Biology lesson. Topic: "The adaptation of organisms to the environment as a result of natural selection." The fitness of organisms is the result of the action of evolutionary factors. Relative nature of fitness Adaptability of organisms to conditions

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

In external structure prime examples of adaptability are body shape and special means of protection. For example, the streamlined shape of the body of fish and birds, the bizarre shape of animals hiding while waiting for prey or hiding from enemies (rag-picker seahorse, clown fish). The spines of the hedgehog and porcupine protect these animals from enemies.

Vivid examples fitness are protective colors animals: patronizing, warning, mimicry(Fig. 346). Protective coloration of a green grasshopper, praying mantis, birds hatching eggs on the ground. Warning colors in poisonous or stinging animals. For example, wasps, bumblebees, ladybugs are inedible and, with their bright colors, seem to 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 looks like a bee, a bumblebee fly looks like a bumblebee, a stick insect looks like a twig.

In addition to the shape of the body and color, it is also of great importance adaptive behavior animals. For example, many rodents store food for the winter, some animals hide in times of danger, and many are characterized by frightening behavior.

Adaptability also appears in features of reproduction and care of offspring. Many fish protect their eggs (the male of the three-spined stickleback even builds a nest, drives water over the laid eggs with his fins, “herds” the larvae at first), some bear eggs in their mouths (tilapia). If care for offspring is poorly expressed, then in this case the animals have a very high fecundity, as is observed in invertebrates and lower vertebrates, that is, the rules are followed - “ less is more, more is less"- the less offspring, the more care for him and vice versa.

But any adaptation relative: it is expedient only in specific conditions, when they change, the adaptations turn out to be useless for the body. For example, needles save a hedgehog on land; in water, a hedgehog turns around and becomes defenseless against a fox.

Thus, Charles Darwin's theory gave answers to the main questions of biological science: how did the diversity and amazing adaptability of species arise. The material for selection provides hereditary, mutational variability; as a result of sexual reproduction (combinative variability), these mutations spread and fall under the control of natural selection. As a result of selection from a variety of diverse, undirected mutations, individuals with mutations that are useful for given conditions survive predominantly. As a result of divergence, divergence of characters, the differences become so serious that genetic isolation occurs, leading to the formation of new species.

View. View criteria

Species - a set of individuals that have a hereditary similarity of morphological, physiological and biochemical features, freely interbreed and give fertile offspring, adapted to certain living conditions and occupying a certain area in nature - an area.

The characteristics by which species differ from each other are called species criteria. There are the following type criteria.

© Morphological criterion implies the external similarity 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 that are morphologically almost indistinguishable, the so-called sibling species that do not interbreed are genetically isolated. For example, two species of black rats: one species has 38 chromosomes in the karyotype, the other has 42. Therefore, one morphological criterion not enough to determine 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-crossing between individuals different types. Even if interspecific hybrids appear, they are sterile, the process of formation of germ cells is disrupted. But sometimes this criterion also fails, since fertile offspring can appear when individuals belonging to different species are crossed.

© Individuals of the same species are similar in all physiological processes - nutrition, respiration, excretion, reproduction, which underlies physiological criterion. 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 kinds, primarily a comparison of DNA and proteins. By the similarity in the structure of DNA and proteins, one can show with sufficient probability how close relatives are certain species. For example, chimpanzee hemoglobin does not differ in amino acid sequence from human hemoglobin.

© Geographic criterion is the area in which the species lives (habitat). Some endemic species have a small range, there are species - cosmopolitans, distributed everywhere. But the areas of distribution of different species often overlap, so this criterion cannot be decisive.

© Each species is adapted to certain conditions of existence, to certain environmental factors that form the basis ecological criterion. For example, polar bear adapted to some environmental factors, brown - to others.

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

Biology knows many cases when a group that accidentally broke away from the main population can, in a few centuries, form a completely the new kind. Sometimes it even happens that, at the same time, individuals of the maternal species continue to live in the same territory.

There are also many examples where species are forced to live in a constantly changing environment. Often, “change” refers to the constant deterioration of some vital indicator. When outside this range, the species most often simply dies out.

Survival Prerequisites

Scientists came to the conclusion that the species has a chance of survival only if it begins to actively change, adapting to dramatically changed conditions. This phenomenon is called phyletic speciation. In this case, not only the adaptability of organisms to the environment is formed, but completely new signs for living beings develop.

Millions of species now live on our planet. Is this not evidence of the power of life, its constant variability?! Unfortunately, several million years ago there were much more living beings. Several ice ages and constant climate perturbations have led to the fact that the species diversity has sharply decreased. Only the fittest survived.

Important examples of adaptations

From time immemorial, the ingenious correspondence of the organs of living beings and the function they perform has attracted the attention of people: attempts to create gliders with a bird-shaped wing, the construction of ships with contours resembling bodies marine fish. But much more striking is the perfect, harmonious correspondence appearance animals and plants with their natural habitat.

Of course, the examples are endless. Therefore, within the framework of this article, there is an opportunity to talk only about some living creatures, whose features of adaptability to the environment most clearly and clearly prove the correctness of Darwin.

Birds

Thus, man has long been aware of the importance of protective coloration for birds, as well as their chicks and eggs in particular. In capercaillie, black grouse and partridge (openly nesting), the eggshell merges almost perfectly with the background of the surrounding area. In general, the back of the female is also indistinguishable from the surrounding landscape when viewed from the side. The more interesting is the fact that females and eggs of birds that nest in hollows and other hidden places often have a very bright color (the same parrots, for example).

Insects

What traits of adaptation to the environment do insects have? Well, they are even more numerous than all the representatives of this class. We think that everyone knows the striking resemblance of stick insects to dry twigs. Some research in this area is still used by the military in the field of creating "forest" camouflage suits.

However, the bodies of many caterpillars are very reminiscent of twigs, and the wings of butterflies can pass for the leaves of the trees of the area where they live. Here it should be noted that in this case there is a harmonious combination of the protective form of the body and the protective coloration. Some butterflies, when they merge with their surroundings, are difficult to distinguish from the leaves even at close range. If you more or less know biology, then you perfectly imagine the whole diversity of the class of insects. Getting into a forest or a field, you see no more than 2-3% of their total number. The rest are just in disguise.

But! It should not be assumed that examples of the fitness of organisms are limited to banal disguise. Remember the adaptive coloration, when brightly colored, “colorful” insects are just not popular with predators, since they are well aware of their sharply negative nutritional qualities. So, a titmouse or a sparrow, having tried a couple of times in their youth to eat a bug-soldier, until the end of their life they remember their caustic, poisonous taste.

In addition, the features of the adaptability of organisms to the environment include mimicry. This phenomenon resembles a patronizing coloration, but "on the contrary." So, some defenseless and edible species they can perfectly imitate those insects that are poisonous or have a disgusting taste. For example, wasp flies are very similar to wasps, which even many birds are afraid of. All this suggests that the adaptability of organisms to environmental conditions is just the same adaptive, adaptive character.

higher mammals

All this can be seen in the example of higher mammals. The coloration of zebras seems bright and even somewhat ridiculous to us, only it perfectly repeats the alternation of light and shadow in the thickets of grass, which allows these animals to perfectly disguise themselves in the savannah. Eyewitnesses confirm that unprepared people sometimes do not notice zebras even in open areas, from a distance of only 50-70 m.

Other features

Some living beings have an even more amazing and effective adaptation to It's about about chameleons and flounder, which can change the color of their body by redistributing organic pigments in the chromatophores of the skin. Do not forget that protective coloration and other protective factors dramatically improve their effectiveness, subject to appropriate behavior. This includes the freezing reflex, taking a resting posture, which is typical for a huge number of animal species.

Where do living beings get this ability?

In general, where did the adaptability of organisms to the environment come from? In general, in the previous part, we have already expressed the opinion of the great Darwin: if an animal or plant can survive a sharp change in climate or other conditions, then it is its descendants that will become the most common. Thus, the main reason for the emergence of some new adaptations in living beings is precisely natural selection. Let's show this with a practical example by discussing the life of the grouse family of birds that live in the lower canopy of the forest.

Structural features

Let's remember the main features external structure these birds: the beak is short, does not interfere with pecking food directly from the forest floor (including from the snow cover); on the paws - a thick fringed substrate, with the help of which they can safely walk even in deep snow. The structural features of the feather allow them to spend their nights buried headlong in the snow, and short, wide wings make black grouse few of the birds that can take off directly, almost vertically.

It would be quite logical to assume that their distant ancestors did not have such devices at all. Most likely, after changing a number of some environmental factors (it got colder), they were forced to adapt to a dramatically changed environment, including cold.

Change process

New mutations continually arose, their various combinations occurred during crossing, and the wave abundance made the population more heterogeneous and stable. It is not surprising that birds were distinguished from each other by a number of signs: someone had fringes on their fingers, some individuals had a shortened beak or wings.

What is the adaptation of organisms to the environment? The fact is that during the constant, only those birds survived, the structural parameters of which most corresponded to the surrounding world. In the process of selection, only they left more offspring, and it was they who survived most often and in numbers sufficient to form a new population. The new generation brought with it new mutations and the whole process was repeated from the very beginning.

Consolidation of useful features and qualities

Surely among the mutations there were those that strengthened and fixed the manifestation of the signs that appeared earlier. Naturally, the birds in which these changes manifested themselves were significantly more likely not only to survive, but also to subsequently give offspring. Over the generations, all these signs accumulated and consolidated until those black grouses that we know now appeared.

The contradictions of Lamarck's theory

As you know, Darwin's theory is fundamentally different from the assumption that was put forward by Jean-Baptiste Lamarck. The latter said that all living organisms can change under the influence of environment but only in the direction that is exceptionally useful to them. But this is absurd: what kind of influence could contribute to the emergence of spines in hedgehogs?

Only the influence of natural selection can explain the emergence of such a useful adaptation. It is assumed that the very distant ancestors of hedgehogs were able to survive, becoming covered with increasingly coarse hair. Staying alive and giving offspring turned out to be an advantage for those “proto-Hedgehogs” who were lucky to have the longest and toughest spines.

Other "prickly" examples

The bristly hedgehogs from Madagascar followed exactly the same path. We are talking about tenrecs and a few species of prickly mice and hamsters.

Does the adaptation of organisms to the environment have at least some common features? Scientists suggest that the mechanism for the emergence of such devices remains common in all cases: the fact is that they do not appear immediately, not in one or two generations. On the contrary, their emergence is a long and complex process. It should never be forgotten that the evolutionary path is full of dead ends and unsuccessful "technical solutions" of nature. We will talk about this now.

Fitness Relativity

In the period before Darwin, the adaptability of animals to their environment served as unanimous proof of the existence of the Lord and the immense wisdom of the Creator: how could nature, without such “guidance”, independently arrange the world in such a reasonable, balanced way!?

The opinion prevailed that every feature of any living organism was absolutely perfect and exactly corresponded to the task that was entrusted to it. So, the proboscis extended into the proboscis helps her to extract nectar even from the most “complex” flowers, and the adaptability of plants to the habitat in the form of thick trunks of cacti and other succulents is ideally suited for storing water for a long time.

Unfortunately, even many modern scientists continue to treat nature as a brilliant sculptor, each creation of which is perfect and infallible. But! It is important to clearly understand that this is far from the case!

The modern study of adaptability to the environment has shown that all changes are always relative, since they are formed much more slowly than the actual change in environmental conditions. Accordingly, many traits may turn out to be unnecessary, and even directly harmful to the body, if the world around changes.

Evidence for Relativity

The proof of the fact that the fitness of living organisms is a very, very relative concept is the following examples:

• From some enemies, protective devices are very effective, but from other animals they are not saved very well. happy to eat cone snails, and poisonous hairy caterpillars includes cuckoo in his diet.
• Not all animal reflexes are really expedient and adequately correlated with environmental conditions. Think of night butterflies that collect pollen from light flowers that are clearly visible at night: they fly just as quickly into the flames of fires and candles, although they die in the process.
• Organs of adaptation, which in one environment are really useful, in other conditions turn out to be harmful and even dangerous. So, those who never go down into the water in their lives have membranes on their paws.
• Beavers, one of the best "engineers" in nature, actively build dams even in stagnant ponds and pools, which is a waste of energy.

Relativity is especially pronounced in the case of those animals whose homeland is located at the other end of the world. globe, but which were brought by man into a completely new habitat for them. Simply put, it is the most revealing and convincing proof that nature is far from always infallible.

Sections: Biology

Target: to form students' knowledge about the adaptability of organisms to the environment.

Tasks:

educational: the formation of knowledge about the various ways of adaptability of organisms to the environment;

developing: the ability to work with a textbook, analyze, compare, highlight the main thing, think logically

educational: promotion of aesthetic education, the formation of a scientific worldview.

Equipment: table “Fitness and its relative nature”, photographs, drawings, collections of plant and animal organisms, presentation.

During the classes

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

1. How to explain the adaptability of living beings to the environment?

2. How did the variety of species existing in nature arise?

3. Why is there an increase in the organization of living beings in the course of evolution?

To the questions: what explanation of the fitness of organisms was widespread in the 18th century? How did Lamarck explain these phenomena? - students easily give answers, which the teacher generalizes the remark about the contradictions between the scientific facts, revealing the perfection of the organic world, and the then offered explanations.

Students in groups receive tasks and various objects for work:

Consider the fruits and seeds of birch, pine, dandelion, poppy, etc. and determine the nature of their adaptability to distribution.

Students write down the results of their work in a table.

Each group of students makes a report on the results of the work, demonstrating objects. Then, based on the conclusions from the groups, generalizations are made about various adaptations in the same environment.

Much attention should be paid to the explanation of the emergence of adaptations according to Darwin's theory of natural selection in comparison with Lamarck's explanation.

It is necessary to ensure that students can correctly explain from the standpoint of Darwin's teachings how this or that adaptation arose.

The description of the formation of long legs and a long neck according to Lamarck and Darwin is read and analyzed.

Students are then asked to explain the occurrence of:

• white color of polar animals;
• hedgehog's needles;
• shells in mollusks;
• the scent of a wild rose;
• similarities of a moth caterpillar with a knot

When answering, students give explanations of the facts on the basis of Darwin's teachings, comparisons with the possible interpretation of the same examples according to Lamarck reveal its ideological essence.

The main attention is paid to clarifying the reasons why Lamarck's theory was powerless to explain the origin of organic evolution, which was brilliantly done by C. Darwin.

Adaptation, or adaptation, is the ability of an organism to survive and leave offspring in a given habitat.

fitness examples

To morphological adaptations include - protective coloration, disguise, mimicry, warning coloration.

To ethological or behavioral include - threatening postures, food storage.

Physiological adaptation - a set of physiological reactions that underlie the adaptation of the body to changes in environmental conditions and aimed at maintaining the relative constancy of its internal environment - homeostasis.

Chemical interaction (ants secrete enzymes that are used by family members to coordinate activities)

Conservation of water in a cactus

Caring for offspring is a chain of successive reflexes developed in the process of evolution that ensure the preservation of the species.

Tilapia fish carry eggs and juveniles in their mouth! The fry calmly swim around their mother, swallow something, wait. But as soon as the slightest danger arises, the mother gives a signal, sharply moving her tail and trembling in a special way with her fins, and ... the fry immediately rush to the shelter - the mother's mouth.

Some species of frogs hatch eggs and larvae in special brood bags.

In mammals - in the construction of lairs, burrows and other shelters for future offspring, maintaining the cleanliness of the body of the cubs, then this instinct, apparently, is characteristic of all mammals without exception.

The origin of fitness and its relativity

Ch. Darwin showed that adaptations arise as a result of natural selection. The following examples can serve as proof of the relativity of devices:

1) useful organs in some conditions become useless in others: the relatively long wings of swifts, adapted for rapid flight, create certain difficulties when taking off from the ground

2) protective devices against enemies are relative: Poisonous snakes(e.g. vipers) are eaten by hedgehogs

3) the manifestation of instincts may also be inappropriate: for example, a defensive reaction (releasing a stream of foul-smelling liquid) of a skunk directed against a walking car

4) the observed “overdevelopment” of some organs, which becomes a hindrance to the body: the growth of incisors in rodents during the transition to eating soft food.

Students should firmly grasp that Darwin's doctrine of relative fitness as a result of natural selection, it completely refutes idealistic assertions about the divine origin and the absolute nature of organic expediency (K. Linnaeus), as well as about the innate ability of an organism to change under the influence only in a direction that is beneficial for them (Lamarck).

1. An example of protective coloration is:

a) the similarity of the shape and color of the body with the surrounding objects;

b) imitation of the less protected more protected;

c) alternation of light and dark stripes on the body of a tiger.

2. The bright color of ladybugs, many types of butterflies, some types of snakes and other animals with odorous or poisonous glands is called:

a) camouflage

b) demonstrating;

c) mimicry;

d) warning.

3. The variety of devices is explained by:

a) only the influence of environmental conditions on the body;

b) the interaction of the genotype and environmental conditions;

c) only features of the genotype.

4. An example of mimicry:

b) bright red color in a ladybug;

c) the similarity in the color of the abdomen of the hoverfly fly and the wasp.

5. An example of disguise:

a) the green color of the song grasshopper;

b) the similarity in the color of the abdomen of the hoverfly and the wasp;

c) a bright red color in a ladybug;

d) the similarity in color of the caterpillar and the moth with a knot.

6. Any fitness of organisms is relative, because:

a) life ends with death;

b) adaptation is expedient in certain conditions;

c) there is a struggle for existence;

d) adaptation may not lead to the formation of a new species.

Bibliography

1. Mamontov S.G. General biology: Proc. for secondary special students. textbook institutions - 5th ed., Sr. - M .: Higher. school, 2003.
2. General biology: textbook. for stud. Educated. medium institutions. prof. education / V.M. Konstantinov, A.G. Rezanov, E.O. Fadeev; ed. V.M. Konstantinov. -M.: Publishing Center "Academy", 2010.

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

Some forms of fitness in animals:

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

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

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

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

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

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