Natural selection always has the character of an adaptive reaction to the conditions of existence. All signs of living organisms are adapted to the conditions of their existence. Adaptability is distinguished by the internal and external structure of organisms, the behavior of animals, etc.

So, for example, the intensity of reproduction is higher in those creatures whose offspring in their mass dies. Cod, not taking care of their offspring, lays about 5 million eggs during the spawning period. The female of a small sea fish, a fifteen-spined stickleback, whose male guards the nest with eggs, lays only a few dozen eggs. The elephant, whose offspring in nature is almost never threatened, during her long life brings no more than 6 elephant calves, but the human roundworm, the vast majority of whose offspring dies, lays 200 thousand eggs every day during the year.

Wind pollinated plants produce huge amounts of fine, dry, very light pollen. The stigmas of the pistils of their flowers are large and feathery in shape. All this helps them pollinate more efficiently. And in insect-pollinated plants, pollen is much less, it is large and sticky, their flowers have nectaries and bright colors to attract pollinating insects.

Vivid examples of fitness are protective coloration and mimicry. Mimicry - imitation of dangerous species - is observed in many animals. For example, some harmless non-venomous snakes have acquired a significant resemblance to their venomous relatives, which helps them avoid predation.

Darwin's theory explains the emergence of fitness by hereditary variability and natural selection.

However, one should always keep in mind that fitness is relative. That is, any adaptation helps to survive only in the conditions in which it was formed. As soon as the conditions change, a previously useful trait will turn into a harmful one and lead to death. For example, a beautifully flying swift has very long narrow wings. However, this specialization of the wing has led to the fact that the swift cannot take off from flat surfaces and, if it has nothing to jump off, it dies.

The relative nature of fitness can also be considered in the following example: in the industrial regions of Europe, where, due to the intensive development of production, light-colored lichens that covered tree trunks died, dark-colored individuals of butterflies replaced light-colored individuals. This phenomenon is called industrial melanism. The fact is that light insects are very clearly visible against a dark background and are mainly eaten by birds. And in rural areas, on the contrary, dark insects are clearly visible on light trunks, and it is they that are destroyed by birds. Thus, natural selection marked the beginning of divergence (divergence) within a species, which can lead first to the appearance of subspecies, and then to new species.

The formation of new species is the most important stage in the evolutionary process.

The evolutionary process is divided into micro- and macroevolution. Microevolution is a process of restructuring within a species, leading to the formation of new populations, subspecies, and ending in the formation of new species.

Thus, microevolution is the very initial stage of the evolutionary process, which can take place in relatively short periods of time and which can be observed and studied directly.

As a result of hereditary (mutational) variability, random changes in the genotype occur. The spontaneous mutation rate is quite high, and 1-2% of germ cells have mutated genes or altered chromosomes. Mutations are most often recessive and rarely beneficial to the species. However, if as a result of a mutation beneficial changes occur for any individual, then it receives some advantages over other individuals of the population: it receives more food or becomes more resistant to the influence of pathogenic bacteria and viruses, etc. For example, the emergence of a long neck allowed the ancestors of the giraffe to feed on leaves from tall trees, which provided them with more food than individuals in the population with a short neck.

Thus, with the emergence of a new trait, the process of divergence begins, that is, the divergence of traits within the population.

In a population of any species, there are waves of abundance. In favorable years, the population increases: intensive reproduction occurs, most young and old individuals survive. In unfavorable years, the population size can drop sharply: many individuals, especially young and old, die, and the intensity of reproduction decreases. Such waves depend on many factors: climate change, the amount of food, the number of enemies, pathogens, etc. In years that are unfavorable for the population, conditions may arise when only those individuals that, as a result of mutation, have acquired a useful trait, will survive. For example, during a drought, short-necked giraffe ancestors could starve to death, and long-necked individuals and their offspring began to dominate the population. Thus, in a fairly short period of time, as a result of natural selection, a “long-necked” population of artiodactyl animals could appear. But if individuals of this population could freely interbreed with "short-necked" relatives from neighboring populations, then a new species could not arise.

Thus, the next necessary factor of microevolution is the isolation of a population of individuals with a new trait that has arisen from a population of individuals that do not have this trait. Isolation can be done in several ways.

1. Geographic isolation as a factor in speciation. This kind

isolation associated with the expansion of the species habitat - range.

At the same time, new populations fall into different conditions compared to other populations: climatic, soil, etc. Hereditary changes constantly occur in a population, natural selection acts - as a result of these processes, the gene pool of the population changes, and a new subspecies arises. The free interbreeding of new populations or subspecies may be hindered by range gaps due to rivers, mountains, glaciers, etc. So, for example, on the basis of geographical isolation factors, a number of species arose from one species of lilies of the valley over several million years. This way of speciation is slow, occurring over hundreds, thousands and millions of generations.

2. Temporal isolation as a factor in speciation. This type of isolation is due to the fact that if the timing of reproduction does not coincide, two close subspecies will not be able to interbreed, and further divergence will lead to the formation of two new species. Thus, new species of fish arise if the timing of spawning of subspecies does not coincide, or new species of plants, if the timing of flowering of subspecies does not coincide.

3. Reproductive isolation as a factor of speciation. This type of isolation occurs when it is impossible to cross individuals of two subspecies due to a mismatch in the structure of the genital organs, differences in behavior, and incompatibility of the genetic material.

In any case, any isolation leads to reproductive disunity - i.e. to the impossibility of crossing the emerging species.

Thus, the process of microevolution can be divided into the following stages:

1. Spontaneous mutations and the onset of divergence within the same population.

2. Natural selection of the fittest individuals, continuation of divergence.

3. The death of less adapted individuals as a result of the influence of environmental conditions - the continuation of natural selection and the formation of new populations and subspecies.

4. Isolation of subspecies, resulting in the emergence of new species due to reproductive disunity.

The adaptability of an organism to its environment is of great importance in the process of survival of living beings and is the result of natural selection.

The existence of an evolutionary mechanism of fitness ensures maximum adaptation to the conditions in which the species lives.

Fit - what is it?

It consists in the correspondence of the structural features, physiological processes and behavior of a living organism to the environment in which it lives.

This mechanism increases the chances of survival, optimal nutrition, mating and raising healthy offspring. This is a universal feature inherent in all creatures of the planet from bacteria to higher forms of life.

This mechanism of adaptation manifests itself in a very diverse way. Plants, animals, fish, birds, insects and other representatives of flora and fauna are quite inventive in choosing the means that contribute to the preservation of their species.

The result is a change in color, body shape, structure of organs, methods of reproduction and nutrition.

Features of adaptability to the environment and their result

For example, the body of a frog merges with the color of water, grass and makes it invisible to predators. The white hare changes color from gray to white in winter, which helps it to be invisible against the background of snow.

The champion in camouflage practice is the chameleon. But, alas, the opinion that it adapts to the color of the place in which it is located somewhat simplifies the real picture. The color change of this amazing lizard is a response to exposure to air temperature, solar UV rays, and even mood.

And instead of camouflage, the ladybug uses a different coloring strategy - scaring away. Its rich red color with black dots gives a signal that this insect can be poisonous. This is not so, but what difference does it make if such a move helps to survive?

The head of a woodpecker is an excellent example of the formation of a certain body shape, structure and functioning of organs. The bird has a powerful but elastic beak, a very long thin tongue and a cushioning system that protects the brain from injury when the bird's beak hits the tree trunk with the strongest blows.

A curious finding is “aggression” in plants. Stinging nettle petals are a great defense against herbivores. Camel thorn has modified leaves and roots, thanks to which it successfully retains moisture in desert conditions. The method of feeding sundew, eating flies, allows it to obtain nutrients in a very uncharacteristic way for a plant.

Geographic speciation

It is also appropriate to use the term “allopatric” formation of species. It is associated with the expansion of the habitat, when the species occupies more and more territories. Or with the fact that the territory is divided by natural barriers - rivers, mountains, etc.

In such a situation, there is a collision with new conditions and new “neighbors” - species with which you need to learn how to interact. Over time, this leads to the fact that, thanks to the ability to adapt, the species is forming and genetically fixing new beneficial traits.

Representatives of geographically isolated populations do not interbreed. As a result, they begin to have a number of rather striking differences from their relatives. So, the marsupial wolf and the wolf from the order of predators, as a result of selection, diverged quite far in their features.

Ecological speciation

It is not associated with a direct expansion of the range. It occurs as a result of the fact that within the same range, habitat conditions may vary.

So, among plants, an example can be the species diversity of dandelion, which differs in the territory of Eurasia.

The relative nature of the fitness of the cactus

The plant demonstrates an amazing ability to survive in the harshest drought conditions: a wax film and thorns minimize evaporation, a well-developed root system is able to go deep into the soil and accumulate moisture, needles protect against herbivores. But, in a situation of heavy rains, the cactus dies from an excess of moisture due to rotting of the root system.

The relative nature of the fitness of the polar bear

In Latin, this bear is called Ursus maritima, which means sea bear. Its coat is perfectly adapted to cold water.

It does not allow water to pass during swimming and almost completely delays the release of heat from the skin of the animal. But, if you place a polar bear in warmer living conditions for its brown relatives, it will die from overheating.

The relative nature of the fitness of the mole

This animal lives mainly in the ground. It has a streamlined body shape, powerful spade-shaped limbs with developed claws. He very cleverly digs multi-meter tunnels.

And at the same time, he does not orient himself on surfaces at all: his visual system is undeveloped, and he can only move by crawling.

The relative nature of the fitness of the camel

The camel's hump is his pride! Precious water accumulates there in drought conditions. Of course, not in the literal sense of water, these are H2O molecules associated with lipid, fat cells.

The animal can endure hunger for a long time, lie on hot sand, and sweating is minimized. It was not just that the nomads of the Sahara traveled on camels. But, alas, in snowy conditions, this hardy handsome man will not be able to cope with movement, nutrition and maintaining body temperature.

How do plants adapt to pollination by insects?

The flowers of plants are beautiful, unlike each other, you want to admire them! True, the biological significance of this beauty is not at all to please a person.

The main task of a flowering plant is to attract an insect pollinator. For this, several main ways are used: the bright color of large flowers, the aroma pleasant for insects, the crowding of small flowers in inflorescences and, of course, the nutritious nectar inside the flower.

Conclusion about the adaptability of organisms to the environment

The identification of patterns and the study of the adaptations of the animal world in various forms of terrestrial, aquatic, air life is an important and infinitely interesting topic for researchers. Because it reveals the main ways of the evolutionary process of modification of living beings.

Organisms that are best adapted to their environment survive through selection, but adaptations are always relative. Enough minor 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.

Sections: Biology

Lesson Objectives:

• repetition and consolidation of knowledge about the driving forces of evolution;
• to form the concept of the adaptability of organisms to the environment, knowledge about the mechanisms of the emergence of fitness as a result of evolution;
• to continue the development of skills to use the knowledge of theoretical laws to explain the phenomena observed in wildlife;
• to form specific knowledge about the adaptive features of the structure, body color and behavior of animals.

Equipment:

Table "Fitness and its relative nature", photographs, drawings, collections of plant and animal organisms, cards for performing tests, presentation.

1. Repetition of the studied material:

In the form of a frontal conversation, it is proposed to answer questions.

a) Name the single directing driving force of evolution.
b) What is the supplier of material for selection in the population?
c) It is known that the hereditary variability that supplies material for selection is random and not directed. How does natural selection become directional?
d) Give an evolutionary explanation for the following expression: “It is not individual genes that are selected, but integral phenotypes. The phenotype acts not only as an object of selection, but also acts as a transmitter of hereditary information in generations.

As the question is posed, its text is displayed on the screen (a presentation is used)

2. The teacher leads the conversation to the formulation of the topic of the lesson.

In nature, there is a discrepancy between the ability of organisms to reproduce indefinitely and limited resources. Is this the reason...? struggle for existence, as a result of which the individuals most adapted to environmental conditions survive. (Output of the scheme on the screen, students write in a notebook)

So, one of the results of natural selection can be called the development of adaptations in all living organisms - adaptations to the environment, i.e. fitness is the result of the action of natural selection in given conditions of existence.

(Lesson topic message, notebook entry)

Think and try to formulate what is the essence of adaptability to environmental conditions? (Together with the students, the teacher gives a definition of fitness, which is written in a notebook, displaying a slide on the screen)

Fitness of organisms or adaptations- a set of those features of their structure, physiological processes and behavior that provide for a given species the possibility of a specific lifestyle in certain environmental conditions.

What do you think fitness is for organisms?

Meaning: adaptation to environmental conditions increases the chances of organisms to survive and leave a large number of offspring. (Writing in a notebook, displaying a slide)

The question arises, how are adaptations formed? Let's try to explain the formation of an elephant's trunk from the point of view of C. Linnaeus, J. B. Lamarck, C. Darwin.

(On the screen is a photograph of an elephant and the wording of the question posed)

Suggested student responses:

According to Linnaeus: the fitness of organisms is a manifestation of the original expediency. God is the driving force. Example: Elephants, like all animals, were created by God. Therefore, all elephants from the moment of their appearance have a long trunk.

According to Lamarck: the idea of ​​the innate ability of organisms to change under the influence of the external environment. The driving force behind evolution is the striving of organisms for perfection. Example: Elephants, when getting food, had to constantly stretch their upper lip to get food (exercise). This trait is inherited. So there was a long trunk of elephants.

According to Darwin: among the many elephants were animals with trunks of different lengths. Those with slightly longer trunks were more successful at foraging and surviving. This trait was inherited. So, gradually, a long trunk of elephants arose.

Which explanation is more realistic? Let's try to describe the mechanism of occurrence of adaptations. (Scheme on screen)

3. Variety of adaptations.

On the tables of students there are drawings, collections illustrating the various adaptations of organisms to the environment. Work in pairs or groups. Students describe adaptations, name them themselves or with the help of a teacher. On the screen, these devices appear in the course of the conversation.

1. Morphological adaptations (changes in body structure).

• streamlined body shape in fish and birds
• webbing between fingers in waterfowl
• thick coat in northern mammals
• flat body in demersal fish
• creeping and cushion-like form in plants in northern latitudes and high mountainous regions

2. Camouflage: body shape and coloring merge with surrounding objects (slide).

(Sea horse, stick insects, caterpillars of some butterflies).

3. Protective coloring:

developed in species that live openly and may be accessible to enemies (eggs from openly nesting birds, grasshopper, flounder). If the background of the environment is not constant depending on the season of the year, the animals change their color (hare, white hare).

4. Warning coloring:

Very bright, characteristic of poisonous and stinging forms (wasps, bumblebees, ladybugs, rattlesnakes). Often combined with demonstrative scaring behavior.

5. Mimicry:

similarity in color, body shape of unprotected organisms with protected ones (a hoverfly and a bee, tropical snakes and poisonous snakes; snapdragon flowers look like bumblebees - insects try to establish a marriage relationship, which contributes to pollination; eggs laid by the cuckoo). Imitators never outnumber the original species. Otherwise, the warning coloring will lose its meaning.

6. Physiological adaptations:

adaptability of life processes to living conditions.

• accumulation of fat by desert animals before the onset of the dry season (camel)
• glands that get rid of excess salts in reptiles and birds that live near the sea
• water conservation in cacti
• rapid metamorphosis in desert amphibians
• thermal imaging, echolocation
• a state of partial or complete anabiosis

7. Behavioral adaptations:

changes in behavior in certain conditions

• caring for offspring improves the survival of young animals, increases the stability of their populations
• the formation of separate pairs during the mating season, and in winter they unite in flocks. What facilitates food and protection (wolves, many birds)
• scare behavior (bombardier beetle, skunk)
• freezing, imitation of injury or death (opossums, amphibians, birds)
• prudent behavior: hibernation, food storage

8. Biochemical adaptations:

associated with the formation in the body of certain substances that facilitate the defense of enemies or attacks on other animals

• poisons of snakes, scorpions
• fungal and bacterial antibiotics
• crystals of potassium oxalate in the leaves or spines of plants (cactus, nettle)
• special structure of proteins and lipids in thermophilic (resistant to high temperatures)

and psychrophilic (cold-loving), allowing organisms to exist in hot springs, volcanic soils, permafrost conditions.

The relative nature of fixtures.

It is proposed to pay attention to the table: hare. Invisible to predators in the snow, well visible against the background of tree trunks. Together with students, other examples are given: moths collect nectar from light flowers, but also fly into the fire, although they die in the process; poisonous snakes are eaten by mongooses, hedgehogs; if the cactus is watered abundantly, it will die.

What conclusion can be drawn?

Conclusion: any adaptation is expedient only in the conditions in which it was formed. When these conditions change, adaptations lose their value or even harm the body. Therefore, fitness is relative.

When studying the topic, we relied on the teachings of Charles Darwin on natural selection. It explained the mechanism of the emergence of the adaptability of organisms to living conditions and proved that adaptability is always relative.

4. Consolidation of knowledge.

on the students' tables sheets with tests and cards for answers.

1 option.

1. A phenomenon that serves as an example of camouflage coloring:

a) coloration of sika deer and tiger;
b) spots on the wings of some butterflies, similar to the eyes of vertebrates;
c) the similarity of the color of the wings of the pierid butterfly with the color of the wings of the inedible heliconid butterfly;
d) the color of ladybugs and the Colorado potato beetle.

2. How modern science explains the formation of organic expediency:

a) is the result of an active desire of organisms to adapt to specific environmental conditions;
b) is the result of natural selection of individuals who have turned out to be more adapted than others to environmental conditions due to the presence of random hereditary changes in them;
c) is the result of the direct influence of external conditions on the development of corresponding traits in organisms;
d) it was originally predetermined at the time of creation by the creator of the main types of living beings.

3. Phenomenon. An example of which is the similarity of the lion fly and wasps in the color of the abdomen and the shape of the antennae:

a) warning color
b) mimicry;
c) adaptive coloring;
d) disguise.

4. An example of protective coloration:

5. An example of a warning color:

a) the bright red color of the flower of a rose;


d) similarity in color and body shape.

Option 2.

1. The main effect of natural selection:

a) increasing the frequency of genes in the population that ensure reproduction in generations;
b) an increase in the frequency of genes in a population that provide a wide variability of organisms;
c) the appearance in the population of genes that ensure the preservation of the characteristics of the species in organisms;
d) the appearance in the population of genes that determine the adaptation of organisms to living conditions;

2. An example of protective coloration:

a) the green color of the song grasshopper;
b) green color of leaves in most plants;
c) a bright red color in a ladybug;
d) the similarity in the color of the abdomen of the hoverfly fly and the wasp.

3. An example of masking:

a) the green color of the song grasshopper;
b) the similarity in the color of the abdomen of the hoverfly and the wasp;
c) a bright red color in a ladybug;

4. An example of a warning color:

a) bright red color of a rose flower;
b) bright red color in a ladybug;
c) the similarity in coloration between the hoverfly and the wasp;
d) the similarity in color and shape of the body of the moth caterpillar with a knot.

5. An example of mimicry:

a) the green color of the song grasshopper;
b) bright red color in a ladybug;
c) the similarity in the color of the abdomen of the hoverfly and the wasp;
d) the similarity in color and shape of the body of the moth caterpillar with a knot.

Answer card:

	1	2	3	4	5
a
b
in
G

Homework:

1. paragraph 47;
2. fill in the table according to paragraph 47:

The relative nature of fitness

The development of organs for capturing, holding, killing prey (tentacles).

Masking color.

Isolation of paralyzing poisons.

Development of special ways of behavior (waiting in an ambush).

The mechanism of occurrence of adaptations

According to Charles Darwin, under conditions of natural selection, the fittest survive. Therefore, it is selection that is the main reason for the emergence of various adaptations of living organisms to their environment. The explanation of the emergence of fitness, given by Charles Darwin, is fundamentally different from the understanding of this process by Jean-Baptiste Lamarck, who put forward the idea of ​​the innate ability of organisms to change under the influence of the environment only in a direction that is beneficial for them. In all known octopuses, the changing coloration reliably protects them from most predators. It is difficult to imagine that the formation of such a changing color is caused by the direct influence of the medium. Only the action of natural selection can explain the emergence of such an adaptation: even a simple disguise could have helped the distant ancestors of the octopus to survive. Gradually, over millions of generations, only those individuals remained alive who happened to be the owners of more and more developed colors. It was they who managed to leave offspring and pass on their hereditary characteristics to him.

Corresponding to a specific habitat, adaptations lose their meaning when it changes. Evidence of the relative nature of fitness can be the following facts:

protective devices from some enemies are not effective from others;

the manifestation of instincts in animals may be inappropriate;

an organ that is useful under certain conditions becomes useless and even relatively harmful in another environment;

better adaptations to a given environment are also possible.

Some species of animals and plants multiplied rapidly and spread widely in areas of the globe that were completely new to them, where they were accidentally or deliberately introduced by man.

Thus, the relative nature of fitness contradicts the assertion of absolute expediency in living nature.

Such adaptations as protective coloration arose by the gradual selection of all those small deviations in body shape, in the distribution of certain pigments, in innate behavior that existed in the populations of the ancestors of these animals. One of the most important characteristics of natural selection is its cumulativeness - its ability to accumulate and strengthen these deviations in a number of generations, adding up changes in individual genes and the systems of organisms controlled by them.

Natural selection picks up all those minute changes that increase the similarity in color and shape with the substrate, the similarity between the edible species and the inedible species that it imitates. It should be borne in mind that different types of predators use different methods of finding prey. Some pay attention to shape, others to color, some have color vision, others do not. So natural selection automatically enhances, as far as possible, the similarity between imitator and model, and leads to those amazing adaptations that we see in nature.