Competition between plant species. Competition as a mechanism for the emergence of ecological diversity

“Ecological pyramid of energy” - Physical Education Minute. Energy transfers to each subsequent food level from the previous one. In a simplified ecological pyramid, the ratio of individuals of different trophic levels of the ecosystem is 1: 3: 4: 5: 17. Pyramid of numbers and biomass. Flows of matter and energy in an ecosystem. In the ocean, the biomass of living organisms is represented. Length food chain. The ocean contains the biomass of living organisms. The higher the level, the lower the total biomass and number of organisms.

“Cycle of matter and energy” - The mass of the dolphin is 50 kg. How does the circulation of substances occur in biogeocenosis? Some areas of the ocean. Most of the energy contained in food is released. Growth per unit of time. Ecological pyramid of biomass. Food chains are divided into two types. Producers (first level) have a 50% increase in biomass. Flow of energy and circulation of substances in ecosystems. The circulation of substances and the flow of energy. Number of individuals at each nutritional level.

“Types of relationships between organisms” - Continuous improvement. Phoric relations. Centipedes. The commensal lives inside the host. Cannibalism. Sinoikia. Forms of relationships between organisms. Commensalism in animals. Paroikia is a type of commensalism. Sinoikia - tenancy. Interpopulation relationships. Stuck. Nutcracker bird. Epioikia is called epiphytism. Predation is a type of antibiosis. Forms of biotic connections.

“Energy in Ecosystems” - Position. Enzyme in nature. Structure of chlorophyll. Chemosynthesis. Flow of energy through living organisms. Biological cycle. Photomorphogenesis. Components of the photosynthetic apparatus. Optical absorption spectrum of chlorophylls. Absorption of light quanta. Molecules. Education. The meaning of photosynthesis. Converting energy into animal cell. Energy in ecosystems. Productivity is provided by plant photosynthesis.

“Ecological pyramid” - Purpose of the study: To prove that the number of individuals included in the food chain is consistently decreasing. Ecological pyramid. Research on the topic: “Ecological pyramid.”

Competitive relations.

If in an ecological system two or more species (populations) with similar ecological requirements live together, a negative type of relationship arises between them, which is called competition (? ?). IN in a general sense The word "competition" means clash, 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. For example, all plants compete (compete) for light, moisture, soil nutrients and to expand 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, rarely occurring species, the ecological significance of competition will be negligible: 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 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 important factor 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 defends 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 intraspecific competition, which 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 suppressing herbaceous plants located under their crowns (this is 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 grass anymore, 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 relationship between the number of parental pairs and the number of offspring they produce. Such connections act as regulators of population fluctuations...

Not all relationships between populations are equal in environmentally: some of them are rare, others are optional, and others, such as competition, are the main mechanism for the emergence of ecological diversity.

Competition(from Latin concurrere - collide) - interaction in which two populations (or two individuals) in the struggle for the conditions necessary for life influence each other negatively, i.e. mutually oppress each other.

It should be noted that competition can also manifest itself when a resource is sufficient, but its availability is reduced due to the active opposition of individuals, which leads to a decrease in the survival rate of competing individuals.

Organisms that can potentially use the same resources are called competitors. Plants and animals compete with each other not only for food, but also for moisture, living space, shelter, nesting sites - for everything on which the well-being of the species may depend.

Intraspecific competition

If competitors belong to the same species, then the relationship between them is called intraspecific competition. Competition between individuals of the same species is the most intense and severe in nature, since they have the same needs for environmental factors. Intraspecific competition can be observed in penguin colonies, where there is a struggle for living space. Each individual maintains its own section of territory and is aggressive towards its neighbors. This leads to a clear division of territory within the population.

Intraspecific competition almost always occurs at one stage or another in the existence of a species; therefore, in the process of evolution, organisms have developed adaptations that reduce its intensity. The most important of them are the ability to disperse descendants and protect the boundaries of an individual site (territoriality), when an animal defends its nesting site or a specific area. Thus, during the breeding season of birds, the male guards certain territory, which, except for its female, does not allow any individual of its species. The same picture can be observed in some fish.

Interspecific competition

If competing individuals belong to different species, then this interspecific competition. The object of competition can be any resource whose reserves in a given environment are insufficient: a limited distribution area, food, a site for a nest, nutrients for plants.

The result of competition may be the expansion of the distribution area of ​​one species due to the reduction in numbers or extinction of another. An example is an active extension with late XIX V. range of the long-clawed crayfish, which gradually captured the entire Volga basin and reached Belarus and the Baltic states. Here he began to displace related species- broad-clawed crayfish.

Competition can be quite intense, for example in the fight for nesting territory. This type is called direct competition. In most cases, these conflicts occur between individuals of the same species. However, often the competitive struggle is outwardly bloodless. For example, many predatory animals that compete for food are not directly affected by other predators, but indirectly, through a decrease in the amount of food. The same thing happens in the plant world, where, during competition, some influence others indirectly, through interception nutrients, sun or moisture. This type is called indirect competition.

Competition is one of the reasons that two species, slightly different in the specifics of nutrition, behavior, lifestyle, etc., rarely coexist in the same community. Studies of the causes and consequences of interspecific competition have led to the establishment of special patterns in the functioning of individual populations. Some of these patterns have been elevated to the rank of laws.

Studying the growth and competitive relationships of two species of ciliated ciliates, Soviet biologist G.F. Gause conducted a series of experiments, the results of which were published in 1934. Two species of ciliates - Paramecium caudatum and Paramecium aurelia - grew well in monoculture. Their food was bacterial or yeast cells growing on regularly added oatmeal. When Gause placed both species in the same container, each species initially increased in number rapidly, but over time P. aurelia began to grow at the expense of P. caudatum until the second species disappeared completely from the culture. The period of disappearance lasted about 20 days.

Thus, G.F. Gause formulated law (principle) of competitive exclusion, which states: two species cannot exist in the same habitat (in the same area) if their ecological needs are identical. Therefore, any two species with identical ecological needs are usually separated in space or time: they live in different biotopes, in different forest layers, live in the same body of water at different depths, etc.

An example of competitive exclusion is the change in the numbers of roach, rudd and perch when they live together in lakes. Over time, roach displaces rudd and perch. Research has shown that competition affects the fry stage when the feeding spectra of the juveniles overlap. At this time, roach fry turn out to be more competitive.

In nature, species competing for food or space often avoid or reduce competition by moving to another habitat with acceptable conditions, or by switching to more inaccessible or difficult-to-digest food, or by changing the time (place) of foraging. Animals are divided into diurnal and nocturnal (hawks and owls, swallows and bats, grasshoppers and crickets, various types fish that are active at different times of the day); lions hunt larger animals, and leopards hunt smaller ones; For tropical forests The distribution of animals and birds by tiers is characteristic.

An example of the division of living space is the division of food spheres between two species of cormorant - great and long-nosed. They live in the same waters and nest on the same cliffs. Observations have shown that the long-billed cormorant catches fish swimming in upper layers water, while the great cormorant forages mainly at the bottom, where it catches flounder and hip invertebrates.

Spatial separation can also be observed among plants. Growing together in one habitat, plants extend their root systems to different depths, thereby separating the areas of absorption of nutrients and water. The depth of penetration can vary from a few millimeters in root-litter plants (such as wood sorrel) to tens of meters in large trees.

IN natural communities animals of one and different types 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 They 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.

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 resource consumption plays a special role in critical periods their shortage (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 both cases when 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 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 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 soils are formed. 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 that can mass reproduction destroy most of the grass. 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 with more individuals has a greater chance of winning the competition and, accordingly, will more actively reproduce “its army” (the so-called mass effect).

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 consuming by biochemical means, producing when eating increases toxic substances, 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 in the relationship “phytophage - plant” tradeoff can be traced: the faster the plant grows (and, accordingly, the faster better conditions for its growth), the better it is eaten, and vice versa, the slower the plant grows, the less attractive it is 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 the spring and, as a result, to the destruction of the steppe ecosystem. Instead of steppe plants (feather grass, fescue) they develop abundantly meadow species and shrubs. U northern border In 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. Ecological balance between predators and prey is maintained special mechanisms, excluding the complete extermination of 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 in different times year, which allows it to camouflage itself in the foliage in summer, and in winter against the background white 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.