1. Introduction: phyletic evolution.

2. The origin of fitness in organisms.

3. Examples of adaptations.

4. The relativity of fitness.

5. References.

Introduction: phyletic evolution.

In the course of ecological differentiation, a population that has split off from a species may eventually become a new species. Note that in this case the initial (maternal) species can continue to live. A different fate develops for a species when its habitat is slowly but steadily deteriorating. Typically, such a deterioration concerns a single vital parameter. It goes without saying that any species exists only within a very specific range of variation of such a parameter and dies out when the medium goes beyond these limits. Therefore, survival with a gradual deterioration of the environment should be associated with a special form of speciation, in which the maternal species ceases to exist. This speciation is called phyletic.

There are currently millions of species of animals and plants on the earth, which means that there are as many uninterrupted phyletic lines (chains of ancestral species). Is this not evidence of the power of life! Unfortunately, only a small part of the lines was able to survive to this day. If we had a fantastic opportunity to rise from the past to the present, then in most cases we would not be able to achieve modernity. Very often, we would stumble upon the final links, that is, the species that have become extinct. In addition, climbing phylet chains, we would very often meet with their branching, where we would face the problem of choosing a route. Such forks are most easily interpreted as the completion of the ecological differentiation of isolated populations.

Newly formed branches can branch again, transforming the phyletic line into a phyletic bunch. The fate of the phyletic lines of such a bundle often develops of the same type - on some very short, from a geological point of view, time interval, all of them can die out. Conversely, a separate beam line may experience violent branching, which will lead to the emergence of a new beam - a daughter in relation to the original. The process of splitting phyletic bundles can continue further. As a result, a hierarchy of beams of different caliber arises from one phyletic line. Such a monophyletic collection of bundles is called a phyletic group.

Speaking of macroevolution, we use the widely accepted analogy between the phylet group and the tree. Developing it further, one can compare phyletic speciation with the growth of branches. True, unlike an ordinary tree, this “phylogenetic tree” is monitored by a “gardener,” who from time to time cuts the shoots, depriving the branches of the ability for further growth. This “gardener” adheres to some rules in his work: firstly, he cuts only the branches located at maximum height, and secondly, all shoots of one large branch, which includes many smaller branches and branches, are often subjected to this operation .

It is clear that environmental changes act as a “gardener”, which some phylet lines could not adapt to, while the growth of branches and the formation of lateral shoots are always a successfully completed process of adaptation to new (usually not favorable) environmental conditions. The strange addiction of the "gardener" to some large branches suggests that all species of the monophyletic taxon inherit from their common ancestor something that determines their ability to survive in a changing environment.

Mass extinctions have long worried biologists. Is it a joke when in a matter of millions of years the bundles represented by thousands of phyletic lines die? Suffice it to recall the death of the most advanced reptiles along the path of progress at the end of the Cretaceous, with as many as dinosaurs on land, pterosaurs in the air and ichthyosaurs in the water. In the end, the death can always be somehow explained (supernova explosion, asteroid crash, massive volcanic eruptions, etc.); it’s not only clear why some die, while others, seemingly no better and no worse, continue to flourish. If the heyday of mammals and birds can be explained by their warm-bloodedness, then why did not lizards and snakes die with the dinosaurs? Why did the sad fate of the ammonoids not befall the cephalopods with the inner shell?

So, what determines the evolutionary fate of phyletic groups?

The origin of fitness in organisms.

According to the teachings of Charles Darwin, under the conditions of natural selection, the fittest survives. Therefore, selection is the main reason for the emergence of various adaptations of living organisms to the environment. We show this by the example of the formation of adaptations in grouse birds for life in the lower tier of the forest. To do this, let us recall some features of the external structure and lifestyle of these birds: a short beak that allows peeling berries and seeds from forest litter, and in winter from the surface of the snow; horn fringes on the fingers providing walking in the snow, the ability to escape from the cold, burrowing into the snow at night; short, wide wings, making it possible to quickly and almost vertically take off from the ground.

Suppose that in the ancestors of grouse birds, the adaptations described above were not developed. However, when the habitat changed (due to cooling or due to some other circumstances), they were forced to winter in the forest, nest and feed on forest litter.

The continuous process of the emergence of new mutations, their combination during crossing, and waves of numbers ensured the genetic heterogeneity of the population. Therefore, the birds differed from each other in a number of hereditary characters: the absence or presence of fringes on the fingers, the size of the wings, the length of the beak, etc.

The intraspecific struggle for existence contributed to the survival of individuals in whom the signs of the external structure corresponded more to living conditions. In the process of natural selection, it was these birds that left prolific offspring and their number in the population increased.

A new generation of birds again carried a variety of mutations. Among the mutations, there could be those that enhanced the manifestation of previously selected traits. The owners of these traits were again more likely to survive and leave offspring. And so, from generation to generation, on the basis of strengthening and accumulating useful hereditary changes, the traits of adaptability of grouse to life in the lower tier of the forest have been improved.

The explanation of the occurrence 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 \u200b\u200bthe innate ability of organisms to change under the influence of the environment only in a direction useful to them. Everyone has famous hedgehogs sharp thorns reliably protect them from most predators. It is hard to imagine that the formation of such spines is caused by the direct influence of the environment. The occurrence of such a device can only be explained by the action of natural selection: even a slight coarsening of the hair could help the distant ancestors of the hedgehog. Gradually, over millions of generations, only those individuals who accidentally turned out to be owners of more and more developed spines survived. It was they who managed to leave offspring and pass on to them their hereditary characteristics. Instead of hair, the Madagascar “bristled hedgehogs” —tracks and some prickly-haired species of mice and hamsters — went along the same path of needle formation.

Considering other examples of adaptation in living nature (the appearance of thorns in plants, various hooks, hooks, flies in the seeds of plants in connection with the distribution of their animals), we can assume that the mechanism of their occurrence is common: in all cases, the devices do not immediately appear ready-made as something given, but they are long formed in the process of evolution through the selection of individuals that have a trait in the most pronounced form.

Examples of adaptations.

Correspondence of the structure of organs to the functions performed (for example, perfection aircraft birds, bats, insects) always attracted the attention of man and encouraged researchers to use the principles of organization of living beings when creating many machines and devices. No less striking is the harmonious relationship between plants and animals with the environment.

The facts testifying to the adaptability of living beings to living conditions are so numerous that it is not possible to give a somewhat complete description of them. Here are just some vivid examples of adaptive coloring?

To protect eggs, larvae, chicks, protective coloring is especially important. In openly nesting birds (capercaillie, eider, black grouse), the female sitting on the nest is almost indistinguishable from the surrounding background. Corresponds to the background and pigmented eggshell. It is interesting that in birds nesting in the hollow, females often have a bright color (tits, woodpeckers, parrots).

A surprising resemblance to twigs is observed among stick insects. Caterpillars of some butterflies resemble knots, and the body of some butterflies resembles a leaf. Here, the protective color is combined with the protective form of the body. When the stick stops, even at close range it is difficult to detect its presence - it merges with the surrounding vegetation. Each time, getting into the forest, on meadows, in the field, we don’t even notice how many insects are hiding on the bark, leaves, in the grass.

In the zebra and tiger, the dark and light stripes on the body coincide with the alternation of shadow and light of the surrounding area. In this case, animals are hardly noticeable even in open space from a distance of 50-70 m. Some animals (flatfish, chameleon) are even capable of rapidly changing protective color due to redistribution of pigments in the skin chromatophores. The effect of protective color increases when it is combined with the corresponding behavior: at the time of danger, many insects, fish, birds freeze, taking a rest pose.

A very bright warning color (usually white, yellow, red, black) is characteristic of well-protected poisonous stinging forms. Having tried several times to try the “soldier” bug, the ladybird, the wasp, the birds finally refuse to attack the victim with a bright color.

Interesting examples adaptations are associated with mimicry (from the Greek mimos - actor). Some defenseless and edible animals mimic species that are well protected from attack by predators. For example, some spiders resemble ants, and wasp-like flies are similar in appearance to wasps.

These and many other examples speak of the adaptive nature of evolution.

The relativity of fitness.

In the pre-Darwinian period of the development of biology, the fitness of living beings served as evidence of the existence of God: without an omnipotent creator, nature itself could not have arranged living beings so intelligently and so wisely adapted them to the environment. The prevailing opinion was that each individual device is absolute, since it corresponds to a specific goal laid down by the creator: the mouth parts of the butterfly are extended into the proboscis so that they can get nectar hidden in the depths of the corolla; a thick stalk of cactus is needed for storing water, etc.

The adaptability of organisms to the environment was developed during a long historical development under the influence of natural causes and is not absolute, but relative, since environmental conditions often change faster than adaptations are formed. Corresponding to a specific habitat, devices lose their value when it changes. The following facts may be evidence of the relative nature of fitness:

· Protective devices from some enemies are not effective from others (for example, poisonous snakes, dangerous for many animals, eat mongooses, hedgehogs, pigs);

· The manifestation of instincts in animals may be inappropriate (nocturnal butterflies collect nectar from light flowers, clearly visible at night, but also fly to the fire, although they die at the same time);

· An organ useful in some conditions becomes useless and even relatively harmful in another environment (membranes between the fingers of mountain geese, which never sink into the water);

· More advanced adaptations to this environment are also possible. Some species of animals and plants multiplied rapidly and spread widely in areas completely new to them. the globewhere they were accidentally or intentionally introduced by a person.

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

List of references.

· "The evolution of the organic world" N.N. Vorontsov, L.N. Sukhorukov;

· “Evolution and progress” V.A. Berdnikov;

· “Game of life” M. Eigen, R. Winkler;

· "Theory of Evolution" N.N. Vorontsov;

· "Principles of evolution" P. Keylow.

Animals that are able to maintain body temperature due to internal heat production are called endothermic - in contrast to ectothermic, whose body temperature depends on the ambient temperature. Endotherms are primarily all warm-blooded, i.e. mammals and birds (warm-blooded and cold-blooded animals are often called homeothermic and poikilothermic, respectively). ...

Animals,%; in hatched - dead,%; in squares - the dose of radiation, µC / kg The influence of the organism’s adaptation to increased muscular activity on its resistance to a large number of damaging environmental factors has been thoroughly studied. Such an influence is extremely great. First of all, it is an increase in the body's resistance to high-altitude hypoxia and the acceleration of acclimatization in ...

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In the far north (in the southern hemisphere there are none, since the continents do not reach such high latitudes), but also at high altitudes in the mountains. 3. Changes in the environment as a result of human activities Human activities can adversely affect living organisms, and cause the extinction of certain species (example with a turtle). In this section, we will look at how some species ...

The emergence of the fitness of organisms.
The main reason for the emergence of various adaptations of living organisms to the environment is selection. For example, it is known that partridge is a forest bird. Depending on the habitat, various adaptations appear in it: a) shortening of the beak in connection with the extraction of food from under the snow and leaf litter: b) the appearance of horn folds at the ends of the fingers to facilitate movement along the thick snow cover; c) expansion, rounding of the wings for quick lifting into the air (the ancestors of the partridge did not have such a structure).
For further distribution, the fruits and seeds of plants also underwent various changes. These are hooks, thorns with which they are attached to animals, or light fluff, which is scattered by the wind.
The appearance of fitness in plants and animals is a characteristic phenomenon, but in any case fitness does not appear immediately. As a result of a long evolutionary process, individuals with special traits adapted to environmental conditions appear.
Features of fitness in the structure, color, body shape and behavior are clearly visible on the example of an aquatic mammal - a dolphin. The pointed shape of the body gives him the ability to easily and freely move in water in different directions. Dolphin speed reaches 40 km / h. And in birds, flight fitness indicators are the presence of feathers covering the body; lack of auricles and teeth; the ability to rotate the head 180 "; light bones; fast digestion of food in the stomach, etc.
In many animals, fitness is so developed that it is difficult to distinguish them from the environment. The shape of the body, the color of fish, animals living in dense thickets of algae, help them successfully hide from enemies.

Types of fitness:

1. Patronizing (masking) coloring and its types.
2. Instinctive device.
3. Caring for the offspring.
4. Physiological adaptation.

Fig. 21. Fitness of night butterflies by changing the color to the corresponding colors of the tree trunk: 1 - the same number of marked dark and light butterflies; 2 - light tree trunk; 3 - increase in the number of light butterflies; 4 - increase in the number of dark butterflies; 5 - dark tree trunk

1. Patronizing (masking) coloring and its types. Patronizing coloring is the fitness of organisms that live openly and may be accessible to enemies. Birds hatching eggs on the ground (capercaillie, partridge, quail, etc.) merge with the surrounding background. A bird sitting on a nest motionless is almost invisible to its enemies. Eggs having a pigmented shell and the chicks hatching from them are hardly noticeable. Large predators whose eggs are inaccessible to enemies, or birds laying eggs high on rocks or burying them. into the ground, the protective color of the shell does not develop. Butterfly caterpillars are usually green in the color of leaves, or dark in color of the bark. Bottom fish (stingray, flounder) are often colored in the color of sand.
Desert animals are usually sandy yellow. Plain patronizing coloration is characteristic of insects (locusts), lizards, saigas, and lions. Many animals change color depending on the time of year. For example, arctic fox, white hare, partridge in winter are white. Day butterflies have a protective color on the lower part of the wings, and at night - on the upper part of the wings, so during the day they become noticeable to enemies and can die (the lower part of the wings is light). Patronizing coloration can also be observed by the shape of insects: the pupa of butterflies on a branch is very similar to a kidney; a larva attached to a branch in a stationary state is similar to a tree branch, etc.
Patronizing coloring is especially useful in the initial stages. individual development organism (eggs, larva, chick). A protective coloration is necessary for slowly moving animals or those that have entered a state of rest.
Many animals are able to quickly change color depending on the color of the environment, and this ability is inherited. For example: chameleon, flounder, agama.

Types of protective color:

1. protective coloring;
2. attractive coloring;
3. threatening coloration;
4. imitative coloring.

1. Protective warning painting peculiar to poisonous, stinging, or burning insects. For example, a ladybug (red, yellow, brown, dark red, striped) birds never peck due to the release of poisonous, bitter yellowish liquid (Fig. 22). If the chicks accidentally peck this beetle, then the next time they do not fit it. The scavenger beetle emits an unpleasant burning fluid, has a bright red striped color. The coloring of bees, bumblebees, wasps, poisonous snakes protects them from predators. Protective coloration also depends on the behavior of some insects and animals. Sometimes creeping bugs freeze in danger. A bittern nesting in the reeds, accidentally seeing the enemy, cranes its neck, raises its head and freezes. Cautious coloration in animals is combined with behavior that repels a predator.

Fig. 22. Warning color: 1 - ladybug; 2 - naryvnik

2. Attracting coloring. This coloration is especially important during breeding. The bright color of red butterflies, blue-winged grasshoppers, jerboas, plumage of male birds attracts females during the breeding season. On ordinary days, the color merges with the environment and becomes invisible to enemies (Fig. 23).

Fig. 23. Attracting coloring: 1 - red sash; 2 - blue-winged filly; 3 - jerboa

3. Threatening coloring. During danger animals take a threatening pose. For example, in moments of danger, a cobra raises its head straight, inflates its neck and assumes a threatening pose; the dark beetle raises its abdomen and gives off an unpleasant odor. The eared round head instantly reveals skin folds on the head and freezes with an open mouth. On the open wings of a mantis there are spots that look like eyes. In case of danger, spreading wings, the mantis scares away its enemy. Moths have the same spots (Fig. 24).

Fig. 24. Threatening color: eye spots on the wings of a butterfly (1) in a pose of threat are similar to the eyes of an elf owl (2)

4. Imitative coloring - mimicry (Greek. mimikos - "imitation"). This is an imitation of animals and plants by living organisms or certain inanimate objects of the environment. The precautionary coloration of unprotected organisms resembles one or more species. For example, in terms of body shape, size, bright color, the cockroach is similar to a ladybug. The shape of the body of a seahorse and fish-go resemble algae. The white butterfly mimics the inedible butterflies of the heliconid family (Fig. 25), and the flies - wasps. The similarity of poisonous snakes with poisonous snakes helps them protect themselves from enemies and survive.

Fig. 25. Imitative coloring: the butterfly-whit (T) is similar to the poisonous butterfly-heliconida (2)

Examples of mimetic coloring of plants.
Imitative coloring in plants is necessary to attract or intimidate animals. Usually there is no nectar on the flower of Belozor. To attract insects, it looks like a honey plant. Insects, sitting on a flower, contribute to its pollination. The flowers of the insectivorous plant (nepentes) are brightly colored. Insects, sitting on a flower, instantly fall into the "trap" and die. The shape of the flower and the smell of an orchid resembles a female of some insects, therefore male insects unwittingly sit on a flower and pollinate it.
Mimicry arises "under control" of natural selection. Its occurrence is associated with the accumulation of small beneficial mutations in edible species in the conditions of their joint dwelling with inedible. One of the main tools for protecting against enemies and adaptive signs is: for bugs and crabs - a chitin cover, for mollusks - shells, for crocodiles - scales, for armadillos and turtles - a shell, for a hedgehog and porcupine - needles.

Fitness. Protective coloration. Protective coloring. Attractive coloring. Threatening coloring. Mimetic coloring (mimicry).

1. main reason various adaptations of organisms to environmental conditions - this is selection.
2. Protective coloring - the fitness necessary to protect organisms that lead an open lifestyle from enemies.
3. Protective coloration is a type of protective coloration characteristic of poisonous, stinging, burning insects.
4. Attracting coloring - a type of protective color during the reproduction of organisms.
5. Threatening coloring is a way to protect animals from enemies by adopting a threatening pose.
6. Imitation of living organisms and inanimate objects of the environment is the fitness of organisms that are not able to defend themselves or are inactive.
7. What signs of organisms determine fitness?
8. How does fitness come about?
9. What are the types of protective color.
10. Demonstrate a protective coloring.
1. Which organisms are mimetic?
2. Give examples to prove the utility of eye-catching coloring.
3. What are examples of mimetic coloring in plants?

The task
Have you encountered insects in nature, freezing when touched? Pay attention to their actions, immobility. Pay attention to insects that produce an unpleasant odorous smell. Compare them. This task will help you become more familiar with the protective and threatening color of animals.
Try to complete the task.
What kind of examples are given patronizing coloring? Record, respectively, in capital letters: "ZSC" - protective; "PR" - attractive; "PD" is imitative.

1. Ladybug. 5. Nepentes (insectivorous plant).
2. Butterfly. 6. Bittern.
3. Dark beetle. 7. Male pheasant.
4. Sea Horse. 8. Mantis.

Sections: Biology

Lesson Objectives:

• repetition and consolidation of knowledge about the driving forces of evolution;
• to form the concept of adaptability of organisms to the environment, knowledge of the mechanisms of occurrence 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 living nature;
• to formulate specific knowledge about adaptive structural features, body color and animal behavior.

Equipment:

Table “Fitness and its relative nature”, photographs, drawings, collections of organisms of plants and animals, 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) What is the only directing driving force of evolution.
b) What is the supplier of selection material for the population?
c) It is known that hereditary variability, supplying material for selection, is random and not directed. How does natural selection become directed?
d) Give an explanation from evolutionary positions to the following expression: “Not individual genes, but whole phenotypes are selected. The phenotype is not only 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 (presentation is used)

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

In nature, there is a mismatch between the ability of organisms to unlimited reproduction and limited resources. Is that the reason ...? struggle for existence, as a result of which individuals who are most adapted to environmental conditions survive. (The output of the diagram to the screen, students write in a notebook)

So, one of the results of natural selection is the development of adaptations in all living organisms - adaptations to the environment, i.e. fitness is the result of natural selection under 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 students, the teacher gives a definition of fitness, which is written in a notebook, and displays on the slide screen)

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

What do you think fitness is for organisms?

Value:adaptability to environmental conditions increases the chances of organisms to survive and leave a large number of offspring. (Recording in notebooks, output to slide screen)

The question is, how are the devices formed? Let us try to explain the formation of the trunk of an elephant from the point of view of C. Linnaeus, J.B.B. Lamarck, C. Darwin.

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

Predictive student responses:

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

According to Lamarck: the idea of \u200b\u200bthe innate ability of organisms to change under the influence of the external environment. The driving force of evolution is the striving of organisms for perfection. Example: when getting food, elephants 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 a slightly longer trunk were more likely to get their own food and survive. This trait was inherited. So, gradually, a long trunk of elephants arose.

Which explanation is more real? Let's try to describe the mechanism of occurrence of devices. (On-screen diagram)

3. The variety of adaptations.

On student tables, drawings, collections illustrating various adaptations of organisms to the environment. Work in pairs or groups. Pupils describe adaptations, call them themselves or with the help of a teacher. On the screen, these devices appear during the conversation.

1. Morphological adaptations (changes in the structure of the body).

• streamlined body shape in fish and birds
• membranes between fingers in waterfowl
• dense coat in northern mammals
• flat body in bottom fish
• creeping and pillow-like form in plants in the northern latitudes and high mountains

2. Disguise: body shape and color merge with surrounding objects (slide).

(Seahorse, stick insects, caterpillars of some butterflies).

3. Patronizing coloring:

developed in species that live openly and may be accessible to enemies (eggs in 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, hare).

4. Cautious coloring:

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

5. Mimicry:

similarity in color, body shape of unprotected organisms to protected ones (fly-beetle and bee, tropical snakes and poisonous snakes; snapdragon flowers are similar to bumblebees - insects try to establish mating relationships, which contributes to pollination; eggs laid by a cuckoo). Copycats never outnumber the original view. Otherwise, the warning coloring will lose its meaning.

6. Physiological adaptations:

adaptability of life processes to living conditions.

• fat accumulation by desert animals before the dry season (camel)
• glands, eliminating excess salts in reptiles and birds living by the sea
• water conservation in cacti
• rapid metamorphosis in desert amphibians
• sonar, echolocation
• partial or complete suspended animation

7. Behavioral adaptation:

behavioral changes in certain conditions

• care for offspring improves the survival of young animals, increases the stability of their populations
• single pair formation in mating season, and in winter unification in packs. What makes feeding and protection easier (wolves, many birds)
• intimidating behavior (bombardier beetle, skunk)
• fading, imitation of injury or death (possums, amphibians, birds)
• prudent behavior: hibernation, feed storage

8. Biochemical adaptations:

are associated with the formation in the body of certain substances that facilitate the protection of ghosts or attack other animals

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

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

The relative nature of the devices.

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

What conclusion can be made?

Conclusion: any device is advisable only in the conditions in which it was formed. When these conditions change, adaptations lose their value or even harm the body. Consequently - fitness is relative.

In studying the topic, we relied on the teachings of C. Darwin on natural selection. It explained the mechanism by which organisms adapt to their living conditions and proved that fitness is always relative.

4. Consolidation of knowledge.

student tables have test sheets and answer cards.

1 option.

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

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

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

a) is the result of the active desire of organisms to adapt to specific environmental conditions;
b) is the result of a natural selection of individuals that turned out to be more adapted than others to environmental conditions due to the presence of hereditary changes that have arisen accidentally;
c) is the result of the direct influence of external conditions on the development of the corresponding attributes in organisms;
d) it was originally predetermined at the time the creator created the main types of living creatures.

3. The phenomenon. An example of which is the similarity of a lion fly and wasp in the color of the abdomen and the shape of the antennae:

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

4. An example of protective color:

5. An example of cautionary coloring:

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


g) the similarity in color and shape of the body.

Option 2.

1. The main effect of natural selection:

a) an increase in the frequency of genes in a population that ensures generational reproduction;
b) increasing the frequency of genes in the population, providing wide variability of organisms;
c) the appearance in the population of genes that ensure the preservation of the traits of a species in organisms;
d) the appearance in the population of genes that condition the adaptation of organisms to living conditions;

2. An example of protective color:

a) the green color of the singing grasshopper;
b) green color of leaves in most plants;
c) bright red color of a ladybug;
g) the similarity in the color of the abdomen in the flies and the wasp.

3. Masking example:

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

4. An example of cautionary coloring:

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

5. An example of mimicry:

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

Answer card:

	1	2	3	4	5
and
b
in
g

Homework:

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

The adaptability of the organism to its environment plays a huge role in the process of survival of living things 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.

Fitness - what it is

It lies in the correspondence of structural features, physiological processes and the 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 characteristic of all creatures of the planet from bacteria to higher life forms.

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

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

Habitat adaptability traits and their outcome

For example, the frog's body 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 him to be invisible against the background of snow.

The champion in camouflage practice is considered a 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 the effects of air temperature, solar UV rays, and even depends on the mood.

And the ladybug, instead of disguising, uses a different strategy for choosing a color - repelling. 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 woodpecker head is an excellent example of the formation of a certain body shape, structure and functioning of organs. The bird has a powerful but resilient beak, a very long thin tongue and a cushioning system that protects the brain from trauma during severe blows of a bird's beak to a tree trunk.

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

Geographical speciation

The use of the term “allopathic” species formation is also appropriate. 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 separated by natural barriers - rivers, mountains, etc.

In such a situation, there is a clash with new conditions and new “neighbors” - the species with which you need to learn how to interact. Over time, this leads to the fact that, due to the ability to adapt to the species, the formation and genetic fixing of new beneficial traits takes place.

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

Ecological speciation

Not associated with direct expansion of the range. It occurs as a result of the fact that within one area habitat conditions may vary.

So, among plants, an example is the species diversity of dandelion, which varies in Eurasia.

The relative nature of cactus fitness

The plant demonstrates an amazing ability to survive in the harshest conditions of drought: a wax film and spines 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 torrential downpours, 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 pass water during swimming and almost completely delays the transfer of heat from the skin of the animal. But, if you place a polar bear in a warmer habitat for its brown relatives, it will die from overheating.

The relative nature of the mole's fitness

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

And at the same time he does not focus on the surface at all: his visual system is undeveloped, and he can only move crawling.

The relative nature of the fitness of a camel

The hump of a camel is his pride! Precious water accumulates there under conditions of drought. 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 the hot sand, it has minimized perspiration. It’s not just that the nomads of the Sahara rode precisely on camels. But, alas, in snowy conditions, this hardy handsome man can not cope with movement, nutrition and maintaining body temperature.

What characterizes the adaptability of plants to pollination by insects

Plant flowers are beautiful, unlike each other, I want to admire them! True, the biological significance of this beauty is not to please a person.

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

Conclusion on the adaptability of organisms to the environment

Revealing patterns and studying the adaptations of the animal world in various forms of land, water, 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.

"The fitness of organisms and the formation of new species"

1. The fitness of organisms and its relativity

In the XIX century. studies have brought new data revealing the adaptability of animals and plants to environmental conditions; the question of the reasons for this perfection of the organic world remained open. Darwin explained the origin of fitness in the organic world through natural selection.

Let's get acquainted with some facts proving the fitness of animals and plants.

Examples of fitness in the animal kingdom. In the animal kingdom, various forms of protective coloring are widespread. They can be reduced to three types: patronizing, warning, camouflage.

Protective coloration Helps the body become less noticeable in the background. Among green vegetation, bugs, flies, grasshoppers and other insects are often colored green. The fauna of the Far North (polar bear, polar hare, partridge) is characterized by a white color. In deserts, yellow tones of animal coloration predominate (snakes, lizards, antelopes, lions).

Caution coloring clearly distinguishes the body in the environment with bright, motley stripes, spots (fly-leaf 2). It is found in poisonous, burning or stinging insects: bumblebees, wasps, bees, buzzing bugs. Bright, warning coloring usually accompanies other means of protection: hairs, spikes, stings, pungent or pungent smelling liquids. This type of coloring is threatening.

Disguise it can be achieved by similarity in body shape and color with any object: leaf, branch, twig, stone, etc. When in danger, the caterpillar of the moth butterfly stretches out and freezes on the branch like a knot. A butterfly rotten scoops in a stationary state can easily be mistaken for a piece of rotten wood. Disguise is also achieved. mimicry. By mimicry we mean similarities in color, body shape, and even in behavior and habits between two or more kinds of organisms. For example, bumblebees, prominent and wasp-like flies devoid of stings, are very similar to bumblebees and stinging insects.

You should not think that protective coloring is necessary and always saves animals from destruction by enemies. But organisms or groups that are more adapted by coloration die much less frequently than less adapted ones.

Along with the protective coloration, animals developed many other adaptations to living conditions, expressed in their habits, instincts, and behavior. For example, quail in case of danger quickly sink to the field and freeze in a motionless position. In the deserts, snakes, lizards, beetles hide from the heat in the sand. At the time of danger, many animals take 16 threatening poses.

Examples of fitness in plants. Tall trees, the crowns of which are freely blown by the wind, as a rule, have fruits and seeds with volatiles. The undergrowth and shrubs where the birds live are characterized by bright fruits with edible flesh. In many meadow grasses, the fruits and seeds have hooks with which they attach to the hair of mammals.

A variety of devices prevent self-pollination and provide cross-pollination of plants.

In monoecious plants, male and female flowers do not ripen at the same time (cucumbers). Plants with bisexual flowers are protected from self-pollination by the simultaneous maturation of stamens and pistils or by the peculiarities of their structure and relative position (in the primrose).

We give further examples: the delicate sprouts of spring plants - anemones, cleaners, blue copses, goose onions, etc. - transfer temperatures below zero due to the presence of a concentrated solution of sugar in the cell sap. Very slow growth, stunting, small leaves, the surface location of the roots of trees and shrubs in the tundra (willow, birch, juniper), extremely rapid development of the polar flora in spring and summer are all adaptations to life in permafrost.

Many weeds produce an immeasurably greater amount of seeds than cultivated ones - this is an adaptive attribute.

Manifold fixtures. Species of plants and animals are notable for their adaptability not only to inorganic environment conditions, but also to each other. For example, in a broad-leaved forest, grass-loving plants (crested anemone, anemone, lunatic, chistyak) form a grass cover in spring, and shade-tolerant plants (budra, lily of the valley, zelenchuk) in summer. Pollinators of early flowering plants are mainly bees, bumblebees and butterflies; summer flowering plants are usually pollinated by flies. Numerous insectivorous birds (Oriole, nuthatch), nesting in a deciduous forest, destroy its pests.

In the same habitat, organisms possess various adaptations. The dipper bird does not have swimming membranes, although it gets its own food by the water, diving, using its wings and clinging to the rocks with its feet. The mole and mole rat belong to burrowing animals, but the first digs with limbs, and the second makes underground passages with the head and powerful incisors. A seal swims with flippers, and a dolphin uses a tail fin.

The origin of adaptations in organisms. Darwin's explanation of the appearance of complex diverse adaptations to specific environmental conditions was fundamentally different from Lamarck's understanding of this issue. These scientists also sharply diverged in determining the main driving forces of evolution.

Darwin Theory gives a completely logical materialistic explanation of the origin, for example, of a patronizing coloration. Consider the appearance of the green color of the body of caterpillars living on green leaves. Their ancestors could be painted in some other color and not eat leaves. Suppose that due to some circumstances they were forced to switch to green leaf nutrition. It is easy to imagine that the birds stuck together a lot of these insects, clearly visible on a green background. Among the various hereditary changes that are always observed in the offspring, there could be changes in the color of the body of the caterpillars, which made them less noticeable on green leaves. Of the caterpillars with a greenish tint, some individuals survived and gave rise to prolific offspring. In subsequent generations, the process of predominant survival of caterpillars, less noticeable in color on green leaves, continued. Over time, due to natural selection, the green color of the body of the caterpillars more and more corresponded to the main background.

The appearance of mimicry can also be explained only by natural selection. Organisms with the slightest deviations in body shape, color, behavior, reinforcing similarities with protected animals, had more opportunities to survive and leave numerous offspring. The percentage of death of such organisms was lower than those that did not have beneficial changes. From generation to generation, the beneficial change has been enhanced and improved through the accumulation of signs of similarity with protected animals.

Driving force of evolution - natural selection.

Lamarck Theory turned out to be completely helpless in explaining organic expediency, for example, the origin of various types of protective coloring. It is impossible to assume that the animals "practiced" in the color or firm of the body and through exercise acquired fitness. The mutual adaptation of organisms to each other cannot be explained. For example, the origin of the proboscis in working bees in the flower structure of certain species of the pollinated plants is completely inexplicable. Worker bees do not breed, and the queen bees, although they produce offspring, can’t “exercise” the proboscis, since they do not collect pollen.

Let us recall the driving forces of evolution according to Lamarck: 1) “the desire of nature to progress”, as a result of which the organic world develops from simple forms to complex ones, and 2) the changing effect of the external environment (direct on plants and lower animals and indirectly involving nervous system on higher animals).

Lamarck's understanding of gradation as a gradual increase in the organization of living beings according to "immutable" laws essentially leads to the recognition of faith in God. The theory of direct adaptation of organisms to environmental conditions through the appearance in them of only adequate changes and the obligatory inheritance of attributes acquired in this way logically follows from the idea of \u200b\u200binitial expediency. Inheritance of acquired characters has not been experimentally confirmed.

To more clearly show the main difference between Lamarck and Darwin in understanding the mechanism of evolution, we will give an explanation in their own words of the same example.

The formation of long legs and a long neck in giraffes

By Lamarck

“It is known that this highest of mammals lives in the interior of Africa and is found in places where the soil is always dry and devoid of vegetation. This makes the giraffe eat around the foliage of the trees and make constant efforts to reach it. Due to this habit, which has long existed in all individuals of this breed, the front legs of the giraffe became longer than the hind legs, and its neck is so lengthened that this animal, without even lifting itself on its hind legs, raising its head only, reaches six meters (about twenty feet) in height ... Any change acquired by the body through habitual use, sufficient to make this change, is preserved in the future by reproduction, provided that it is inherent in both individuals jointly participating in fertilization in the reproduction of their species. This change is passed on and goes, therefore, to all individuals of subsequent generations who are exposed to the same conditions, although the descendants no longer have to acquire it in the way in which it was really created. "

According to Darwin

“The giraffe, by its high growth, very long neck, front legs, head and tongue, is perfectly adapted to picking leaves from the upper branches of trees ... the tallest individuals, which were an inch or two taller than others, could often survive during periods of drought, wandering in looking for feed across the country. This insignificant difference in size, due to the laws of growth and variability, does not matter for most species. But it was different with the emerging 10 giraffe, if we take into account its probable way of life, because those individuals in which any or several different parts of the body were longer than usual should have experienced at all. When crossing, they should have left offspring either with the same structural features or with a tendency to change in the same direction, while individuals organized less favorably in this regard should have been more prone to death. ... natural selection protects and thereby separates all higher individuals, giving them the full opportunity to interbreed, and contributes to the destruction of all lower individuals. "

The theory of direct adaptation of organisms to environmental conditions through the appearance of adequate changes and their inheritance finds supporters at the present time. To reveal its idealistic character is possible only on the basis of a deep assimilation of Darwin's teachings on natural selection - the driving force of evolution.

Relativity of adaptations of organisms. Darwin’s doctrine of natural selection not only explained how fitness could have arisen in the organic world, but also proved that it always has relative nature. In animals and plants, along with useful signs, useless and even harmful ones are found,

Here are a few examples of organs that are useless for organisms: the slate bones in a horse, the remains of the hind limbs in a whale, the remains of the third century in monkeys and humans, the vermiform appendix of the cecum in humans.

Any adaptation helps organisms survive only in those conditions in which it was developed by natural selection. But even in these conditions it is relative. On a bright, sunny day in winter, the white partridge shows itself as a shadow in the snow. A hare, invisible in the snow in the forest, becomes visible against the background of trunks, running out to the edge of the forest.

Observations of the manifestation of instincts in animals in some cases show their inappropriate nature. Butterflies fly to the fire, although they die at the same time. Instinct draws them to the fire: they collect nectar mainly from light flowers, clearly visible at night. The best protection of organisms is far from reliable in all cases. Sheep eat without harm for themselves the Central Asian karakurt spider, whose bite is poisonous to many animals.

The narrow specialization of the organ can cause the death of the body. The Swift cannot take off from a flat surface, since it has long wings, but very short legs. He takes off, only pushing himself from some edge, like from a springboard.

Plant adaptations that prevent animals from eating are relative. Hungry cattle also eat plants protected by thorns. The mutual benefits of organisms linked by symbiotic relationships are also relative. Sometimes the lichen mushroom threads destroy the algae cohabiting with them. All these and many other facts say that expediency is not absolute, but relative.

Experimental evidence of natural selection. After Darwin's time, a series of experiments were carried out confirming the presence of natural selection in nature. For example, fish (gambusia) were placed in pools with a differently colored bottom. Birds destroyed 70% of the fish in the basin where they were more visible, and 43% where they were better suited to the background of the bottom in color.

In another experiment, we observed the behavior of a wren (a detachment of passerines), which did not peck the moth caterpillars with a protective color until they moved.

Experiments have confirmed the value of cautionary coloring in the process of natural selection. At the edge of the forest, insects belonging to 200 species were spread on the boards. Birds flew about 2000 times and pecked only those insects that did not have a warning color.

It was also experimentally established that most birds avoid hymenopteran insects with an unpleasant taste. Having pecked a wasp, the bird does not touch wasp-like flies from three to six months. Then he starts pecking them until he hits the wasp, after which he again does not touch the flies for a long time.

Experiments were conducted on "artificial mimicry." The birds eagerly ate the larvae of the beetle, the flour Khrushchak, stained with tasteless carmine paint. Some of the larvae were coated with a mixture of paint with quinine or another unpleasant taste substance. Birds, having encountered such larvae, stopped pecking all colored larvae. The experience was changed: various drawings were made on the body of the larvae, and the birds took only those whose drawing was not accompanied by an unpleasant taste. Thus, a conditioned reflex to warning bright signals or patterns arose in birds.

An experimental study of natural selection was also carried out by botanists. It turned out that weeds have a number of biological characteristics, the appearance and development of which can be explained only as adaptations to the conditions created by human culture. For example, plants camelina (sem. Cruciferous) and torica (sem. Clove) have seeds that are very similar in size and weight to flax seeds, the crops of which they clog. The same can be said about the seeds of the rattle wingless (sem. Norichniki), which clogs the crops of rye. Weed plants usually ripen simultaneously with cultivated plants. The seeds of those and others are difficult to separate from each other during winnowing. The man mowed, threshed the weeds with the crop, and then sowed on the field. Involuntarily and unconsciously, he contributed to the natural selection of seeds of various weeds along the lines of similarity with seeds of cultivated plants.

2. The formation of new species

For a long time, man was struck by the diversity of the organic world. How did it come about? The doctrine of natural selection explained how new species are formed in nature. Darwin proceeded from facts regarding domestic breeds. Initially, the breeds of domestic animals were less diverse than modern ones. Pursuing different goals, people carried out artificial selection in various directions. As a result of the breed diverged, i.e., diverged in signs with each other and with their common parent breed .

Divergence in vivo. Divergence occurs all the time in nature, and its driving force is natural selection. The more the descendants of a species differ from each other, the easier they spread over more numerous and more diverse habitats, the easier it will reproduce. Darwin reasoned this way. Some predatory four-legged in number has reached the limit of the possibility of existence in this area. Assume that the physical conditions of the country have not changed; can this predator breed further? Yes, if descendants capture places occupied by other animals. And this can happen in connection with the transition to another food or in new living conditions (on trees, in water, etc.). The more diverse the descendants of this predator will be in their characteristics, the wider they will spread.

Darwin gives an example. If on one plot of land sow grasses of one species, and on another, similar, grasses belonging to several different species or genera, then in the second case the total yield will be greater.

In nature on a site with an area of \u200b\u200bslightly more than 1 m2 Darwin counted 20 various kinds plants belonging to 18 genera and 8 families.

Such facts confirm the correctness of the proposition put forward by Darwin: “... the greatest amount of life is carried out with the greatest variety of structure ...” Between plants of the same species, with their identical needs for soil, moisture, lighting, etc., the most fierce biological competition takes place. With natural selection, the forms that are most different from each other will be preserved. The more noticeable the differences between the adaptive attributes of forms, the more the forms themselves diverge.

Due to natural selection, the evolutionary process is divergent character: a whole “fan” of forms originates from one initial form, like special branches from one common root, but not all of them get further development. Under the influence of natural selection in an infinitely long series of generations, some forms are preserved, others die out; simultaneously with the process of divergence, the process of extinction is going on, and both of them are closely related. The most diverging forms of signs have the greatest potential to survive in the process of natural selection, since they compete less with each other than intermediate and parental ones, which gradually thin out and die out.

A variety is a step towards the formation of a species. Darwin imagined that the process of the formation of new species in nature begins with the decomposition of the species into intraspecific groups, which he named varieties.

Due to natural selection and divergence, varieties acquire more and more distinguishing their hereditary characters and become special, new species.

The difference between species and species is very large. Species of one species interbreed and produce prolific offspring. Species in natural conditions, as a rule, do not interbreed, due to which biological isolation of species occurs.

To better explain how the process of speciation in nature proceeds, Darwin proposed the following scheme (Fig. 11).

The diagram shows the possible evolutionary paths of 11 species of the same genus, indicated by the letters A, B, C, etc., up to and including L. The distances between the letters indicate the proximity between the species.

Thus, the species indicated by the letters D and E or F and G are less similar to each other than the species A and B or K and L, etc. Horizontal lines indicate individual stages in the evolution of these species, with each stage conditionally taken as 1000 generations.

Let us trace the evolution of species A. A bunch of dashed lines from point A depicts its descendants. Due to individual variability, they will differ from each other and from the original species A. Useful changes will be preserved in the process of natural selection. At the same time, divergence will find its beneficial effect: signs that are most different from each other (lines a1 and t1 of the beam) will remain, will accumulate from generation to generation and diverge more and more. Over time, taxonomists recognize A1 and T1 as special varieties.

Suppose that during the first stage - the first thousand years - two distinct varieties a1 and t1 arose from species A. Under the influence of the conditions that caused changes in the parental species A, these varieties will begin to change further. Maybe at the tenth stage they will have such differences between themselves and with type A that they should be considered as two separate types: a10 and t10. Some species will die out, and perhaps the tenth stage will reach only f10, forming a third species. At the last stage, 8 new species are presented, originating from species A: a14, q14, p14, b14, f14, o14, e14 and t14. Species a14, q14 and p14 are closer to each other than to the rest of the species, and form one genus, the remaining species give two more genera. The evolution of species I proceeds in a similar way.

The fate of other species is different: of these, only species E and F survive to the tenth stage, species E then dies out. Particularly note species F14: it has survived to our time almost unchanged compared to the original species F. This can happen if the environmental conditions do not change or change very little over time.

Darwin emphasized that only the most divergent, extreme varieties were not always preserved in nature, the middle ones could also survive and produce offspring. One species can overtake another in its development; only one of the extreme varieties sometimes develops, but three can also develop. It all depends on how the infinitely complex relationships of organisms develop between themselves and with the environment.

Examples of speciation. We give examples of the formation of species, and we will use the term subspecies, accepted in science instead of "variety".

Widely settled species, for example, brown bear, white hare, common fox, common squirrel, are found from the Atlantic to Pacific and have a large number of subspecies. More than 20 species of buttercup grow in the middle zone of the USSR. All of them descended from one parent species. His descendants captured various habitats - steppes, forests, fields - and due to divergence, they gradually separated from each other, first in subspecies, then in species (Fig. 12). Check out the other examples in the same figure.

Speciation continues in our time. A jay with black plumage at the back of the head lives in the Caucasus. It can not yet be considered an independent species; it is a subspecies of an ordinary jay. In America, there are 27 subspecies of the song sparrow. Most of them seem to differ little from one another, but some have sharp differences. Over time, subspecies intermediate in their characteristics may become extinct, while the extreme subspecies will become independent young species, having lost the ability to interbreed with each other.

The value of isolation. The vast territory of the settlement of the species favors natural selection and divergence. This occurs during the resettlement of a species in separate areas. In such cases, the penetration of organisms from one locality to another is very difficult and the possibility of crossing between them is sharply reduced or completely absent.

Here are some examples. In the Caucasus, in areas separated by high mountains, there are special subspecies of butterflies, lizards, etc. Many species and genera of ciliary flatworms, crustaceans, and fish that are not found anywhere else live in Lake Baikal. This lake has been separated from other water basins by mountain ranges for about 20 million years, and only through rivers it communicates with the Arctic Ocean.

In other cases, organisms cannot interbreed due to biological isolation. For example, two species of sparrow - house and field - keep together in winter, but they usually nest differently: the first is under the roofs of houses, the second is in hollows of trees, along the edges of the forest. The species of blackbird is currently divided into two groups, which are still indistinguishable externally. But one of them lives in dense forests, the other keeps close to human habitation. This is the beginning of the formation of two subspecies.

Convergence. In germinating conditions of existence, animals of various systematic groups sometimes acquire similar adaptations to the environment if they are exposed to the same selection factor. This process is called convergence - convergence of signs. For example, the front digging limbs of a mole and a bear are very similar, although these animals belong to different classes. The cetaceans and fish strongly resemble each other in body shape, and the limbs are similar in floating animals belonging to different classes. Convergent are physiological features. The accumulation of fat in pinnipeds and cetaceans is explained by the result of natural selection in the aquatic environment: it reduces the heat loss by the body.

Convergence within the distant systematic groups (types, classes) is explained only by the effect of similar living conditions on the course of natural selection. The convergence of relatively closely related animals is also influenced by the unity of their origin, which, as it were, facilitates the occurrence of similar hereditary changes. That is why it is observed more often within the same class.

The variety of species. Darwin's doctrine of the evolution of the organic world explains species diversity as an inevitable result of natural selection and the associated divergence of traits.

Gradually, in the process of evolution, species became more complex, the organic world rose to an ever higher level of development. However, everywhere in nature, animals and plants coexist at the same time, with varying degrees of complexity of their organization.

Why didn’t natural selection “raise” all low-organized groups to the highest level of organization?

By natural selection, all groups of plants and animals are adapted only to their own conditions of existence, therefore they could not rise to the same high level of organization. If these conditions did not require increasing the complexity of the structure, then its degree did not increase because, according to Darwin, "under very simple living conditions, a high organization would not provide any service." In the Indian Ocean, under more or less constant conditions, species of cephalopods (nautilus) inhabit almost unchanged for many hundreds of millennia. The same applies to modern bristled fish.

Thus, the simultaneous coexistence of organisms of different structural complexity is explained by the theory of natural selection and divergence.

Natural selection results. Natural selection has three closely related important consequences: 1) the gradual complication and increase the organization of living beings; 2) the adaptability of organisms to environmental conditions; 3) variety of species.

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