Types of interspecific relationships in biocenosis. Connections in the biocenosis
Various forms of biotic relationships into which certain types of organisms enter into a biocenosis (competition, commensalism, mutualism, predator-prey, etc.) determine the basic conditions of their life in the community, the possibility of obtaining food and conquering new living space.
Direct and indirect interspecific relationships based on the significance of the living space of organisms that have species to occupy a certain position in the biogeocenosis are divided into the following types of connections: trophic, topical, phoric, factory and others .
Trophic connections observed when one species feeds on another species, either living individuals, or their remains, or products of their vital activity (birds - worms, wolf - hare, beetle - ungulate excrement, etc.).
Phoric connections is the participation of one type of organism in the spread of another. Animals and birds usually act as transport workers. The transfer of seeds, spores, and pollen by animals is called zoochory . The transfer by animals of other animals is called phoresia . Usually the transfer is carried out with the help of special organs. Animal phoresia is widespread among small arthropods. For example, the transfer of various microscopic mites to other animals, which is one of the methods of passive dispersal of small organisms. It is characteristic of those species for which transfer from one biotope to another is vital for the preservation or prosperity of the species. Thus, many flying insects who visit accumulations of rapidly decomposing organic remains and remains (animal corpses, rotting heaps of plants, etc.) carry various mites that move in this way from one accumulation of food materials to another. Mites and bacteria contribute to more intensive decomposition of organic matter.
Factory connections- this is a type of biotic relationship into which a species enters, using excretory products or remains (residues), or even living individuals of another species for its structures (fabrications). For example, birds use tree branches, leaves, animal hair, fluff to build their nests; some insects lay their eggs in the body of another insect, especially predators, etc. In nature, there are other interspecific connections between organisms. Which are listed below.
Predation─ this type of relationship when one species lives at the expense of another, causing damage to it. These relationships are based on food connections (prey ─ predator). For example, a wolf and a herbivore or other predator suitable for food for the next predator.
Mutualism(or symbiosis) is a mutually beneficial cohabitation of different types of organisms. For example, nitrogen-fixing bacteria settle on the roots of a legume plant. The plant provides energy to the bacteria in the form of carbohydrates, and the bacteria, in turn, provide the plant with environmentally friendly nitrogen fixed from the atmospheric air. To fix each gram of nitrogen, bacteria expend energy equal to 10 g of carbohydrates (17 J). Sometimes beneficial organisms living inside another organism that have developed their own mutually beneficial relationships (for example, bacteria in the stomach of ruminants that decompose lignin, for which the animal gives them shelter and food in the form of biomass and its stomach) (Fig. 3.5).
Commensalism(neutralism, freeloading) ─ this is a relationship based on food connections, in which one of the species benefits, but for the other they are indifferent. Usually small organisms, settling near a large animal (for example, dung beetles or various small birds), find food and a place to live.
Amensalism(allelopathy) - a relationship in which negative living conditions arise for one or more populations as a result of intoxication of the habitat (plants secrete toxins that are harmful to plants of another species, the same toxins are secreted by bacteria and fungi, insects). Ecological law of life (according to Yu.N. Kurazhkovsky): Each type of organism, absorbing the substances it needs from the environment and releasing waste of its vital activity into it, changes it in such a way that the environment becomes unsuitable for its existence.
Among representatives of the same species of animals there is such a phenomenon as cannibalism , that is, eating their own kind. It is most developed in predatory fish: pike, perch, cod, saffron cod, etc. It is sometimes found in higher animals and some insects under unfavorable living conditions.
In nature, two types of optimal distribution of the species are noted: physiological and synecological .
Physiological optimum this is a combination of all types of abiotic factors favorable for a species, in which the fastest rates of growth and reproduction of organisms (heat, moisture, food) are possible.
Synecological optimum this is a biotic environment when a species (organism) experiences the least pressure from its enemies, competitors, which allows it to successfully live and reproduce (flock, herd, community, etc.).
The boundary between biocenoses is rarely clearly defined, since neighboring biocenoses gradually transform into one another. As a result of this there is border (edge) zone , characterized by special conditions.
Plants and animals characteristic of each of the adjoining communities penetrate into neighboring territories, creating a specific “edge”, a border strip - an ecotope. It seems to intertwine the typical conditions of neighboring biocenoses, which promotes the growth of plants characteristic of both biocenoses. In turn, this attracts a variety of animals here due to the relative abundance of food. This is how the edge effect of increasing the diversity and density of organisms arises on the outskirts (edges) of neighboring and transitional belts between them. On the “edges” there is a faster change of vegetation than in a stable cenosis.
Biocenosis and biotope (space with more or less homogeneous conditions that the biocenosis occupies) cannot be separated from each other, this is evidenced by a number of principles of their relationship.
1. The principle of diversity (A. Tineman): the more diverse the biota conditions, the more species there are in the biocenosis (tropical forest).
2. Principle of deviation of conditions (A. Tineman): the higher the deviations of biota conditions from the norm, the poorer in species and the more specific the biocenosis, and the higher the number of individuals of its individual species. This principle is manifested in extreme biotopes. They have few species, but the number of individuals in them is usually large, and there may even be an outbreak of mass reproduction of organisms.
3. The principle of smooth changes in the environment (G.M. Franz): the smoother the environmental conditions in a biotope change and the longer it remains unchanged, the richer the biocenosis is in species and the more balanced and stable it is. The practical significance of the principle is that the more and faster the transformation of nature and biotope occurs, the more difficult it is for species to have time to adapt to this transformation, and consequently, biocenoses are depleted of them.
Mutual complementarity of parts of the biocenosis. In communities (biocenoses) only those species coexist that complement each other in the use of habitat resources, that is, they share ecological niches among themselves. For example, layering in a phytocenosis or decomposition by decomposer microorganisms - some species “specialize” in the decomposition of fiber, others in the decomposition of proteins, others in sugars, etc. Mutual complementarity of species: some create, others destroy - the basis of biological cycles.
The basis for the sustainability of biocenoses is their complex species diversity.
Interspecific relationships in specific biocenoses are formed on the basis of complex forms of interaction between populations of different species. There are nine main types of interactions (Table 5.1).
Neutrality is a type of biotic relationship in which species are not directly related to each other, but depend on the state of the community as a whole.
Competition is the relationship between ecologically similar species that exist at the expense of common resources that are in short supply. Competition is the only form of biotic relationships that negatively affects both interacting species. There are two forms of competitive relations: direct competition, or inferential competition, and indirect competition, indirect, or exploitative conference. With direct competition between species in a biocenosis, directed antagonistic relationships arise (fights, chemical suppression of a competitor), leading to mutual oppression of competing species. In the case of indirect competition, one of the species monopolizes a resource, thereby worsening the conditions of existence of another species that needs the same resource. In this case, no direct forms of active influence of species on each other are observed. In general, as a result of competitive interactions, regardless of the form of struggle for common resources, some species are competitively replaced by others, which has a significant impact on the structure of biocenoses.
Amensalism is a form of interaction that leads one of the interacting species to negative consequences, while the other receives neither harm nor benefit from the interaction. For example, light-loving herbaceous plants growing under the crown of spruce experience oppression as a result of strong shading, while for the spruce itself the proximity to these plants may be absolutely indifferent.
Classification of biotic interactions between populations of two species (according to Yu. Odum, 1986)
Table 5.1
Interaction type |
General nature of interaction |
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Neutralism |
Neither population influences the other |
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Competition, direct interaction |
Direct mutual suppression of both types |
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Competition, interaction over resources |
Indirect suppression when there is a shortage of external resources |
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Amensalism |
Population 2 suppresses population 1, but is not itself negatively affected |
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Predation |
Predator 1 individuals are usually larger than prey 2 individuals |
7 Commensalism + 0 Population 1, the commensal, benefits from the union; population 2 this association is indifferent
Note: "O" means that the population is not affected; “+” means that the population benefits from the interaction (improved growth, survival, and other benefits to the population); “-” means that the population is negatively affected by the interaction (slower growth and deterioration of other characteristics).
In true predation, predators are characterized by hunting behavior: lying in wait or searching, pursuing, capturing, overcoming resistance, killing a specific prey individual. At the same time, prey extraction requires significant energy expenditure from the predator, since prey has a wide arsenal of adaptations to protect them from being eaten by predators. Adaptations of victims can be morphological (hard covers, thorns, thorns), behavioral (hiding, running away, active defense) or physiological (production of poisonous or repellent substances). The latter form of adaptation is quite widespread in the animal world and for some species represents the main way to reduce the press.
Gathering is characterized by searching for and simply collecting prey. At the same time, the size of the victims is much smaller than the size of the animals that feed on them, the number of food items is high and they are easily accessible. Gathering requires energy expenditure not to capture prey, but mainly to find food.
Grazing involves eating stationary food that is in relative abundance and does not require much effort to find.
Commensalism (from lat. com - together, mensa - meal) is a form of relationship in which one species (commensal) benefits from the relationship, and for another this relationship is indifferent, i.e. there is unilateral use of one species by another without causing harm to it. There are two forms of commensalism - freeloading and tenantry.
Freezing is a form of commensalism in which one species obtains food from the activities of another species.
For example, the relationship between lions and hyenas (commensals in this case), picking up the remains of prey left uneaten by lions.
Lodging is a form of commensalism in which one species uses the buildings or bodies of another species as shelter. Thus, in almost every burrow of a sea worm, in every shell of a bivalve mollusk, in the body of every sponge there are “uninvited guests” (for example, small crustaceans) that receive shelter here, but in turn do no harm or benefit to the owner. For example, fish, bivalves, polychaetes and crabs live as “guests” in the burrows of large marine worms; small crabs often live in the mantle cavity of oysters; The Mediterranean carp fish uses the body cavity of some species of sea cucumbers as a shelter. A huge number of species of arthropods live in bird nests and rodent burrows. Many commensals use one specific species as a host, others use different species. A number of species are so specialized in this way of life that they are not found outside their burrows. Permanent burrowing or nesting cohabitants are called nidicols.
Proto-cooperation is the interaction of two species in which both species receive benefits from interaction with each other, but are not completely dependent on each other. For example, a hermit crab attaches to its shell a representative of coelenterates, for example, an anemone, which masks and protects it (coelenterates have stinging cells), receiving food debris from the cancer and using it as a means of transportation. Neither crayfish nor coelenterates are completely dependent on each other and can exist separately.
Mutualism, or obligate symbiosis (from lat. mu tu u s- mutual obligatus - obligatory, non-applicable, from Greek. symbiosis- living together, cohabitation), - the mutually beneficial existence of two species, while they are completely dependent on each other, therefore, under natural conditions, neither of them can exist without the other. For example, the mutualistic relationship between ruminants (deer, cattle, antelope) and protozoa living in one of the four sections of the complex stomach of ruminants (in the rumen). Protozoa participate in the processing of rough plant feed, in turn receiving all the conditions for a prosperous existence. An example of a mutually beneficial mutualistic relationship is mycorrhiza (fungal root, from the Greek. miko- mushroom, chasuble- root), which is the mycelium (mycelium) of the fungus, which is in a mutualistic relationship with living plant roots. As in the case of nitrogen-fixing bacteria and legumes, fungi, when interacting with burrow tissue, entwining the root or penetrating inside, increase the plant's ability to extract minerals from the soil. In turn, the fungi receive the necessary products of the photosynthetic activity of the plant.
A striking example of a mutualistic relationship is the interaction between certain species of ants and a species of acacia in the tropics. Ants obtain food and shelter from the acacia tree by nesting at the base of the swollen thorns. Thanks to ants, acacia receives protection from herbivorous insects. If there are no ants on the acacia (this sometimes occurs in nature when trees are treated with insecticides), then the acacia is immediately attacked by leaf-eating insects. As a result, the tree loses its leaves and often dies.
Lichens are a mutualistic relationship between certain types of fungi and algae, as a result of which the fungus receives organic substances from the algae, in turn supplying the algae with water and inorganic substances. The functional and morphological connection between the fungus and algae is so close that their union can be considered as a special single organism, unlike any of its components.
Rice. 5.1.
A- penetration of fungi into algae cells in primitive species of lichens; b, c - harmonious mutually beneficial existence of algae and fungus in evolutionarily more developed species of lichens
In evolutionarily more developed species of lichens, the mycelium of the fungus (its hyphae) penetrates the algae cells, but both organisms live in complete harmony. In 1879, the German botanist and microbiologist Heinrich Anton de Bary proposed the term symbiosis (from the Greek “symbiosis” - joint life, cohabitation) to refer to various forms of coexistence of different types of living organisms. This term was unanimously accepted by the general scientific community. Later, in 1906, the German zoologist Oskar Hertwig (1906) narrowed the scope of the term “symbiosis”, using it only to refer to a mutually beneficial relationship for both partners. In this erroneous interpretation, the concept of “symbiosis” is firmly rooted in Russian literature. In modern biology and ecology, the term “symbiosis” is used in its original broad concept: symbiosis is any form of cohabitation with the formation of a system of relationships; Mutualism in this case means a variant of symbiosis in which these mutually beneficial relationships are constant (obligate symbiosis).
Various interspecific relationships arise between organisms in biocenoses. According to the classification of the famous Russian zoologist V.N. Beklemishev, there are four types of biotic relationships in communities.
1. Trophic connections- food connections in which one species feeds on another: either living individuals, or their dead remains, or waste products. Animals are divided into several ecological groups based on the type of food they eat: predators, or zoophagi(feed on animal food); saprophages(feed on rotting substances); necrophages(feed on animal corpses); coprophagous(feed on excrement); phytophages(eat plant foods). Among the phytophages there are phyllophagous(feed on leaves) carpophagous(feed on fruits) xylophages(feed on wood) rhizophages(feed on roots). According to the degree of selectivity of food objects, three groups of organisms are distinguished: 1) monophagous- monovorous, 2) oligophages- limited eaters, 3) polyphages- polyphagous.
2. Topical connections- relationships related to habitat. For example, competition for feeding, breeding, and nest-building sites.
3. Phoric connections- relationships associated with the participation of one species in the distribution of another (from the word phoresia- transfer by one animal to another). For example, sticky fish attach themselves to sharks or turtles and use them as “transport.” Gamasid mites often use various insects in this way. The seeds of many plants are carried by various animals.
4. Factory connections- relationships in which one species uses other organisms or their remains for its structures. Birds use various plants, fluff, wool and other building materials of biological origin to build nests.
According to another classification, six main types of ecological relationships are possible between organisms in biocenoses (for each type of relationship the corresponding designations are given):
1) mutualism- mutually beneficial relationships between species (+; +). Examples of mutualistic, or symbiotic, relationships:
Lichens (symbiosis of fungi and algae; mushrooms receive nutrients, algae receive water and minerals);
Entomophilous plants are insect pollinators;
Intestinal endosymbionts (bacteria, protozoa) - host animals (ruminant mammals, termites);
Leguminous plants - nodule bacteria (nitrogen fixers);
Trees are mushrooms;
2) commensalism- unilateral use by one species of another without harm to the latter (+; 0). This relationship is where the activities of one species provide food or shelter to another. Examples of commensalism:
Sticky fish on sharks or turtles;
- settlement of epiphytic plants on tree bark;
- Gamasid mites on various insects;
- Egyptian heron - cattle (feeds on insects that are scared away by cattle);
- bumblebee flies in bumblebee nests (eat various garbage);
3) neutralism- independent existence of species, in which species do neither harm nor benefit to each other (0; 0);
4) amensalism- interaction of species in which one receives neither harm nor benefit, but for the other this relationship is negative. Light-loving plants growing under spruce experience oppression, but for spruce this relationship is indifferent (-; 0);
5)competition- a form of ecological relationships that negatively affects both interacting species (-; -). Competition arises between species for various resources (trophic, topical);
For normal existence, predators need adaptations that allow them to successfully hunt prey. Therefore, in populations of predators, natural selection will increase the efficiency of searching, catching and eating prey. At the same time, in a population of prey, selective advantage, as a rule, will be given to those individuals that are more successful in avoiding predators. Long-term coevolution (joint evolution) of predator and prey improves the adaptations of the species included in this pair. This includes both complex morphological and behavioral adaptations.
Having worked through these topics, you should be able to:
- Give definitions: “ecology”, “ecological factor”, “photoperiodism”, “ecological niche”, “habitat”, “population”, “biocenosis”, “ecosystem”, “producer”, “consumer”, “decomposer”, "succession", "agrocenosis".
- Give examples of photoperiodic reactions of plants and, if possible, animals.
- Explain the difference between a population's habitat and its niche. Give examples for each of these concepts.
- Comment on Shelford's law and be able to construct a graph of the dependence of organisms on abiotic environmental factors.
- Describe an example of a successful biological pest control method.
- Explain the causes of the population explosion and possible consequences, as well as the significance of the decrease in fertility, which, as a rule, follows a decrease in mortality.
- Construct a food chain diagram; correctly indicate the traffic level of each component of a given ecosystem.
- Construct a diagram of the simple cycle of the following elements: oxygen, nitrogen, carbon.
- Describe the events that occur when the lake becomes overgrown; after deforestation.
- Indicate the differences between agrocenosis and biocenosis.
- Talk about the meaning and structure of the biosphere.
- Explain how agriculture, fossil fuel use, and plastic production contribute to environmental pollution and suggest measures to prevent it.
Ivanova T.V., Kalinova G.S., Myagkova A.N. "General Biology". Moscow, "Enlightenment", 2000
- Topic 18. "Habitat. Environmental factors." Chapter 1; pp. 10-58
- Topic 19. "Populations. Types of relationships between organisms." chapter 2 §8-14; pp. 60-99; Chapter 5 § 30-33
- Topic 20. "Ecosystems." chapter 2 §15-22; pp. 106-137
- Topic 21. "Biosphere. Cycles of matter." Chapter 6 §34-42; pp. 217-290
The basis for the emergence and existence of biocenoses is the relationship of organisms, their connections into which they enter into each other, inhabiting the same biotope. These connections determine the basic living conditions of species in a community, the possibilities of obtaining food and conquering new space.
Classifications of biocenotic relations can be built using different principles. One popular approach is to assess the possible the result of contact between two individuals. For each of them, the result is accepted as positive, negative or neutral. Combinations of results for 2 out of 3 possible ones give a formal scheme of 6 options, which forms the basis for this classification.
0 0 Neutralism – cohabitation of two species in the same territory, which has neither positive nor negative consequences for them. For example, squirrels and moose do not have significant effects on each other.
+ + Protocooperation – mutually beneficial, but not obligatory, coexistence of organisms, from which all participants benefit. For example, hermit crabs and sea anemones. A coral sea anemone polyp, which has stinging cells that secrete poison, can settle on the shell of a crayfish. The sea anemone protects the crayfish from predatory fish, and the hermit crab, by moving, contributes to the spread of the sea anemones and an increase in their feeding space.
+ + Mutualism – mutually beneficial cohabitation, when either one of the partners or both cannot exist without a cohabitant. A classic example of a symbiotic relationship is lichens, representing the close coexistence of a fungus and algae. The fungus receives substances assimilated by algae. Algae obtain water and minerals from fungal hyphae. Another example is herbivorous ungulates and cellulose-degrading bacteria. Cellulose-degrading bacteria live in the stomach and intestines of herbivorous ungulates. They produce enzymes that break down cellulose, so they are essential for herbivores who do not have such enzymes. Herbivorous ungulates, for their part, provide bacteria with nutrients and a habitat with optimal temperature, humidity, etc. It is known that many species of trees coexist with mycorrhizal fungi, and legumes with nodule bacteria that fix molecular nitrogen in the air.
0 Commensalism – relationships in which one of the partners benefits from cohabitation, and the other is indifferent to the presence of the first. There are two forms of commensalism: synoikia (lodging) And trophobiosis (freeloading). An example of synoikia is the relationship between some sea anemones and tropical fish. Tropical fish take refuge from predators among the tentacles of sea anemones, which have stinging cells. An example of trophobiosis is the relationship between large predators and scavengers. Scavengers, such as hyenas, vultures, and jackals, feed on the remains of victims killed and partially eaten by large predators - lions.
+ – Predation – a relationship in which one of the participants (the predator) kills the other (the prey) and uses him as food. For example, wolves and hares. The state of the predator population is closely related to the state of the prey population. However, when the population size of one prey species decreases, the predator switches to another species. For example, wolves can use hares, mice, wild boars, roe deer, frogs, insects, etc. as food.
A special case of predation is cannibalism – killing and eating one's own kind. It is found, for example, in rats, brown bears, and humans.
– – Competition – relationships in which organisms compete with each other for the same environmental resources when the latter are scarce. Organisms may compete for food resources, sexual partners, shelter, light, etc. There are direct and indirect, interspecific and intraspecific competition.
Indirect (passive) competition – consumption of environmental resources needed by both species. Direct (active) competition – suppression of one species by another.
Intraspecific competition is competition between individuals of the same species, interspecific – between individuals of different species. Interspecific competition occurs between individuals of ecologically similar species. Its result can be either mutual adjustment two types, or substitution a population of one species of a population of another species that moves to another place, switches to another food, or goes extinct.
Competition leads to natural selection in the direction of increasing ecological differences between competing species and the formation of different ecological niches by them.
0 – Amensalism – relationships in which one organism influences another and suppresses its vital activity, while it itself does not experience any negative influences from the suppressed one. For example, spruce and lower tier plants. The dense crown of spruce prevents the penetration of sunlight under the forest canopy and suppresses the development of plants in the lower tier. A special case of amensalism is allelopathy (antibiosis) – the influence of one organism on another, in which waste products of one organism are released into the external environment, poisoning it and making it unsuitable for the life of another. Allelopathy is common in plants, fungi, and bacteria. For example, the penicillium fungus produces substances that suppress the activity of bacteria. Penicill is used to obtain penicillin. This is the first antibiotic discovered in medicine.
Mutualistic and competitive relationships represent the basic essence of intraspecific relationships.
Other classifications focus on other aspects of biotic relationships using different approaches. By classification by V.N.Beklemisheva, direct and indirect interspecific relationships By that meaning that they can have in the biocenosis, are divided into 4 types:
Trophic connections arise between species when one species feeds on another: living individuals, dead remains, waste products. Trophic connections can be direct or indirect. A direct connection is manifested when lions feed on live antelopes, hyenas feed on the corpses of zebras, dung beetles feed on the droppings of large ungulates, etc. An indirect relationship occurs when different species compete for the same food resource.