Textbook for grades 10-11
Chapter XI. Mechanisms of the evolutionary process
Charles Darwin in his classic work "The Origin of Species" solved the problem of the main driving forces (factors) of the evolutionary process. He singled out the following factors: heredity, variability, the struggle for existence and natural selection. In addition, Darwin pointed out the important role of limiting the free interbreeding of individuals due to their isolation from each other, which arose in the process of evolutionary divergence of species.
Modern knowledge about evolution and its factors has developed into the so-called synthetic theory of evolution, which is the result of the development of Darwinism, genetics, ecology and other biological sciences.
The evolutionary theory proceeds from the fact that the elementary evolutionary unit, that is, the minimum cell that is capable of historical change (evolve), is the population.
§ 45. The role of variability in the evolutionary process
All individuals of the same species of animals and plants are more or less different from each other. The variability of organisms is an important factor in the course of the evolutionary process.
mutational variability. Mutational variability plays the role of the main supplier of hereditary changes. It is she who is the primary material of all evolutionary transformations. One of the common types of genomic mutations is polyploidy, which is important in plant evolution. Polyploid plant species often occupy arctic and alpine zones. It is believed that this is due to their increased resistance to adverse environmental factors.
Chromosomal mutations also play an important evolutionary role. First of all, it is necessary to point out the duplication of genes in one chromosome. It is thanks to the doubling of genes that genetic material accumulates in the process of evolution. The increase in the complexity of the organization of living things in the course of historical development was largely based on an increase in the amount of genetic material. Suffice it to say that the amount of DNA in a cell in higher vertebrates is about 1000 times greater than in bacteria. Another type of chromosomal mutation, which is quite often found in animals and plants, is the displacement of a chromosome segment.
Individuals heterozygous for such mutations often have reduced fertility, while homozygotes reproduce normally. Some scientists believe that the appearance of such mutations can break the genetic unity of the species and lead to isolation within its reproductively isolated populations.
SERGEI SERGEEVICH CHETVERIKOV (1882-1959) - Russian scientist, evolutionist and geneticist. His work gave rise to the modern synthesis of genetics and classical Darwinism.
The most common type of mutations are genes. They play a very important role in the evolutionary process. Mutations of individual genes are rare. A gene mutation occurs on average in one in 100,000 gametes. But since the number of genes in an organism (for example, mammals) is about 40,000, almost every individual carries a newly emerged mutation. Most mutations are recessive, dominant mutations occur much less frequently. Dominant and recessive mutations behave differently in populations. Dominant mutations, even if they are in a heterozygous state, appear in the phenotypes of individuals already in the first generation and are subject to natural selection. Recessive mutations appear in the phenotype only in the homozygous state.
A recessive mutation, before it manifests itself in the phenotype of homozygotes, must accumulate in significant numbers in the population. This idea was first expressed by the domestic geneticist S. S. Chetverikov. He was the first scientist to take a major step towards the unification of genetics with evolutionary theory. In 1926, Chetverikov published the famous work "On Some Moments of the Evolutionary Process from the Point of View of Modern Genetics", which began a new stage in the development of evolutionary theory.
S. S. Chetverikov made an important conclusion about the saturation of natural populations with a large number of recessive mutations. He wrote that a population, like a sponge, absorbs recessive mutations while remaining phenotypically homogeneous. The existence of such a hidden reserve of hereditary variability creates the possibility for evolutionary transformations of populations under the influence of natural selection. As I. I. Shmalgauzen showed, the very ability of populations to accumulate genetic variability is the result of natural selection.
Recently, thanks to the advances in molecular genetics and developmental genetics, it has become increasingly clear what a huge role is played in evolution by mutations that occur not in the structural (protein-coding) genes themselves, but in the regulatory regions of these genes. They can modify the level of transcription of structural genes, the time and place of their switching on and off, creating a huge variety of forms and functions of organisms. Significant morphological differences between classes of vertebrates depend on the accumulation of small mutations in regulatory elements.
Let's consider a simple example. The size and position of the chest in chicken, mouse, and boa constrictor are controlled by the same structural gene. The nucleotide sequence in this gene is the same in all three species (as in all other vertebrates). However, the changes that have occurred in its regulatory elements lead to the fact that in the boa constrictor this gene works in almost all cells of the notochord of the embryo, in the mouse - in the anterior part, and in the chicken - in the back of the notochord. As a result, the chest of the boa constrictor is formed from the head almost to the tip of the tail, in the mouse - closer to the head, and in the chicken - closer to the tail.
In natural populations, a huge number of mutations in the regulatory elements of various structural genes has been accumulated.
Combination variability. As you already know, combinative variability is a consequence of the crossing of homologous chromosomes, their random divergence in meiosis and the random combination of gametes during fertilization. Combinative variability leads to the appearance of an infinitely large variety of genotypes and phenotypes. It serves as an inexhaustible source of hereditary diversity of species and the basis for natural selection. If we assume that in each pair of homologous chromosomes there is only one pair of allelic genes, then for a person whose haploid set of chromosomes is 23, the number of possible gametes will be 2 23, and the number of possible genotypes - 3 23. Such a huge number of genotypes is 20 times greater than the number of all people on Earth. However, in reality, homologous chromosomes differ in several genes, and the phenomenon of crossover is not taken into account in the calculation. Therefore, the number of possible genotypes is expressed by an astronomical number, and it can be safely stated that the appearance of two identical people is almost unbelievable. Identical twins are an exception.
The enormous genotypic and, consequently, phenotypic diversity in natural populations is the initial evolutionary material with which natural selection operates.
- What kind of variability, in your opinion, plays a leading role in evolution? Justify the answer.
- Describe the role of variability in the evolutionary process.
- How can one explain the phenotypic homogeneity of populations of one species? Can it be argued that the gene pools of populations of the same species are the same?
- What biological processes occurring in the body underlie combinative variability?
OPTION - 2
1. According to Ch. Darwin, the driving forces of evolution are:
A) the struggle for existence; B) natural selection;
B) hereditary variability; D) all of the above.
2. The following type of variability plays a leading role in evolution:
A) certain B) group;
B) modification; D) mutational.
3. The driving form of selection usually leads to:
A) the destruction of individuals with deviations; B) the expansion of the previous norm of reaction;
from the previous rate of reaction;
B) narrowing of the previous norm of reaction; D) shift of the previous rate of reaction.
4. Similar bodies are:
A) crayfish gills and fish gills; C) birch leaves and cactus needles;
B) a dog's paw and a bird's wing; D) all of the listed pairs.
5. In the era of glaciation lived:
A) Cro-Magnons B) synanthropes;
B) Neanderthals; D) all of the above.
6. The productivity of an ecosystem is called:
A) its total biomass; C) total biomass of producers;
B) the growth of this biomass per unit of time; D) total biomass of consumers.
7. In prokaryotic cells there are:
A) nuclei B) mitochondria;
B) ribosomes; D) all of the listed organelles.
8. According to the views of A.I. Oparin, the main sources of energy for the abiogenic synthesis of organic substances from inorganic substances on the ancient Earth were:
a) electric projectiles; b) ultraviolet radiation;
9. Life on Earth arose:
a) originally on sushi; b) initially in the ocean;
10. The panstermia hypothesis suggests
a) life is brought to our planet from outside;
b) life arose repeatedly from non-living matter;
c) the gradual emergence of life on Earth from inorganic substances
by long-term abiogenic molecular evolution;
d) life has always existed.
11. The gene refers to the structural and functional unit of the level of organization of life
A) organismic B) molecular-genetic C) organoid-cellular D) population-species
12. A population is a collection of individuals of a particular species occupying a certain territory and
13 The main reason for the biological regression of many species at present is:
A) climate change B) human economic activity
C) change in relief D) increase in the number of predators.
14. The science of cytology studies:
15. A reservoir inhabited by various species of plants and animals is:
16. The theory of abiogenesis was supported by:
a) Aristotle b) F. Redi; c) L. Pasteur; d) K. Linney
17. Changes that are not inherited and arise as adaptations to the external environment are called:
A) indefinite B) individual C) mutational
D) modification
18. Deoxyribonucleic acid is the level of organization of wildlife:
19. The ancient people include:
20. Fitness in the process of evolution arises as a result of:
OPTION - 3
1. Deoxyribonucleic acid is the level of organization of wildlife:
A) cellular; B) molecular;
B) organismic; D) population
2. The science of cytology studies:
A) the structure of cells of unicellular and multicellular organisms;
B) the structure of organs and organ systems of multicellular organisms;
C) the phenotype of organisms from different kingdoms;
D) plant morphology and features of their development.
3. The ancient people include:
A) Neanderthal B) Pithecanthropus
C) Sinanthropus D) Cro-Magnon.
4. There is competition between elk and bison, as they:
A) eat the same food B) have approximately the same body parameters
C) have few offspring D) belong to the class of mammals.
5. Fitness in the process of evolution arises as a result of:
A) geographical isolation B) interaction of the driving forces of evolution
C) mutational variability D) artificial selection.
6. A reservoir inhabited by various species of plants and animals is:
A) biogeocenosis B) noosphere C) biosphere D) agroecosystem.
7. Life on Earth arose:
a) originally on sushi; b) initially in the ocean;
c) on the border of land and ocean; d) simultaneously on land and ocean.
8. Deoxyribonucleic acid is the level of organization of wildlife:
A) cellular; B) molecular; B) organismic; D) population
9. A population is a collection of individuals of a particular species occupying a certain territory and
A) have a common gene pool
B) similar to each other in all respects of the external structure
C) having various obstacles for free crossing
D) do not compete with each other for food and other favorable environmental conditions
10. According to the views of A.I. Oparin, the main sources of energy for the abiogenic synthesis of organic substances from inorganic substances on the ancient Earth were:
a) electric projectiles;
b) ultraviolet radiation;
c) thermal radiation from volcanic eruptions;
d) energy of chemical reactions
11. New species in nature arise as a result of interaction:
A) hereditary variability, struggle for existence, natural selection
B) non-hereditary changes and seasonal changes in nature
C) adaptability of organisms and artificial selection
D) abiotic environmental factors
12. . Ch. Darwin considered the most intense form of struggle for existence:
A) the fight against adverse conditions; B) interspecific;
B) intraspecific; D) all of the listed forms equally.
Option 1
ANSWER: 1 - C, 2 - B, 3 - B, 4 - C, 5 - C, 6 - B, 7 - D, 8 - B, 9 - D, 10 - B,
11 - C, 12 - C, 13 - B, 14 - C, 15 - A, 16 - A, 17 - B, 18 - A, 19 - A,
20 - G.
Option 2
ANSWER: 1 - D, 2 - D, 3 - D, 4 - A, 5 - B, 6 - B, 7 - B, 8 - D, 9 - A, 10 - A,
11 - B, 12-A, 13-B, 14-A, 15-A, 16-A, 17-G, 18-B, 19-A, 20-B
Option 3
Answers: 1 - B, 2 - A, 3 - a, 4 - C, 5 - B, 6 - A, 7 - B, 8 - B, 9 - A
10 - D, 11 - A, 12 - B, 13 - C, 14 - A, 15 - B, 16 - D, 17 - A, 18 - A,
19 - B, 20 - B.
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General lesson on the topic: "Fundamentals of the doctrine of evolution"
Level A
1. The following type of variability plays a leading role in evolution
A) certain
B) modification
B) group
D) mutational
2. The ability of living beings to produce a large number of offspring and the limited habitats and life resources are the immediate causes of:
A) hereditary variation
B) struggle for existence
B) extinction
D) speciation
3. Charles Darwin considered the most intense form of struggle for existence:
A) dealing with adverse conditions
B) intraspecific
B) interspecies
D) all of the above equally
4. Hereditary variability in the process of evolution:
A) create new species
B) supplies material for evolution
C) fixes the material created in the process of evolution
D) saves the most useful changes
5. Natural selection operates at the level of:
A) individual organism
B) populations
D) biocenosis
6. The driving form of selection usually results in:
A) to the destruction of individuals with deviations from the previous norm of reaction
B) expansion of the previous rate of reaction
B) narrowing the previous reaction norm
D) a shift in the previous rate of reaction
7. The result of natural selection is not:
A) adaptability of organisms to the environment
B) the diversity of the organic world
B) struggle for existence
D) improvement of the organization of living beings
A) aromorphosis
B) idioadaptation
B) general degeneration
D) directed evolution
11. Idioadaptations include:
A) multicellularity
B) four-chambered heart of mammals
B) needle-like leaves of desert plants
D) all of the above evolutionary changes
12. An example of aromorphosis is:
A) flattening of the body in bottom fish
B) protective coloration
D) the occurrence of the sexual process
13. Natural selection is:
A) complex relationships between organisms and inanimate nature
B) the process of preserving individuals with useful hereditary traits
C) the process of formation of new species in nature
D) the process of population growth
14. The struggle for existence plays a big role in evolution:
A) preserves individuals predominantly with beneficial changes
B) preserves individuals with any hereditary changes
B) supplies material for selection
D) aggravates the relationship between individuals
15. As a result of the interaction of the driving forces of evolution, the following occurs:
A) reproduction of organisms
B) the formation of new species in nature
B) mutation process
D) isolation of populations
16. Point out the incorrect statement: “In the process of evolution, the struggle with adverse conditions leads to ...”
A) to increase the resistance of organisms
B) the survival of the most viable individuals
B) species extinction
D) improving the view
17. The driving forces of evolution include:
A) variety of species
B) struggle for existence
B) speciation
D) fitness
18. The factor of evolution, the basis of which is the emergence of barriers to free crossing of individuals, is called:
A) modification
B) natural selection
B) insulation
D) population waves
19. Among the driving forces of evolution, leading to the emergence of adaptations in individuals to the environment, the guiding character has:
A) natural selection
B) artificial selection
B) isolation
D) struggle for existence
20. The type of selection acting in populations living in relatively constant environmental conditions, - ...
A) natural
B) stabilizing
B) driving
D) sexual
21. What are the consequences of stabilizing selection?
A) preservation of old species
B) maintaining the reaction rate
C) the emergence of new species
D) preservation of individuals with unchanged characteristics
22. What are the consequences of motive selection?
A) preservation of old species
B) maintaining the reaction rate
C) the emergence of new species
D) elimination of individuals with new mutations
23. The formation of new species in nature occurs as a result of
A) methodical selection
B) artificial selection
B) human activities
D) interactions of the driving forces of evolution
24. In case of geographical speciation, the formation of a new species occurs as a result of:
A) disintegration or expansion of the original range
B) artificial selection
C) isolation of populations within the old range
D) genetic drift
Level B.
Establish correspondences between the signs of variability and its types:
- It is caused by the appearance of new combinations of genes a. Mutational
Caused by changes in genes and chromosomes b. combinative
The offspring have new traits
Offspring have parental traits
In individuals, the amount or structure of DNA changes
Individuals do not change the amount or structure of DNA
Adaptations to life in the water, formed in the process of evolution in whales:
B) breathing oxygen dissolved in water
B) streamlined body shape
D) developed subcutaneous fat layer
D) constant body temperature
The result of evolution is:
B) the emergence of new drought-resistant plant varieties
C) breeding of highly productive breeds of cattle
D) the formation of new adaptations to life in changed conditions
E) conservation of new species in changed conditions
E) obtaining highly productive broiler chickens
Level C.
What aromorphoses allowed the ancient amphibians to master the land?
What aromorphoses allowed angiosperms to occupy a dominant position on Earth?
The theory of evolution by Ch. Darwin and A. Wallace.
Basic provisions:
1. All kinds of living organisms arose naturally.
2. Organisms slowly and gradually transformed and improved.
3. The basis for the transformation of species is variability, heredity and natural selection. Selection is carried out through the interactions of organisms with each other and environmental factors. These interactions are called the struggle for existence.
4. Individuals that are most adapted to changing environmental conditions survive and give full-fledged offspring.
Synthetic theory of evolution - this is a rethinking of a number of provisions of Darwinism from the standpoint of genetics (S. Chetverikov, J. Haldane, N. Timofeev-Resovsky, R. Fisher). It is characterized as a theory of evolution occurring through natural selection of traits determined genetically.
Basic provisions:
1. The elementary unit of evolution is the population.
2. The material for evolution is mutational and combinational variability.
3. Natural selection is considered as the main reason for the development of adaptations, speciation and the origin of supraspecific taxa.
4. A species is a group of populations reproductively isolated from populations of other species.
5. Speciation consists in the emergence of genetic isolating mechanisms and is carried out in conditions of geographic isolation.
The process of formation of new genera from species, from genera to families, from families to orders, etc. called macroevolution. Unlike microevolution occurring within a population, macroevolution is supraspecific and very long-term evolution.
The proof of evolutionary processes are paleontological, morphological, embryological and biochemical data.
There are three main directions of evolution.
Aromorphosis – evolutionary changes leading to a qualitatively new level of organization (multicellularity, central nervous system, photosynthesis). Thanks to aromorphosis, new large taxonomic units arise: types (departments), classes.
Idioadaptation - small evolutionary changes, expressed in adaptation to the environment. There is no increase in the level of organization. Thanks to idioadaptation, small taxonomic groups are formed: species, genera, families.
Mutations constantly arise in populations under the influence of factors and cause changes in its gene pool. population waves- this is a phenomenon of fluctuations in the number of populations, which are associated with periodic changes in the intensity of environmental factors (change of seasons, precipitation, temperature fluctuations).
Insulation contributes to the prevention of interbreeding between individuals of different parts of the population and leads to a divergence of characters within the same species.
Geographic isolation leads to a rupture of a single range of a species into separate parts and prevents crossing. The reasons for its appearance are the emergence of mountains, new rivers, straits, etc.
Environmental isolation based on differences in dispersal or breeding times. For example, some species of salmon spawn in a year, and in the same rivers one population of fish spawns in one year, and another in another.
biological isolation associated with differences in the structure of the genital organs, in marriage songs, courtship rituals, emitted odors, etc.
The greatest importance in the evolutionary process is natural selection. It plays a creative role in nature, distinguishing from undirected hereditary changes only those that lead to the formation of new groups of individuals that will be more adapted to new environmental conditions.
Soviet biologist I.I. Schmalhausen developed (1946) the concept of group selection - the survival of populations, species, genera, families, orders, etc. But since group selection occurs on the basis of the experience of the organisms that make up these groups, the leading role in evolution is also played by individual natural selection - the selection of the most adapted individuals.
