Types of adaptations of organisms. The adaptability of organisms to the environment. Aquatic habitat

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 coloring 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: “It is not individual genes that are selected, but whole phenotypes. 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 matters 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's 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 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 like 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
• crystals of oxalic potassium in the 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.

When 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 traits 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
at
g

Homework:

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

§ 7 - ADAPTIVE FEATURES OF STRUCTURE, BODY PAINT AND BEHAVIOR OF ANIMALS

1) Expand the content of the concept of "adaptability of the species to environmental conditions."

• Answer: Plants and animals are adapted to the conditions of their environment, not only externally, but also in their internal structure. The structure of the organs and physiological functions of the body correspond to the living conditions. Their complexity and variety.

2)   List the main types of adaptations of organisms to the environment.

• Answer:
• 1- Body shape.
• 2- Various types of coloring and mimicry.
• 3- Features external structure.
• 4- Adaptive behavior.

3)   Compare such stains as cautionary stain, protective stain, and mimicry by special attention  on their distinguishing features. Give examples of animals with such devices. Fill the table.

• 4) Complete the above diagram of the evolutionary mechanism of the appearance of mimicry.

  5) Answer whether the animal’s behavior falls within the scope of natural selection. If yes, give an example.

  • Answer: The behavior of the animal falls within the scope of natural selection. These are behaviors such as demonstrative, frightening and others that ensure the survival of the species. Example, winter feed supply.

  6)   Insert the missing word.

  • Answer: The main consequence of acquiring adaptations is the state fitness  organisms to the habitat.

  § 8- CARE FOR EMPLOYMENT

  1) Invertebrates and lower vertebrates, fertility, as a rule, is significantly higher compared with highly organized vertebrates. Suggest an explanation for this biological pattern.

  • Answer: This is because more developed animals take better care of their offspring, while lower animals put off a large number of  eggs and leave them to their own devices.

  2) Complete the sentence.

  • Answer: In animals with pronounced care for offspring, the number of cubs is relatively lessthan animals that care little for offspring.
  • Give examples: most species of fish, Mammals, carry one or more cubs in the womb and then feed them for a long time.

  3)   Give examples of fish care for offspring.

  • Answer:
  • 1- Azov and Caspian bulls lay eggs in the pits and protect it.
  • 2- Male stickleback builds a nest with an exit and an entrance and guards.
  • 3- American catfish carries eggs on the belly.

  4) Give examples of progeny care for amphibians.

  • Answer: A female marsupial frog carries eggs in a bag on its back.

  5)   Add the sentence.

  • Answer: The greatest safety of young animals is achieved with such a form of care for offspring as embryo development in the mother’s body.

  6) It is known that the care of the offspring of some arthropods is carried out in the form of providing them with food. Give an example.

  • Answer: Insects lay eggs (larvae) in the body of animals. Larvae feed on animal tissues.

  7)   Indicate by what physiological mechanisms the methods of caring for offspring in higher vertebrates achieve high perfection.

  • Answer: Physiological mechanisms: complex instincts, the ability to individual learning.
  • Examples:
  • In birds - nest building.
  • In mammals - feeding, protecting offspring, training them to catch prey and avoid dangers.

  § 9- PHYSIOLOGICAL ADAPTATIONS

  1)   Expand the content of the concept of “physiological adaptation”.

  • Answer: Physiological adaptation - a combination of all the characteristics of the species with the adaptability of life processes to the living conditions, which ensures success in the struggle for existence.

  2)   Try to explain the evolutionary mechanism of physiological adaptations.

  • Answer: All evolutionary changes — the formation of new populations and species, the complexity of organization — are due to the development of numerous adaptations and adaptations to the living conditions of the species.

  3) Explain how to adapt to a lack of water:

  • Answer:
  • A) in amphibians - they become active in the period after rain and at night.
  • B) in birds - they accumulate fat, which then, when split, forms water.
  • C) in mammals - they accumulate fat, some regulate the loss of water from the surface of the respiratory tract

  4)   Complete the sentence.

  • Answer: The essence of a functional device that allows you to form an oxygen depot in the body of diving animals is the presence of the respiratory pigment myoglobin in the muscles, allowing you to save 10 times more oxygen.

  5)   Describe the physiological adaptations that increase the efficiency of food searches:

  • Answer:
  • A) in insects, organs of chemical sensation that capture odors over a long distance.
  • B) in snakes - the ability to thermolocation.
  • C) in nocturnal predators - the ability to echolocation.

  6) Confirm the thesis: "Adaptations do not ensure the absolute safety of their carriers." Give three specific examples.

  • Answer: Most birds do not eat wasps and bees, but some eat. Hedgehogs eat snakes. Predator birds  they lift the turtles into the air and smash their carapace, and then eat them.

  7)   Complete the statement.

  • Answer: It has been shown that if rats are transferred to a soft diet and all solid objects are removed from the cage, then giant fangs grow in them, which prevent them from eating. This observation is another argument in favor of the assertion that any devices "work" only in the usual kind of environment.

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

Adherents of idealistic views and ministers of the church in the manifestations of the fitness of organisms and their expedient structure saw an expression of the general harmony of nature, allegedly emanating from its creator. The theory of C. Darwin rejects any participation in the emergence of adaptations of supernatural forces; it convincingly proved that the whole animal and vegetable world  since its inception, it has been improving along the path of appropriate adaptations to living conditions: water, air, sunlight, gravity. The amazing harmony of wildlife, its perfection is created by nature itself: the struggle for survival. This struggle is the force that gives strength to the roots, sophisticated beauty of flowers, causes a bizarre mosaic of leaf arrangement and grinds teeth, gives powerful muscles, visual acuity, hearing and intuition to many animals.

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

A variety of devices exclude the possibility of self-pollination in most plants, allow them to distribute fruits and seeds or, thanks to thorns, withstand eating herbivores. The aroma and bright color of the flowers arose as a device for attracting insects, which, visiting flowers, cross-pollinate these plants, or as a device for more efficient absorption of sunlight of a certain length.

Protective coloration. Patronizing coloring is developed for species that live openly and may be accessible to enemies. Such coloring makes organisms less noticeable against the background of the surrounding area. Some people have a bright pattern (coloring of a zebra, tiger, giraffe) - an alternation of light and dark stripes and spots. This dissecting color, as it were, imitates the alternation of spots of light and shadow.

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

Mimicry. Mimicry - imitation of a less protected organism of one species to a more protected organism of another species. This imitation can manifest itself in the form of a body, coloring, etc. So, some species do not poisonous snakes  and insects look like poisonous. Mimicry is the result of the selection of similar mutations in different species. It helps unprotected animals to survive, helps to preserve the body in the struggle for existence.

Warning (threatening) coloring Species often have a bright, catchy color. Once trying to taste the inedible ladybug stinging wasp, the bird will remember them for life bright coloring.

  (Based on materials from the personal page of Ivanov Andrey)

In the doctrine of natural selection, Darwin not only materialistically substantiated the fitness of organisms (their expedient structure), but also showed its relative nature. So, preventive and protective coloring, various other protective devices do not work on all pursuers, but, having devices, individuals are less likely to be attacked. The owners of the sting - wasps, bees, hornets - are easily eaten by flytraps, bee-eater. Flying fish, jumping out of the water into the air, cleverly escapes from predatory fish, but this is used by the albatross, overtaking his prey in the air. The tortoise shell is a good defense, but the eagle lifts it into the air and throws it on the rocks; the shell breaks, and the eagle eats the turtle.

Each animal and plant cannot be fully adapted to all the conditions that developed during the whole life on Earth. Any adaptation persists as long as it is supported by natural selection, but disappears as soon as it ceases to be useful. An example of a change in devices is the development of protective color in the butterfly of the birch moth.

Thus, the basis of Darwin's theory is the doctrine of natural selection - the main and guiding factor in evolution. In the struggle for existence based on hereditary variation occurs sequential shift  adaptations and survival of the fittest, the diversity of wildlife forms is increasing, the process of speciation is taking place and the general progressive development of the plant and animal world is being carried out. Two problems have been resolved in this theory: the mechanism of speciation and the origin of the expediency of the organic world.

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

Fitness indicators	Plants	Animals
Ways to get food	The absorption of water and mineral salts is ensured by the intensive development of roots and root hairs;    absorption of solar energy is carried out most successfully by wide and thin leaves;    capture and digestion by swamp plants of insects and small amphibians	Leaf eating on tall trees; capture with the help of a hunting net and trapping food objects; the special structure of the oral organs ensures the capture of insects from long, narrow holes, biting grass, catching flying insects; Grabbing and holding prey by predatory mammals and birds
Protection against eating	They have thorns providing protection against herbivores; contain toxic substances; rosette leaf shape not available for etching	Saved by a quick run; have needles, shells, a scaring smell, and other protection; protective coloring saves in certain conditions
Adaptation to abiotic factors (to cold)	Falling of foliage; cold resistance; preservation; vegetative organs in the soil	Flight south; thick coat; hibernation; subcutaneous fat
Spread to new territories	Light, winged seeds; tenacious hooks	Overflights of birds; animal migration
Breeding efficiency	Attraction of pollinators: flower color, smell	Attraction of a sexual partner: bright plumage, sexual attractants

Each organism is surprisingly adapted to certain living conditions. This fitness is manifested in the features of the external and internal structure, in behavior, in reproduction and care for offspring.

In external structure  striking examples of fitness are body shape  and special protective equipment. For example, the streamlined shape of the body of fish and birds, the bizarre shape of animals lurking while waiting for prey or hiding from enemies (seahorse-rag, clown fish). Spines of a hedgehog and porcupine protect these animals from enemies.

Vivid examples of fitness are protective stains  animals: patronizing, warning, mimicry(Fig. 346). Patronizing coloration of a green grasshopper, mantis, birds, hatched eggs on the ground. Warning stains in poisonous or stinging animals. For example, wasps, bumblebees, ladybugs are inedible and, as it were, with their bright colors, warn of danger. Mimicry  - resemblance to inedible objects or poisonous animals that have a warning color. For example, a glass-butterfly is very similar to a wasp, a bee-fly is like a bee, a bumblebee is like a bumblebee, and a stick is like a twig.

In addition to body shape and color, great importance  has and adaptive behavior   animals. For example, many rodents store food for the winter, some animals lurk during danger, many are characterized by frightening behavior.

Fitness manifests itself in features of reproduction and care for offspring. Many fish guard their eggs (a male of a three-spined stickleback even builds a nest, drives the water over the laid caviar with fins, "grazes" the first time of the larvae), some carry eggs in the mouth (tilapia). If care for the offspring is weakly expressed, then in this case the animals have very high fecundity, as is observed in invertebrates and lower vertebrates, that is, the rules are followed - “ the less - the more, the more - the less"- the less offspring, the more care for him and vice versa.

But any fitness relative: it is advisable only in specific conditions, when they change, the devices are useless for the body. For example, needles save a hedgehog on land, in the water the hedgehog unfolds, becomes defenseless in front of a fox.

Thus, the theory of C. Darwin answered the main questions. biological science: how variety and amazing fitness of species arose. Material for selection gives hereditary, mutational variation, as a result of sexual reproduction (combinatorial variation), these mutations spread and fall under the control of natural selection. As a result of selection from a variety of diverse, non-directional mutations, individuals with mutations useful for these conditions predominantly survive. As a result of divergence, divergence of characters, differences become so serious that genetic isolation occurs, leading to the formation of new species.

View. View criteria

Species - a collection of individuals possessing a hereditary similarity of morphological, physiological and biochemical characteristics, freely interbreeding and producing prolific offspring, adapted to certain living conditions and occupying a specific area in nature - range.

Characteristics by which species differ from each other are called species criteria. The following view criteria are distinguished.

© Morphological criterion  implies the outward resemblance of individuals belonging to the same species. But sometimes individuals of the same species are very different (dachshund and Great Dane), or vice versa, there are species morphologically almost indistinguishable, the so-called double speciesthat do not cross are genetically isolated. For example, two species of black rats: one species has 38 chromosomes in the karyotype, the other 42. The morphological criterion is therefore not enough to determine the species.

© The main one is genetic criterion: each species has its own karyotype - its own chromosome set. Species usually differ in the number and structure of chromosomes. It is this criterion that provides genetic isolation, non-crossbreeding between individuals different types. Even if interspecific hybrids appear, they are sterile, the process of the formation of germ cells is disrupted. But sometimes this criterion also fails, since prolific offspring can appear when mating individuals belonging to different species.

© Individuals of one species are similar in all physiological processes - nutrition, respiration, excretion, reproduction, which underlies physiological criterion. The differences in the physiology of reproduction are especially important: in the structure of the reproductive apparatus, in the timing of reproduction.

© Biochemical criterion - Comparison of organic macromolecules in various species, primarily a comparison of DNA and proteins. By similarity in the structure of DNA and proteins, it is possible to show with sufficient probability how close relatives these or those species are. For example, chimpanzee hemoglobin in amino acid sequence does not differ from human hemoglobin.

© Geographic criteria  - this is the territory on which this species lives (range). Some endemic species have a small range; there are species - cosmopolitans, which are ubiquitous. But the distribution areas of various species often overlap, so this criterion cannot be decisive.

© Each species is adapted to certain conditions of existence, to certain environmental factorsthat make up the foundation environmental criteria. For instance, polar bear  adapted to one environmental factor, brown - to others.

To establish the species affiliation, one cannot rely on one of the criteria, it is necessary to take into account their combination.

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 original (maternal) species can continue to live. A different fate develops for the species when its habitat slowly but steadily worsens. 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. Such 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 emerged 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 bunch collection 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 their ability to grow further. This "gardener" in his work adheres to some rules: firstly, he cuts only the branches located on maximum height, and, secondly, all the 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 bunches 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, mass eruptions of volcanoes, 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 cephalopods with an inner shell?

So, what determines the evolutionary fate of phyletic groups?

The origin of fitness in organisms.

According to the teachings of Charles Darwin, the fittest survives in conditions of natural selection. 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 snow surface; 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 sheerly 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 when crossing, 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 survived who accidentally turned out to be owners of more and more developed thorns. 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 wildlife (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?

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

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 ladybug, the wasp, the birds finally refuse to attack the victim with a bright color.

Interesting examples of adaptation 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 proof of the existence of God: without an omnipotent creator, nature itself would not be able to arrange living beings so intelligently and adapt them so wisely to the environment. The prevailing opinion was that each individual device is absolute, as 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 is developed in the process of 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 can 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 completely new regions of the globe for which they were accidentally or intentionally introduced by humans.

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

Bibliography.

· "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.

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