active competition, intensifies in direct proportion to the number of competing individuals and, therefore, is directly determined by the progression of reproduction. However, it is precisely this form of struggle that we cannot attribute to being the main factor in progressive evolution.
Charles Darwin believed that the struggle for existence is a consequence of two mutually exclusive reasons:
- unlimited ability of living organisms to reproduce;
- limited natural resources.
By "fight" is meant not a direct collision of individuals, leading to the displacement of some of them. This is the whole complex of complex relationships between living organisms, including:
- mutual assistance,
- passive competition
- the whole spectrum of symbiotic relationships.
Traditionally, the struggle for existence is divided into three types:
- intraspecific struggle,
- interspecies struggle,
- fight against abiotic factors.
Darwin identified three forms of struggle for existence:
Intraspecific struggle for existence- This is a fight between individuals of the same species. This struggle is the most fierce and especially stubborn. It is accompanied by oppression and displacement of less adapted individuals of a given species. During this struggle, organisms of the same species constantly compete for living space, for food, for shelter, a sexual partner, and a place for reproduction. The intraspecific struggle for existence intensifies with an increase in population size and increased specialization of the species.
Interspecies struggle for existence
Each species of plants, animals, fungi, and bacteria in the ecosystem enters into certain relationships with other members of the biocenosis. Interspecific struggle for existence is a struggle between individuals of different species. Darwin, in a cleared and dug area measuring three by two feet, counted all the weed seedlings. There were 367 of them. After some time, when counting, it turned out that 295 seedlings were destroyed by slugs and insects. A particularly persistent struggle for existence exists between organisms that belong to closely related species: the gray rat displaces the black rat, in Russia the Prussian cockroach displaces the black cockroach, in Australia the imported honey bee displaces the small, stingless native bee.
The relationships between species are complex, since all species in natural communities are interconnected. The relationship can be:
- antagonistic,
- symbiotic (plants cannot exist without cohabitation with certain types of fungi, bacteria and animals).
Darwin described the dependence of clover yield on the number of cats in a given area. This is due to the fact that cats eat mice, which destroy bumblebee honeycombs and their nests. Bumblebees turned out to be the only full-fledged clover pollinators.
Ecologists in the 20th century identified a wide variety of relationships between organisms in communities:
- predation,
- antibiosis,
- amensalism,
- competition,
- various forms of symbiosis.
Control of abiotic conditions
Organisms for their existence and reproduction have a certain optimum range for all abiotic environmental factors:
- illumination,
- temperature,
- humidity,
- chemical composition of the air, water and soil environment.
The exit of an environmental factor beyond the optimum zone, beyond the comfort zone, has a depressing and eliminating effect. So, due to the low temperature on Darwin’s estate in the winter of 1854-1855. 4/5 birds died. The optimal temperature for the winter cutworm is 22.5° C. At a temperature of 30° C, the fertility of this butterfly decreases by 10%. Fall armyworm caterpillars overwinter in the soil. In winters with little snow, they die even at relatively low temperatures. Abiotic factors act not only directly, but also indirectly. For example, by reducing the amount of food. The fight against the physical conditions of life (constitutional fight) leads to the selection of the most resistant individuals to the complex of physical conditions in which organisms live. The struggle with physical conditions intensifies the intraspecific and interspecific struggle for existence. Charles Darwin used the term struggle for existence in a broad and metaphorical sense, including in it the dependence of one creature on another and on environmental conditions, meaning by this not only the life of an individual, but also its success in leaving behind offspring.
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