The role of mutations in the evolution of the spread of mutations. The role of mutation in evolution

Subject: Biology

Topic: “The evolutionary significance of mutations”

Purpose of the lesson: create conditions for mastering the concept of mutation, consider the evolutionary role of mutations.

Lesson objectives:

Educational: patriotic education using the example of domestic scientists who have studied the mutation process;

Developmental: formation of skills and abilities for independent work, laying the foundations for the study of genetics;

Educational: consider the essence of the mutation process, identify its role in evolution.

Lesson type: Combined.

Method of implementation: conversation, explanation, independent work, group work.

Lesson progress:

Organizational moment . Greetings. Preparing the audience for work. Checking the availability of students.

Testing students' knowledge and goal setting .

Teacher: Now we will complete a test task, with the help of which we will find out what we will study in today's lesson. (students begin to take the test). Appendix 1.

The teacher, together with the students, using a correctly completed test, communicate the topic of the lesson and the purpose of the lesson.

Presentation of new material.

Teacher: Write down the topic of the lesson.

Let us remember that evolution is divided into two types:

Evolution

Microevolution Macroevolution

Define the concept of microevolution? (speciation).

The teacher conducts a frontal survey to direct students to independently study this topic:

The unit of heredity is...?

Where is the chromosome located?

Using a drawing on the presentation and reasoning together with the teacher, students themselves formulate a definition of the term gene. (A gene is a section of a DNA molecule containing hereditary information.)

Teacher: a living organism and each of its cells are always exposed to various environmental influences. Exposure to the external environment can cause disturbances in the process of cell division and “errors” in the copying of genes and chromosomes. What do you think these “mistakes” lead to? (Mutations)

Mutation is a change in the hereditary apparatus of a cell, affecting whole cells or parts thereof.

Teacher: Question to the class: What is the role of mutations in the evolutionary process? To answer this question, we will look at the mutation process in more detail. What are the types of mutations?

Beneficial mutations: mutations that lead to increased resistance of the body (resistance of cockroaches to pesticides). Harmful mutations: deafness, color blindness. Neutral mutations: mutations do not affect the viability of the organism (eye color, blood type).

Mutation as a factor of evolution.

Teacher: Our domestic scientist S.S. studied natural mutations. Chetverikov. Most mutations are harmful, but rare beneficial mutations are the starting material for evolution.

Emerging recessive mutations become heterozygous and are invisible. But each species (population), like a sponge, is saturated with these mutations. Thus, there is hidden variability. Since genetic diversity is the result of evolution, mutation is necessary for evolutionary progress.

Processes that change the genetic structure of a population.

It is known that in different populations of the same species the frequency of mutant genes is not the same:

Natural disasters;

Migrations;

"Waves of numbers";

Insulation.

Students need to divide into groups and make a plan to speak to the class on the topic of the chosen process that changes the genetic structure of the population.

Summing up (reflection)

Today in class I...

The most useful and interesting thing for me was...

I encountered difficulty with...

Teacher: How do you rate today's class work?

Reinforcing the material learned (lesson conclusion):

What role do mutations play in the process of evolution?

Homework. Fill out the table (Appendix 3) and answer the questions on page 58.

Appendix 1.

Test on the topic: “A species is an evolutionary unit. Its criteria and structure"

Which of the following statements is most correct:

2) Which of the following organisms cannot evolve?

U) female bee.

I) bee population.

T) A flock of pigeons.

3) The criterion characterizing a certain area occupied by a species in nature is...
K) Ecological criterion
B) Morphological criterion
T). Geographical criterion
D) Physiological criterion

4) A set of geographically and ecologically close populations that are capable of interbreeding and have common morpho-physiological characteristics is...
A) View
N) Individual
B) Population
Ш) Class

5) The degree of mobility of individuals is expressed by the distance over which the animal can move - this distance is called ...
C) Radius of individual activity
G) Migration
D) Isolation
I) There is no correct answer

6) For species living in Baikal, the range is limited to this lake - this is an example of ... criterion
K) Ecological
T) Morphological
I) Geographical
D) Physiological

7).The criterion of a species, which includes a set of environmental factors that make up the immediate habitat of the species, is ... criterion
I) Ecological
U) Geographical
I) Morphological
D) There is no correct answer

In all centuries, humanity has tried to find answers to the questions: How was this colossal diversity formed? Why is each species optimally adapted to its habitat conditions? How do some species differ from others? Why do some species thrive while others die out and disappear from the face of the Earth?

1. Elementary unit of evolution Population 2. Elementary evolutionary material Mutations - genotypic diversity in populations 3. Elementary evolutionary phenomenon Long-term and directed change in the gene pool 4. Elementary evolutionary factors Hereditary variability, struggle for existence, natural selection - directing factor 5. Elementary object of selection Separate an individual with a certain phenotype

S.S. Chetverik Populations, like a sponge, absorb recessive mutations while remaining phenotypically homogeneous. The existence of such an open reserve of hereditary variability creates the opportunity for evolutionary transformations of the population under the influence of natural selection. He studied natural mutations and changes in the hereditary properties of the body. Made a significant contribution to the development of population genetics.

The mutation process is a constantly operating source of hereditary variability. Genes mutate at a certain frequency. During sexual reproduction, mutations can spread widely throughout populations. Most organisms are heterozygous for many genes, that is, in their cells homologous chromosomes carry different forms of the same gene. Heterozygous organisms are better adapted than homozygous ones.

The mutation process is a source of reserve of hereditary variability of populations. By maintaining a high degree of genetic diversity in populations, it provides the basis for natural selection to operate. In different populations of the same species, the frequency of mutant genes is not the same. There are no populations with exactly the same frequency of occurrence of mutant traits. These differences may be due to the fact that populations live in different environmental conditions. Directed changes in gene frequency in populations are due to the action of natural selection.

Waves of life - fluctuations in the number of individuals in a population. The term was introduced by the Russian biologist S. S. Chetverikov in 1915. Such fluctuations in numbers may be seasonal or non-seasonal, repeating at various intervals; Usually they are longer, the longer the development cycle of organisms. Subsequently, the term was replaced by the concept of population waves (one of the 4 elementary evolutionary factors: mutation process, population waves, isolation and natural selection). The main significance comes down to random changes in the concentrations of various mutations contained in populations, as well as to the weakening of selection pressure as the number of individuals in the population increases and its intensification when the number of individuals decreases. The term sometimes refers to stages of development of flora and fauna, approximately corresponding to the change of geological cycles.

Evolutionary factors are factors causing the evolution of populations. “Waves of life” and “genetic drift”, as a rule, accompany the evolutionary process of each population, if we are talking about a long process (period of time). However, the historical development of the organic world is theoretically possible without them, that is, only on the basis of variability, heredity, the struggle for existence and natural selection.

Can all causes that cause the death of organisms be considered natural selection? Natural selection is not the only reason for the death of organisms. The death of an animal may be the result of a random event (a forest fire, flood or other natural disaster that leaves no chance of survival).

Evolutionary factors Directing the evolutionary process Non-directing the evolutionary process Natural selection (against the background of the struggle for existence) - Hereditary variability. -- Genetic drift. - Waves of life. -- Isolation. Acts in a population, changing its gene pool. Possible result: the emergence of new populations, subspecies, species (speciation)

The set of evolutionary processes occurring in populations of a species and leading to changes in the gene pools of these populations and the formation of new subspecies and species is called microevolution. Evolution at the level of systematic units above the species, which takes place over millions of years and is inaccessible to direct study, is called macroevolution. These two processes are one. Homework: Page Give examples of aromorphoses, idioadaptations and degenerations. Repeat the definitions: species, population, evolution, macroevolution, microevolution.

Thanks to the study of genetic processes in populations of living organisms, evolutionary theory received a new impetus and further development. The Russian scientist S. Chetverikov made a great contribution to population genetics. He drew attention to the saturation of natural populations with recessive mutations, as well as fluctuations in the frequency of genes in populations, depending on the action of environmental factors, and substantiated the position that these two phenomena are the key to understanding the processes of evolution.

Indeed, the mutation process is a constantly operating source of hereditary variability. Genes mutate at a certain frequency. It is estimated that on average one gamete out of 10 thousand - 1 million gametes carries a newly emerging mutation at a certain locus. Since many gametes mutate at the same time, 10-15% of gametes carry one or another mutation allele. Therefore, natural populations are saturated with a wide variety of mutations. Due to combinative variability, mutations can spread widely in populations. Most organisms are heterozygous for many genes. One might assume that as a result of sexual reproduction, homozygous organisms will constantly be isolated among the offspring, and the proportion of heterozygotes should steadily fall. However, this does not happen. The fact is that in the overwhelming majority of cases, heterozygous organisms are better adapted than homozygous ones.

In the example with the birch moth butterfly, it would seem that light-colored butterflies, homozygous for the recessive allele (aa), living in a forest with dark birch trunks, should quickly be destroyed by enemies and the only form in these living conditions should be dark-colored butterflies, homozygous for the dominant allele (AA). But for a long time, light-colored birch moth butterflies have been constantly found in the smoky birch forests of the South of England. It turned out that caterpillars homozygous for the dominant allele poorly digest birch leaves covered with soot and soot, while heterozygous caterpillars grow much better on this food. Consequently, the greater biochemical flexibility of heterozygous organisms leads to their better survival and selection acts in favor of heterozygotes.

Thus, although most mutations under given specific conditions are harmful and in the homozygous state, mutations, as a rule, reduce the viability of individuals, they are preserved in populations due to selection in favor of heterozygotes.

To understand evolutionary transformations, it is important to remember that mutations that are harmful in some conditions can increase viability in other environmental conditions. In addition to the above examples, you can point to the following. A mutation that causes underdevelopment or complete absence of wings in insects is certainly harmful under normal conditions, and wingless individuals are quickly replaced by normal ones. But in ocean spaces and mountain passes where strong winds blow, such insects have an advantage over individuals with normally developed wings.

Thus, the mutation process is a source of reserve of hereditary variability of populations. By maintaining a high degree of genetic diversity in populations, it provides the basis for natural selection to operate.

Genetic processes in populations

In different populations of the same species, the frequency of mutation genes is not the same. There are practically no two populations with a perfect frequency of occurrence of mutational traits. These differences may be due to the fact that populations live in different environmental conditions. Directed changes in gene frequency in populations are due to the action of natural selection. But closely located, neighboring populations can differ from each other just as significantly as distantly located ones. This is explained by the fact that in populations a number of processes lead to undirected random changes in the frequency of genes, or, in other words, their genetic structure.

For example, when animals or plants migrate, a small part of the original population appears in a new habitat. The gene pool of the newly formed population is inevitably smaller than the gene pool of the parent population, and the frequency of genes in it will differ significantly from the frequency of genes in the original population. Genes, previously rare, quickly spread among a new population due to sexual reproduction. At the same time, widespread genes may be absent if they were not in the genotype of the founders of the new population.

Another example. Natural disasters - forest or steppe fires, floods, etc. – cause massive, inevitable death of living organisms, especially sedentary forms: plants, fungi, mollusks, amphibians, etc. Individuals that escaped death remain alive due to pure chance. In a population that has survived a disaster, there is a decrease in numbers. In this case, allele frequencies will be different than in the original population. Following the decline in numbers, mass reproduction begins, which is initiated by the remaining, small group. The genetic composition of this group determines the genetic structure of the entire population during its heyday. In this case, some mutations may completely disappear, while the concentration of others may accidentally increase sharply.

In a biocenosis, periodic fluctuations in population numbers are often observed, associated with predator-prey relationships. Increased reproduction of predators' prey based on an increase in food resources leads, in turn, to increased reproduction of predators. An increase in the number of predators causes mass destruction of their victims. The lack of food resources causes a reduction in the number of predators and a restoration of the size of prey populations. These fluctuations in numbers are called population waves. They change the frequency of genes in populations, which is their evolutionary significance.

Changes in gene frequency in populations are also caused by limited gene exchange between them due to spatial isolation. Rivers serve as barriers to land species, mountains and elevations isolate lowland populations. Each isolated population has specific characteristics associated with living conditions. An important consequence of isolation is inbreeding - inbreeding. Thanks to inbreeding, recessive alleles, spreading through a population, appear in a homozygous state, which reduces the viability of organisms. In human populations, isolates with a high degree of inbreeding are found in mountainous areas and on islands. The isolation of certain groups of the population for caste, religious, racial and other reasons still remains important.

The evolutionary significance of various forms of isolation is that it perpetuates and enhances genetic differences between populations, and also that separated parts of a population or species are subject to unequal selection pressure.

Thus, changes in gene frequency caused by certain environmental factors serve as the basis for the emergence of differences between populations and subsequently determine their transformation into new species. Therefore, changes in populations during natural selection are called microevolution.

Security questions

1. S. Chetverikov’s work in the field of population genetics.

2. The evolutionary role of mutations.

3. The mutation process is a source of reserve of hereditary variability of populations.

4. Changes in gene frequency in the population.

5. What is microevolution?

The evolutionary role of mutations

Mutation

mutagens

Genotype

allele (allele homozygote heterozygote(Ah).

The evolutionary role of mutations

The body and each of its cells are continuously exposed to various environmental influences, which can cause disturbances in the process of cell division and “errors” in the copying of genes and chromosomes, i.e. mutation.

Mutation- a change in the hereditary apparatus of a cell, affecting entire chromosomes or parts thereof.

The study of natural mutations was carried out by the domestic scientist S.S. Chetverikov and the Dutch botanist De Vries.

Mutation is a continuous, random process, but not without cause!

The influences that cause mutations are called mutagens. The main mutagens are: all types of radiation, chemicals, viruses, bacteria, excessive high or low temperature, etc.

Mutations are: harmful, neutral and harmful. The same mutation can change its meaning under changing conditions. Most mutations are harmful, but rare beneficial mutations are the starting material for evolution.

All organisms in their natural state are characterized by free crossing - a stabilizing apparatus of genotypes in a population. ( Genotype - a set of genes of an organism).

A gene is a section of a DNA molecule containing hereditary information. The gene has two allele (allele – specific state of the gene): dominant gene – A, recessive gene – a. When two cells merge, a zygote is formed; if it has two identical alleles of a gene, then it is called homozygote(AA, aa), if different alleles – heterozygote(Ah).

Emerging recessive mutations become heterozygous and are invisible. But each species (population), like a sponge, is saturated with such mutations. Thus, hidden variability occurs.

Mutation frequency 10 -4, 10 -8.

Each organism has a large number of genes, therefore the probability of occurrence of a mutation is greater, the number of individuals in the population is large. Thus, we can say that mutation is a common phenomenon.

Since genetic diversity is a result of evolution, mutation is necessary for the evolutionary process.

The frequency of mutations depends on: natural disasters (some mutations disappear, while the concentration of others increases); migration (gene frequency changes - differs from the original); “waves of numbers”, isolation.

Changing the directions of natural selection in accordance with new conditions of the struggle for existence

Selection of individuals, inheritance. changes in which allow them to develop new territories or habitats

Geographic speciation

Ecological speciation

Settlement in a new territory

Development of new ecological niches within the old range

Geographic isolation between populations

The emergence of subspecies

Biological isolation

The emergence of new species

Selection under new environmental conditions

Selection under new environmental conditions

Biological isolation

The emergence of subspecies

The emergence of new species

Sequence of events during speciation

Change in habitat or position of a species (population) in it

Intensification of the struggle for existence between individuals