* Symbiosis and mutualism
* Predation
Interspecific competition
Competition between species is extremely widespread in nature and affects almost everyone, since it is rare that a species does not experience at least a little pressure from individuals of other species. However, does ecology view interspecific competition in a specific, narrower sense? only as mutually negative relationships between species occupying a similar ecological niche.
The forms of manifestation of interspecific competition can be very diverse: from fierce struggle to almost peaceful coexistence. But, as a rule, of two species with the same ecological needs, one necessarily displaces the other.
Let us give several examples of competition between ecologically similar species.
In Europe, in human settlements, has the gray rat completely replaced another species of the same genus? the black rat, which now lives in steppe and desert areas. The gray rat is larger, more aggressive, and swims better, so it managed to win. In Russia, the relatively small red Prussian cockroach completely replaced the larger black cockroach only because it was able to better adapt to the specific conditions of human housing.
Spruce seedlings develop well under the protection of pines, birches, and aspens, but then, as the spruce crowns grow, the seedlings of light-loving species die. Weeds inhibit cultivated plants by intercepting soil moisture and mineral nutrients, as well as by shading and releasing toxic compounds. In Australia, the common bee, introduced from Europe, replaced the small stingless native bee.
Interspecific competition can be demonstrated in simple laboratory experiments. Thus, in the studies of the Russian scientist G.F. Gause, cultures of two species of slipper ciliates with a similar feeding pattern were placed separately and together in vessels with hay infusion. Each species, placed separately, reproduced successfully, reaching optimal numbers. However, when living together, the number of one of the species gradually decreased, and its individuals disappeared from the infusion, while the ciliates of the second species remained. It was concluded that long-term coexistence of species with similar ecological requirements is impossible. Did this conclusion get a name? competitive exclusion rule.
In another experiment, researchers investigated the influence of temperature and humidity on the outcome of interspecific competition between two species of flour beetles. Several individuals of one and the other species were placed in vessels with flour (under a certain combination of heat and moisture). Here the beetles began to multiply, but after a while only individuals of one species remained. It is noteworthy that at high levels of heat and moisture one species won, but at low levels? another.
Consequently, the outcome of competition depends not only on the properties of the interacting species, but also on the conditions in which competition occurs. Depending on the conditions prevailing in a particular habitat, the winner of the competition may be either one or the other species.
In some cases, this leads to the coexistence of competing species. After all, heat and humidity, like other environmental factors, are not evenly distributed in nature. Even within a small area (forest, field or other habitat) you can find zones that differ in microclimate. In this variety of conditions, each species masters the place where its survival is ensured.
The main resource that is a subject of competition among plant organisms is light. Of two similar plant species coexisting in the same habitat, the advantage is achieved by the species that is able to reach the upper, better-lit layer earlier. This can be facilitated, on the one hand, by rapid growth and early achievement of foliage, on the other? the presence of long petioles and high-set leaves. Does rapid growth and early achievement of foliage provide advantages in the early growing season, long petioles and high-set leaves? at the adult stage.
Observations of populations of two cohabiting clover species (one of which has advantages in growth rate, and the other in the length of leaf petioles) show that in mixed herbs, each species suppresses the development of the other. However, both are able to complete the life cycle and produce seeds, that is, complete displacement of one species by the other does not occur. Both species, despite strong competition for light, can coexist. This is due to the fact that the developmental stages when the growth rate of these species reaches its maximum (and the need for light is especially high) do not coincide in time.
Thus, only those competing species that have adapted to diverge at least slightly in their environmental requirements coexist in a community. Thus, in African savannas, ungulates use pasture food in different ways: zebras pluck the tops of grasses, wildebeests eat plants of certain species, gazelles pluck only the lower grasses, and topi antelopes feed on tall stems.
In our country, insectivorous birds that feed on trees avoid competition with each other due to the different nature of their search for prey on different parts of the tree.
Competition as an environmental factor
Competitive relations play an extremely important role in the formation of species composition and regulation of the number of species in a community.
It is clear that strong competition can only be found between species occupying similar ecological niches. The concept of “ecological niche” reflects not so much the physical position of a species in an ecosystem, but rather the functional one, characterizing the specialization (“profession”) of these organisms in nature. Therefore, severe competition can only occur between related species.
Ecologists know that organisms that lead a similar lifestyle and have a similar structure do not live in the same places. And if they live nearby, they use different resources and are active at different times. Their ecological niches seem to diverge in time or space.
The divergence of ecological niches when related species live together is well illustrated by the example of two species of sea fish-eating birds? great and long-billed cormorants, which usually feed in the same waters and nest in the same vicinity. It was possible to find out that the composition of the food of these birds differs significantly: the long-nosed cormorant catches fish swimming in the upper layers of the water, while the great cormorant catches it mainly at the bottom, where flounders and bottom invertebrates, such as shrimp, predominate.
Competition has a profound effect on the distribution of closely related species, although this is often only indirectly demonstrated. Species with very similar needs usually live in different geographic areas or different habitats within the same area. Or they avoid competition in some other way, for example, due to differences in food or differences in daily, or even seasonal activity.
The ecological action of natural selection is apparently aimed at eliminating or preventing prolonged confrontation between species with a similar lifestyle. Ecological separation of closely related species is consolidated in the course of evolution. In Central Europe, for example, there are five closely related species of tits, the isolation of which from each other is due to differences in habitat, sometimes in feeding areas and prey sizes. Ecological differences are also reflected in a number of small details of the external structure, in particular in changes in the length and thickness of the beak. Changes in the structure of organisms that accompany the processes of divergence of their ecological niches suggest that interspecific competition is one of the most important factors in evolutionary transformations.
Interspecific competition can play an important role in shaping the appearance of a natural community. By generating and consolidating the diversity of organisms, it helps to increase the sustainability of communities and more efficient use of available resources...
Antibiosis is a form of relationship in which both interacting species or one of them experiences a harmful, life-suppressing influence from the other.
Neutrality is a form of relationship in which there are no direct interactions between species and they do not significantly influence each other.
In nature, such relationships between organisms are quite difficult to detect, since the complexity of biocenotic connections leads to the fact that most species at least indirectly influence each other.
For example, many forest animals (shrews, small rodents, squirrels, woodpeckers) are not directly related within the biocenosis, but all depend on the supply of coniferous seeds and on this basis they indirectly influence each other.
Relations of neutralism are characteristic of species-rich communities.
Competition (- -).
Competition(from Latin concurro - collide, knock) - This is a form of relationship that is observed between organisms when they share environmental resources, the quantity of which is not enough for all consumers.
Competitive relationships play an extremely important role in the formation of species composition, the distribution of species in space and the regulation of the number of species in a community.
Distinguish intraspecific and interspecific competition.
Intraspecific competition - This is a struggle for the same environmental resources that occurs between individuals of the same species.
Intraspecific competition is the most important form of struggle for existence, which significantly increases the intensity of natural selection.
In this case, interspecific competition manifests itself more sharply, the more similar the ecological needs of competitors are.
There are two forms of interspecific competitive relations: direct and indirect competition.
Direct (active) competition - suppression of one species by another.
With direct competition between species, directed antagonistic relationships develop, which are expressed in various forms of mutual oppression (fights, blocking access to a resource, chemical suppression of a competitor, etc.).
Moreover, in many birds and animals aggression is the main form of relationship that determines the competitive displacement of one species by another in the process of struggle for common resources.
For example:
- in forest biocenoses, competition between wood mice and bank voles leads to regular changes in the habitats of these species. In years with increased numbers, wood mice inhabit a variety of biotopes, displacing bank voles to less favorable places. And, conversely, voles, with their numerical superiority, widely settle in places from which they were previously driven out by mice. It was shown that the mechanism of competitive habitat division is based on aggressive interactions;
- sea urchins that have settled in coastal algae physically eliminate other consumers of this food from their pastures. Experiments with the removal of sea urchins have shown that the seagrass beds are immediately colonized by other species of animals;
- in European human settlements, the gray rat, being larger and more aggressive, completely replaced another species - the black rat, which now lives in steppe and desert areas.
Indirect (passive) competition - consumption of environmental resources needed by both species.
Indirect competition is expressed in the fact that one of the species worsens the conditions of existence of another species that has similar environmental requirements, without having a direct impact on the competitor.
With indirect competition, success in competition is determined by the biological characteristics of the species: intensity of reproduction, growth rate, population density, intensity of resource use, etc.
For example:
- broad-toed and narrow-toed crayfish cannot co-exist in the same reservoir. Usually the winner is the narrow-clawed crayfish, as the most prolific and adapted to modern living conditions;
- in human settlements, the small red Prussian cockroach replaced the larger black cockroach only because it is more fertile and better adapted to the specific conditions of human housing.
A classic example of indirect interspecific competition are laboratory experiments conducted by the Russian scientist G.F. Gause, based on the joint maintenance of two types of ciliates with a similar feeding pattern.
It turned out that when two types of ciliates were grown together, after some time only one of them remained in the nutrient medium. At the same time, ciliates of one species did not attack individuals of another species and did not release harmful substances to suppress a competitor. This was explained by the fact that these species were distinguished by unequal growth rates and the faster growing and reproducing species won in the competition for food.
Model experiments conducted by G.F. Gause, led him to formulate the widely known principle of competitive exclusion (Gause’s theorem):
Two ecologically identical species cannot exist together in the same territory, i.e. cannot occupy exactly the same ecological niche. Such species must necessarily be separated in space or time.
From this principle it follows, that coexistence of closely related species in the same territory is possible in cases where they differ in their ecological requirements, i.e. occupy different ecological niches.
For example:
- insectivorous birds avoid competition with each other by searching for food in different places: on tree trunks, in bushes, on stumps, on large or small branches, etc.;
- hawks and owls, which feed on approximately the same animals, avoid competition due to the fact that they hunt at different times of the day: hawks hunt during the day, and owls hunt at night.
Thus, interspecific competition that occurs between closely related species can have two consequences:
- displacement of one species by another;
- different ecological specialization of species, allowing them to exist together.
Biological interspecific competition is a natural process of struggle between different individuals for space and resources (food, water, light). It occurs when species have similar needs. Another reason for the start of competition is limited resources. If natural conditions provide an excess of food, competition will not arise even between individuals with very similar needs. Interspecific competition can lead to the extinction of a species or its displacement from its former habitat.
Struggle for existence
In the 19th century, interspecific competition was studied by researchers involved in the formation of the theory of evolution. Charles Darwin noted that the canonical example of such a struggle is the coexistence of herbivorous mammals and locusts, feeding on the same plant species. Deer eating tree leaves deprive bison of food. Typical rivals are a mink and an otter, driving each other out of contested bodies of water.
The animal kingdom is not the only environment where interspecific struggle is observed; such struggles are also found among plants. It’s not even the above-ground parts that are in conflict, but the root systems. Some species oppress others in different ways. Soil moisture and minerals are taken away. A striking example of such actions is the activity of weeds. Some root systems, with the help of their secretions, change the chemical composition of the soil, thereby inhibiting the development of neighbors. Interspecific competition between creeping wheatgrass and pine seedlings manifests itself in a similar way.
Ecological niches
Competitive interaction can be very different: from peaceful coexistence to physical struggle. In mixed plantings, fast-growing trees suppress slow-growing ones. Fungi inhibit bacterial growth by synthesizing antibiotics. Interspecific competition can lead to the demarcation of ecological poverty and an increase in the number of differences between species. Thus, environmental conditions and the totality of connections with neighbors change. is not equivalent to habitat (the space where an individual lives). In this case we are talking about the entire lifestyle. A habitat can be called an “address,” and an ecological niche can be called a “profession.”
In general, interspecific competition is an example of any interaction between species that negatively affects their survival and growth. As a result, rivals either adapt to each other, or one opponent displaces the other. This pattern is typical for any struggle, be it the use of the same resources, predation or chemical interaction.
The pace of the struggle increases when we are talking about species that are similar or belong to the same genus. A similar example of interspecific competition is the story of gray and black rats. Previously, these different species of the same genus lived next to each other in cities. However, due to their better adaptability, gray rats supplanted black rats, leaving them with forests as their habitat.
How can this be explained? They swim better, they are larger and more aggressive. These characteristics influenced the outcome to which the described interspecific competition led. Examples of such collisions are numerous. The struggle between wood thrushes and song thrushes in Scotland was very similar. And in Australia, bees brought from the Old World replaced the smaller native bees.
Exploitation and interference
To understand in what cases interspecific competition occurs, it is enough to know that in nature there are no two species that occupy the same ecological niche. If organisms are closely related and lead a similar lifestyle, they will not be able to live in the same place. When they do occupy a common territory, these species feed on different foods or are active at different times of day. One way or another, these individuals necessarily have a different trait, which gives them the opportunity to occupy different niches.
Apparently peaceful coexistence can also be an example of interspecific competition. The relationships of certain plant species provide a similar example. Light-loving species of birch and pine protect spruce seedlings that die in open areas from freezing. This balance is sooner or later upset. Young spruce trees close in and kill new shoots of species that need sun.
The proximity of different species of rock nuthatches is another striking example of the morphological and ecological separation of species, which leads to interspecific competition of biology. Where these birds live near each other, their method of obtaining food and the length of their beaks differ. This distinction is not observed in different habitat areas. A separate issue of evolutionary teaching is the similarities and differences of intraspecific and interspecific competition. Both cases of struggle can be divided into two types - exploitation and interference. What are they?
During exploitation, the interaction of individuals is indirect. They react to a decrease in the amount of resources caused by the activity of neighboring competitors. consume food to such an extent that its availability is reduced to a level where the rate of reproduction and growth of the rival species becomes extremely low. Other types of interspecific competition are interference. They are demonstrated by sea acorns. These organisms prevent neighbors from attaching to the stones.
Amensalism
Other similarities between intraspecific and interspecific competition are that both can be asymmetrical. In other words, the consequences of the struggle for existence for the two species will not be the same. Such cases are especially common in insects. In their class, asymmetric competition occurs twice as often as symmetric competition. Such an interaction in which one individual adversely affects another, but the other does not have any effect on the opponent is also called amensalism.
An example of such a struggle is known from observations of bryozoans. They compete with each other through fouling. These colonial species live on corals off the coast of Jamaica. The most competitive individuals “defeat” their opponents in the overwhelming majority of cases. These statistics clearly demonstrate how asymmetric types of interspecific competition differ from symmetrical ones (in which the opponents' chances are approximately equal).
Chain reaction
Among other things, interspecific competition can cause the limitation of one resource to lead to the limitation of another resource. If a colony of bryozoans comes into contact with a rival colony, then there is a possibility of disruption of the flow and food supply. This, in turn, leads to the cessation of expansion and occupation of new areas.
A similar situation arises in the case of a “war of the roots.” When an aggressive plant shades a rival, the oppressed organism feels a lack of incoming solar energy. This starvation causes slower root growth, as well as a deterioration in the use of minerals and other resources in the soil and water. Plant competition can influence both from roots to shoots, and vice versa from shoots to roots.
Algae Example
If a species has no competitors, then its niche is considered not ecological, but fundamental. It is determined by the totality of resources and conditions under which an organism can maintain its population. When competitors appear, the view from the fundamental niche falls into the realized niche. Its properties are determined by biological competitors. This pattern proves that any interspecific competition causes a decrease in viability and fertility. In the worst case, neighbors push the organism into that part of the ecological niche where it cannot not only live, but also have offspring. In such a case, the species faces the threat of complete extinction.
Under experimental conditions, the fundamental niches of diatoms are provided by the cultivation regime. It is through their example that it is convenient for scientists to study the phenomenon of biological struggle for survival. If two competing species, Asterionella and Synedra, are placed in the same test tube, the latter will gain a niche suitable for life, while Asterionella will die.
The coexistence of Aurelia and Bursaria gives other results. Being neighbors, these species will have their own realized niches. In other words, they will share resources without fatal harm to each other. Aurelia will concentrate at the top and consume the suspended bacteria. Bursaria will settle to the bottom and begin to feed on the yeast cells.
Resource Sharing
The example of Bursaria and Aurelia shows that peaceful existence is possible with niche differentiation and resource sharing. Another example of this pattern is the struggle between Galium algae species. Their fundamental niches include alkaline and acidic soils. With the emergence of a fight between Galium hercynicum and Galium pumitum, the first species will be limited to acidic soils, and the second to alkaline soils. This phenomenon in science is called mutual competitive exclusion. At the same time, algae need both alkaline and acidic environments. Therefore, both species cannot coexist in the same niche.
The principle of competitive exclusion is also called the Gause principle after the name of the Soviet scientist Georgy Gause, who discovered this pattern. It follows from this rule that if two species cannot, due to some circumstances, share their niches, then one will certainly destroy or displace the other.
For example, Chthamalus and Balanus coexist next door only for the reason that one of them, due to sensitivity to desiccation, lives exclusively in the lower part of the coast, while the other is able to live in the upper part, where it is not threatened by competition. Balanus pushed out Chthamalus, but were unable to continue their expansion on land due to their physical limitations. Displacement occurs under the condition that a strong competitor has a realized niche that completely covers the fundamental niche of a weak opponent involved in a dispute over habitat.
Gause principle
Ecologists are involved in explaining the causes and consequences of biological control. When it comes to a specific example, sometimes it is quite difficult for them to determine what the principle of competitive exclusion is. Such a difficult issue for science is the rivalry between different species of salamanders. If it is impossible to prove that niches are separated (or to prove otherwise), then the operation of the principle of competitive exclusion remains only an assumption.
At the same time, the truth of Gause’s law has long been confirmed by many recorded facts. The problem is that even if niche division occurs, it is not necessarily caused by interspecific competition. One of the pressing problems of modern biology and ecology is the causes of the disappearance of some individuals and the expansion of others. Many examples of such conflicts are still poorly studied, which provides a lot of room for future specialists to work on.
Adaptation and repression
The improvement of one species will necessarily lead to a deterioration in the lives of other species. They are connected by one ecosystem, which means that in order to continue their existence (and the existence of their offspring), organisms must evolve, adapting to new living conditions. Most living beings disappeared not for any reasons of their own, but only due to the pressure of predators and competitors.
Evolutionary race
The struggle for existence has continued on Earth exactly since the first organisms appeared on it. The longer this process lasts, the more species diversity appears on the planet and the more diverse the forms of competition themselves become.
The rules of wrestling change constantly. In this they differ from For example, the climate on the planet also changes without stopping, but it changes chaotically. Such innovations do not necessarily harm organisms. But competitors always evolve to the detriment of their neighbors.
Predators improve their hunting methods, and victims improve their defense mechanisms. If one of them stops evolving, this species will be doomed to displacement and extinction. This process is a vicious circle, since some changes give rise to others. The perpetual motion machine of nature pushes life to constantly move forward. Interspecific struggle plays the role of the most effective tool in this process.
Interspecific competition is the active search by two or more species for the same food resources in their habitat. Competitive relationships typically arise between species with similar ecological requirements. Competition between species is extremely widespread in nature and affects almost all of them, since it is rare that a species does not experience at least a little pressure from individuals of other species. When living together, each of them is at a disadvantage due to the fact that the presence of another species reduces the opportunity to acquire food resources, shelters and other means of subsistence available in the habitat. Ecology considers interspecific competition in a specific, narrower sense - only as mutually negative relations between species occupying a similar ecological niche.
Competitive relationships can be very diverse: from direct physical struggle to almost peaceful coexistence. And at the same time, if two species with the same ecological needs find themselves in the same community, then one competitor necessarily displaces the other. For example: in Europe, in human settlements, the gray rat completely replaced another species of the same genus - the black rat, which now lives in steppe and desert areas. The gray rat is larger, more aggressive, and swims better, so it managed to win. In Russia, on the contrary, the relatively small red cockroach - the Prussian cockroach - completely replaced the larger black cockroach only because it was able to better adapt to the specific conditions of human habitation. In Australia, the common bee, introduced from Europe, replaced the small native bee, which does not have a sting.
Interspecific competition can be demonstrated in simple laboratory experiments. Thus, in the studies of the Russian scientist G.F. Gause, cultures of two types of ciliates - slippers with a similar feeding pattern were placed separately and together in vessels with hay infusion. Each species, placed separately, reproduced successfully, reaching optimal numbers. However, when living together, the number of one of the species gradually decreased, and its individuals disappeared from the infusion, while the ciliates of the second species remained. It was concluded that long-term coexistence of species with similar ecological requirements is impossible. As it turned out, after some time, only individuals of one species remained alive, surviving the struggle for food, since its population grew and multiplied faster. This conclusion is called the rule of competitive exclusion.
But the outcome of competition depends not only on the properties of the interacting species, but also on the conditions in which competition occurs. Depending on the conditions prevailing in a particular habitat, the winner of the competition may be either one or another species, which in a given environmental situation has at least slight advantages over the other, and therefore greater adaptability to environmental conditions.
Researchers investigated the influence of temperature and humidity on the outcome of interspecific competition between two species of flour beetles. Vessels with flour, kept at a certain combination of heat and moisture, were placed with several individuals of both species. Here the beetles began to reproduce, but after a while there remained individuals of only one species. It is noteworthy that at high levels of heat and moisture one species won, and at low levels another species won.
In some cases, this leads to the coexistence of competing species. After all, heat and humidity, like other environmental factors, are not evenly distributed in nature. Even within a small area (forest, field or other habitat) you can find zones that differ in microclimate. In this variety of conditions, each species masters the place where its survival is ensured.
Thus, only those competing species that have adapted to diverge at least slightly in their environmental requirements coexist in a community. Thus, in African savannas, ungulates use pasture food in different ways: zebras pluck the tops of grasses, wildebeests eat plants of certain species, gazelles pluck only the lower grasses, and topi antelopes feed on tall stems.
In our country, insectivorous birds that feed on trees avoid competition with each other due to the different nature of their search for prey on different parts of the tree.
Competition is one of the reasons that two species, slightly different in the specifics of nutrition, behavior, lifestyle, etc., rarely coexist in one
community. Here the competition is in the nature of direct hostility. The most severe competition with unforeseen consequences occurs if a person introduces animal species into communities without taking into account already established relationships.
More often, competition manifests itself indirectly and is insignificant, since different species perceive the same environmental factors differently. The more diverse the capabilities of organisms, the less intense the competition will be.
The importance of competition as an environmental factor.
As already mentioned, competitive relations play an extremely important role in the formation of species composition and regulation of the number of species in a community.
Ecologists know that organisms that lead a similar lifestyle and have a similar structure do not live in the same places. And if they live nearby, they use different resources and are active at different times. Their ecological niches seem to diverge in time and space.
The divergence of ecological niches when related species live together is well illustrated by the example of two species of sea fish-eating birds - great and long-billed cormorants, which usually feed in the same waters and nest in the same neighborhood. Scientists were able to find out that the composition of the food of these birds differs significantly: the long-billed cormorant catches fish swimming in the upper layers of the water, while the great cormorant catches it mainly at the bottom, where flounders and flounders predominate, benthic invertebrates, such as shrimp.
Competition has a profound effect on the distribution of closely related species, although this is often only indirectly demonstrated. Species with very similar needs usually live in different geographic areas or different habitats in the same area, or avoid competition in some other way, for example, due to differences in food or differences in daily or even seasonal activity.
The ecological action of natural selection is apparently aimed at eliminating or preventing prolonged confrontation between species with a similar lifestyle. Ecological separation of closely related species is consolidated in the course of evolution. In Central Europe, for example, there are five closely related species of tits, the isolation of which from each other is due to differences in habitat, sometimes in feeding areas and prey sizes. Ecological differences are also reflected in a number of small details of the external structure, in particular in changes in the length and thickness of the beak. Changes in the structure of organisms that accompany the processes of divergence of their ecological niches suggest that interspecific competition is one of the most important factors in evolutionary transformations. If interspecific competition is weakly expressed, then under the influence of intraspecific competition, populations of a given species expand the boundaries of their habitat.
Thus, interspecific competition can play an important role in shaping the appearance of a natural community. By generating and consolidating the diversity of organisms, it helps to increase the sustainability of communities and more efficient use of available resources.
Intraspecific competition has its own characteristics. The reason for its occurrence is a typical situation when the resource for which individuals of a population are fighting is quantitatively limited. Fierce competition arises (for territory, food resources, etc.), which is observed at high population densities.
Another form of intraspecific competition is rivalry, when one individual prevents another from occupying an existing territory and using its resources. In this case, a form of ideal or uncompromising competition is possible, which is resolved by emigration to other territories.
The intensity of competition and its impact on the population depends on density, which determines the frequency and intensity of contacts between competitors.
Intraspecific competition not only depletes resources and thereby leads to increased mortality and stunted growth of individuals, it encourages self-aggression, cannibalism, and reduces the realization of the potential contribution of an individual to the next generation and the development of the population.
Intraspecific competition between individuals of a population in plants can be characterized as a struggle for light, heat, moisture, and area of mineral nutrition. In this competition, the more developed organisms that are nearby, displace the weak ones completely or strongly suppress their development and lead to gradual death. That is why, in agrophytocenoses, to reduce competition and create optimal conditions for the growth and development of cultivated plants, the density of individuals and the area of their mineral nutrition are regulated by the appropriate type of sowing or thinning of crops, the destruction of weeds and the selection of biologically compatible species for mixed crops.
In natural plant populations, self-regeneration occurs—a decrease in the number of individuals per unit area.
This phenomenon is known to foresters. The number of trees per unit area decreases with the age of the plantings. The liquefaction of the tree stand occurs the faster, the more light-loving the species and the better the environmental conditions. The latter is associated with an increase in the growth rate in good conditions and, accordingly, an increase in its needs, which makes competition intense (Fig. 9.2).
Each species has its own optimal density, i.e. such a degree of saturation of the territory of the population with its individuals, which ensures the best reproduction and greatest stability of the population, reduces the severity of competition.
In the process of evolution, animals of different species also developed appropriate adaptive adaptations to life in an environment that is sparsely saturated or densely populated with individuals of the population.
The corresponding biological properties and life strategy have been developed, allowing organisms to reproduce and survive in conditions of a “competitive vacuum” (absence or little competition). In the first case, small animals can reproduce, their descendants will survive, although the population density will be high.
In the second case, large animals and their relatively similar descendants can survive the competition for space and food. Therefore, the main energy of organisms is aimed at competition, at increasing their survival, at producing competitive descendants.
These tendencies and strategies of different species are reflected in two opposing types of natural selection: r- and k-selection, which are discussed in Chapter 2.
Intraspecific competition between plant individuals of the same population can be calculated using Yoda's equation. According to this equation, the average area per individual (a) is inversely proportional to population density (d).
Competition(from Late Latin concurentia - to collide), a type of relationship between organisms of the same or different species competing for the same things environmental resources(sexual partners, food, territory, shelters, etc.) with a lack of the latter. Intraspecific competition is considered the most important form of struggle for existence, since potentially the most intense competitive relationships arise between more similar individuals. For example, in mammals competition between males for the possession of a female is clearly expressed during the breeding season. During the rut, males of many species ( deer, rams, bears) organize fierce tournament battles.
Competition for territory, shelter and food is most fully expressed in territorial species with a solitary lifestyle (some mouse-like rodents, mole rats, carnivores mammals). However, in nature there are mechanisms (ecological, behavioral, etc.) that reduce the intensity of intraspecific competition. For example, many aggressive actions of animals during mutual contacts are ritualized and are intended, first of all, to intimidate the enemy, without bringing the contact to physical interaction.
Interspecific competition is more often observed between individuals of ecologically similar species that use the same habitats and food resources. Such functionally similar groups of species, which interact strongly with each other and weakly with other species of the biocenosis, are often identified in guilds (the term was proposed by R. B. Root in 1967). The concept of guilds is closely related to the ecological niche model.
Competition can be passive (indirect), through the consumption of environmental resources needed by both species, and active (direct), accompanied by the suppression of one species by the other. The first option is often called exploitative competition, and the second - interference competition. An example of active competition is the relationship between acclimatized American and native European minks, in which the native view turned out to be uncompetitive.
The state of competition in the long-term aspect is energetically unprofitable for both competitors, therefore, in nature, various mechanisms are implemented that reduce the intensity of interspecific competitive relations, based, in particular, on the division of resources and the formation of different ecological niches. The results of intraspecific and interspecific competition are usually different (see also Speciation). The first leads to the culling of the least competitive (least fit) individuals and, under conditions of a constant environment, to a narrowing of the reaction norm of the species, specialization (stabilizing selection; see Natural selection), and in conditions of a directionally changing environment - to a shift in the reaction norm in the direction determined by the changing environment, i.e. to the emergence of a new adaptive form (driving selection; see Natural selection).
Intraspecific competition
Interspecific competition leads to further divergence of species due to the culling of morphs with similar requirements.
Natural selection), and in conditions of a directionally changing environment - to a shift in the reaction norm in the direction determined by the changing environment, i.e. to the emergence of a new adaptive form (driving selection; see Natural selection). Interspecific competition leads to further divergence of species due to the culling of morphs with similar requirements.
In natural communities, animals of the same and different species live together and interact with each other. In the process of evolution, certain relationships are developed between animals that reflect the connections between them. Each animal species performs a specific role in the community in relation to other living organisms.
The most obvious form of relationship between animals is predation. In natural communities, there are herbivores that eat vegetation, and there are carnivores that catch and eat other animals. In relationships, herbivores act victimsami, and carnivores - predatorami. Moreover, each victim has its own predators, and each predator has its own “set” of victims.
INTRASPECIFIC COMPETITION
For example, lions hunt zebras and antelopes, but not elephants or mice. Insectivorous birds only catch certain types of insects.
Predators and prey have evolved to adapt to each other so that some have developed body structures that allow them to catch better, while others have a structure that allows them to better run away or hide. As a result, predators catch and eat only the weakest, sickest and least adapted animals.
Predators don't always eat herbivores. There are second- and third-order predators that eat other predators. This often occurs among aquatic inhabitants. So some species of fish feed on plankton, others on these fish, and a number of aquatic mammals and birds eat the latter.
Competition- a common form of relationships in natural communities. Typically, competition is most intense between animals of the same species living in the same territory. They have the same food, the same habitats. Competition between animals of different species is not so intense, since their lifestyles and needs are somewhat different. So a hare and a mouse are herbivores, but they eat different parts of plants and lead different lifestyles.
Population Relationships between individuals in a population
A population is a collection of individuals of the same species that have a common living space and type of relationship with each other. Individuals of the population differ from each other in age and vitality (i.e.
Competition (biology)
vital force), which can be determined genetically, phenetically, and more often - a combination of these factors.
A number of significant differences that need to be taken into account in population studies exist between plant and animal populations. The main difference is that animals with mobility can react more actively to developing environmental conditions, avoiding unfavorable circumstances or dispersing across the territory to compensate for the decrease in the supply of resources per unit area. Mobility makes it easier for them to protect themselves from predators.
Due to the fact that populations are diverse, the interactions of the individuals within them also differ.
The main type of interaction between individuals in a population is competition, i.e. competition for the consumption of a resource that is in short supply. Competition can be symmetrical (competing individuals have the same influence on each other) or asymmetrical (individuals have different influences on each other).
Features of competition between individuals in a population:
1. Competition reduces the growth rate of individuals, can slow down their development, reduce fertility and, as a result, reduce the contribution to subsequent generations. The number of descendants of a particular individual is smaller, the tougher the competition conditions and the fewer resources it gets.
2. In most cases, individuals compete for resources: each individual receives that limited amount of resources that were not consumed by its competitors. This type of competition is called exploitative competition. Less often, competition for physical space occurs when individuals “mechanically” prevent each other from obtaining a resource, for example, when mobile animals protect their territory. Such relationships are called interference.
3. Different individuals have different competitive abilities. Despite the fact that all individuals of the population are potentially equivalent (their gene pool is constantly leveled due to hybridization), in nature, equivalence of individuals is not observed. As a result of asymmetric competition, the population density decreases: weak plants die, and weak animals migrate to habitats with lower level of competition.
In addition to competition, other forms of relationships between individuals in populations are possible - neutrality (if there are so many resources and so few individuals that they practically do not interfere with each other) and positive relationships.
Mutually beneficial (or beneficial for some individuals) relationships between animals are well known: parents care for their offspring, the formation of large family groups, a herd lifestyle, collective defense from enemies, etc. “Caravans” of birds lining up in ranks, wedges, ledges, etc. ., allow the wings of individual individuals, due to aerodynamic effects, to acquire greater lifting force (it is easier to fly in a group). It is believed that fish swimming in schools also gain hydrodynamic advantages.
The role of mutual aid in plants is much less known. Plants sown in a group develop better, since in this case they more easily form symbiosis with fungi and bacteria of mycorrhiza and rhizosphere (the so-called “group effect”).
Phenomena of mutual assistance between plants are possible during “collective defense” from phytophages that exhibit excessively high activity and can seriously damage plants. In this case, after the start of active consumption by phytophages, biochemical reactions occur in plants and the concentration of substances that reduce their palatability (cyanides, etc.) increases. Cases have been described in which individuals attacked by phytophages released signal substances into the atmosphere (the “I’m being eaten” signal), which caused an increase in the formation of cyanide in those individuals that were not yet damaged.
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Competition is the competition between organisms of the same trophic level (between plants, between phytophages, between predators, etc.) for the consumption of a resource available in limited quantities.
Competition for the consumption of resources plays a special role during critical periods of their scarcity (for example, between plants for water during a drought or predators for prey in an unfavorable year).
There are no fundamental differences between interspecific and intraspecific (intrapopulation) competition. There are cases where intraspecific competition is more intense than interspecific competition, and vice versa. Moreover, the intensity of competition within and between populations can change under different conditions. If conditions are unfavorable for one of the species, then competition between its individuals may increase. In this case, it may be displaced (or more often, displaced) by a species for which these conditions turned out to be more suitable.
However, in multispecies communities, “dueling” pairs most often do not form, and competition is diffuse: many species simultaneously compete for one or several environmental factors. “Duelists” can only be mass species of plants that share the same resource (for example, trees - linden and oak, pine and spruce, etc.).
Plants may compete for light, for soil resources, and for pollinators. On soils rich in mineral nutrition resources and moisture, dense, closed plant communities are formed, where light is the limiting factor for which plants compete.
When competing for pollinators, the species that is more attractive to the insect wins.
In animals, competition occurs for food resources, for example, herbivores compete for phytomass. In this case, competitors of large ungulates can be insects like locusts or mouse-like rodents, which are capable of destroying most of the grass stand during the years of mass reproduction. Predators compete for prey.
Since the amount of food depends not only on environmental conditions, but also on the area where the resource is reproduced, competition for food can develop into competition for space.
As in the relationships between individuals of the same population, competition between species (their populations) can be symmetrical or asymmetrical. Moreover, a situation where environmental conditions are equally favorable for competing species is quite rare, and therefore relations of asymmetric competition arise more often than symmetric ones.
When resources fluctuate, as is usual in nature (moisture or mineral nutrition elements for plants, primary biological production for different types of phytophages, density of prey populations for predators), different competing species alternately gain advantages. This also does not lead to the competitive exclusion of the weaker, but to the coexistence of species that alternately find themselves in a more advantageous and less advantageous situation. At the same time, species can experience deterioration of environmental conditions with a decrease in the level of metabolism or even a transition to a dormant state.
The outcome of the competition is also influenced by the fact that a population that has more individuals and will, accordingly, more actively reproduce “its army” (the so-called mass effect) has a greater chance of winning the competition.
23. Relationship between plant and phytophage and the prey is the predator
RELATIONSHIP "PLANT-PHYTOPHAGE".
The “phytophage-plant” relationship is the first link in the food chain, in which matter and energy accumulated by producers are transferred to consumers.
It is equally “unprofitable” for plants to be eaten completely or not eaten at all. For this reason, in natural ecosystems there is a tendency to form an ecological balance between plants and the phytophages that eat them. For this plant:
– protected from phytophages by spines, forming rosette forms with leaves pressed to the ground, inaccessible to grazing animals;
– protect themselves from complete grazing by biochemical means, producing toxic substances when eating increases, which make them less attractive to phytophages (this is especially typical for slowly growing patients). In many species, when they are eaten, the formation of “unpalatable” substances increases;
– emit odors that repel phytophages.
Protection from phytophages requires significant energy expenditure, and therefore tradeoff can be traced in the “phytophage-plant” relationship: the faster the plant grows (and, accordingly, the better the conditions for its growth), the better it is eaten, and vice versa, the slower the plant grows, the more it is less attractive to phytophages.
At the same time, these means of protection do not ensure complete safety of plants from phytophages, since this would entail a number of undesirable consequences for the plants themselves:
– uneaten steppe grass turns into rags – felt, which worsens the living conditions of plants. The appearance of abundant felt leads to the accumulation of snow, a delay in the onset of plant development in spring and, as a result, to the destruction of the steppe ecosystem. Instead of steppe plants (feather grass, fescue), meadow species and shrubs develop abundantly. At the northern border of the steppe, after this meadow stage, the forest may generally recover;
– in the savanna, a decrease in the consumption of tree shoots by branch-eating animals (antelopes, giraffes, etc.) leads to the fact that their crowns close together. As a result, fires become more frequent and trees do not have time to recover; the savanna degenerates into thickets of bushes.\
In addition, with insufficient consumption of plants by phytophages, space is not freed up for the settlement of new generations of plants.
The “imperfection” of the “phytophage-plant” relationship leads to the fact that short-term outbreaks in the density of phytophage populations and temporary suppression of plant populations occur quite often, followed by a decrease in the density of phytophage populations.
RELATIONSHIP "VICTIM-PREDATOR".
The “predator-prey” relationship represents the links in the process of transfer of matter and energy from phytophages to zoophages or from lower-order predators to higher-order predators.
As in the “plant-phytophage” relationship, a situation in which all victims are eaten by predators, which ultimately leads to their death, is not observed in nature.
The ecological balance between predators and prey is maintained by special mechanisms that prevent the complete extermination of the victims.
So victims can:
- run away from a predator.
In this case, as a result of adaptation, the mobility of both victims and predators increases, which is especially typical for steppe animals that have nowhere to hide from their pursuers (“Tom and Jerry principle”);
– acquire a protective color (“pretend” to be leaves or twigs) or, on the contrary, a bright color (for example, a red color, warning a predator about a bitter taste. It is well known that the color of a hare changes at different times of the year, which allows it to camouflage itself in the leaves in summer, and against a white background in winter snow;
– spread in groups, which makes searching for and catching them more energy-intensive for the predator;
- hide in shelters;
– move to active defense measures (herbivores with horns, spiny fish), sometimes joint (musk oxen can take up “all-round defense” from wolves, etc.).
In turn, predators develop not only the ability to quickly pursue prey, but also a sense of smell, which allows them to determine the location of the prey by smell.
At the same time, they themselves do everything possible to avoid detection of their presence. This explains the cleanliness of small cats, which spend a lot of time toileting and burying excrement to eliminate odors.
With intensive exploitation of phytophagous populations, people often exclude predators from ecosystems (in Great Britain, for example, there are roe deer and deer, but no wolves; in artificial reservoirs where carp and other pond fish are bred, there are no pikes). In this case, the role of the predator is performed by the person himself, removing part of the individuals of the phytophage population.
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Competition is a typical phenomenon for living nature. It is caused by the struggle for resources. But if we talk about intraspecific competition, it should be noted that this type of competition is characterized by the greatest intensity.
This is, first of all, due to the fact that individuals of the same species need some strictly defined resource, which individuals of another species may not need. Therefore, often with this type of competition there is a depletion of a resource or a certain type of resource.
For example, in a grass mixture consisting of peas and barley, the most fierce competition for soil nitrogen will be between the barley plants. This is due to the fact that, due to the ability of peas to fix nitrogen from the air, the need for competition between pea shoots for nitrogen in the soil is reduced.
Distinguish operational And interference competition.
The first is that all individuals simultaneously exploit resources, but each of them uses only what is left after the competitor. In the second case, one individual prevents another from occupying an existing habitat and using its resource. The first form of competition is called fierce competition, and the second is called rivalry. The first type of competition can lead to the death of the entire population. For example, in the green carrion fly, when the population of larvae on the food source becomes overcrowded, this type of competition can lead to the death of the entire population of offspring at a certain age stage.
The rivalry looks a little different. For example, if 150 pairs of birds claim 100 hollows in some forest area, then it becomes obvious that 50 pairs will not be able to establish their nests in this area. Therefore, the only possible option for producing offspring may be the migration of these birds to another territory (i.e., emigration).
For a number of reasons, competing individuals of the same species are not equal in their ability to compete. Therefore, in nature, the strongest or those who are more fortunate due to a combination of circumstances survive. Thus, the most ordinary sprout, which sprouted a little earlier than its fellow tribesmen, will subsequently obscure the low-growing specimens.
Ignorance of the laws related to intraspecific competition can lead to dire consequences. For example, in agricultural production, a significant excess of seed sowing rates per unit area can lead to a complete loss of the crop. Numerous plants exhausted by competition will simply not be able to produce a harvest, but even survive to reproductive age.
Competition is directly related to the concept of an ecological niche, which represents not only certain environmental conditions to which an organism is adapted, but also a way of life and a method of obtaining food. Often this term is applied mainly to interspecific competition, but in fact the ecological niche is characteristic even of each individual organism of the same species.
Another interesting factor in intraspecific competition is the body size of organisms. Thus, the growth of fish does not stop even after reaching sexual maturity, and is determined by food reserves. The American ecologist R. Whittaker gives the following example in this regard. There are two identical ponds. 100 fry are released into the first, and 50 into the second. As a result, after an equal period of time, the size of the fish in the first pond can be half as large as in the second. However, the weight of fish in both the first and second ponds may be approximately the same.
In addition to uniform depletion of resources, intraspecific competition can also lead to intoxication of the entire population. This happens because the excretion products of organisms of the same species are, in fact, poison for them. For example, in a plant community, root secretions of some plant species can provide nutrients for other plant species. Therefore, in the wild you can rarely find communities represented by a single species.
Grandfather Darwin, in his evolutionary theory, noted that the severity of the struggle for existence is most pronounced among representatives of the same species. And although in the field of recent achievements in genetics and a number of other biological sciences, an increasing number of comments and claims are arising to the theory of Charles Darwin, nevertheless, so far no one has come up with anything more significant in biology.
According to the Ukrainian ecologist V. Kucheryavyi: “Intraspecific competition has many negative consequences. It not only depletes resources and leads to environmental toxicity, but also promotes self-injury and cannibalism, social and reproductive failure.”
The above quote, willy-nilly, evokes associations with human society. There was a time when analogies of the laws of nature with relationships within human society led a number of thinkers to the creation of such a doctrine as social Darwinism, which, according to the ecophilosopher M. Bookchin, “connected all the wild features of civilization with our genetic constitution.” According to this doctrine, property inequality in society is explained as interspecific competition between individuals of the same species of the same population.
And geopolitical inequality between states is explained as intraspecific competition between populations of the same species.
At first glance, everything is correct. However, if we take social Darwinism seriously, it turns out that Homo sapiens, in fact, is not such, but is a typical biological species. Obviously this is not the case. But the main flaw of this teaching is that it does not try to change anything for the better, but tries not so much to explain as to justify the existing state of affairs. Social Darwinism does not reflect the most important thing - the future perspective. Indeed, in the current environmental realities, it becomes clear that intraspecific and interspecific human competition is so depleting the resources of the biosphere that it undermines the biological diversity of the entire global ecosystem, and therefore threatens the human species itself.
In modern biological science, scientists are increasingly paying attention not to competition, but to mutual assistance and cooperation. But more about this in one of the following publications. In short, we can say the following. Man is a social being, therefore a number of biological laws are neutralized due to artificial social institutions and established norms of behavior. At the same time, one should not underestimate the biological laws in the life of the human species. We can say that many social mechanisms are just a means that simply delays the reaction of biological laws. And as soon as this mechanism is destroyed due to spontaneous, competitive or resource overload, the biological laws of survival manifest themselves in their entirety.
