R and k survival strategies. K- and r-strategies of populations. Methods of population regulation in humans. Mechanism of modern demographic transition. K-selection and K-strategies

The most strikingly opposite strategies of social contacts are manifested, of course, in reproductive behavior, i.e. in the breeding strategy.

In most species, including humans, both reproductive strategies occur. General direction human evolution can be described as a movement from r-strategy to K- strategies. You can even specify an approximate time when K- strategy began to prevail - this is the III millennium BC, when the myth of the conflict between Niobe and Latona arose on the territory of Asia Minor.

Niobe refused to offer sacrifices to Latona and her children by Zeus to Apollo and Artemis. She explained this, in particular, by the fact that she has seven times more children than Latona. Offended, Latona complained to the children. Apollo and Artemis, who stood up for their mother, killed all the Niobids with arrows.

The biological meaning of this myth is obvious: it is better to have few descendants, but more adapted to environment, which in competition will win over more numerous, but worse adapted individuals. And the great adaptive capabilities of the offspring are achieved, as already noted, firstly, by a careful choice of a reproductive partner and, secondly, by careful care for the offspring - what a person calls upbringing and training.

In human evolution r-strategy is being phased out TO-strategy.

The evolutionary advantage has shifted to K- strategists, i.e. a greater number of reproductively successful offspring began to be left by those women who: 1) carefully chose their reproductive partner (spouse) and 2) had pronounced parental behavior, i.e. provide children with careful care, educate and educate them.

Woman K- the strategist is interested in the fact that the reproductive partner spends all the extracted resources on providing only her offspring.

Despite the fact that, in general, a person is a monogamous species (more precisely, among people there are more representatives K-strategy), often there are carriers of the opposite strategy of reproduction, quite indifferent to their children. Such people, especially women, often painfully experience their indifference, considering themselves to blame for the lack of parental feelings. Doctors distinguish this condition as a special neurosis of the “bad mother”.

The type of reproductive strategy to which a person belongs is revealed only after the birth of a child. Then the hormonal reaction that accompanies childbirth initiates a complex of parental behavior. It is difficult to determine the belonging of a woman to one or another psychological type before childbirth. -r- or TO- strategies. It is impossible to bring up attention to one's own children.

The coldness or hostility of a woman towards her children are variants of the norm. This is the extreme r- breeding strategies.

If a healthy woman has high level cortisol at rest, i.e. it belongs to the psychological type B, then this serves as the basis for predicting intensive parental behavior. The concentration of cortisol in the blood during pregnancy increases in all women. But its increase is greater in those women who subsequently showed more pronounced maternal behavior.

In addition to cortisol, the propensity for parental affiliation is reflected in the ratio of estradiol to progesterone. A gradual increase in this ratio from early to late pregnancy is a marker TO- strategies.

Regarding the hormonal regulation of paternal behavior, i.e. parental behavior of men, very little is known. There is data showing that parental behavior more pronounced in men with low testosterone levels and high prolactin levels. Men who spend a lot of time with their children under 1 year of age have higher levels of cortisol and prolactin in the blood than those who spend little time on such communication, but the differences do not reach the level of statistical significance.

The practical significance of the study of biological markers K-strategy is obvious. A woman makes different, in many ways opposite demands on her sexual and reproductive partner. If a lover should possess the maximum number advantages, then the husband should have a minimum number of shortcomings. And only two positive qualities: to bring money and treat children well. Therefore, the problem of choosing a spouse will be greatly facilitated when specific biological signs a person's tendency to behave in a way that K- breeding strategy. Unfortunately, this problem is still far from being solved.

It should be noted that the behavior characteristic of the two breeding strategies is manifested not only in relations with children and spouses. Reproductive behavior strategies are a special case of social contact strategies.

Choose - me or this cat!

Well, I choose you. Still, I have known you for a long time, and this is the first time I see this cat.

E. Uspensky

The character of E. Uspensky is obvious K- strategist, because in case of need for an alternative choice, he prefers a well-known person. The owner of the opposite psychological type will choose a stranger, since communication with him promises new experiences, it is more interesting with him.

r- And K- breeding strategies are a special case r- and K-strategies of social contacts.

r- And K-strategies of social contacts can be considered as psychological types. Type B animals actively respond with behavior and endocrine responses to the behavior of another animal. Rats of type A are indifferent to the behavior of their neighbor. Differences in the oxytocin system of these animals are very indicative. In animals of type A, the activity of the oxytocin system is two times lower than in animals of type B. Thus, there is a correspondence to the differences in humoral mechanisms and types of social contacts in animals of genetically selected lines.

Consider a few examples of the effect of oxytocin on human behavior.

Volunteers were injected intranasally with oxytocin, which increased trust between people.

Moreover, early social stress caused by separation from the mother leads to altered levels of oxytocin in adults. For example, in rhesus monkeys raised in isolation from their mothers, at the age of 18, 24, and 36 months, the number of affiliative social contacts, including the duration of allogrooming, is dramatically reduced, and the number of agonistic contacts and the duration of stereotyped motor acts are increased. In such isolates, the concentration of oxytocin in the cerebrospinal fluid is significantly lower than in normal ones; raised with mother monkeys.

Similar results were obtained in the study of people with a lack of contact with parents. Children who have been deprived of maternal care since birth, as adults, suffer from emotional disorders and show impaired social behavior. They also showed reduced activity of the oxytocin and vasopressin systems 147 . Disturbances in the oxytocin system have also been noted in children deprived of paternal presence, too. As you know, children of single mothers have an increased risk of emotional disorders. In adult men who grew up without a father, the inhibitory effect of intranasally administered oxytocin on the stress rise in blood cortisol is weakened.

Summing up the discussion of the issue of strategies for human social contacts, it should be said that, undoubtedly, there are two such strategies: r- And TO-. They manifest themselves primarily in relations with children, but also in all other social contacts. K- strategy is associated with high activity of the oxytocin system in the body, and r - with low activity. These two behaviors are genetically determined but can be altered, at least temporarily, by manipulating the body's oxytocin levels.

Populations of species in which fertility and mortality are highly dependent on the action external factors, rapidly changing their numbers. Periodic changes in population size are called population waves. In some cases, the number changes in thousands and millions of times. These populations rarely reach the number K and exist due to the high value of r. This way of reproducing populations is called r-strategy.

R-strategies: (Selection for the number of offspring)

1. High fertility

2. Short regeneration time

3. High strength

4. Usually small sizes of individuals (small seeds in plants)

5. Short life span, high energy costs for reproduction

6. Short duration of habitats

7. Low competitiveness

r-strategists (explerents) are characterized by low competitiveness, high fecundity, lack of care for offspring, rapid development and short life span. r-Strategists are figuratively called "jackals", because they are able to conquer the vacated ecological space in a short time.

Populations of species in which births and deaths depend to a large extent on their density (that is, on the characteristics of the population itself), in lesser degree depend on external factors. They maintain numbers close to the value of K, so the way to reproduce such populations is called the K-strategy.

K-strategy: (Selection for the quality of offspring)

1. low fertility

2. significant life expectancy

3. large sizes of individuals and seeds, powerful root systems

4. high competitiveness, stability in the occupied territory

5. high specialization lifestyle

6. care for offspring

K-strategists (violents) are characterized by high competitiveness, low fertility, care for offspring, long development and long life expectancy. K-Strategists are figuratively called "lions" because they are able to for a long time maintain ecological space.

In addition to the r-strategy and K-strategy, there is also an S-strategy. S-strategists (patients) inhabit habitats with unfavorable living conditions for most organisms, in which there is practically no competition. Therefore, S-strategists are figuratively called "camels". According to the low value of r, they are close to "lions" (violents), and according to the high value of K, they are close to "jackals" (explerents). In terms of the duration of development and life span, S-strategists can be similar to both r-strategists and K-strategists.

For large (global) human populations, at a certain stage, hyperbolic growth

Opening Heinz von Foerster(Science, 1960): the growth of the Earth's population from ancient times to the 1960s–1970s is described very simple equation and precise schedule hyperbole(R 2 = 0.996, for the period 1000 - 1970)

Proof that human growth is not an exponent: specific growth rate increases with population growth (through a decrease in mortality)

Causes of hyperbolic growth - in addition to the "usual" positive feedbacks of unlimited exponential growth of any population, in human society there are its additional "accelerators".

For any level of technological development, there is a strictly defined level of population ( conjecture by Simon Kuznets - Michael Kremer) the rate of technological growth proportional, on the one hand, to the available level of technological development(the wider the technological base, the more inventions can be made on its basis), and on the other hand, population(how more people the more potential inventors and innovators among them). It turns out a system of double positive feedback , which spins the flywheel of hyperbolic population growth in the world: technological growth - growth of the Earth's carrying capacity - demographic growth - more potential inventors - acceleration of technological growth - accelerated growth of the Earth's carrying capacity - even faster demographic growth - accelerated growth in the number of potential inventors - even faster technological growth - further acceleration of the growth of the Earth's carrying capacity, etc.

Due to the fact that population growth again and again exceeded the next carrier limit of the environment, set by the next jump in the growth of technologies, epidemics, wars, famines and other horrors periodically occurred during the period of hyperbolic growth (the so-called " Malthusian trap»).

But as the general saturation limit of the medium (K) was approached, reverse negative connections already inhibiting growth (women's literacy, family planning) through declining birth rates. Growth rates declined mainly due to a reduction in the birth rate (K-strategy), while before that they grew due to a decrease in mortality.

Strictly hyperbolic growth was observed in humanity from the Late Paleolithic (40 thousand years ago) only until 1970. This was followed by a period of declining growth rates, due to the general demographic transition, When social factors first, the death rate was reduced, and a little later, the birth rate was also reduced. The main factors were: medicine, social security and literacy. All this marked the transition of our global population from the r-strategy to the K-strategy: to grow, albeit small, but high-quality offspring. For people, this means, first of all, - educated, i.e. competitive. And it costs more. Yes, and having many children as in an agrarian society is no longer necessary.

Demographic transition - a historically rapid decline in fertility and mortality, as a result of which the reproduction of the population is reduced to a simple replacement of generations. This process is part of the transition from a traditional society (which is characterized by high birth rates and high death rates) to an industrial one.

Reproduction - the production of offspring in any way available to the body.

biological sense

The biological meaning of reproduction and related processes is quite diverse. These are: firstly, the reproduction of the number of species and its increase, as opposed to natural mortality, predation by predators and other troubles. Secondly, it is the provision of new genetic combinations and the possibility of the appearance of new traits in offspring, which makes the evolutionary development of the group possible. In addition, in the course of reproduction, the problem of spatial distribution is often solved (especially for sedentary species), experiencing a period of unfavorable conditions (most often at the stage of resting eggs), and access to new food resources (available only to juveniles or larvae, but not to adult organisms) can occur.

Problems and adaptations.

Only a few organisms, mostly primitive ones, are able to reproduce passively (for example, when they are torn apart). In addition, a similar method (asexual, it is vegetative reproduction) does not provide one of the main functions - the emergence of new traits in the offspring, which could provide material for further evolution. Therefore, as a rule, the main thing for animals is sexual reproduction. It requires: the development of special organ systems for the maturation of germ cells, ensuring the mating of these cells (male and female) from different individuals, providing these cells with nutrition for the development and growth of the embryo, and often also further care for juveniles until they gain independence.

There are at least a few different difficult moments. First, sedentary (especially attached) organisms must somehow solve the problem of finding a partner and mating (at first glance, practically unsolvable, especially at a low population density). Secondly, the juveniles that appear during reproduction in any case are very different from adults - they are many times smaller, which requires the development of new life strategies (other feeding mechanisms, protection from predators, osmoregulation, etc.). Finally, it is necessary to solve issues related to the growth of juveniles - that is, to specially design all structures, including skeletal ones, in such a way that they can grow more or less continuously, ultimately increasing many times over. However, it is clear that animals managed to successfully solve all these problems, and rather the mechanisms for their solution differ.

K- and R-breeding strategies

Reproduction strategies and offspring care have become the subject of one of the general ecological theories - the theory of R- and K-strategies. It is believed that all organisms gravitate toward one of these two reproductive strategies. K-strategists (usually large animals that dominate stable habitats and established communities, such as elephants) breed slowly and produce few but large offspring who are surrounded by attention and care. On the contrary, R-strategists (generally small animals of disturbed habitats, for example, rats) breed quickly and in large numbers, but care little for offspring, which is accompanied by high infant mortality (adult mortality is also high). The K-strategy is more beneficial under conditions where the well-being of the population is determined mainly by competition, and the R-strategy is more beneficial under the strong influence of hard . In humans, different strategies are manifested even within the species: in urban populations (especially in economically developed countries) people multiply slowly (barely ensuring reproduction), but invest a lot of money in the maintenance, upbringing and education of children. On the contrary, in the poor agrarian countries of the tropics, people multiply rapidly and actively, without the means to adequately clothe, shoe, educate and sometimes even feed children, which often leads to high infant mortality, but can also be accompanied by sharp outbreaks of numbers (which, by the way, partly keep the standard of living low in these countries).

This whole theory, however, was developed mainly for terrestrial vertebrates (and partly for terrestrial higher plants). In the environment of aquatic invertebrates, somewhat different patterns operate. Most often (especially in the sea) the opposite happens - large and massive organisms throw out millions of microscopic settling eggs or larvae; small hydrobionts settle themselves, and produce much fewer offspring. Let's explain this with examples.

Comparative overview of the reproduction of different taxa

Unicellular algae. In each group unicellular algae There are two types of reproduction - vegetative and sexual. Vegetative - cell division as a result of mitosis. When resources are provided, the cells of unicellular algae reproduce predominantly vegetatively, and the population increases exponentially. Under unfavorable conditions for vegetative division or as a result of other reasons, algae undergo sexual reproduction (meiosis), in which male and female gametes are formed, after the fusion of which a cell with a “new” genotype is formed. The life cycles of unicellular algae belonging to different phylogenetic groups differ. The cycles of many algae include resting stages - (resting cells, spores, cysts, etc.) for experiencing adverse conditions.

Invertebrates. The original (for aquatic, primarily marine invertebrates) type of reproduction is believed to be as follows. At about the same time, all adult males and females in in large numbers they sweep their reproductive products (eggs and spermatozoa) directly into the water, which themselves (if you're lucky) find each other in the water column and mate. This is called external fertilization. The body itself can be inactive or sedentary. A microscopic planktonic larva grows from a fertilized zygote, which swims in the water column for quite a long time, settling with currents, undergoing various transformations and eventually moving to external power(most often phytoplankton - the so-called planktotrophic larvae). Growing up and preparing to move to an adult lifestyle, the larva settles on a suitable bottom substrate and acquires signs adult, reaches macroscopic dimensions and further grows for a long time. This type of reproduction and development makes it possible to solve all the problems of settling and intraspecific competition precisely at the expense of larvae (and adults can even be sessile - they do not need to meet each other directly). On the other hand, such an approach is accompanied by enormous mortality both among gametes and among larvae, which requires their massive accumulation and release, and the synchronization of maturation and release of germ cells in different individuals of the population is extremely important. This is achieved by the release of signaling substances into the water, which stimulates the release of all pre-accumulated gametes into the water in individuals. Usually mass spawning occurs once a year, and in many organisms - once in a lifetime. As is easy to understand, such a strategy is convenient for relatively large, massive, massive, and inactive organisms: polyps, sponges, mollusks, large polychaetes, echinoderms, and crustaceans. In general, at sea, this option is considered the most typical.

And also small and mobile invertebrates (cladocerans and copepods, some small polychaetes, oligochaetes, snails) cannot afford mass ejection gametes into water (simply not having enough mass), and internal fertilization is used: they find each other and mate themselves, after which the female, as a rule, carries the developing eggs inside herself for some time (reducing their mortality). Either passive eggs protected by a special shell or already active larvae are born. Larvae most often lead a lifestyle similar to adults; but often more mobile, which provides populations with better distribution in space. Sometimes, in this case, too, the larvae of benthic organisms become planktonic for some time. Often (for example, in oligochaetes), there are no larvae at all, and juveniles are similar in structure and lifestyle to adults (direct development). All this makes it possible to generate several orders of magnitude less reproductive products, reducing reproductive costs, and at the same time reproduce all year round, without worrying about spawning synchronization. Often, at birth, the larva is supplied with a supply of nutrients sufficient for the passage of its entire larval dispersal life, and does not feed at all (lecithotrophic larva).

IN fresh waters reproduction of the first type (with external fertilization and a long planktonic larval stage) is hampered by osmotic problems: osmoregulation of floating gametes and planktonic larvae has proved extremely inconvenient, and most even lower invertebrates use internal fertilization - and no additional planktonic larvae. As a rule, fairly large eggs are laid - in small numbers, but with a decent supply of nutrients, which allows the organism to be largely lecithotrophic and hatch, being already quite macroscopic and with a developed osmoregulation system. This is the path of freshwater worms, snails and most crustaceans. Copepods (like cyclops) still have a planktonic larva (nauplius), but relatively short-lived, in a series of successive molts quickly reaching the definitive (adult) appearance.

Insects, as a group as a whole, are terrestrial, and highly mobile precisely at the stage of an adult (imago), during development aquatic environment developed their own strategy of reproduction and life cycle. They left to the share of adults exactly the dispersal function (as well as mating and oviposition), and the larvae that live in the water (and usually much longer than the adults) are responsible for feeding, growth (and the accumulation of nutrients in the body), as well as experiencing in the water seasons that are unfavorable for life on land (mainly winters). Insect larvae already hatched from eggs are macroscopic, capable of self-feeding, and have a completely perfect system of freshwater (and sometimes brackish-water) osmoregulation. It is interesting that adults in some groups (mayflies, caddisflies, chironomids, part of stoneflies) do not feed at all and live for a very short time, and their synchronized departure from water bodies is used for successful reproduction. Thus, adult insects in non-insects are equated, functionally, with reproductive products (gametes) in many marine invertebrates.

In some groups of invertebrates (more often in fresh water than in marine) hermaphroditism - when both male and female reproductive organs and gametes are formed in each individual. For example, hermaphrodites are all lung snails (Pulmonata), oligochaetes, barnacles. When mating, the organism can act as both a male and a female, and often both at once (then mutual fertilization is observed). The biological meaning of hermaphroditism (that is, growing a double set of organs in each body) is not entirely clear. Sometimes (but apparently rarely) self-fertilization occurs - this partly violates the very idea of ​​\u200b\u200bsexual reproduction (since the organism interbreeds with itself), but it allows a single individual to give rise to a new population in a new place.

Even rarer than hermaphroditism, animals have asexual reproduction, in which the mothers actually clone themselves, giving birth to genetically exactly the same females. This situation is especially typical for periods of outbreaks in the abundance of small freshwater invertebrates - in particular, daphnia and rotifers in the summer. In any case, this is a temporary measure, sooner or later (usually in autumn) being replaced by normal sexual reproduction. However, in unicellular protozoa (as in plants), asexual reproduction is the most common thing, it is due to it that the main reproduction of species occurs.

Fish. As a rule, fish have external fertilization, however, carried out during a personal meeting of parental individuals (the female lays her eggs, and the male immediately pours her milk). Accordingly, fish spawn, usually quite small and in large quantities. The number of eggs averages several thousand, but varies greatly among different types: from 10-30 pieces (in sticklebacks) to 10-100 million (in tuna, cod and many other large marine fish). At the same time, the eggs carry a certain supply of nutrients, which allows already fully formed fry to hatch from the eggs, capable of swimming and feeding. The fish fry do not master any new environments, but they intercept the feeding spectrums that are usually inaccessible to adult fish: they can feed on zooplankton and meiobenthos. True, it is not clear whether the fish as a whole benefit greatly from this circumstance, or whether this is a necessary measure (since the fish fry are not able to eat anything else due to their small size).

Individual species of fish, however, have rather bizarre forms of reproduction and protection of offspring. The most famous are migratory fish that change their habitat for the sake of reproduction. Salmon and sturgeon in their adult state live in the seas, but spawn in rivers (where they originated), and their juveniles, adapted to freshwater osmoregulation, stay in rivers for some time and only then descend into the sea. At the same time, salmon show miracles of heroism, overcoming the rapids of mountain taiga rivers; and soon after spawning they die off - right in the rivers, sharply increasing their saprobity. It turns out that this is such a peculiar way to saturate the habitat of juveniles with organic matter. Another question is how effective it is.

The eel, on the contrary, swims to breed from the rivers in the Sargasso Sea, and for this, its European population overcomes (downstream) almost the entire Atlantic Ocean. Juveniles (again downstream, but in a different way) return to European rivers. It doesn't seem to make much sense. It is believed that eel's extra-long migrations reflect continental drift, during which the Atlantic gradually expands, and eels have to swim further and further into their native sea every million years.

Some groups of fish have moved to an explicit K-strategy, mainly through viviparity. At the same time, fertilization is internal, the number of offspring is much smaller, but they themselves are larger and more viable at the time they enter the water. The best-known example is the live-bearing aquarium fish Peciliidae (guppies and other pecilia). All aquarists know that they are much easier to breed than any other fish. For example, sharks act in a similar way - they lay very few eggs (usually 5-30), but very large ones - in a whale shark up to 60 cm (!) In diameter, which allows very large fish to hatch from them.

Amphibians. Amphibians have internal fertilization and lay quite large caviar- and definitely in the water. Like insects, most amphibians are amphibious - that is, they breed in water and have aquatic fish-like larvae (tadpoles), although adult animals live on land for most of their lives. In general, here we can also talk about the interception of a new habitat and food resources by tadpoles - this is generally true, but in fact it reflects the global inferiority of the entire class - amphibians simply cannot do otherwise.

Crabs and caring for a woman. In many crustaceans, especially higher ones, the adults are so well protected by a chitinous shell that they cannot mate except immediately after the female has molted. Therefore, a male ready for mating must not only find a female of his own species, but also wait for her molt, which can happen, for example, in a few weeks. Moreover, it is necessary to wait nearby, and not look for a molting female - because during and after molting, animals become extremely vulnerable and try to molt in safe shelters (where they are difficult to find). Therefore, for example, in king crabs, adult males gather around themselves several females (harem) and “herd” them, mating with those who shed, and protecting them from being eaten (primarily by other females of their own harem). Such a life necessary care about the female has little to do with the frivolous "courting" of vertebrates. The situation is further complicated by the fact that in the event of a molt of the male himself, he can also be immediately eaten by his females, so for molting he is forced to leave his harem and carefully hide.

Harpacticides and pedophilia. These small copepods have weak sexual dimorphism, and their interspecific differences are small; and age-related changes (from copepodite stages of juveniles to sexually mature ones) are hardly noticeable. But the mating instinct in males is very strong. Therefore, a male ready for mating, rummaging in the bottom silt in search of a sexual partner, does not show legibility and mates with almost anyone - with a female of his own species (if you're lucky!), or with a male, or with a copepodite (that is, a young individual), or with a crustacean of a completely different species. Sometimes their similar activity is mistaken for an attempt to eat a partner, but this is an attempt to copulate. In the state of mating, the crustaceans swim for quite a long time, and if a male is also in the position of the female, he can meanwhile also catch a partner for mating; sometimes quite long chains of individuals are obtained in this way, only a few of which actually mate.

Snails and group mating. Pulmonary freshwater snails are hermaphrodites, and in some of them sex determination during mating is directly determined by the position of the animal itself - approximately according to the principle "who is on top, that is the male." For example, river cups ( Ancylus fluviatilis) for mating, they simply crawl one on top of the other, and then the copulatory organs hang down. This situation does not prevent another cup from crawling on top and copulating with the one below, and so on. As a result, a stack of copulating individuals can form, of which the lowest acts only as a female, and the highest as a male, and all the rest work with both organ systems (unlike stupid harpacticids, which can only imitate such a situation). Then they all crawl away and lay eggs together.

Bonellia and sex determination by fate. In the sessile marine echiurida bonellia, the planktonic larva, leaving for open swimming, does not yet have a definite sex, but already has not only a resettlement, but also a sexual task - to search for a female. If the larva manages to find an adult female bonellia, it penetrates into it and develops into a male (who then lives inside the female for the rest of her life, fertilizing her). If it is not possible to find a female, the larva eventually settles to the bottom and becomes a female itself.

Environmental Strategies
Fundamentals of ecology

Have you ever wondered why some organisms leave numerous offspring, while others give birth to only a few individuals? It turns out that the number of offspring and care for them is part of the ecological strategy of the species, which is polished by millennia of evolution and ensures success in the struggle for existence for representatives of this species. In this lesson, you will learn about the features of radically different breeding programs: R-strategy and K-strategy, about the reasons for their emergence and consolidation in the evolutionary process.

Environmental strategy is a set of evolutionary adaptations aimed at the survival of the species.

The choice of environmental strategy is determined by factors mortality.

In some cases, mortality factors lead to indiscriminate death of individuals, regardless of their individual fitness. For example, krill individuals die in the mouth blue whale regardless of their individual characteristics and fitness.

In other cases, mortality is determined by factors that the individual can resist due to individual fitness. In these cases, the individual will participate in intense interspecific or intraspecific competition.

In the first case, there R-strategy.

R-strategists survive due to the huge birth rate with a low individual survival rate of individuals.

R-strategists features:

Low life expectancy;

Small size;

High birth rate;

As a rule, one reproduction during a lifetime.

Due to their enormous numbers and rapid development, R-strategists are the first to occupy new habitats before more competitive organisms get there.

Most of the descendants of R-strategists do not survive, so their numbers are subject to very strong fluctuations.

In the second case, there K-strategy .

K-strategists survive due to the high individual adaptability of organisms. Such creatures compete effectively for environmental resources and easily evade predators.

K-strategists are characterized by low mortality and high life expectancy.

Due to their high adaptability, almost all offspring of K-strategists survive, so their numbers fluctuate very little and are in the region of their upper limit.

Typical examples of K-strategists and R-strategists can be found among plants. A typical K-strategist is an oak, he is able to form a colossal crown on high altitude, collecting all available light. No other plants are able to shade the oak. Its roots will get minerals from depths not accessible to other plants. Storms and windblows are practically unable to knock it down.

Herbivores cannot cause significant damage to the oak due to its size. However, the oak gives very few germinating acorns and grows for a very long time.

A typical R-strategist is birch; it cannot compete with oak either in crown area or root system power. But one birch produces millions of seeds carried by the wind, which are scattered on large area. As soon as a free space appears as a result of windblows, fires or the natural death of another tree, a birch seed will germinate there. Usually the birch has time to successfully grow and produce millions more seeds before an oak or spruce sprouts nearby and destroys it with the shadow of its crown.

From animals, an example can be given of mammals: voles and horses (Fig. 1).

The vole gives rise to dozens of offspring and is ready to breed already in the first year of life, however, it often becomes a victim of predators and even its own brethren. Only rapid reproduction makes it possible to compensate for the large losses and low life expectancy of the vole.

The horse, on the contrary, brings one foal in the offspring, and even then not every year, but it is able to travel hundreds of kilometers in search of food, and only a few predators pose a danger to it. The survival of a horse species is due precisely to the individual perfection of each organism.

Rice. 1. Examples of K-strategists (horse - on the right) and R-strategists (mouse-vole - on the left) among mammals

There are striking examples of the separation of ecological strategies among fish.

Cod serves as food for many fish and marine mammals. She has no way to escape from a predator or protect her eggs, but one cod produces about a hundred million eggs a year. In the end, all the same, a lot of eggs and adults survive to give birth again.

Rice. 2. Examples of K-strategists (shark - on the left) and R-strategists (cod with its eggs - on the right) among fish

The reverse situation is observed in the blue shark. This is one of the fastest creatures in the world. Thanks to its speed and strength, it has no natural enemies and no problems with food. She brings only one cub per year, bearing a single egg in the genital tract (Fig. 2).

Thus, both K-strategists and R-strategists successfully survive in nature, while using completely different ecological strategies.

Bibliography

1. A.A. Kamensky, E.A. Kriksunov, V.V. Beekeeper. General biology, 10-11 class. - M .: Bustard, 2005. Download the textbook from the link: ()
2. D.K. Belyaev. Biology 10-11 class. General biology. A basic level of. - 11th edition, stereotypical. - M.: Education, 2012. - 304 p. (

Story development of the concept of "ecological strategy" in plants .

Firstly, the term "strategy" meant a set of properties that help organisms survive in given conditions, and was applied only to animal organisms.

R- and K-strategies were distinguished according to the ratio of the costs of reproduction and maintenance of offspring.

K-strategists are distinguished by concern for a small number of offspring, this is observed, for example, in elephants. R-strategists are characterized by maximum fecundity and lack of care for offspring, for example, roundworms.

Properties K- andRstrategies in animals.

Later, the term "ecological strategy" began to be used in relation to plant organisms. (20).

For domestic literature, the term "strategy" in relation to plants is quite new and was the first to be used by T.A. Rabotnov (1975), who named the isolated L.G. Ramensky (1936) "coenobiotic types".

Under the strategy of a species, Rabotnov proposed to understand "a set of adaptations that provide it with the opportunity to live together with other organisms and occupy a certain place in the corresponding biogeocenosis." (10)

As early as 1894, McLeod was the first to point out the presence of prerequisites for plants that determine their status in the community, and he divided all species into “capitalists” and “proletarians”.

However, both the analogy with society itself and the main criterion for distinguishing types were unsuccessful. cross pollination and self-pollination, although the scientist tried to make the assessments complex and wrote that “capitalists” are characterized by the presence of a supply of nutrients, polycarpicity, intolerance to shading, etc.

This issue was brilliantly developed in the works of Ramensky, published in the 30s, where he wrote about 3 types of plants, which he called violents, patients and explerents and likened them to lions, camels and jackals.

After 40 years, a monograph by J. Grime "Plant strategies and processes in vegetation" was published in England. , in which the author, not knowing the works of Ramensky, re-described the same three types of strategies under the names of competitors, stress-tolerants and ruderals.

To understand the type of strategies, much has also been done by E. Pianka, R. Whittaker and T.A. Rabotnov. (11)

The main systems of ecological and cenotic strategies .

E. Pianka's system.

Pianka's system, which is the most widely used in ecology, includes two types of strategies associated with K-selections and r-selections (according to the ratio of the shares of energy costs for maintaining adults and for reproduction processes).

K-selection is selection in a constant (predictable) environment, where the main part of the population's energy is spent on competition, and with r-selection, reproduction is the main energy expenditure item.

The system was the result of the development of ideas that were formulated earlier by R.Kh. MacArthur and E.O. Wilson, but it was E. Pianka who comprehensively analyzed the consequences that arise as a result of the implementation of two types of selection.

The two types of Pianka strategy are the most widespread in the plant world. And even the emergence of heterospores in club mosses or ferns can ultimately be considered as a replacement of the r-strategy of isospores with the K-strategy of the female gametophyte, which guarantees better survival of the offspring and replaces a huge number of small isospores with a limited number of megaspores, providing the necessary conditions development of the female growth.

K-strategists are confined to more or less stable environmental conditions, have equilibrium populations, where mortality is regulated by density, and are adapted to conditions of intense competition. They are usually polycarpic with slow development and life form from grasses to trees. In successional series, these species increase their participation as the successional stage approaches the climax.

r-strategists, on the other hand, prefer unstable habitats characterized by non-equilibrium populations, whose mortality does not depend or only slightly depends on density. The competition between such plants is weak, these are juvenile monocarpics, usually grasses, less often shrubs. In the successional series, they are associated with the pioneer stages and do not play a significant role in mature communities preceding the climax.

Thus, E. Pianka's type system is simple - one-dimensional, but it fully corresponds to the continuum perception of types.

He notes the relativity of dividing all types into 2 types of strategies, emphasizing that the world is not painted only in black and white, and extreme options, as a rule, are connected by a whole range of transitions (E. Pianka, 1981, p. 138). (13)

R. Whittaker's system.

R. Whittaker (1980) distinguished not 2, but three types of strategies, denoted letters K, r and L. His system is based on the patterns of fluctuations in the number of populations between two limits: K-upper limit, corresponding to the maximum saturation density and L-lower limit, meaning a certain “population zero”, corresponding to a population that is not able to ensure the survival of the population.

K-strategists strive to achieve the level of K, achieving this, firstly, by limiting niche differentiation. K-selection affects the mechanisms by which they maintain their population in the process of competition and other interactions within the boundaries of the environment they occupy. The number of populations is significantly reduced, but the general trend of such populations is fluctuations around the level of K.

The second group of populations_r-strategists. They are characterized by sharp fluctuations between the levels of K and L. Such populations are unstable and survive only thanks to high speed producing diaspores, they are poorly adapted both to the conditions of increased competition and to unfavorable conditions that cause stress.

The third group of populations are L-strategists, which fluctuate around the lower limit of abundance L, although they can at times increase their abundance explosively. In such populations, selection tends to improve the mechanism for surviving adverse periods, and the rate of reproduction may or may not be high.

Distinguishing three types of selection with their result - three primary types, at the same time, Whittaker, like Pianka, did not make his system absolute.

If we compare Whittaker's and Pianka's systems, it is obvious that his types K and r correspond to Pianka's K and r, and niche differentiation is indeed under the influence of K-selection. These are mainly perennial species, often propagating vegetatively, and consuming relatively little energy in the generative sphere.

Ruderal plants, on the contrary, are characterized by a short life cycle and high seed productivity, and therefore the costs of reproduction are higher here. This is a consequence of r-selection.

Group L occupies a transitional position, since desert annuals are among the ephemerals with a very fast development cycle and high seed production (result of r-selection), but shrubs, as well as some herbaceous turf plants, experience stress in the vegetative state and therefore represent the result of K-selection. (10)

Ramensky-Grime system.

Ramensky proposed a system of three types. He distinguished three "coenobiotic types".

The first type, which he called "violents" or "lions", is characterized by the ability to vigorously seize territory, the fullness of the resources used, and powerful competitive suppression of rivals.

The second type - patients or "camels" are distinguished by their ability to endure extreme environmental conditions, that is, endurance.

The third type - explerents or jackals are neither resistant to stressful situations nor high competitive power, but are capable of quickly capturing gaps between stronger plants, and when they close, they are also easily forced out. (13)

In the future, the representations and classification of L.G. Ramensky (1935-38) were developed by T.A. Rabotnov. (1966, 1975, 1978, 1980). He showed the complex nature of patient (stress tolerance) in plants and identified ecological and phytocenotic patients.

The former are able to exist in adverse conditions due to ecological specialization (on saline, acidic, dry or stony substrates, etc.) and most closely correspond to L.G. Ramensky. They have the same autecological and synecological optima.

The latter are able to survive for a long time under the pressure of violets in ecologically optimal conditions with the help of a maximum reduction in vital processes. Synecological and autecological optima usually do not coincide with them. (6 )

Further development ideas about the types of strategies we find in numerous works by J. Grime (J. Grime, 1974, 1978, 1979).

He offers, in essence, 3, the same as those of L.G. Ramensky, the type of ecological-coenotic strategies, calling these types: competitors, stress tolerants and ruderals (respectively K, S and R).