ecological niche- a set of all environmental factors within which the existence of a species in nature is possible. concept ecological niche is usually used in the study of the relationship of ecologically close species belonging to the same trophic level. The term "ecological niche" was proposed by J. Grinell (1917) to characterize the spatial distribution of species (i.e., the ecological niche was defined as a concept close to habitat).
Later, Ch. Elton (1927) defined an ecological niche as the position of a species in a community, emphasizing the particular importance of trophic relationships. Back in the late 19th and early 20th centuries, many researchers noticed that two species that are ecologically close and occupy a similar position in the community cannot coexist stably in the same territory. This empirical generalization was confirmed in the mathematical model of the competition of two species for one food (V. Volterra) and in the experimental works of G.F. Gause ( Gause principle).
Modern concept ecological niche formed on the basis of the ecological niche model proposed by J. Hutchinson (1957, 1965). According to this model, an ecological niche can be represented as a part of an imaginary multidimensional space (hypervolume), the individual dimensions of which correspond to the factors necessary for the normal existence of a species.
The divergence of ecological niches of different species through divergence occurs mainly due to confinement to different habitats, different food and different times of using the same habitat. Methods for estimating the width of the ecological niche and the degree of overlapping of ecological niches of various species have been developed. Liter: Giller P. Community structure and ecological niche. - M .: 1988 (according to BES, 1995).
In environmental modeling, the concept ecological niche characterizes a certain part of the space (abstract) of environmental factors, a hypervolume in which none of the environmental factors goes beyond the tolerance of a given species (population). The set of such combinations of values of environmental factors under which the existence of a species (population) is theoretically possible is called fundamental ecological niche.
Realized ecological niche name a part of the fundamental niche, only those combinations of factor values under which a stable or prosperous existence of a species (population) is possible. Concepts sustainable or prosperous existence require the introduction of additional formal restrictions in modeling (for example, mortality should not exceed the birth rate).
If, with a given combination of values of environmental factors, a plant can survive, but is not able to reproduce, then one can hardly speak of well-being or sustainability. Therefore, this combination of environmental factors refers to the fundamental ecological niche, but not to the realized ecological niche.
Outside the framework of mathematical modeling, of course, there is no such rigor and clarity in the definition of concepts. In modern ecological literature, four main aspects can be distinguished in the idea of an ecological niche:
1) spatial niche including a complex of favorable environmental conditions. For example, insectivorous birds of blueberry spruce live, feed and nest in different forest layers, which largely allows them to avoid competition;
2) trophic niche. It stands out especially because of the great importance of food as an environmental factor. The division of food niches in organisms of the same trophic level living together allows not only avoiding competition, but also contributes to a more complete use of food resources and, consequently, increases the intensity of the biological cycle of matter.
For example, the noisy population of "bird markets" creates the impression of a complete absence of any order. In fact, each bird species occupies a trophic niche strictly defined by its biological characteristics: some feed near the coast, others at a considerable distance, some fish at the surface, others at depth, etc.
The trophic and spatial niches of different species may overlap (remember: the principle of ecological duplication). Niches can be broad (non-specialized) or narrow (specialized).
3) multidimensional niche, or a niche as a hypervolume. The concept of a multidimensional ecological niche is associated with mathematical modeling. The whole set of combinations of values of environmental factors is considered as a multidimensional space. In this huge set, we are only interested in such combinations of values of environmental factors under which the existence of an organism is possible - this hypervolume corresponds to the concept of a multidimensional ecological niche.
4) functional idea of an ecological niche. This view complements the previous ones and is based on the functional similarity of a wide variety of ecological systems. For example, they talk about the ecological niche of herbivores, or small predators, or animals that feed on plankton, or burrowing animals, etc. The functional concept of the ecological niche emphasizes role organisms in an ecosystem and corresponds to the usual concept of "occupation" or even "position in society". It is in functional terms that they talk about environmental equivalents– species occupying functionally similar niches in different geographic regions.
“The habitat of an organism is the place where it lives, or the place where it can usually be found. ecological niche- a more capacious concept, including not only the physical space occupied by a species (population), but also the functional role of this species in the community (for example, its trophic position) and its position relative to the gradients of external factors - temperature, humidity, pH, soil, etc. other conditions of existence. These three aspects of ecological niche are conveniently referred to as spatial niche, trophic niche, and multidimensional niche, or niche as hypervolume. Therefore, the ecological niche of an organism depends not only on where it lives, but also includes the total amount of its environmental requirements.
Species that occupy the same niche in different geographical areas are called environmental equivalents"(Yu. Odum, 1986).
V.D. Fedorov and T.G. Gilmanov (1980, pp. 118-127) note:
“The study of realized niches by describing the behavior of the well-being function on a section of their straight lines and planes corresponding to some selected environmental factors is widely used in ecology (Fig. 5.1). At the same time, depending on the nature of the factors that correspond to the considered particular function of well-being, one can distinguish between “climatic”, “trophic”, “edaphic”, “hydrochemical” and other niches, the so-called private niches.
A positive conclusion from the analysis of particular niches can be the conclusion from the contrary: if the projections of particular niches on some (especially some) of the axes do not intersect, then the niches themselves do not intersect in a space of higher dimension. ...
Logically, there are three options for the mutual arrangement of niches of two types in the space of environmental factors: 1) separation (complete mismatch); 2) partial intersection (overlapping); 3) complete inclusion of one niche into another. ...
Separation of niches is a rather trivial case, reflecting the existence of species adapted to different ecological conditions. Of much greater interest are cases of partial intersection of niches. As mentioned above, the overlapping of projections even in several coordinates at once, strictly speaking, does not guarantee the actual overlapping of the multidimensional niches themselves. Nevertheless, in practical work, the presence of such intersections and data on the occurrence of species in similar conditions is often considered sufficient arguments in favor of overlapping species niches.
To quantitatively measure the degree of overlapping of niches of two types, it is natural to use the value of the ratio of the volume of the intersection of sets ... to the volume of their union. ... In some special cases, it is of interest to calculate the measure of intersection of niche projections.”
LEARNING TESTS FOR TOPIC 5
Ministry of Education and Science of the Russian Federation
Federal State Budgetary Educational Institution
higher professional education
"Siberian State Industrial University"
Department of Ecology
discipline: Social ecology
on the topic: "Ecological niche"
Completed:
Student gr. ERM-12
Belichenko Ya.V.
Checked:
Assoc. Dugin
Novokuznetsk
Introduction………………………………………………………..……………….…. 3
1. Ecological niche…………………………….…………………………........... 4
1.1. The concept of an ecological niche……………….…………………………. 4
1.2. Width and overlap of niches…………………….……………………. 5
1.3. Niche Evolution……………………………………….……………….…10
2. Aspects of ecological niche…………………………….……………….….….12
3. The modern concept of ecological niche……………..………...................... 13
Conclusion………………………………………….……………………………… 16
List of used literature………………………………….………...... 19
Introduction
In this paper, the topic "Ecological niches" is considered. An ecological niche is a place occupied by a species (more precisely, its population) in a community, a complex of its biocenotic relationships and requirements for abiotic environmental factors. This term was introduced in 1927 by Charles Elton. The ecological niche is the sum of factors for the existence of a given species, the main of which is its place in the food chain.
An ecological niche is a place occupied by a species in a community. The interaction of a given species (population) with partners in the community to which it belongs as a member determines its place in the cycle of substances due to food and competitive links in the biocenosis. The term "Ecological niche" was proposed by the American scientist J. Grinnell (1917). The interpretation of an ecological niche as the position of a species for the purpose of feeding one or more biocenoses was given by the English ecologist C. Elton (1927). Such an interpretation of the concept of ecological niche makes it possible to give a quantitative description of the ecological niche for each species or for its individual populations. To do this, the abundance of the species (number of individuals or biomass) is compared in the coordinate system with indicators of temperature, humidity, or any other environmental factor.
In this way, it is possible to single out the optimum zone and the limits of the deviations tolerated by the species - the maximum and minimum of each factor or set of factors. As a rule, each species occupies a certain ecological niche, for the existence in which it is adapted by the entire course of evolutionary development. The place occupied by a species (its population) in space (spatial ecological niche) is more often called a habitat.
Let's take a closer look at ecological niches.
ecological niche
Any kind of organisms is adapted for certain conditions of existence and cannot arbitrarily change the habitat, diet, feeding time, breeding place, shelter, etc. The whole complex of relations to such factors determines the place that nature has allocated to a given organism, and the role that it must play in the general life process. All this is combined in the concept of an ecological niche.
1.1. The concept of an ecological niche
An ecological niche is understood as the place of an organism in nature and the whole way of its life activity, its life status, fixed in its organization and adaptations.
At different times, different meanings were attributed to the concept of an ecological niche. At first, the word "niche" denoted the basic unit of distribution of a species within the space of an ecosystem, dictated by the structural and instinctive limitations of a given species. For example, squirrels live in trees, moose live on the ground, some bird species nest on branches, others in hollows, etc. Here the concept of an ecological niche is interpreted mainly as a habitat, or a spatial niche. Later, the term "niche" was given the meaning of "the functional status of an organism in a community." This mainly concerned the place of a given species in the trophic structure of the ecosystem: the type of food, the time and place of feeding, who is the predator for this organism, etc. This is now called a trophic niche. Then it was shown that a niche can be considered as a kind of hypervolume in a multidimensional space built on the basis of environmental factors. This hypervolume limited the range of factors in which a given species could exist (the hyperspace niche).
That is, in the modern understanding of the ecological niche, at least three aspects can be distinguished: the physical space occupied by an organism in nature (habitat), its relationship to environmental factors and living organisms adjacent to it (connections), as well as its functional role in the ecosystem. All these aspects are manifested through the structure of the organism, its adaptations, instincts, life cycles, life “interests”, etc. The right of an organism to choose its ecological niche is limited by rather narrow limits assigned to it from birth. However, its descendants can claim other ecological niches if they have undergone appropriate genetic changes.
1. General provisions. Living beings, both plants and animals, are many and varied. There is no doubt that this diversity and abundance of organisms is determined by environmental factors. Thus, each species occupies a strictly assigned place in the geographic space with a specific set of physical and chemical parameters. However, the position of a species depends not only on abiotic environmental factors, but also on the relationships of a given organism with other organisms, both within its own species and with representatives of other species. The wolf will not live in those geographic areas, even if the set of abiotic factors is quite acceptable for him, if there is no food resource for him here. Therefore, the place that a species occupies in a particular habitat must be determined not only by the territory, but also be associated with the need for food and the function of reproduction. Each of the species, as well as a specific organism, in a community (biocenosis) has its own time of stay and its place, which distinguish it from other species.
Thus, we meet with different concepts. First, this range species - the distribution of the species in geographic space (the geographical aspect of the species), secondly, species habitat(habitat or biotope) is the type of geographic space in terms of a set of physical and chemical parameters and (or) biotic characteristics where the species lives and, thirdly, ecological niche, implying something more than just the place where this species lives. A species can occupy a number of different habitats in different parts of its range.
The best and most accurate comparative definition of the ecological niche and environment was given by the French ecologists R. Wiebert and C. Lagler: Wednesday is the address where the given organism resides, while niche additionally indicates the type of his occupation in this place, his profession.
Some ecologists are more willing to use the term "habitat," which is almost synonymous with "habitat," and the two terms often overlap, but remember that "habitat" refers only to the space in which a species occurs. In this sense, this term is very close to the concept of the range of a species.
2. habitat. This is a piece of land or a reservoir occupied by a population of one species or part of it and having all the necessary conditions for its existence (climate, topography, soil, nutrients). The habitat of a species is a set of sites that meet its ecological requirements within the species range. Thus, a habitat is nothing but a component of an ecological niche. According to the breadth of the use of habitats, they distinguish stenotopic And eurytopic organisms, i.e. organisms that occupy specific spaces with a specific set of environmental factors, and organisms that exist in a wide range of environmental factors (cosmopolitans). If we are talking about the habitat of a community of organisms or the place of a biocenosis, then the term "biotope" is more often used. Location has another synonym ecotope– geographical space characterized by a specific set of environmental parameters. In this case, the population of any species living in a given space is called ecotype.
The term "habitat" can be applied both to specific organisms and to communities as a whole. We can point to a meadow as a single habitat for various herbs and animals, although both herbs and animals occupy different ecological niches. But this term should never replace the concept of "ecological niche".
Habitat can refer to a complex of interconnected some living and non-living characteristics of a geographic space. For example, the habitat of aquatic insects of the smooth bug and the float is shallow, vegetated areas of lakes. These insects occupy the same habitat, but have different trophic chains (smooth is an active predator, while float feeds on decaying vegetation), which distinguishes the ecological niches of these two species.
Habitat can also refer only to the biotic environment. This is how bacilli and bacteria live inside other organisms. Lice live in the hairline of the host. Some mushrooms are associated with a particular type of forest (boletus). But the habitat can also be represented by a purely physical-geographical environment. You can point to the tidal coast of the sea, where such a variety of organisms live. It can be a desert, and a separate mountain, dunes, a stream and a river, a lake, etc.
3. ecological niche concept, according to Y. Oduma, more capacious. Ecological niche, as shown by an English scientist C. Elton(1927), includes not only the physical space occupied by the organism, but also the functional role of the organism in the community. Elton distinguished niches as the position of a species in relation to other species in a community. Ch. Elton's idea that a niche is not a synonym for a habitat has received wide recognition and distribution. The trophic position, way of life, connections with other organisms, etc. are very important for the organism. and its position relative to the gradients of external factors as conditions of existence (temperature, humidity, pH, soil composition and type, etc.).
These three aspects of the ecological niche (space, the functional role of the organism, external factors) can be conveniently referred to as spatial niche(niche place) trophic niche(functional niche), in the understanding of Ch. Elton, and multidimensional niche(the whole volume and set of biotic and abiotic characteristics are taken into account, hypervolume). The ecological niche of an organism depends not only on where it lives, but also includes the total amount of its environmental requirements. The body not only experiences the action of environmental factors, but also makes its own demands on them.
4. The modern concept of ecological niche formed on the basis of the model proposed J. Hutchinson(1957). According to this model, an ecological niche is a part of an imaginary multidimensional space (hypervolume), individual dimensions of which correspond to the factors necessary for the normal existence and reproduction of an organism. Hutchinson's niche, which we will call multidimensional (hyperspace), can be described using quantitative characteristics and operated with it using mathematical calculations and models. R. Whittaker(1980) defines an ecological niche as the position of a species in a community, implying that the community is already associated with a particular biotope, i.e. with a certain set of physical and chemical parameters. Therefore, an ecological niche is a term used to denote the specialization of a population of a species within a community. Groups of species in a biocenosis with similar functions and niches of the same size are called guilds. Species that occupy the same niche in different geographical areas are called environmental equivalents.
5. Individuality and originality of ecological niches. No matter how close in habitat organisms (or species in general) are, no matter how close their functional characteristics in biocenoses are, they will never occupy the same ecological niche. Thus, the number of ecological niches on our planet is uncountable. Figuratively, one can imagine a human population, all individuals of which have only their own unique niche. It is impossible to imagine two absolutely identical people with absolutely identical morphophysiological and functional characteristics, including such as mental, attitude towards their own kind, an absolute need for the type and quality of food, sexual relations, norms of behavior, etc. But the individual niches of different people can overlap in certain ecological parameters. For example, students can be linked by one university, specific teachers, and at the same time, they can differ in their behavior in society, in the choice of food, biological activity, etc.
6. Measuring ecological niches. To characterize a niche, two standard measurements are usually used - niche width And niche overlap with neighboring niches.
Niche width refers to gradients or the range of some environmental factor, but only within a given hyperspace. The width of a niche can be determined by the intensity of illumination, by the length of the trophic chain, by the intensity of the action of some abiotic factor. The overlapping of ecological niches means overlapping along the width of niches and overlapping of hypervolumes.
7. Types of ecological niches. There are two main types of ecological niches. First, this fundamental(formal) niche - the largest "abstract inhabited hypervolume”, where the action of environmental factors without the influence of competition ensures the maximum abundance and functioning of the species. However, the species experiences constant changes in environmental factors within its range. In addition, as we already know, an increase in the action of one factor can change the relation of a species to another factor (a consequence of Liebig's law), and its range can change. The action of two factors at the same time can change the attitude of the species to each of them specifically. There are always biotic restrictions (predation, competition) within ecological niches. All these actions lead to the fact that in reality the species occupies an ecological space that is much smaller than the hyperspace of the fundamental niche. In this case, we are talking about realized niche, i.e. real niche.
8 . Principle VanderMeer And Gause. J.H. Vandermeer (1972) greatly expanded the concept of Hutchinson's realized niche. He came to the conclusion that if N interacting species coexist in a given particular habitat, then they will occupy completely different realized ecological niches, the number of which will be equal to N. This observation is called the Vandermeer principle.
Competitive interaction can concern both space, biogenic elements, the use of light (trees in the forest), and the process of fighting for a female, for food, as well as dependence on a predator, susceptibility to disease, etc. Usually, the toughest competition is observed at the interspecific level. It can lead to the replacement of a population of one species by a population of another species, but it can also lead to an equilibrium between two species (usually this the balance of nature is established in the predator-prey system). Extreme cases are the displacement of one species by another outside the given habitat. There are cases when one species displaces another in the trophic chain and forces it to switch to the use of other food. Observation of the behavior of closely related organisms with a similar way of life and similar morphology shows that such organisms try never to live in the same place. This observation was made Joseph Grinell in 1917-1928, who studied the life of California mockingbirds. Grinell actually introduced the concept "niche", but did not introduce into this concept the distinction between niche and habitat.
If closely related organisms live in the same water and in the same place, then they will either use different food resources or lead an active lifestyle at different times (night, day). This ecological separation of closely related species is called principle of competitive exclusion or Gause principle named after the Russian biologist who experimentally demonstrated the operation of this principle in 1932. In his conclusions, Gause used Elton's concept of the position of a species in a community depending on other species.
9. niche space. The ecological niches of species are more than the relation of a species to a single environmental gradient. Many signs or axes of multidimensional space (hypervolume) are very difficult to measure or cannot be expressed by linear vectors (for example, behavior, addiction, etc.). Therefore, it is necessary, as rightly noted by R. Whittaker (1980), to move from the concept of the niche axis (remember the width of the niche in terms of one or more parameters) to the concept of its multidimensional definition, which will reveal the nature of species relationships with their full range of adaptive relationships .
If a niche is a "place" or "position" of a species in a community according to Elton's concept, then it is right to give it some measurements. According to Hutchinson, a niche can be defined by a number of environmental variables within a community to which a species must be adapted. These variables include both biological indicators (for example, food size) and non-biological ones (climatic, orographic, hydrographic, etc.). These variables can serve as axes along which a multidimensional space is recreated, which is called ecological space or niche space. Each of the species can adapt or be resistant to some range of values of each variable. The upper and lower limits of all these variables delineate the ecological space that a species can occupy. This is the fundamental niche in Hutchinson's understanding. In a simplified form, this can be imagined as an "n-sided box" with sides corresponding to the stability limits of the view on the axes of the niche.
By applying a multidimensional approach to the space of a community niche, we can find out the position of species in space, the nature of the response of a species to exposure to more than one variable, the relative sizes of niches.
One of the main concepts in modern ecology is the concept of an ecological niche. For the first time, zoologists started talking about an ecological niche. In 1914, the American naturalist zoologist J. Grinnell and in 1927 the English ecologist C. Elton used the term "niche" to define the smallest unit of distribution of a species, as well as the place of a given organism in the biotic environment, its position in food chains.
The generalized definition of an ecological niche is the following: this is the place of a species in nature, due to a cumulative set of environmental factors. The ecological niche includes not only the position of the species in space, but also its functional role in the community.
- this is a set of environmental factors within which a particular type of organism lives, its place in nature, within which this species can exist indefinitely.
Since a large number of factors should be taken into account when determining an ecological niche, the place of a species in nature, described by these factors, is a multidimensional space. This approach allowed the American ecologist G. Hutchinson to give the following definition of an ecological niche: it is a part of an imaginary multidimensional space, the individual dimensions of which (vectors) correspond to the factors necessary for the normal existence of a species. At the same time, Hutchinson singled out a niche fundamental, which can be occupied by a population in the absence of competition (it is determined by the physiological characteristics of organisms), and a niche implemented, those. part of the fundamental niche within which a species actually occurs in nature and which it occupies in the presence of competition with other species. It is clear that the realized niche, as a rule, is always less than the fundamental one.
Some ecologists stress that, within their ecological niche, organisms must not only occur, but also be able to reproduce. Since there is species specificity to any ecological factor, the ecological niches of species are also specific. Each species has its own ecological niche.
Most species of plants and animals can only exist in special niches that support certain physico-chemical factors, temperature, and food sources. After the destruction of bamboo began in China, for example, the panda, whose diet for 99% consists of this plant, was on the verge of extinction.
Species with common niches can easily adapt to changing habitat conditions, so the danger of their extinction is low. Typical representatives of species with common niches are mice, cockroaches, flies, rats and humans.
G. Gause's law of competitive exclusion for ecologically close species in the light of the doctrine of the ecological niche can be formulated as follows: two species cannot occupy the same ecological niche. An exit from competition is achieved by a divergence of requirements for the environment, or, in other words, by delineation of the ecological niches of species.
Competing species that live together often "share" available resources to reduce competition. A typical example is the division into animals that are active during the day and those that are active at night. Bats (one in four mammals in the world belong to this suborder of bats) share the airspace with other insect hunters - birds, using the change of day and night. True, bats have a few relatively weak competitors, such as owls and nightjars, which are also active at night.
A similar division of ecological niches into day and night "shifts" is observed in plants. Some plants bloom during the day (most wild-growing species), others - at night (two-leafed love, fragrant tobacco). At the same time, nocturnal species also emit an odor that attracts pollinators.
Ecological amplitudes of some species are very small. So, in tropical Africa, one of the species of worms lives under the eyelids of a hippopotamus and feeds exclusively on the tears of this animal. A narrower ecological niche is hard to imagine.
The concept of the ecological niche of a species
The position of the species that it occupies in the general system of biocenosis, including the complex of its biocenotic relationships and requirements for abiotic environmental factors, is called ecological niche of the species.
The concept of an ecological niche has proved to be very fruitful for understanding the laws of cohabitation of species. The concept of "ecological niche" should be distinguished from the concept of "habitat". In the latter case, that part of the space is meant which is inhabited by the species and which has the necessary abiotic conditions for its existence.
The ecological niche of a species depends not only on abiotic environmental conditions, but also, to no lesser extent, on its biocenotic environment. This is a characteristic of the lifestyle that a species can lead in a given community. How many species of living organisms there are on Earth - the same number of ecological niches.
Competitive exclusion rule can be expressed in such a way that two species do not get along in the same ecological niche. The way out of competition is achieved due to the divergence of requirements for the environment, a change in lifestyle, which is the delimitation of the ecological niches of species. In this case, they acquire the ability to coexist in one biocenosis.
Separation of ecological niches by cohabiting species with partial overlap one of the mechanisms of sustainability of natural biocenoses. If any of the species drastically reduces its numbers or falls out of the community, others take over its role.
The ecological niches of plants, at first glance, are less diverse than those of animals. They are clearly delineated in species that differ in nutrition. In ontogenesis, plants, like many animals, change their ecological niche. As they age, they use and transform their environment more intensively.
Plants have overlapping ecological niches. It intensifies in certain periods when environmental resources are limited, but since species use resources individually, selectively and with different intensity, competition in stable phytocenoses is weakened.
The richness of ecological niches in the biocenosis is influenced by two groups of reasons. The first is the environmental conditions provided by the biotope. The more mosaic and diverse the biotope, the more species can demarcate their ecological niches in it.
Detailed solution paragraph § 76 in biology for students of grade 10, authors Kamensky A.A., Kriksunov E.A., Pasechnik V.V. 2014
- Gdz workbook in Biology for grade 10 can be found
1. What is a habitat?
Answer. Habitat (habitat) - a set of biotic, abiotic and anthropogenic (if any) environmental factors in any particular territory or water area, which is formed on the site of the primary complex of abiotic factors - an ecotope. The habitat of a species or population is an important component of his/her ecological niche. In relation to terrestrial animals, the term is considered synonymous with the concepts of station (species habitat) and biotope (community habitat).
Habitats characterized by different severity of environmental factors, but having a similar vegetation cover, are called biologically equivalent. Their existence is possible due to the partial compensation of factors by each other.
T. Southwood (1977) proposed to classify habitats according to the nature of the change in factors over time, highlighting the following:
unchanged - environmental conditions remain favorable indefinitely;
predictably seasonal - there is a regular change of favorable and unfavorable periods;
unpredictable - favorable and unfavorable periods have different durations;
ephemeral - with a short favorable period.
2. What is a food chain?
Answer. Food (trophic) chain - a series of species of plants, animals, fungi and microorganisms that are related to each other by relationships: food - consumer (a sequence of organisms in which there is a phased transfer of matter and energy from source to consumer).
The organisms of the next link eat the organisms of the previous link, and thus the chain transfer of energy and matter is carried out, which underlies the cycle of substances in nature. With each transfer from link to link, a large part (up to 80-90%) of the potential energy is lost, dissipating in the form of heat. For this reason, the number of links (species) in the food chain is limited and usually does not exceed 4-5.
3. What is interspecific struggle?
Questions after § 76
1. What is the difference between the concepts of "habitat" and "ecological niche"?
Answer. The position of the species that it occupies in the biogeocenosis, the complex of its relationships with other species and the requirements for abiotic environmental factors is called an ecological niche. The concept of "ecological niche" should be distinguished from the concept of "habitat". In the latter case, we are talking about a part of the space where the species lives and where there are the necessary abiotic conditions for its existence. The ecological niche of a species depends not only on abiotic conditions; it characterizes the entire way of life that a species can lead in a given community. According to the figurative expression of the ecologist Yu. Odum, the habitat is the address of the species, and the ecological niche is its "profession". There are fundamental (or potential) and realized niches. A fundamental ecological niche is a set of optimal conditions under which a given species can exist and reproduce. A realized niche is the conditions where a species actually occurs in a given ecosystem; it always constitutes some part of the fundamental niche.
For the reproduction and long-term existence of many animal species, the differentiation of niches at different stages of ontogenesis is of great importance: caterpillars and adults of Lepidoptera, larvae and beetles of the Maybug, tadpoles and adult frogs do not compete with each other, since they differ in their habitat and enter different food chains.
Interspecific competition leads to a narrowing of the ecological niche, does not allow its potential to manifest itself. Intraspecific competition, on the contrary, contributes to the expansion of the ecological niche. In connection with the increase in the number of species, the use of additional feed, the development of new habitats, the emergence of new biocoenotic relationships begins.
2. Can different species occupy the same ecological niche?
Answer. No, they can't. A large number of organisms of different species live in one habitat. For example, a mixed forest is a habitat for hundreds of species of plants and animals, but each of them has its own and only one "profession" - an ecological niche.
In the forest, elk and squirrel have a similar habitat, but their niches are completely different: the squirrel lives mainly in the crowns of trees, feeds on seeds and fruits, and reproduces there. The entire life cycle of an elk is associated with the undergrowth space: feeding on green plants or their parts, reproduction and shelter in thickets.
Elements of an ecological niche:
food (species);
time and ways of eating;
breeding place;
shelter place.
Ecological niches exist according to certain rules:
the wider the requirements (tolerance limits) of a species to any or many environmental factors, the greater the space that it can occupy in nature, and hence the wider its distribution;
if the regime of any, at least one ecological factor in the habitat of individuals of one species has changed in such a way that its values go beyond the niche, then this means the destruction of the niche, i.e., the restriction or impossibility of preserving the species in this habitat. Other important regularities are also associated with the concept of "ecological niche" - each species has its own, unique ecological niche, i.e. how many species on Earth, so many ecological niches (2.2 million species of living organisms, of which 1.7 million animal species). Two different species (even very close ones) cannot occupy the same ecological niche in space;
in each ecosystem there are species that claim the same niche or its elements (food, shelter). In this case, competition is inevitable, the struggle for possession of a niche. Such relationships reflect the Gause rule: if two species with similar requirements for the environment (nutrition, behavior, breeding sites) enter into competitive relations, then one of them must die or change its lifestyle and occupy a new ecological niche.
An ecological niche is a set of all the requirements of a species (population) to environmental conditions (the composition and regime of environmental factors) and the place where these requirements are met.
The ecological niches of cohabiting species may partially overlap, but never completely coincide, because. the law of competitive exclusion comes into play.
3. Can one species occupy different ecological niches? What does it depend on?
4. What is the importance of ecological niches in community life?
Answer. The concept of an ecological niche is very useful for understanding the laws of the coexistence of species. For example, any green plant, taking one or another part in the formation of biogeocenosis, ensures the existence of a number of ecological niches. Among them, there may be niches that include organisms that feed on root tissues (root beetles) or leaf tissues (leaf beetles and sap beetles), flowers (flower beetles), fruits (fruit beetles), root secretions (eccrisotrophs), etc. All together they constitute an integral system of diverse uses. plant matter of the body. At the same time, all heterotrophs that eat plant biomass almost do not compete with each other.
Each of these niches includes groups of organisms that are heterogeneous in species composition. For example, the ecological group of root beetles includes both nematodes and the larvae of some beetles (May beetle, nutcracker), and bugs and aphids are in the niche of plants sucking juices.
Ecological niches of animals feeding on plant biomass
Groups of species in a community that have similar functions and niches of the same properties are called guilds by some authors (the guild of root beetles, the guild of nocturnal predators, the guild of scavengers, etc.).
Consider Figure 122. Are herbivores occupying the same or different niches in the African savannah? Justify your answer. Consider Figure 123. Do the dragonfly and its larva occupy the same or different niches? Justify the answer.
Answer. In the savanna, animals occupy different ecological niches. An ecological niche is a place occupied by a species in a biocenosis, including a complex of its biocenotic relationships and requirements for environmental factors. The term was introduced in 1914 by J. Grinnell and in 1927 by Charles Elton.
The ecological niche is the sum of factors for the existence of a given species, the main of which is its place in the food chain.
An ecological niche can be:
fundamental - determined by a combination of conditions and resources that allows the species to maintain a viable population;
realized - the properties of which are due to competing species.
This difference emphasizes that interspecific competition leads to a decrease in fertility and viability and that there may be a part of a fundamental ecological niche that a species, as a result of interspecific competition, can no longer live and reproduce successfully.
An ecological niche cannot be empty. If a niche is empty as a result of the extinction of a species, then it is immediately filled with another species.
The habitat usually consists of separate areas ("spots") with favorable and unfavorable conditions; these spots are often only temporarily available, and they occur unpredictably both in time and space.
Habitat gaps or gaps occur unpredictably in many habitats. Fires or landslides can lead to the formation of wastelands in forests; a storm can bare an open stretch of the seashore, and voracious predators can exterminate potential victims anywhere. These vacant plots are invariably repopulated. However, the very first settlers will not necessarily be those species that for a long time are able to successfully compete with other species and displace them. Therefore, the coexistence of transient and competitive species is possible as long as uninhabited areas appear with suitable frequency. A transient species usually first populates a free area, develops it and reproduces. A more competitive species populates these areas slowly, but if the settlement has begun, then over time it defeats the transient species and multiplies.
The doctrine of ecological niches is of great practical importance. When introducing foreign species into the local flora and fauna, it is necessary to find out what ecological niche they occupy in their homeland, whether they will have competitors in the places of introduction. The wide distribution of the muskrat in Europe and Asia is explained precisely by the absence of rodents with a similar lifestyle in these regions.
In related species living together, there is a very fine delineation of ecological niches. So, ungulates grazing in the African savannas use pasture food in different ways: zebras mainly cut off the tops of grasses, wildebeests feed on what zebras leave them, gazelles pluck out the lowest grasses, and topi antelopes are content with dry stems left after other herbivores. Due to the division of niches, the total bioproductivity of such a herd with a complex species composition increases. A peasant herd, consisting of cows, sheep, goats, uses meadows and pastures much more efficiently from an environmental point of view than a single-species herd, monoculture is the least efficient way of farming.
If we compare an adult insect and dragonfly larvae, we can draw conclusions:
1) Larvae usually serve as a dispersal stage and ensure the spread of the species.
2) Larvae differ from adults both in nutritional biology, and in their habitat, and in methods of movement (a flying dragonfly and its swimming larva), and behavioral features. Thanks to this, one species can use the opportunities provided by two ecological niches throughout the entire life cycle. This increases the chances of survival of the species.
3) they can adapt to the various conditions that await them in the second life, they have physiological endurance.
