The emergence of fitness and its relative nature. Adaptation of organisms to environmental conditions as a result of natural selection. The study of the fitness of organisms

08.03.2020

Having explained the origin of species on the basis of natural selection as a grandiose and all-encompassing process of successive change of adaptations, Darwin's theory also explained the phenomenon of the purposeful structure of organic forms. The forms of adaptations, as a reflection of expediency, are infinitely varied: the swim bladder in the body of a fish is filled with air and lightens the mass of its body; it is more convenient to overcome swamps on long legs with widely spaced fingers, like a heron, or with wide hooves, like an elk; jumping animals have more developed hind limbs (kangaroo, grasshopper, frog). In animals that lead an underground lifestyle, the limbs are spade-shaped and adapted for digging the earth. There are expedient adaptations in plants and animals to daily and annual fluctuations in temperature and humidity.

Adherents of idealistic views and ministers of the church in the phenomena of the adaptability of organisms and their purposeful structure saw an expression of the general harmony of nature, allegedly emanating from its creator. Ch. Darwin's theory rejects any participation in the emergence of adaptations of supernatural forces, it convincingly proved that the entire animal and plant world since its inception has been improving along the path of expedient adaptations to living conditions: to water, air, sunlight, gravity . The amazing harmony of living nature, its perfection are created by nature itself: the struggle for survival. This struggle is the force that gives strength to roots, sophisticated beauty to flowers, causes a bizarre mosaic of leaf arrangement and sharpens teeth, gives powerful strength to muscles, sharpness of vision, hearing and instinct for many animals.

Adaptability as an expression of expediency is manifested in everything. For example, predators have claws, fangs, beaks, poisonous teeth, from which it can be very difficult for the victim to escape. But in the struggle for life, protective means were also developed: some respond to force with force, others save their legs, others have a shell, shell, needles, etc. Many weak and defenseless insects, being harmless or edible, over the long years of natural selection adopted the color and shape of hornets, wasps, became similar to poisonous or inedible forms. Their imitative color or shape is at the same time protective, as it coincides with the background of the environment: it makes predators invisible and helps them sneak up on prey, and makes it possible for pursued species to hide from enemies. If the insects pursued by birds were not colored like green grass or tree bark, they would be exterminated by birds. The plumage of the tundra partridge merges with the tone of the rocks and peaks covered with lichens, the woodcock is invisible among the dried and fallen oak leaves, etc. eye-like spots; at the moment of danger, it raises the front of the body, thus scaring away the birds.

A variety of adaptations prevent most plants from self-pollinating, allowing them to spread fruits and seeds, or, thanks to their spines, to resist being eaten by herbivores. The fragrance and bright colors of the flowers originated as adaptations to attract insects that visit the flowers to cross-pollinate these plants, or as an adaptation to more effectively absorb sunlight of a certain length.

Protective coloration. Protective coloration is developed in species that live openly and can be accessible to enemies. This coloration makes organisms less visible against the background of the surrounding area. Some have a bright pattern (the color of a zebra, tiger, giraffe) - alternating light and dark stripes and spots. This dismembering coloring imitates the alternation of spots of light and shadow.

Disguise. Camouflage - a device in which the shape of the body and color of the animal merges with the surrounding objects. For example, the caterpillars of some butterflies resemble knots in body shape and color.

Mimicry. Mimicry is the imitation of a less protected organism of one species by a more protected organism of another species. This imitation can manifest itself in body shape, coloration, and so on. So, some types of non-venomous snakes and insects are similar to poisonous ones. Mimicry is the result of selection for similar mutations in different species. It helps unprotected animals to survive, contributes to the preservation of the organism in the struggle for existence.

Warning (threatening) coloring Species often have a bright, memorable coloration. Once trying to taste an inedible ladybug that stings a wasp, the bird will remember their bright color for life.

(According to the personal page of Andrey Ivanov)

In the doctrine of natural selection, Darwin not only materialistically substantiated the fitness of organisms (their expedient structure), but also showed its relative nature. So, warning and protective coloration, various other protective devices do not act on all pursuers, but, having devices, individuals are less likely to be attacked. The owners of the sting - wasps, bees, hornets - are easily eaten by flycatchers, bee-eaters. Flying fish, jumping out of the water into the air, deftly escape from predatory fish, but this is used by the albatross, which overtakes its prey in the air. The tortoise shell is a good defense, but the eagle picks it up in the air and throws it on the rocks; the shell breaks and the eagle eats the turtle.

Each animal and plant cannot be fully adapted to all the conditions that have developed throughout life on Earth. Any adaptation lasts as long as it is supported by natural selection, but disappears as soon as it ceases to be useful. As an example of a change in adaptations, one can cite the development of protective coloration in the birch moth butterfly.

Thus, the basis of Darwin's theory is the doctrine of natural selection, the main and guiding factor in evolution. In the struggle for existence on the basis of hereditary variability, there is a successive change of adaptations and the survival of the fittest, the diversity of forms of living nature increases, the process of speciation takes place, and the general progressive development of the plant and animal world takes place. In this theory, two problems were resolved: the mechanism of speciation and the origin of the expediency of the organic world.

Adaptability of organisms as a result of evolution (T.A. Kozlova, V.S. Kuchmenko. Biology in tables. M., 2000)

fitness scores	Plants	Animals
Ways to get food	The absorption of water and mineral salts is ensured by the intensive development of roots and root hairs; absorption of solar energy is carried out most successfully by wide and thin leaves; capture and digestion of insects and small amphibians by marsh plants	Eating leaves on tall trees; capture with the help of a trapping net and lie in wait for food objects; the special structure of the oral organs ensures catching insects from long, narrow burrows, biting grass, catching flying insects; Grasping and holding prey by predatory mammals and birds
Eating protection	They have spines that provide protection against herbivores; contain toxic substances; the rosette shape of the leaves is not available for etching	They are saved by a quick run; have needles, shells, a frightening smell, and other protection; protective coloring saves in certain conditions
Adaptation to abiotic factors (to cold)	falling leaves; cold resistance; preservation; vegetative organs in the soil	Flight south; thick coat; hibernation; subcutaneous fat layer
Spread to new territories	Light, winged seeds; tenacious hooks	Flights of birds; animal migration
Breeding efficiency	Attracting pollinators: flower color, smell	Attracting a sexual partner: bright plumage, sexual attractants

Organisms that are best adapted to their environment survive through selection, but adaptations are always relative. Enough insignificant changes in the environment, as what was useful in the previous conditions, loses its adaptive value.

Examples of Relative Fittings

The Ussuri tiger has a protective coloration that hides it well in the thickets in summer, but in winter, after the snow falls, the coloring unmasks the predator. With the onset of autumn, the hare molts, but if the snowfall is delayed, then the whitened hare becomes clearly visible against the dark background of bare fields.

The characteristics of an organism, even under the conditions in which they have been preserved by selection, never achieve absolute perfection. So, the roundworm egg is well protected from the effects of poisons, but quickly dies from a lack of moisture and from high temperature.

Poisonous glands are a reliable defense of many animals, but the poison of the karakurt, which is deadly for camels and cattle, is safe for sheep and pigs. The viper does not pose a danger to the hedgehog.

Euphorbia stalks are not eaten by herbivorous mammals, but remain defenseless against caterpillars of Euphorbia hawk, etc. Selection always has a wide field of activity for the further improvement of adaptations.

If conditions change, then arrangements that were previously expedient cease to be so. Then new adaptations appear, and forms that were previously "expedient" die out.

If genetic differences affect fitness, genotype frequencies will change over generations, and less fit genotypes will be eliminated by natural selection.

The fitness of an individual is manifested through its phenotype. Since the phenotype of an individual is determined by the genotype and the environment, the fitness of different individuals with the same genotype may differ depending on the living conditions. However, since fitness is an average value, it reflects the results of reproduction of all individuals with a given genotype. The main measure of an individual's fitness may be its fecundity.

Since fitness is a measure of quantity copies genes in the next generation, then various strategies for maximizing it are possible for an individual. For example, it may be “profitable” for an individual to reproduce itself or to help its relatives who carry the same or close copies of genes to reproduce. The selection that promotes this behavior is called group or kin selection(English) kin selection).

Fitness measures

Distinguish between absolute and relative fitness.

Absolute Fitness() genotype is defined as the ratio of the number of individuals with a given genotype after and before the start of selection. It is calculated for one generation and can be expressed as an absolute number or frequency. If the fitness is greater than 1.0, the genotype frequency increases; if the ratio is less than 1.0, the genotype frequency decreases.

The absolute fitness of a genotype can also be expressed as the product of the percentage of surviving organisms and the average fecundity.

Relative Fitness expressed as the average number of surviving offspring of a given genotype compared to the average number of surviving offspring of competing genotypes in one generation. That is, one of the genotypes is normalized to and in relation to it the fitness of other genotypes is measured. In this case, the relative fitness can have any non-negative value.

fitness and reproductive success

In some cases, the choice of females is based on traits associated with the general fitness of males. So in butterflies Colias (C. eurytheme and C. philodice), females choose males based on flight kinetics. Preferred males achieve the greatest mating success and appear to also have the best flight ability (Watt et al., 1986). In the frog Physalaemus pustalosus in Panama, females have a preference for a particular type of call. Males that make such calls are more likely to mate. These successfully mating males are also older and larger, so that in this case, as in Colias butterflies, fitness seems to play a role (Ryan, 1980; 1983; 1985).

At the same time, it is believed that an extensive class of male display traits do not give their owners any advantages and may even have a detrimental effect on their viability. For example, it is generally accepted that the long tails of some male birds of paradise reduce their fitness. Mating calls of male Panamanian frogs increase the probability of their destruction by predators - bats (Trachops cirrhosus) (Tuttle and Ryan, 1981).

Story

British sociologist Herbert Spencer used the phrase "survival of the fittest" (survival of the fittest) in his work Social statics (Social Statics, 1851) and later used it to characterize natural selection. The British biologist D. Haldane was the first to quantify fitness in a series of works that linked Darwin's theory of evolution and Gregor Mendel's theory of heredity- Mathematical Theory of Natural and Artificial Selection (1924). Further development was associated with the introduction by W. Hamilton of the concept of inclusive fitness in his work The genetic evolution of social behavior (The genetic evolution of Social Behavior, 1964).

Literature

Group selection, the origin of man and the origin of the family (A. I. Fet. Instinct and social behavior. Second edition)

Types of adaptability of organisms

Morphological adaptations include:

Transformation of the body, namely: streamlining or flattening of the shape, webbed paws, thick hair.
With the help of disguise, you can become invisible against the background of the environment, become similar in color and shape to a leaf, stone, twig (insects, fish).
With a protective and dismembering coloration, one can merge with the environment in a changing situation (hare - hare, bird eggs, zebra).
Warning coloration is distinguished by a bright color, specks, stripes, and is needed to scare away or warn of an attack (bees, snakes, ladybugs).
To warn and protect oneself, a weak one, from a stronger one, becoming similar in color, body shape or behavior, is called mimicry (tropical snake, fly - murmuring, cuckoo eggs).

Physiological adaptations include:

Preparation for life in changing conditions: - the camel accumulates fat; - the formation of glands that get rid of excess salt (marine reptiles and birds). - location of heat and sound; - falling into hibernation.
Behavior: - the smaller the number of cubs, the more care for them for the purpose of conservation; - the formation of mating pairs for the period of reproduction of offspring and life in packs with complication of conditions (birds, wolves). - scaring away (cobra, grin and growl of a dog, smell of a skunk). - imitation of the wounded or dead, hiding (opossum, frog, bird). - prudence (winter sleep, food storage).
With the help of biochemical devices (special substance), the animal can defend itself or attack the enemy (poisons, antibiotic bacteria, special proteins and fats).

The nature of the fitness of organisms

Natural selection leaves only the fittest alive. But the slightest change in the environment can render useless or even harmful those devices that worked well before.

As a result, those organisms that have managed to adapt faster survive, and those who are late die out, making it possible for a new species to form. Such adaptations are formed for a very long time in a natural way and are relative, because the conditions of life change much faster than the necessary changes appear in animals.

Evidence for the relativity of fixtures:

methods of protection are not universal (a poisonous snake that is dangerous for some is eaten by a mongoose, a hedgehog);
in some cases, instinct fails (a night butterfly flies for nectar to a light flower, or it can confuse it with fire);
an organ that is necessary in one environment is useless or harmful in other conditions (mountain geese with membranes they do not need);
the fish is adapted to separate oxygen from the water, on land it cannot do this; - green insects are not visible on the grass, on clean ground they will be quickly eaten.

Causes of adaptability of organisms

It has been established that individuals of a species will survive if they change faster, adapting to new environmental requirements. The emergence of new characters and the appearance of a new species is called phyletic speciation.

Today, the diversity of species has noticeably decreased compared to several thousand years ago. This is due to constant climate change, ice ages, volcanic eruptions, earthquakes, environmental degradation, and the barbaric attitude of people. As a result, the most adapted organisms survive, and the main reason for adaptability belongs to natural selection.

Adaptation of organisms to the environment

To survive, you need to adapt to the conditions of life, and she will choose the best individuals and remove the weak. All animals live in different parts of nature and their adaptive features depend on this.

Laboratory work fitness of organisms

Laboratory work, with a problematic situation in the content, is necessary for the development of independent skills for studying and researching objects of biology. The existing problem generates hypotheses, versions, proofs and teaches to draw conclusions. Each work has a goal, questions, tasks and applications. And the progress of work is more convenient to display in the table.

Example. L. r. "Adaptation to the environment".

Target: to define the concept of the adaptability of animals, to train the ability to determine adaptations.

Fly - hoverfly can be found everywhere, except for the tundra and the desert. It is a short-whiskered two-winged insect similar to a wasp, but completely harmless. Hoverflies fly very fast. Their relationship with ants, bumblebees leading a social lifestyle has been proven.

Adaptability of organisms to environmental factors

All living organisms are affected by natural factors. Inanimate nature includes: temperature, change of day and night, seasons, features of the soil, landscape, chemical composition of air and water, noise, radiation. Organisms adapt to this, but they cannot influence these conditions, which are called abiotic factors.

Of no small importance for the survival of animals are adaptations to changes in nature by man (anthropogenic factor). Being in natural communities, all living inhabitants of the planet are divided into groups with similar signs of adaptation to a single environmental factor. These changes can be expressed both externally and internally, with a change in the nature of behavior.

For example, body temperature depends on weather conditions in most representatives of the animal world. These are cold-blooded animals. They react either by decreasing or increasing the metabolic rate. When slowed down, they experience suspended animation, which helps to conserve energy. In warm-blooded species, the temperature is always constant and does not affect metabolism. There are predators that hunt during the day, and there are those that come out only at night. Pets are active mainly during the daytime.

Examples of the fitness of organisms

The horse can run fast with wide, comfortable hooves. Cats are able to silently sneak up, pulling in their claws. Birds lightened their body for flight, getting rid of the bladder, one ovary, teeth and acquiring wings with different plumage.

Insects - caterpillars have adapted to become like a leaf of a plant, a twig. Crocodiles have special glands near their eyes that help remove excess salt. The camel stores fat in its humps, which breaks down to release water. The polar bear keeps warm with a layer of subcutaneous fat and thick fur, wide paws allow you to walk on thin ice.

The study of the fitness of organisms

Initially, during the reign of religion, it was argued that all life on Earth was created by the existing wise God. That nature itself could not do this. The Creator created everyone in such a way that they could do what was entrusted to them. K. Linnaeus also adhered to this theory.

J. B. Lamarck argued that all organisms are born with the ability to change, and throughout their lives they can only improve these skills. Thus, new species with useful properties arise. But this theory does not explain the different colors of bird eggs and the benefits of thorns for hedgehogs.

C. Darwin expressed his opinion; “... if an animal or plant can survive a sharp change in climate or other conditions, then it is its descendants that will become the most common.” A new emerging trait is passed on to offspring if it contributes to survival.

Modern scientists, studying adaptation, have come to the conclusion that any useful variability comes later than the right time. Some new signs even harm the animal in suddenly changed conditions.

Pronghorns rank second among all animals in terms of running speed. But a special feature is the muscles that change the slope of the coat. This ability helps in heat or cold. And most importantly, seeing the danger, the observer fluffs up the hair of his backside, which immediately notices the whole herd.
The secret of toothfish, an Antarctic fish, is that with the help of a special protein that acts as an antifreeze, its blood remains unfrozen even at a temperature of minus 2 degrees.
African protopter fish, which can sleep up to 4 years, will be envied even by a bear. It is a lungfish, having, along with gills, also a pulmonary system.
Toad - the water carrier sleeps in its shelter of slime, waiting for a new rain, as many as seven.
The vulture bird is not only a nurse - it eats carrion, but it can also cool its body by urinating on its plumage.

conclusions

Each organism is best adapted to the conditions where it has to live. This change only serves where it was purchased and is therefore considered relative. Natural selection leaves individuals with only those traits that have withstood the greatest deviation in the significance of a certain environmental factor.

One of the results, but not, which is the natural guiding driving force of the process, can be called the development of all living organisms - adaptations to the environment. Ch. Darwin emphasized that all adaptations, no matter how perfect they are, are relative. Natural selection forms adaptation to specific conditions of existence (at a given time and in a given place), and not to all possible environmental conditions. The variety of specific adaptations can be divided into several groups, which are forms of adaptability of organisms to the environment.

Some forms of fitness in animals:

Protective coloration and body shape (camouflage). For example: grasshopper, snowy owl, flounder, octopus, stick insect.

Warning coloration. For example: wasps, bumblebees, ladybugs, rattlesnakes.
Frightening behavior. For example: bombardier beetle, skunk or American stink bug.

Mimicry(external similarity of unprotected animals with protected ones). For example: a hoverfly fly looks like a bee, harmless tropical snakes look like poisonous snakes.
Some forms of fitness in plants:

Dry adaptations. For example: pubescence, accumulation of moisture in the stem (cactus, baobab), turning leaves into needles.
Adaptations to high humidity. For example: large leaf surface, many stomata, increased evaporation rate.
Pollination by insects. For example: bright, attractive flower color, presence of nectar, smell, flower shape.
Adaptations for wind pollination. For example: the removal of stamens with anthers far beyond the flower, small, light pollen, the pistil is strongly pubescent, the petals and sepals are not developed, do not interfere with the blowing of other parts of the flower by the wind.
Fitness of organisms - the relative expediency of the structure and functions of the body, which is the result of natural selection, eliminating individuals unadapted to the given conditions of existence. Thus, the protective coloration of a brown hare in summer makes it invisible, but unexpectedly falling snow makes the same protective coloration of a hare inappropriate, as it becomes clearly visible to predators. Wind-pollinated plants remain unpollinated in rainy weather.

Plants and animals are remarkably adapted to the environment in which they live. The concept of “fitness of a species” includes not only external signs, but also the correspondence of the structure of internal organs to the functions they perform (for example, the long and complex digestive tract of ruminants that eat plant foods). The correspondence of the physiological functions of the organism to the conditions of its habitat, their complexity and diversity is also included in the concept of fitness.

Adaptive behavior is of great importance for the survival of organisms in the struggle for existence. In addition to hiding or demonstrative, frightening behavior when an enemy approaches, there are many other options for adaptive behavior that ensures the survival of adults or juveniles. So, many animals store food for the unfavorable season of the year. In the desert, for many species, the time of greatest activity is at night, when the heat subsides.