Intraspecific and interspecific competition. Interspecific competition in biology

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.

special role competition for the consumption of resources during critical periods of their scarcity plays a role (for example, between plants for water during a drought or predators for prey in an unfavorable year).

Fundamental differences There is no interspecific and intraspecific (intrapopulation) competition. There are cases where intraspecific competition is more intense than interspecific competition, and vice versa. At the same time, the intensity of competition within and between populations can vary depending on the different conditions. If conditions are unfavorable for one of the species, then competition between individuals may increase. In this case, it should 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 in nature; many species simultaneously compete for one or several environmental factors. "Duelists" can only be mass species 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, where the limiting factor for which plants compete is light.

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) must 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, which is usually the case in nature (moisture or mineral nutrition elements for plants, primary biological products for different types 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 concept of competition is increasingly highlighted in the field of economics, but its origins still come from biology. What does this concept mean? What is the role of competition in wildlife? Read about the types and mechanisms of competition further in the article.

Various effects on organisms

No living organism exists in isolation. It is surrounded by many living and inanimate nature. Therefore, to one degree or another, it constantly interacts with the environment and other organisms. First of all on Living being influences the biosphere, its components include the lithosphere, hydrosphere, and atmosphere. The vital activity of plants and animals is directly related to the amount sunlight, access to water resources etc.

Organisms also experience significant influence from interaction with each other. This influence is called biotic factors, which manifest themselves as the impact of living organisms on plants, which, in turn, affects the habitat. In biology, they are divided into trophic (according to food relations among organisms), topical (relative to environmental changes), factory (depending on place of residence), phoric (the possibility or impossibility of transportation by one organism of another) factors.

Interaction of living organisms

Carrying out their life activities, living organisms certainly affect the “personal space” of other organisms. This can happen between representatives of the same species or different ones. Depending on whether the interaction harms organisms or not, neutral, positive and negative types of relationships are distinguished.

A relationship in which both organisms receive nothing is called neutralism. Positive interaction is considered mutualism - mutually beneficial cohabitation of individuals. A completely negative relationship can be called allelopathy, when cohabitation harms both participants. This also includes intraspecific and interspecific competition.

Important factors for the normal life of animals, plants, and microorganisms are environmental resources and space. When there is a shortage of them, competition appears between living organisms. This is a type of antibiosis - an antagonistic relationship where different individuals are forced to fight for their existence.

Rivalry in wildlife often occurs when individuals have similar needs. If the struggle occurs among individuals of the same species, it is intraspecific competition; if it occurs among different individuals, it is interspecific.

Living organisms can compete openly, directly interfering with the life of their opponent. For example, when the roots of some plants oppress others, or some animals drive others away from a hot spot. Competition can also be indirect. It manifests itself when the opponent more actively destroys the necessary resource.

Intraspecific competition

Examples can be found quite often. This type of competition is observed between individuals of one or more populations. The main reason For this purpose, the same structure of organisms serves, and therefore the same requirements for factors environment and food.

Intraspecific competition is more severe than interspecific competition. The manifestation of such a struggle can be observed in the delimitation of territory between individuals. Thus, bears leave claw marks on tree trunks, warning of their presence. To divide space, they often use smell and a loud signal cry. Sometimes individuals simply attack each other.

If competition occurs for resources, then sometimes it is asymmetrical. In this case, one side suffers more than the other. As a result intraspecific competition eventually one of the populations may disappear or mutate.

Why is there competition?

One of the most important tasks of living organisms is to survive, while passing on the best genetic material to their offspring. IN ideal conditions, an ecological vacuum, there are no obstacles to this, which means there is no rivalry.

Intraspecific competition occurs when unfavorable conditions environments where organisms are forced to fight for light, water or food. Harsh conditions may lead to change life cycle species, accelerate its development. However, this is not necessary. Sometimes rivalry occurs when individuals fight for dominance in a herd, pack, or pride. This behavior is observed in animals that have a developed social hierarchy.

Quite a lot important role plays Excessive growth of the population of one species over time leads to a shortage of resources, which can lead to the extinction of the species. To avoid this, some species, such as rodents, even develop shock illness. The ability of animals to reproduce sharply decreases, but their susceptibility to various diseases increases.

The role and mechanisms of competition

Competition is nature's most important tool. First of all, it is designed to regulate the number of individuals. Each species has its own permissible density values, and when there are too many individuals within one population, control mechanisms are activated. To fulfill this role, nature uses various ways: increased mortality, division of territory.

In conditions of high numbers and limited space, some individuals may leave their usual habitat and develop another. This is how two different ones are distinguished from one population. This ensures a wide distribution of the species and high survival rate. U certain types this process is temporary, for example in migrating birds.

As a result of intraspecific competition, more resilient and viable individuals ultimately survive. Their physiological qualities are transmitted genetically, which means they contribute to the improvement of the species.

Examples of intraspecific and interspecific competition

It is not always easy to distinguish between the two main types of competition. It’s better to understand this visually. may serve as a “victory” of a gray rat over a black one. They belong to the same genus, but are different species. Gray rat more aggressive and dominant in size, so she was able to easily push the black one out of human homes. But the black one was a frequent guest on the ships of seafarers.

As a model of intraspecific competition, we can mention cannibalism, which is observed in approximately 1,300 animal species. Female praying mantises eat males immediately after mating. The same behavior is observed among karakurt packs. Scorpions and salamanders eat some of their offspring. In many beetles, the larvae eat their fellows.

A type of internal competition is territoriality. It is observed in fish, penguins and most other birds. During the breeding season, they do not allow representatives of their species into their own territory, which they carefully guard.

Competition in plants

Plants, although they cannot openly attack an opponent and scare him away, also have their own methods of competition. Their struggle occurs mainly for light, water and free space. In harsh conditions of existence, intraspecific competition of plants manifests itself in the form of self-thinning.

This process begins with the dissemination of seeds and the plant’s takeover of territory. Sprouted seedlings cannot develop in the same way; some grow more actively, others more slowly. Tall trees with spreading crowns shade other trees, taking all the solar energy for themselves, and their powerful roots block the path to nutrients. This is how small and weak plants dry out and die.

Competition is displayed on appearance plants. Representatives of the same species can vary significantly, depending on the degree of their isolation from other individuals. This phenomenon can be observed in oak trees. Growing separately, it has a wide, spreading crown. The lower branches are strong and well developed, no different from the upper ones. In the forest, among other trees, the lower branches cannot receive enough light and die. The oak takes on a narrow, elongated crown shape instead of a spherical one.

Conclusion

Competition is one of the types of relationships. It occurs between all living organisms without exception. The main task of competition is to regulate the density of individuals, as well as increase their ability to survive. Often competition occurs due to competition for food, water, light or territory. It can arise as a result of a sharp shortage of one of these resources.

Rivalry typically occurs between species that have similar needs. The more similarities living organisms have, the stronger and more aggressive the struggle. Individuals of the same or different species can compete for a resource. Intraspecific competition often occurs to establish a dominant individual and also to ensure that the population does not grow excessively.

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. 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 aquatic mammals and the birds are eaten second.

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.

Competitive relations.

If in ecological system two or more species (populations) with similar ecological requirements live together, and relationships of a negative type arise between them, which are called competition (? ?). In the general sense of the word “competition” means confrontation, rivalry, competition. In fact, when two populations use the same environmental resources, competition inevitably arises between species for the mastery of these resources. Moreover, each population experiences oppression from the other, which negatively affects their growth and survival and can even lead to the displacement and disappearance of one of them, which is less adapted.

Competition is extremely widespread in nature. So, for example, all plants compete (compete) for light, moisture, nutrients soil and for expanding the territory of their habitat. Animals fight for food resources and for shelters (if they are in short supply), that is, ultimately, also for territory. However, if the population is not large and consists of a few, rare species, ecological significance there will be little competition: for example, in arctic or desert areas there is almost no plant competition for light.

Competition cannot be considered simply by organisms using the same thing. natural resource. Negative interaction can only be discussed when this resource is scarce and when joint consumption has an adverse effect on the population.

Types of competitive relationships

Competitive interaction may concern territory, food, light, shelters and all other types of environmental resources. The outcome of competition is of great interest not only for ecologists studying the processes of formation of the composition of natural communities, but also for evolutionists studying the mechanisms of natural selection.

Competition is divided into intraspecific and interspecific. Both intraspecific and interspecific competition can play a large role in the formation of species diversity and population dynamics of organisms.

Intraspecific competition. Territoriality

Intraspecific competition? it is a struggle for the same resources that occurs between individuals of the same species. This is an important factor in the self-regulation of population numbers.

In some organisms, under the influence of intraspecific competition for living space, a interesting guy behavior? territoriality. It is characteristic of many birds, some fish, and other animals.

In birds, territoriality manifests itself as follows. At the beginning of the breeding season, the male identifies “his” territory (habitat) and protects it from invasion by males of the same species. Let us note that the loud voices of males, which we hear in the spring, only signal “ownership” of the site they like, and do not at all set themselves the task of entertaining the female, as is usually believed.

A male who strictly guards his territory has a greater chance of successfully mating and building a nest, while a male who is unable to secure a territory for himself will not participate in reproduction. Sometimes the female also takes part in protecting the territory. In a protected area, the difficult care of the nest and young will not be disturbed by the presence of other parental pairs.

Defense of territory is not necessarily accompanied by active struggle. Loud singing and threatening poses are usually enough to drive away a competitor. However, if one of the parent partners dies, it is quickly replaced by a bird from among the individuals that have not yet settled. Thus, territorial behavior can be considered a regulator that prevents both overpopulation and underpopulation.

A striking example of intraspecific competition that everyone could see in the forest? so-called self-thinning in plants. This process begins with the seizure of territory: for example, somewhere in an open place, not far from a large spruce tree that produces many seeds, several dozen seedlings appear? small Christmas trees. Is the first task completed? the population has grown and taken over the territory it needs to survive. Thus, territoriality in plants occurs differently than in animals: a site is occupied not by an individual, but by a group of them (part of the population).

Young trees grow, simultaneously shading and oppressing those under their crowns herbaceous plants(this is already an example of interspecific competition (see here)). Over time, an inevitable difference in growth appears between trees: some, which are weaker, lag behind, others? are overtaking. Because spruce? is a very light-loving plant (its crown absorbs almost all the incident light), then weaker young fir trees begin to experience more and more shading from the side tall trees and gradually dry out and die.

In the end, after many years in a clearing, out of hundreds of fir trees, only two or three trees remain (the strongest individuals of the entire generation). But there are no longer any grasses, the roots of the trees are spread throughout the clearing, and nothing prevents the lush coniferous crown from being pulled even higher towards the sun.

In some species, intraspecific regulation begins long before serious competition is detected. Thus, a high density of animals is a depressive factor that reduces the rate of reproduction of this population even with an abundance of food resources. (See Part II. Population ecology? deecology.)

Intraspecific competition is an important regulator controlling population growth. Thanks to this competition, a certain relationship arises between population density and the rate of death (mortality) or reproduction (fertility) of individuals. This, in turn, leads to the emergence of a certain connection between the number of parental pairs and the number of offspring they produce. Such connections act as regulators of population fluctuations...

Competitive interaction may concern space, food, light, shelter and all other environmental resources. The outcome of competition is of great interest not only for ecologists studying the processes of formation of the composition of natural communities, but also for evolutionists studying the mechanisms of natural selection.

For a species under competitive pressure, this means that its population density, as well as the role it plays in the natural community, will decrease or be regulated by the effects of competition.

Distinguish between competition intraspecific And interspecific. Both intraspecific and interspecific competition can play a large role in the formation of species diversity and population dynamics of organisms.

Intraspecific competition is the struggle for the same resources that occurs between individuals of the same species; this is an important factor in the self-regulation of population numbers.

In some organisms (birds, fish and other animals), under the influence of intraspecific competition for space, a type of behavior has formed, which is called territoriality. For example, in birds, at the beginning of the breeding season, the male identifies a habitat - a territory. He protects her from invasion by males of the same species.

Intraspecific competition regulates population growth.

Interspecific competition extremely widespread in nature, since it is rare that a species does not experience at least a little pressure from organisms of other species.

The forms of competition between species can be very different: from fierce struggle to almost peaceful coexistence. But, as a rule, of two species with the same ecological needs, one necessarily displaces the other.

For example, in European 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, the relatively small red Prussian cockroach replaced the larger black cockroach only because it was able to better adapt to the specific conditions of human housing.

Having conducted studies of interspecific competition in laboratory experiments on the joint keeping of two species of ciliates with similar nutritional patterns, our domestic scientist G.F. Gauze came to the conclusion that long-term coexistence of species with similar ecological requirements is impossible. This conclusion is called competitive exclusion rules.

In nature, only those competing species that manage to diverge at least slightly in their environmental requirements coexist. So, in African savannas Ungulates use pasture food in different ways: zebras pluck the tops of grasses, wildebeests eat plants of certain types, 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 searching for prey on different parts tree.

Competitive relations as an environmental factor play an extremely important role in the formation species composition and regulation of the number of species in a community.

It is clear that severe competition can only be found between species occupying similar ecological niches. Typically this is related species. It is known that organisms leading a similar lifestyle and having a similar structure live in different places, and if they live nearby, they use different resources and are active in different time. Their ecological niches seem to diverge in time or space.

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, as well as in small details external structure. Changes in the structure of organisms that accompany the processes of divergence of their ecological niches allow us to say that interspecific competition is one of the the most important factors evolutionary transformations.

The role of competition in habitat partitioning can be illustrated with a simple diagram. In the presence of competition with closely related or ecologically similar species the habitat zone is reduced to optimal boundaries. That is, the species spreads in the most favorable zones for it, where it has advantages over its competitors. 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 may play an important role in the formation of appearance 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.