What is the evolutionary significance? Types of evolution: history of development and definition. Evolution of modern species

Progress and regression in evolution. The evolutionary process as a whole continuously moves towards the maximum adaptation of living organisms to environmental conditions. Changing conditions often lead to the replacement of some devices with others. However, the same applies to adaptations of a broad nature that give organisms advantages in various environmental conditions. This is, for example, the importance of the lungs as a universal organ of gas exchange in terrestrial vertebrates or the flower as a perfect reproductive organ in angiosperms. Thus, biological progress can occur as a result of both private and general adaptations of organisms. Biological progress should be understood as an increase in the adaptability of organisms to the environment, leading to an increase in the number and wider distribution of the species.

Evolutionary changes occurring in some species and larger taxa (families, orders) cannot always be recognized as progressive. In such cases they talk about biological regression. Biological regression is a decrease in the level of adaptability to living conditions, a decrease in the number of a species and the area of ​​the species' range.

What are the ways to achieve biological progress?

Aromorphosis. The question of possible ways to achieve biological progress was developed by A. N. Severtsov, a major evolutionary scientist. One of the main such paths, according to Severtsov, is morphophysiological progress, or aromorphosis, i.e., the emergence during evolution of characteristics that significantly increase the level of organization of living organisms. Aromorphoses provide great advantages in the struggle for existence and open up the possibility of developing a new, previously inaccessible habitat.

ALEXEY NIKOLAEVICH SEVERTSOV (1866-1936) - domestic evolutionist. Author of studies on comparative anatomy of vertebrates. Created the theory of morphophysiological and biological progress and regression.

In the evolution of mammals, several major aromorphoses can be distinguished: the appearance of fur, viviparity, feeding the young with milk, the acquisition of a constant body temperature, the progressive development of the lungs, circulatory system and brain. The high general level of organization of mammals, achieved thanks to the listed aromorphic changes, allowed them to master all possible habitats and ultimately led to the emergence of higher primates and humans.

The formation of aromorphosis is a long process that occurs on the basis of hereditary variability and natural selection. Morphophysiological progress is the main path of evolution of the organic world. In the development of each major taxonomic group, aromorphoses can be found, as you will learn about in the following material.

Idioadaptation. In addition to such a major transformation as aromorphosis, during the evolution of individual groups a large number of small adaptations to certain environmental conditions arise. A. N. Severtsov called such adaptive changes idioadaptations.

Idioadaptations are adaptations of the living world to the environment, opening up for organisms the possibility of progressive development without a fundamental restructuring of their biological organization. An example of idioadaptation is the diversity of finch bird species described by Charles Darwin (Fig. 65). Different types of finches, having a similar level of organization, were, however, able to acquire properties that allowed them to occupy completely different places in nature. Some species of finches have mastered feeding on plant fruits, others - seeds, and others have become insectivores.

Rice. 65. Diversity of finches in the Galapagos Islands

Despite the fact that general degeneration leads to a significant simplification of organization, species following this path can increase their numbers and range, that is, move along the path of biological progress.

Correlation of directions of evolution. The paths of evolution of the organic world either combine with each other or replace each other. Moreover, aromorphoses occur much less frequently than idioadaptations, but it is aromorphoses that determine new stages in the development of the organic world. Having emerged through aromorphosis, new, higher-organized groups of organisms occupy a different habitat. Further, evolution follows the path of idioadaptation, and sometimes degeneration, which provide organisms with the ability to settle into a new habitat for them (Fig. 67).

Rice. 67. Scheme of relationships between aromorphosis, ideological adaptation and degeneration

So, let us list the general features of the evolutionary process. First of all, this is the emergence of the adaptability of organisms, that is, their compliance with living conditions and the ability to change as these conditions change. Natural selection of hereditary changes in natural populations is the most important cause of fitness.

Another important characteristic of the evolutionary process is speciation, i.e., the constant emergence of new species. Over the course of evolution, there have been tens and perhaps hundreds of millions of species of living organisms on Earth.

And finally, the third integral property of the evolutionary process is the constant complication of life from primitive precellular forms up to humans.

1. Explain the terms: biological progress, biological regression, aromorphosis, idioadaptation.
2. Can the concepts “biological regression” and “degeneration” be considered identical? Justify your answer.
3. What is the evolutionary significance of aromorphosis and idioadaptation?

Questions about evolution_level "C"

Find errors in the text, name the numbers of sentences in which errors were made. Explain them.

1. Scientists believe that the first organisms to appear on Earth were eukaryotes.

2. The first organisms were anaerobic heterotrophs.

3. Then evolution moved towards the development of autotrophic methods

4. The first autotrophic organisms were algae and bryophytes.

5. As a result of photosynthesis, free oxygen appeared in the Earth's atmosphere.

Errors were made in sentences 1.4.

1 - prokaryotes; 4 - chemosynthetic bacteria.

Isolation consists in the emergence of barriers to interbreeding between individuals of different populations of the same species. In isolated populations, such a random process as the occurrence of mutations can proceed differently. The direction of natural selection can also be different. Over the course of tens or hundreds of thousands of generations, isolated populations can accumulate significant differences, due to which individuals from different populations lose the ability to interbreed. In this case, we can talk about the formation of new species. If populations are not isolated from each other, but, on the contrary, exchange hereditary information, then the emergence of significant differences and the formation of new species on their basis is impossible.

Microorganisms are able to quickly adapt to changing environmental conditions. What are the mechanisms of such high adaptability?

Response elements:

1) microorganisms multiply quickly, and their populations consist of a very large number of individuals;

2) therefore, a large number of mutations accumulate in populations of microorganisms, which are material for natural selection;

3) bacteria are haploid and mutations always appear in them, which speeds up the selection process;

4) in addition, “horizontal” gene transfer is observed in microorganisms using plasmids, that is, one individual can transfer its properties to other members of the population.

What is the evolutionary significance of indirect development?

It consists in weakening competition between parents and offspring. Larvae and adults often occupy different habitats and/or use different food resources.

Why are populations the unit of evolution?

Because a population is a structural unit of a species, i.e. the smallest group of individuals capable of evolutionary development. Evolution occurs only in a group of individuals, since the genotype of one organism cannot change during life, and a group of individuals (isolated from other groups) is capable of change, since it is a heterogeneous mixture of different genotypes. The reason for the evolution of populations may be their isolation, changes in living conditions, competition with other populations of the species (or with other species), or changes in population size.

How can we explain the coincidence of the shape of some flowers with the shape of the body of insects or with the shape of its individual parts?

This is explained by the long-term co-evolution of plants and insects. Natural selection preserved both the best pollinators and plants that were pollinated by insects whose shapes matched the shape and size of the flower. Some plant species end up being pollinated only by certain pollinators, for example clover is pollinated by bumblebees.

What are the main provisions of the synthetic theory of evolution?

The synthetic theory of evolution expands the teachings of Charles Darwin about causes and drivers

forces of the evolutionary process. This theory distinguishes micro- and macroevolution and determines the criterion for the type of form of natural selection. The main evolving unit is the population; the factors of evolution are the mutation process, population waves, isolation, and genetic drift. The driving forces of evolution are heredity, variability, natural selection. Natural selection is divided into several forms, among which are driving and stabilizing. The final stage of microevolution is the formation of new species. Larger systematic groups appear through aromorphoses. It should be noted that the causes and possible mechanisms of the evolutionary process are actively discussed by modern science.

What is the difference between natural and artificial selection?

Artificial selection, being the guiding factor of evolution, plays a leading role in the emergence of diversity in the organic world.

As a result of natural selection, new species arise, and as a result of artificial selection, varieties and breeds arise.

The criterion of natural selection is the adaptability of the species. The criterion of artificial

selection is the utility of a trait for a person.

Natural selection has been occurring on Earth since the emergence of life. Artificial

selection has been around since the advent of domestic animals and agriculture.

Artificial selection is carried out in a much shorter time and often leads to the appearance of completely new plants and animals, the emergence of which is impossible under natural conditions.

What are the evolutionary consequences of isolating a small population?

Response elements:

1) crossing in a small isolated population leads to an increase in the level of homozygotes;

2) this leads to a decrease in the overall viability of the population due to homozygosity for many recessive alleles;

3) on the other hand, an increase in the level of homozygosity provides new material for natural selection, which can lead to the consolidation of new characteristics.

What are the main differences between the theories of J.B. Lamarck and Charles Darwin?

J.B. Lamarck believed that acquired characteristics are inherited, that heritable changes are always beneficial, and the influence of the external environment that causes this change is always positive.

Darwin's evolutionary doctrine refuted these provisions of Lamarck's theory. Characteristics acquired during life are not inherited; both beneficial and harmful and indifferent mutations can be hereditary, and the influence of the external environment on organisms can be both positive and negative.

Why are homologous organs considered one of the proofs of evolution?

These organs among representatives of different groups have a common origin.

Define aromorphosis, give 1-2 examples and prove that it is aromorphosis.

Aromorphosis is an abrupt, sudden mutation that leads to an increase in the general level of organization of living beings. As a rule, aromorphoses contribute to the occurrence of changes leading to the emergence of new systematic groups. For example, the emergence of photosynthesis ensured the gradual flowering of various plant departments; the appearance of a four-chambered heart in birds and mammals contributed to the development of warm-bloodedness, and consequently, the conquest of almost all geographical areas of the Earth by these animals

Why are adaptations to environmental conditions relative?

When environmental conditions change, existing devices may turn out to be useless and even harmful.

What is the role of crossing over in the evolutionary process?

Crossing over is the crossing of homologous chromosomes in meiosis, leading to a diversity of gametes and, as a consequence, genetic combinations in the offspring. This, in turn, provides the opportunity for natural selection to act and produce a greater variety of adaptations to environmental conditions.

If, as a result of a violation of the crossing-over process, the structure of the chromosome changes, this can lead to the formation of pathological gametes and the development of hereditary diseases in the offspring.

Find the mistakes made in the text. Indicate the numbers of the sentences in which they are made and explain them.

1. The most important aromorphoses in the evolution of multicellular organisms were: the development of movable jaws, the formation of five-fingered limbs, and the appearance of protective coloration.

2.With the emergence of animals onto land, external fertilization arose.

3. The flourishing of mammals was ensured by the emergence of warm-bloodedness, a three-chambered heart and an internal skeleton.

Errors were made in sentences 1, 2, 3.

1. The most important aromorphoses in the evolution of multicellular organisms were: the development of movable jaws, the formation of five-fingered limbs, and the appearance of protective coloration.

2. With the emergence of animals onto land, external fertilization arose.

3 The flourishing of mammals was ensured by the emergence of warm-bloodedness, a three-chambered heart and an internal skeleton.

What types of paleontological finds provide evidence for evolution?

Response elements:

1) fossils and imprints

2) transitional forms

3) phylogenetic series

Why does high abundance of a species promote biological progress?

Response elements:

1)increases the possibility of free crossing

2) the exchange of genetic material increases, heredity is enriched

What impact did the creation of evolutionary theory have on the formation of the modern natural scientific picture of the world?

Evolutionary theory approved and proved the historical development of living nature, the variability of species

What aromorphoses allowed ancient amphibians to colonize land?

Response elements:

1) the appearance of pulmonary breathing

2) formation of dismembered limbs

3) the appearance of a three-chambered heart and two circulation circles

Why is the resistance of insect pests to pesticides increasing?

1) Due to the appearance of mutations, the population of insect pests becomes heterogeneous.

2) Natural selection preserves individuals resistant to pesticides.

3) From generation to generation, the number of individuals resistant to pesticides increases.

4) After a few years, the pesticide in the same doses ceases to act on insect pests.

What processes confirm that life in the Proterozoic becomes a geological factor?

Living organisms participated in the formation of sedimentary rocks and iron ores.

Bee flies, which do not have a stinging apparatus, are similar in appearance to bees. Explain, based on evolutionary theory, the emergence of mimicry in these insects.

Response elements:

1) insects of different species have developed similar mutations in external characteristics (color, body shape);

2) individuals with characteristics that enhance their similarity to protected insects had more opportunities to survive in the struggle for existence;

3) as a result of natural selection, such insects were less likely to be pecked by birds and spread throughout the population.

In industrial areas of England during the 19th-20th centuries, the number of birch moth butterflies with dark colored wings increased compared to light colored ones. Explain this phenomenon from the perspective of evolutionary theory and determine the form of selection.

Response elements:

1) both light and dark forms are born in the offspring of a butterfly population;

2) in industrial areas contaminated with soot, birds eliminate light-colored individuals from darkened trunks, so dark-colored butterflies have become the predominant form in populations;

3) a change in color in a butterfly population is a manifestation of the driving form of natural selection.

Why does high abundance of a species serve as an indicator of biological progress?

Response elements:

1) the possibility of free crossing increases;

2) the exchange of genetic material is enhanced and heredity is enriched;

3) promotes the distribution of individuals and expansion of the range.

Explain why people of different races are classified as the same species?

Response elements:

1) people of different races contain the same set of chromosomes in their cells;

2) interracial marriages will produce children who, upon reaching puberty, are capable of reproducing;

3) people of different races are similar in structure, life processes, and development of thinking.

The house mouse is a mammal of the genus Mouse. The original range is North Africa, the tropics and subtropics of Eurasia; following man, it spread everywhere. Lives in natural conditions, feeds on seeds. Leads a nocturnal and twilight lifestyle. A litter usually produces 5 to 7 babies. What species criteria are described in the text? Explain your answer.

Response elements:

1) geographical criterion - area;

2) environmental criterion - feeding habits, changes in activity during the day, living in certain environmental conditions;

3) physiological criterion - the number of cubs in the litter.

What aromorphoses led to the emergence of the phylum Arthropods?

Response elements:

1) the appearance of the exoskeleton;

2) the appearance of articulated limbs;

3) the appearance of striated muscles.

What type of natural selection is aimed at preserving mutations leading to less variability in the average value of a trait?

Stabilizing selection.

What is the unit of evolution according to the synthetic theory of evolution (STE)?

Population.

What characterizes biological progress?

Response elements:

1) an increase in the number of individuals of a given systematic group;

2) expansion of the area;

3) expansion of species diversity within a group (populations and subspecies within a species, species within a genus, etc.).

What social factors are the driving forces of anthropogenesis?

Response elements:

1) work activity;

2) social way of life;

3) speech and thinking.

What evidence is there of the origin of humans from animals?

Response elements:

1) general structural features of humans and animals;

2) similarities in the development of human and animal embryos;

3) similarities between humans and apes.

What does the hypothesis (law) of gamete purity mean?

When germ cells are formed, only one allele from an allelic pair enters each gamete, that is, the gametes are genetically pure.

Name the type, explain the meaning of protective coloring, as well as the relative nature of the adaptability of flounder, which lives in sea reservoirs near the bottom.

Response elements:

1) type of coloring - protective - merging with the background of the seabed;

2) the ability to change the color of the upper side of the body makes the fish invisible against the background of the ground, allowing it to hide from enemies and from possible prey;

3) fitness is disrupted when the fish moves, and it becomes accessible to enemies.

Explain why atavisms appear in certain people?

Response elements:

1) believe that man is of animal origin;

2) signs of ancient ancestors (atavisms) are embedded in the human genome;

3) in rare cases, a person experiences a violation of the individual development of the body, and signs of animal ancestors appear.

Name the type of protective device, explain its meaning and relative nature in the caterpillar of the moth butterfly, which lives on tree branches and at the moment of danger becomes like a twig.

Response elements:

1) type of adaptation - imitation of motionless bodies of nature (imitative resemblance), protective coloring and shape - camouflage;

2) the caterpillar freezes motionless on the branch and becomes like a twig and invisible to insectivorous birds;

3) fitness becomes useless when the caterpillar moves or the background of the substrate changes/

Name the aromorphoses that accompanied the evolution of reptiles during their exploration of land

Response elements:

1) transition to pulmonary breathing only;

2) the appearance of dry, keratinized skin without glands;

3) internal fertilization, the appearance of embryonic and egg membranes

Name the type of protective device against enemies, explain its significance and relative nature in the small seahorse fish that lives at shallow depths in the environment of aquatic plants.

Response elements:

1) the resemblance of an animal to a stationary natural object - a plant is called protective resemblance (camouflage);

2) the seahorse hangs among aquatic plants and is invisible to predators;

3) when the fish moves or in open space, it becomes accessible and noticeable to enemies.

Explain the changes that have occurred in the structure of the limb and the method of movement of the horse during the process of evolution. What environmental conditions of the horses' ancestors caused this?

Response elements:

1) the number of fingers has decreased from multi-fingered to one;

2) fast running became the main method of transportation;

3) the ancestors of the horse moved from living among dense vegetation to living in open spaces.

What differences in the body structure of humans and apes arose during the process of evolution?

Many differences are due to a person’s adaptation to upright walking: an S-shaped spine, an arched foot, a wide pelvis, a flat, wide chest, massive lower limbs, shorter and thinner bones of the upper limbs, etc. The transformation of the human hand from an organ of support into an organ of labor made the hand more mobile.

Vivid differences between humans and apes are observed in the structure of the skull and brain. The brain part of the human skull predominates over the facial part. Monkeys, on the contrary, have a highly developed facial part, especially the jaws. The human skull does not have continuous brow ridges and bony ridges, the forehead is high and convex, the jaws are weak, the fangs are small, and there is a chin protrusion on the lower jaw. The human brain is 2-2.5 times larger in volume and mass than the brain of apes. The parietal, temporal and frontal lobes of the cerebral hemispheres, in which the most important centers of mental functions and speech are located, are much more developed in humans

An example of which way to achieve biological progress (aromorphosis, idioadaptation or general degeneration) is the diversity of finches described by Charles Darwin on the Galapagos Islands?

This is an example of idioadaptation. Different species of finches, having a similar level of organization, were able to acquire properties that allowed them to occupy completely different ecological niches in natural communities. Some species of finches have mastered feeding on plant fruits, others - seeds, and others have become insectivores.

Let us formulate the answer: “Due to adaptation to different food sources, finches have changed the shape of their beaks. This small adaptation did not increase their level of organization, and therefore is an idio-adaptation.”

Why is isolation considered an important condition for the formation of new species in modern evolutionary theory?

Isolation consists of the emergence of barriers to interbreeding between individuals of different populations of the same species. In isolated populations, such a random process as the occurrence of mutations can proceed differently. The direction of natural selection can also be different. Over tens or hundreds of thousands of generations, isolated populations can accumulate significant differences such that individuals from different populations lose the ability to interbreed. In this case, we can talk about the formation of new species. If populations are not isolated from each other, but, on the contrary, exchange hereditary information, then the emergence of significant differences and the formation of new species on their basis is impossible.

Which species criterion is the main one when determining the species identity of an individual?

None of the species criteria can be absolute. For example, most often a morphological criterion is used to determine whether an individual belongs to a particular species. However, sometimes species are almost indistinguishable in appearance, although in nature they are strictly isolated and do not interbreed. These are twin species with different numbers of chromosomes, which serves as an insurmountable obstacle to their crossing. The genetic criterion is quite reliable. But there are cases when species have chromosomes that are practically indistinguishable in structure. In addition, chromosomal mutations may be widespread within a species, making precise species identification difficult.

Therefore, each criterion separately cannot be the basis for determining the type; Only together do they make it possible to accurately determine the species identity of an individual.

Under what conditions does stabilizing selection operate in natural populations?

Stabilizing selection operates as long as the living conditions of the population do not change significantly.

What is the significance of mutations in the evolutionary process?

Mutations create the basis for the action of other factors of evolution, primarily natural selection. Most mutations are harmful to the body, but while they are harmful in some conditions, they may be beneficial in others. For example, a mutation that causes reduction of wings in insects is harmful to them under normal land conditions, since it deprives them of the ability to fly. At the same time, it turned out to be useful on oceanic islands, since here winged insects are picked up by the wind and blown into the sea. The mutation process leads to the emergence of a reserve of hereditary variability that can provide the ability for a population to adapt to new conditions.

How many forms of struggle for existence did Charles Darwin distinguish?

Darwin distinguished 3 forms of struggle for existence: intraspecific, interspecific and struggle against unfavorable environmental conditions.

Is it possible to talk about the emergence of a new adaptation if individuals with new successful traits appear in the population?

For adaptation to occur, the presence of elementary evolutionary material - hereditary variability - is necessary. The appearance in a population of individuals with a new successful phenotype cannot yet be considered as adaptation. We can talk about adaptation only after the emergence of a specialized trait in the entire population or species. This is achieved under the influence of various evolutionary factors, and primarily natural selection. It is selection that can turn specific beneficial deviations of individuals into the norm for the population as a whole.

What reasons can cause biological isolation between populations of the same species?

Biological isolation is due to a number of reasons: being confined to different habitats within the species range; differences in the behavior of animals of different populations during the breeding season, different times of sexual activity, and the emergence of polyploids.

Why did the appearance of man become an event of great significance in the evolution of the biosphere?

Because gradually man turned into a powerful geological force transforming the planet. The development of science and production allowed man to actively change the nature around him.

The body shape of the Kalima butterfly resembles a leaf. How did the butterfly develop such a body shape?

the appearance of various hereditary changes in individuals;

preservation by natural selection of individuals with altered body shape;

reproduction and distribution of individuals with a body shape resembling a leaf.

What organic substances ensured the reproduction breeding of organisms during the origin of life?

Nucleic acids are capable of replication, that is, the creation of new copies indistinguishable from maternal molecules. Answer: Nucleic acids.

Why, when determining whether an individual belongs to one form or another takes into account a complex of criteria riev?

Criteria characterizing the species: morphological, genetic, physiological, biochemical, physiological, ecological, geographical. There are species that are similar in one or more criteria, therefore, in order to determine a species, it is necessary to take into account the totality of all its criteria.

Answer: None of the criteria alone provides a complete description of the species.

What is the convergent similarity of croco dila, frogs and hippopotamus?

All of these animals spend most of their lives in water. While in the water, they raise their eyes and nostrils located on the top of their heads above its surface, thus gaining the opportunity to better navigate and breathe oxygen in the air.

Answer: Similar arrangement of eyes and nostrils on the head.

Why are people of different races classified as the same species?

Race is a historically established group of people characterized by common hereditary physical characteristics (color of skin, eyes and hair, eye shape, etc.).

Answer:

due to the similarity of structure, life processes, behavior;

due to genetic unity - the same set of chromosomes;

interracial marriages produce offspring capable of reproduction.

What was the advantage of the development of the first living organisms of the Earth in the hydrosphere?

The hydrosphere protected living organisms from ultraviolet rays.

The absence of which component of the external environment prevented the development of life on land in the early stages of evolution?

Lack of oxygen

What are laboratory-produced coacervates?

Clusters of protein molecules

What is the result of the struggle for existence?

Natural selection.

What is the role of the driving forces of evolution in shaping the fitness of organisms?

1) Thanks to mutations and reproduction, the population becomes heterogeneous.

2) There is a struggle for existence in the population, which aggravates the relationships between individuals.

3) Natural selection acts on the population, which promotes the preservation of individuals with useful hereditary changes to life in certain conditions, ensuring their adaptability to the environment.

What is the significance of hereditary variation in evolution?

1) Thanks to hereditary variability, heterozygosity and genetic heterogeneity of individuals in a population increases, resulting in an increase in the efficiency of natural selection.

2) When conditions change, natural selection will promote the preservation of individuals with hereditary changes that are useful under given conditions and can lead to the formation of a new species or fitness.

3) Due to the genetic heterogeneity of populations due to hereditary variability, it can quickly change in accordance with the directing action of natural selection.

Why does a decrease in a species' range lead to biological regression?

1) The ecological diversity of the environment is depleted due to the reduction of the area.

2) Undesirable inbreeding occurs.

3) Competition with other species and within the species increases.

Remember:

Why do species exist in the form of populations?

Answer. The species consists of a large number of individuals. These individuals settle in a certain territory. Environmental conditions in this territory may vary greatly (there may be areas that are generally unsuitable for the species to live in, or barriers separating populations). Each specific combination of environmental factors requires its own adaptations, so populations of the same species may differ from each other. If a species existed in an indivisible form, it could live only in a certain small area and would disappear if environmental conditions changed. Thus, species exist in the form of populations because:

1) This allows you to make better use of available resources (occupy a larger territory, etc.)

2) It helps the species better adapt to environmental conditions

3) It promotes the independent accumulation of changes within a species, which increases biological diversity

4) Increases the likelihood of survival of the species (if environmental conditions suddenly change sharply, then some population may have a trait that will help the species survive).

What is characteristic of mutational variability?

Answer. Mutations are a persistent change in the genotype, changes in the body, under the influence of factors that are inherited. Reasons - a) entry of mutagens (factors that cause mutation: physical, chemical and biological). b) a change in the number of individual homologous chromosomes, or changes in their structure. c) gene change. d) increase or decrease in the number of chromosomes. Mutational variability, depending on the scale of the disorder, can appear either immediately in the phenotype (dominant trait), or after a number of generations, encountering the fusion of gametes with the same latent form (recessive trait). Changes the phenotype and genotype.. The biological significance is ambiguous, more often it has a negative meaning, even death. However, there are also positive changes, which subsequently serve as material for evolution.

What are the causes of combinational variability?

Answer. Combinative variability is based on the emergence of new combinations of parental genes. With combinative variability, as a result of the fusion of parental gametes, new combinations of genes arise, but the genes and chromosomes themselves remain unchanged (example: each new organism is a new combination of the genes of the parents).

As a result of combinative variability, organisms arise that differ from their parents in genotypes and phenotypes. Some combinational changes may be harmful to an individual. For a species, combinative changes are, in general, useful, since they lead to genotypic and phenotypic diversity. This promotes the survival of species and their evolutionary progress.

Questions after § 23

Why is a population considered the unit of evolution?

Answer. An individual cannot evolve. It can change, adapting to environmental conditions. But these changes are not evolutionary, since they are not inherited. The species is usually heterogeneous and consists of a number of populations. The population is relatively independent and can exist for a long time without connection with other populations of the species. All evolutionary processes take place in a population: mutations occur in individuals, crossing occurs between individuals, the struggle for existence and natural selection operate. As a result, the gene pool of the population changes over time, and it becomes the ancestor of a new species. That is why the elementary unit of evolution is a population, not a species.

What is meant by the gene pool of a population? What is the significance of changing it?

Answer. An indicator of the genetic composition of the entire population is the gene pool. The gene pool is the sum of all genotypes represented in the population.

The gene pool of a population is constantly changing under the influence of various factors. Firstly, this is due to the variability of genotypes. Secondly, the gene pool can change under the influence of selection; Such changes in the gene pool are directional.

The explanation for the driving forces of evolution is the idea that some individuals of a species have characteristics that increase their chances of surviving and producing offspring. If this is so, then the genetic properties of such organisms (“beneficial genes or alleles”) should be carried along in the population (together with the descendants of the organisms that possess them), changing the composition of its gene pool. In harsh climatic conditions, for example, in populations there should be an increase in the proportion of genotypes containing alleles that increase the thermal insulation of organisms; such changes make the population more adapted to specific living conditions. In other cases, the survival of organisms may be determined by genes encoding the color of the animal (when the camouflage factor becomes important for the survival of individuals), or the synthesis of certain types of enzymes, or the nature of behavior, etc. in other words, the gene pool of the population must change over time as a result natural selection. This phenomenon is called gene flow. It ensures the genetic unity of the species.

Answer. An important evolutionary factor is the process of mutation. It supplies evolutionary material - new hereditary changes. Due to the constant action of the mutation process and the large number of genes, the total number of mutant alleles in each individual reaches from several percent to tens. Because of this, the mutation process significantly affects the gene pool of the population. Its pressure is enhanced by combinational variability and gene flow.

Another evolutionary factor that supplies material for evolution and changes the gene pool is fluctuations in population numbers - population waves. As the population size increases, the number of new mutations increases. As a result, the gene pool of the population is enriched with new genotypes. After a decline in numbers, some genotypes randomly disappear with the death of the individuals carrying them, and the concentration of other genotypes also randomly decreases or increases. After the restoration of numbers, the gene pool of the population will be different, represented by a different ratio of genotypes.

What evolutionary factors provide material for natural selection?

Answer. In the teaching of evolution, there are two sides: the teaching about the material for evolution and the teaching about its factors, its driving force. The driving force of evolution is natural selection. Inheritance is based on indivisible and unmixable factors - genes. It is through selection that the directed influence of living conditions on hereditary variability occurs. Hereditary variability itself is random. Under the influence of the environment, traits are selected that best suit living conditions. "

What is the evolutionary role of selection?

Answer. Natural selection plays a creative role. The creative role of natural selection is that, by changing characteristics in accordance with changes in environmental conditions - strengthening useful and weakening characteristics that have lost adaptive significance, natural selection transforms the organization of descendants in comparison with ancestors, creating new species.

How does driving selection differ from stabilizing selection?

Answer. The driving form of natural selection leads to the consolidation of new adaptations of the organism, which corresponds to changed environmental conditions.

The stabilizing form of selection is aimed at preserving the adaptive characteristics established in the population. Adaptation to certain environmental conditions does not mean the termination of selection in a population. Since mutational variability always exists in any population, individuals constantly appear with characteristics that significantly deviate from the average value typical for the population or species. With stabilizing selection, such individuals are eliminated.

What is the role of isolation as a factor in evolution?

Answer. Isolation is the emergence of any barriers that interfere with free crossing, which leads to an increase and consolidation of differences between populations and individual parts. There are geographical, environmental, and ethological isolation.

Geographical (or spatial) isolation is associated with the rupture of a single habitat of a species into parts that do not communicate with each other. Mutations can occur randomly in any isolated population. Due to population waves and the action of natural selection, the genotypic composition of isolated populations varies more and more. The reasons leading to the emergence of geographic isolation are numerous: the presence of mountains and rivers, isthmuses or straits, the extermination of populations in certain areas, etc.

Ecological isolation is associated with a preference for a particular habitat. Sevan trout is an example of such isolation. Different populations of trout spawn at the mouths of different streams and mountain rivers flowing into the lake, so free interbreeding between them is extremely difficult. Ecological isolation thus prevents the interbreeding of individuals from different populations and, like geographic isolation, serves as the initial stage of population divergence.

The evolutionary essence of the various variants of spatial and ecological isolation is the same - a break in the single gene pool of a species into two or more gene pools isolated from each other (cessation of the exchange of genetic material between them; independent evolutionary process in isolated parts of the species). Its end result, although with a small probability, is the formation of new species. That is why primary forms of isolation are considered as triggers for the speciation process.

Disputes about the origins of man have been going on for a long time. One of the theories, namely evolutionary, was developed by Charles Darwin. This concept forms the basis of all modern biology.

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Errors and

Evidence for Darwin's theory

According to Charles Darwin's theory of natural selection, man evolved from apes. Traveling around the world and studying different types of flora and fauna, the scientist came to the conclusion that constant evolution is taking place in the world. Living organisms, adapting to changing environmental conditions, change themselves. Having studied the results of research in physiology, geography, paleontology and other sciences that existed at that time, Darwin created his theory that described the origin of species.

• The scientist was prompted to think about the evolution of living organisms by the discovery of a sloth skeleton, which differed from modern representatives of this species in its larger size;
• Darwin's first book was a phenomenal success. During the first 24 hours, all books in the circulation were sold;
• the explanation of the process of the appearance of all life on the planet did not have a religious connotation;
• Despite the popularity of the book, this theory was not immediately accepted by society, and it took time for people to appreciate its significance.

Basic principles of Darwin's theory

If we remember the school biology course, its distinctive feature is a unique approach to structuring materials. Species are not considered separately, but in such a way that one of the species is derived from the other. Let's try to explain what we mean. The basic principles of the theory demonstrate that amphibians evolved from fish. The next stage of evolution was the transformation of amphibians into reptiles, etc. A natural question arises: why then are transformation processes not occurring now? Why did some species take the path of evolutionary development, while others did not?

The provisions of Darwin's concept are based on the fact that the development of nature occurs according to natural laws, without the influence of supernatural forces. The main postulate of the theory: the cause of all changes is the struggle for survival based on natural selection.

Prerequisites for the emergence of Darwin's theory

• socio-economic - the high level of development of agriculture has made it possible to pay considerable attention to the selection of new species of animals and plants;
• scientific - a large amount of knowledge has been accumulated in paleontology, geography, botany, zoology, geology. Now it is difficult to say what data from geology served to develop the concept of evolution, but together with other sciences they made their contribution;
• naturally scientific - the emergence of cell theory, the law of germinal similarity. Darwin's personal observations made during his travels provided the basis for a new concept.

Comparison of the evolutionary theories of Lamarck and Darwin

In addition to the well-known evolutionary theory of Darwin, there is another theory, authored by J. B. Lamarck. Lamarck argued that changes in the environment change habits, and therefore some organs change. Since parents have these changes, they are passed on to their children. As a result, depending on the habitat, degrading and progressive series of organisms arise.

Darwin refutes this theory. His hypotheses show that the environment influences the death of unadapted species and the survival of adapted ones. This is how natural selection occurs. Weak organisms die, while strong ones reproduce and increase the population. Increased variability and adaptability leads to the emergence of new species. To understand the big picture, it is important to analyze the similarities and differences between Darwin's conclusions and the synthetic theory. The differences are that the synthetic theory arose later, as a result of combining the achievements of genetics and the hypotheses of Darwinism.

Refutation of Darwin's theory

Darwin himself did not claim that he put forward the only correct theory of the origin of all living things and that there could be no other options. The theory has been repeatedly disproven. The criticism is that, given the evolutionary concept, for further reproduction there must be a pair with the same characteristics. What cannot happen according to Darwin's concept and what confirms its inconsistency. Facts that refute evolutionary hypotheses reveal lies and contradictions. Scientists have not been able to identify genes in fossil animals that would confirm that a transition is occurring from one species to another.

A natural question arises: what had to happen for creatures that reproduced by laying eggs to reproduce sexually? Thus, humanity was deluded for a long period, blindly believing evolutionary theories.

What is the essence of Darwin's theory?

In building his theory of evolution, Darwin was based on several postulates. He revealed the essence through two statements: the world around us is constantly changing, and the decrease in resources and limited access to them leads to a struggle for survival. Perhaps this makes sense, since such processes result in the strongest organisms that are capable of producing strong offspring. The essence of natural selection also boils down to the fact that:

• variability accompanies organisms throughout their lives;
• all differences that a creature acquires during its life are inherited;
• organisms with useful skills have a higher propensity to survive;
• organisms multiply indefinitely if conditions favor it.

Mistakes and advantages of Darwin's theory

When analyzing Darwinism, it is important to consider the pros and cons. The advantage of the theory, of course, is that the influence of supernatural forces on the emergence of life was refuted. There are many more disadvantages: there is no scientific evidence to support the theory and no examples of “macroevolution” (the transition from one species to another) have been observed. Evolution is not possible at the physical level, this is explained by the fact that all natural objects age and collapse, for this reason evolution becomes impossible. Rich imagination, curiosity in studying the world, lack of scientific knowledge in biology, genetics, botany, led to the emergence of a movement in science that has no scientific basis. Despite criticism, all evolutionists can be divided into two large groups who speak out for and against evolution. They present their arguments, speaking for and against. And it’s difficult to say who is actually right.

There is debate in scientific circles on the topic: “Darwin abandoned his theory before his death: true or false?” There is no real evidence of this. Rumors arose after the statements of one pious person, but the scientist’s children do not confirm these statements. For this reason, it is not possible to reliably establish whether Darwin abandoned his theory.

The second question that scientific followers struggle with is: “In what year was Darwin’s evolutionary theory created?” The theory appeared in 1859, after the publication of the results of scientific research and discoveries of Charles Darwin. His work “The Origin of Species by Means of Natural Selection or the Preservation of Favored Breeds in the Struggle for Life” became the basis for the development of evolutionism. It is difficult to say when the idea of ​​creating a new trend in the study of the development of the world arose, and when Darwin formulated the first hypotheses. Therefore, it is the date of publication of the book that is considered the beginning of the creation of the evolutionary movement in science.

Evidence for Darwin's theory

Is Darwin's hypothesis true or false? There is no clear answer to this question. Followers of evolutionism cite scientific facts and research results that clearly show that when living conditions change, organisms acquire new abilities, which are then passed on to other generations. In laboratory research, experiments are carried out on bacteria. And Russian scientists went even further; they conducted experiments on sea fish, stickleback. Scientists moved fish from sea waters to fresh waters. Over 30 years of habitat, the fish has perfectly adapted to new conditions. Upon further study, a gene was discovered that is responsible for the possibility of their habitat in fresh water bodies. For this reason, whether or not to believe in the evolutionary origin of all living things is a personal matter for everyone.

In the process of historical development, some species die out, others change and give rise to new species. What are the species? Do species really exist in nature?

The term “species” was first introduced by the English botanist John Ray (1628-1705). The Swedish botanist K. Linnaeus considered the species as the main systematic unit. He was not a supporter of evolutionary views and believed that species do not change over time.

J. B. Lamarck noted that the differences between some species are very insignificant, and in this case it is quite difficult to distinguish species. He concluded that species do not exist in nature, and the taxonomy was invented by man for convenience. Only an individual really exists. The organic world is a collection of individuals connected to each other by family ties.

As you can see, the views of Linnaeus and Lamarck on the real existence of a species were directly opposite: Linnaeus believed that species exist, they are unchangeable; Lamarck denied the real existence of species in nature.

Currently, the generally accepted point of view of Charles Darwin is that species actually exist in nature, but their constancy is relative; species arise, develop, and then either disappear or change, giving rise to new species.

View is a supraorganismal form of existence of living nature. It is a collection of morphologically and physiologically similar individuals, freely interbreeding and producing fertile offspring, occupying a certain area and living in similar environmental conditions. Species differ according to many criteria. The criteria by which individuals belong to the same species are presented in the table.

Type criteria

When determining whether an individual belongs to any species, one cannot limit oneself to just one criterion, but must use the entire set of criteria. So, it is not possible to limit ourselves to only morphological criterion, since individuals of the same species can differ in appearance. For example, in many birds - sparrows, bullfinches, pheasants, males differ significantly in appearance from females.

In nature, albinism is widespread in animals, in which pigment synthesis is disrupted in the cells of individual individuals as a result of mutation. Animals with such mutations are white in color. Their eyes are red because there is no pigment in the iris, and the blood vessels are visible through it. Despite external differences, such individuals, for example, white crows, mice, hedgehogs, tigers, belong to their own species and are not distinguished as independent species.

In nature, there are outwardly almost indistinguishable twin species. So, previously, the malaria mosquito was actually called six species, similar in appearance, but not interbreeding and differing in other criteria. However, of these, only one species feeds on human blood and spreads malaria.

Life processes in different species often proceed very similarly. This speaks of relativity physiological criterion. For example, some species of Arctic fish have the same metabolic rate as fish living in tropical waters.

You can't use just one molecular biological criterion, since many macromolecules (proteins and DNA) have not only species, but also individual specificity. Therefore, it is not always possible to determine from biochemical indicators whether individuals belong to the same or different species.

Genetic criterion also not universal. Firstly, in different species the number and even the shape of chromosomes can be the same. Secondly, in one species there may be individuals with different numbers of chromosomes. Thus, one type of weevil has diploid (2p), triploid (Zp), and tetraploid (4p) forms. Thirdly, sometimes individuals of different species can interbreed and produce fertile offspring. Hybrids of wolf and dog, yak and cattle, sable and marten are known. In the plant kingdom, interspecific hybrids are quite common, and sometimes there are more distant intergeneric hybrids.

Cannot be considered universal geographical criterion, since the ranges of many species in nature coincide (for example, the range of Dahurian larch and fragrant poplar). In addition, there are cosmopolitan species that are ubiquitous and do not have a clearly limited range (some species of weeds, mosquitoes, mice). The ranges of some rapidly expanding species, such as the housefly, are changing. Many migratory birds have different breeding and wintering areas. The ecological criterion is not universal, since within the same range many species live in very different natural conditions. Thus, many plants (for example, creeping wheatgrass, dandelion) can live both in the forest and in floodplain meadows.

Species actually exist in nature. They are relatively constant. Species can be distinguished by morphological, molecular biological, genetic, environmental, geographical, and physiological criteria. When determining whether an individual belongs to a particular species, one should take into account not just one criterion, but their entire complex.

You know that a species consists of populations. Population is a group of morphologically similar individuals of the same species, freely interbreeding with each other and occupying a specific habitat in the species’ range.

Each population has its own gene pool- the totality of genotypes of all individuals in a population. The gene pools of different populations, even of the same species, can differ.

The process of formation of new species begins within a population, that is, a population is an elementary unit of evolution. Why is it that a population, and not a species or an individual, is considered as the elementary unit of evolution?

An individual cannot evolve. It can change, adapting to environmental conditions. But these changes are not evolutionary, since they are not inherited. The species is usually heterogeneous and consists of a number of populations. The population is relatively independent and can exist for a long time without connection with other populations of the species. All evolutionary processes take place in a population: mutations occur in individuals, crossing occurs between individuals, the struggle for existence and natural selection operate. As a result, the gene pool of the population changes over time, and it becomes the ancestor of a new species. That is why the elementary unit of evolution is a population, not a species.

Let us consider the patterns of the succession of traits in populations of different types. These patterns are different for self-fertilizing and dioecious organisms. Self-fertilization is especially common in plants. In self-pollinating plants, such as peas, wheat, barley, oats, populations consist of so-called homozygous lines. What explains their homozygosity? The fact is that during self-pollination, the proportion of homozygotes in the population increases, and the proportion of heterozygotes decreases.

Clean line- these are the descendants of one individual. It is a collection of self-pollinating plants.

The study of population genetics began in 1903 by the Danish scientist V. Johannsen. He studied a population of a self-pollinating bean plant that easily produces a pure line - a group of descendants of an individual whose genotypes are identical.

Johannsen took seeds of one bean variety and determined the variability of one trait - seed weight. It turned out that it varies from 150 mg to 750 mg. The scientist sowed two groups of seeds separately: weighing from 250 to 350 mg and weighing from 550 to 650 mg. The average weight of the seed of newly grown plants was 443.4 mg in the light group, and 518 mg in the heavy group. Johannsen concluded that the original bean variety was composed of genetically different plants.

For 6-7 generations, the scientist selected heavy and light seeds from each plant, that is, he carried out selection in pure lines. As a result, he came to the conclusion that selection in pure lines did not produce a shift either towards light or towards heavy seeds, which means that selection in pure lines is not effective. And the variability of seed mass within a pure line is modification, non-hereditary and occurs under the influence of environmental conditions.

The patterns of inheritance of characters in populations of dioecious animals and cross-pollinated plants were established independently of each other by the English mathematician J. Hardy and the German physician W. Weinberg in 1908-1909. This pattern, called the Hardy-Weinberg law, reflects the relationship between the frequencies of alleles and genotypes in populations. This law explains how genetic balance is maintained in a population, that is, the number of individuals with dominant and recessive traits remains at a certain level.

According to this law, the frequencies of dominant and recessive alleles in a population will remain constant from generation to generation under certain conditions: a high number of individuals in the population; their free crossing; lack of selection and migration of individuals; the same number of individuals with different genotypes.

Violation of at least one of these conditions leads to the displacement of one allele (for example, A) by another (a). Under the influence of natural selection, population waves and other evolutionary factors, individuals with the dominant allele A will displace individuals with the recessive allele a.

In a population, the ratio of individuals with different genotypes may change. Let's assume that the genetic composition of the population was as follows: 20% AA, 50% Aa, 30% aa. Under the influence of evolutionary factors, it may turn out to be as follows: 40% AA, 50% Aa, 10% aa. Using the Hardy-Weinberg law, you can calculate the frequency of occurrence of any dominant and recessive gene in a population, as well as any genotype.

A population is an elementary unit of evolution, since it has relative independence and its gene pool can change. Patterns of inheritance are different in populations of different types. In populations of self-pollinating plants, selection occurs between pure lines. In populations of dioecious animals and cross-pollinated plants, patterns of inheritance obey the Hardy-Weinberg law.

In accordance with the Hardy-Weinberg law, under relatively constant conditions, the frequency of alleles in a population remains unchanged from generation to generation. Under these conditions, the population is in a state of genetic equilibrium and no evolutionary changes occur. However, there are no ideal conditions in nature. Under the influence of evolutionary factors - the mutation process, isolation, natural selection, etc. - the genetic balance in the population is constantly disrupted, and an elementary evolutionary phenomenon occurs - a change in the gene pool of the population. Let us consider the effect of various evolutionary factors.

One of the main factors of evolution is the mutation process. Mutations were discovered at the beginning of the 20th century. Dutch botanist and geneticist De Vries (1848-1935).

He considered mutations to be the main cause of evolution. At that time, only large mutations affecting the phenotype were known. Therefore, De Vries believed that species arise as a result of large mutations immediately, spasmodically, without natural selection.

Further research showed that many large mutations are harmful. Therefore, many scientists believed that mutations could not serve as material for evolution.

Only in the 20s. our century, domestic scientists S.S. Chetverikov (1880-1956) and I.I. Shmalgauzen (1884-1963) showed the role of mutations in evolution. It was found that any natural population is saturated, like a sponge, with various mutations. Most often, mutations are recessive, are in a heterozygous state and do not manifest themselves phenotypically. It is these mutations that serve as the genetic basis of new evolution. When heterozygous individuals are crossed, these mutations in the offspring can become homozygous. Selection from generation to generation preserves individuals with beneficial mutations. Beneficial mutations are preserved by natural selection, while harmful ones accumulate in the population in a latent form, creating a reserve of variability. This leads to a change in the gene pool of the population.

The accumulation of hereditary differences between populations is facilitated by insulation, thanks to which there is no crossing between individuals of different populations, and therefore no exchange of genetic information.

In each population, due to natural selection, certain beneficial mutations accumulate. After several generations, isolated populations living in different conditions will differ in a number of characteristics.

Widespread spatial, or geographical isolation when populations are separated by various barriers: rivers, mountains, steppes, etc. For example, even nearby rivers are inhabited by different populations of fish of the same species.

There are also environmental insulation, when individuals of different populations of the same species prefer different places and living conditions. Thus, in Moldova, forest and steppe populations formed among the yellow-throated wood mouse. Individuals of forest populations are larger and feed on seeds of tree species, while individuals from steppe populations feed on cereal seeds.

Physiological isolation occurs when in individuals of different populations maturation of germ cells occurs at different times. Individuals of such populations cannot interbreed. For example, in Lake Sevan there are two populations of trout, the spawning of which occurs at different times, so they do not interbreed.

There is also behavioral isolation. The mating behavior of individuals of different species varies. This prevents them from crossing. Mechanical insulation associated with differences in the structure of the reproductive organs.

Changes in allele frequencies in populations can occur not only under the influence of natural selection, but also independently of it. Allele frequency can change randomly. For example, the premature death of an individual - the only owner of any allele - will lead to the disappearance of this allele in the population. This phenomenon is called genetic drift.

An important source of genetic drift is population waves- periodic significant changes in the number of individuals in the population. The number of individuals changes from year to year and depends on many factors: the amount of food, weather conditions, the number of predators, mass diseases, etc. The role of population waves in evolution was established by S. S. Chetverikov, who showed that changes in the number of individuals in a population influence on the effectiveness of natural selection. Thus, with a sharp reduction in population size, individuals with a certain genotype may accidentally survive. For example, individuals with the following genotypes may remain in a population: 75% Aa, 20% AA, 5% aa. The most numerous genotypes, in this case Aa, will determine the genetic composition of the population until the next “wave”.

Genetic drift typically reduces genetic variation in a population, mainly through the loss of rare alleles. This mechanism of evolutionary change is especially effective in small populations. However, only natural selection based on the struggle for existence contributes to the preservation of individuals with a certain genotype corresponding to the habitat.

An elementary evolutionary phenomenon - a change in the gene pool of a population occurs under the influence of elementary factors of evolution - the mutation process, isolation, genetic drift, natural selection. However, genetic drift, isolation and the mutation process do not determine the direction of the evolutionary process, that is, the survival of individuals with a certain genotype corresponding to the environment. The only guiding factor in evolution is natural selection.

The main provisions of the evolutionary teachings of Charles Darwin.

1. Hereditary variability is the basis of the evolutionary process;
2. The desire to reproduce and limited means of life;
3. The struggle for existence is the main factor in evolution;
4. Natural selection as a result of hereditary variability and the struggle for existence.

FORMS OF NATURAL SELECTION

TYPES OF NATURAL SELECTION

Tasks and tests on the topic "Topic 14. "Evolutionary teaching"."

• Having worked through these topics, you should be able to:

  1. Formulate in your own words the definitions: evolution, natural selection, struggle for existence, adaptation, rudiment, atavism, idioadaptation, biological progress and regression.
  2. Briefly describe how a particular adaptation is preserved by selection. What role do genes play in this, genetic variability, gene frequency, natural selection.
  3. Explain why selection does not produce a population of identical, perfectly adapted organisms.
  4. Formulate what genetic drift is; give an example of a situation in which it plays an important role, and explain why its role is especially important in small populations.
  5. Describe two ways species arise.
  6. Compare natural and artificial selection.
  7. Briefly list aromorphoses in the evolution of plants and vertebrates, idioadaptations in the evolution of birds and mammals, angiosperms.
  8. Name the biological and social factors of anthropogenesis.
  9. Compare the effectiveness of consuming plant and animal foods.
  10. Briefly describe the features of the most ancient, ancient, fossil man, modern man.
  11. Indicate the developmental features and similarities of human races.

  Ivanova T.V., Kalinova G.S., Myagkova A.N. "General Biology". Moscow, "Enlightenment", 2000

  • Topic 14. "Evolutionary teaching." §38, §41-43 pp. 105-108, pp.115-122
  • Topic 15. "Adaptability of organisms. Speciation." §44-48 pp. 123-131
  • Topic 16. "Evidence of evolution. Development of the organic world." §39-40 pp. 109-115, §49-55 pp. 135-160
  • Topic 17. "The Origin of Man." §49-59 pp. 160-172