Modern ideas about the evolution of the organic world. Biology presentation "Modern ideas about the evolution of the organic world" (Grade 9) Preventing the collapse of Darwinism

Modern evolutionary teaching is often referred to as synthetic, because it includes not only Darwinism (i.e., the teachings of Charles Darwin about selection and the struggle for existence), but also data from genetics, taxonomy, morphology, biochemistry, physiology, ecology and other sciences. Especially valuable for understanding the essence of evolution were the discoveries made in genetics and molecular biology.

Chromosomal theory and gene theory have revealed the nature of mutations and the laws of heredity transmission, while molecular biology and molecular genetics have established ways of storing, implementing and transmitting genetic information using DNA. It was determined that the elementary evolutionary unit capable of responding to changes in the environment by rearranging its gene pool is the population. Therefore, not a species, but its populations are saturated with mutations and serve as the main material of the evolutionary process under the influence of natural selection.

The modern doctrine of evolution is based on the population idea .

A population is the structural unit of a species. It represents a set of individuals of a species that have a common gene pool and occupy a certain territory within the range of this species.

Gradually, there is a divergence between such populations ( divergence ) for a number of genetic traits that accumulate through combinations and mutations. Gradually, individuals of populations acquire noticeable differences from the original parental species. If the resulting differences ensure the non-crossing of individuals of one population with individuals of other populations of the original species, then the isolated population becomes an independent new species, isolated by divergences from the original view.

In modern evolutionary teaching, elementary units of evolution, elementary material and elementary factors of evolution are distinguished.

• elementary unit evolution serves population. Each population is characterized by such properties as range, abundance and density, genetic heterogeneity of individuals, age and sex structure, special functioning in nature (intrapopulation and interpopulation contacts, relationships with other species and with the environment).

elemental material evolution is hereditary variability - combinative and mutational.

These two types of hereditary variability lead to the emergence of both qualitative and quantitative phenotypic differences in organisms.

Under certain conditions and for some time, new inherited traits that have arisen can reach sufficiently high concentrations in one or several adjacent populations of the species. Groups with special characters that have arisen in this way can be found in a certain area within the range of the species.

Different types.

Elementary Factors of Evolution are natural selection, mutation process, population waves and isolation.

Natural selection eliminates individuals with unsuccessful combinations of genes from the population and preserves individuals with genotypes that do not violate the process of adaptive morphogenesis. Natural selection directs evolution.

mutation process maintains the genetic heterogeneity of natural populations.

population waves supply the mass character of elementary evolutionary material for natural selection. Each population is characterized by a certain fluctuation in the number of individuals in the direction of either increase or decrease. In 1905, the Russian geneticist Sergei Sergeevich Chetverikov called these fluctuations waves of life.

Insulation provides barriers preventing free interbreeding of organisms . It can be caused by territorial-mechanical (spatial, geographical) or biological (behavioral, physiological, ecological, chemical and genetic) incompatibility.

Breaking the cross insulation divides the original population into two or more, differing from each other, and fixes the differences in their genotypes. The divided parts of the population are already independently subjected to the action of natural selection.

Isolation, the mutation process and population waves, being factors of evolution, influence its course, but do not direct evolution.

The direction of evolution provides natural selection.

Modern evolutionary doctrine is often called synthetic, because it includes not only Darwinism (i.e., Charles Darwin's doctrine of selection and the struggle for existence), but also data from genetics, taxonomy, morphology, biochemistry, physiology, ecology and other sciences . Especially valuable for understanding the essence of evolution were the discoveries made in genetics and molecular biology.

Chromosomal theory and gene theory have revealed the nature of mutations and the laws of heredity transmission, while molecular biology and molecular genetics have established ways of storing, implementing and transmitting genetic information using DNA. It was determined that the population is an elementary evolutionary unit capable of responding to changes in the environment by rearranging its gene pool. Therefore, not a species, but its populations are saturated with mutations and serve as the main material of the evolutionary process under the influence of natural selection.

The modern doctrine of evolution is based on the population idea. A population is the structural unit of a species. It represents a set of individuals of a species that have a common gene pool and occupy a certain territory within the range of this species.

Gradually, a divergence (divergence) occurs between such populations in a number of genetic traits that accumulate through combinations and mutations. Gradually, individuals of populations acquire noticeable differences from the original parental species. If the differences that appear ensure the non-crossing of individuals of one population with individuals of other populations of the original species, then the isolated population becomes an independent new species, isolated by divergence from the original species.

In modern evolutionary teaching, elementary units of evolution, elementary material and elementary factors of evolution are distinguished. The elementary unit of evolution is the population. Each population is characterized by such properties as range, number and density, genetic heterogeneity of individuals, age and sex structure, special functioning in nature (intrapopulation and sexual contacts between individuals within one population are carried out much easier and more often than with individuals from different populations of the same population). species. Therefore, changes that accumulate in one population with the help of recombinations, mutations and natural selection determine its qualitative and reproductive isolation (divergence) from other populations. Changes in individual individuals do not lead to evolutionary changes, since a significant accumulation of similar inherited traits is necessary, but it is available only to a complete group of individuals, which is a population.

elemental materialevolution is hereditary variability - combinative and mutational. These two types of hereditary variability lead to the emergence of both qualitative and quantitative phenotypic differences in organisms.

Elementary Factors of Evolutionare natural selection, mutation process, population waves and isolation. Natural selection eliminates individuals with unsuccessful combinations of genes from the population and preserves individuals with genotypes that do not violate the process of adaptive morphogenesis. Natural selection directs evolution. The mutation process maintains the genetic heterogeneity of natural populations.

population wavessupply the mass character of elementary evolutionary material for natural selection. Each population is characterized by a certain fluctuation in the number of individuals in the direction of either increase or decrease. In 1905, the Russian geneticist Sergei Sergeevich Chetverikov called these fluctuations the waves of life.

Insulation provides barriers preventing free interbreeding of organisms. It can be caused by territorial-mechanical (spatial, geographical) or biological (behavioral, physiological, ecological, chemical and genetic) incompatibility.

Violating crossing, isolation divides the initial population into two or more, differing from each other, and fixes the differences in their genotypes. The divided parts of the population are already independently subjected to the action of natural selection.

Isolation, the mutation process and population waves, being factors of evolution, influence its course, but do not direct evolution.The direction of evolution provides natural selection.

All species arose in the process evolution and continue to evolve. But there are organisms populations which are so well adapted to their environment that their species features have remained virtually unchanged for tens and hundreds of millions of years. These include the first autotrophs - blue-green algae, the descendants of the first cartilaginous fish - sharks, the same age as dinosaurs - crocodiles. For more than four hundred million years in Africa, South America and Australia, almost unchanged, live fish that can breathe not only with gills, but also through a swim bladder that differs little from real lungs. They are perfectly adapted to the drought, which lasts in those places from 6 to 9 months a year. When the reservoirs dry up, these fish (protopters) hibernate - they fall asleep with their nose up in peculiar holes dug in the muddy bottom, until the rainy season wakes them up. However, in a laboratory experiment, an experimental fish slept for more than 3 years without water and food ... The modern theory of evolution explains the mysteries of the appearance of such amazing natural phenomena.

The theme of the lesson is "Modern ideas about the evolution of the organic world."

The basis of these ideas is "The Evolutionary Theory of Charles Darwin". However, Darwin proposed his theory 150 years ago, and since then many important discoveries in population ecology, genetics, and molecular biology have taken place. The most important of them were: the rediscovery of the laws of G. Mendel at the beginning of the 20th century, the introduction of the concept of the gene of V. Johansen, the formulation of the chromosome theory of inheritance by T. Morgan, the mutation theory of G. Fries, the population ideas of S. S. Chetverikov and many others () ( see Fig. 1, 2).

Rice. 1

Rice. 2

The first discoveries of genetics, and this is the genetic nature of heredity and the mutational theory, caused a crisis in evolutionary theory. Scientists of that time could not correctly combine these discoveries and the provisions of the theory of evolution. A major breakthrough in the field of evolutionary ideas was the work of the English biologist J. Huxley () - "Evolution - a modern synthesis." It served as an impetus for the formulation of a synthetic theory of evolution. At the moment, the synthetic theory of evolution contains the following provisions:

1. The material for the evolutionary process is mutations, as well as their combinations during the sexual process.

2. The main driving force of evolution is natural selection, which occurs against the background of the struggle for survival.

Excess numbers of individuals are no longer the driving force behind evolution, as Darwin previously suggested.

3. The smallest unit of evolution is the population.

One individual is not capable of reproduction and transmission of its characteristics to offspring, therefore, an individual cannot be considered as a unit of evolution.

4. Evolution is divergent in nature, that is, as a rule, one species gives rise to several other species at once.

5. Evolution is gradual and long lasting.

Speciation is a continuous series of changes in different characters. It is impossible to distinguish the beginning and end of speciation.

6. A species is a collection of populations.

Between populations, gene flow is possible as a result of crossing. When for some reason the flow of genes is interrupted, one speaks of isolation. Isolation leads to the accumulation of differences between populations and, ultimately, to speciation.

7. Macroevolution follows the same path as microevolution.

There are no specific ways of macroevolution that would not be characteristic of microevolution.

8. All taxa are of monophyletic origin.

This means that all species of one taxon have a common ancestor.

9. Evolution has an undirected course, that is, its movement is not subject to any logic whatsoever.

Indeed, completely identical populations that have undergone isolation will develop, as a rule, in completely independent directions.

These provisions of modern evolutionary theory make it possible to explain the diversity of species on Earth. However, there are still many experimental data that contradict these theses. But let's hope that further discoveries will be able to overcome these contradictions.

Experiments of the first evolutionists

Modern synthetic evolutionary theory is based on hundreds of complex genetic and molecular biological experiments. At the same time, it practically does not contradict Darwin's basic theory of evolution in any way. It is completely incomprehensible how one scientist could create this theory 150 years ago without even relying on such concepts as a gene or a chromosome. Darwin's genius lies in the fact that he created his theory based only on the paleontological method and the method of observing wildlife.

Preventing the collapse of Darwinism

Huxley's work - "Evolution - the modern synthesis" practically saved Darwinism from collapse (see Fig. 3). The fact is that in the middle of the century, many scientists were ready to abandon Darwinism, based only on the fact that some experiments contradicted it. However, Huxley was able to prove that these experiments not only did not contradict Darwinism, but, moreover, confirmed it.

Rice. 3

An experiment confirming microevolution

Evolution is practically inaccessible for experiment. The change of generations in living beings lasts for months, years or even decades, so it is simply impossible to trace the evolutionary path of a species. A great success in the field of experiments with evolution was the observation of microorganisms. The fact is that a new generation of E. coli is formed already in 10 - 20 minutes, so a huge number of generations can be accumulated within a few days, weeks or months (see Fig. 4). At this scale, mutations will show up sufficiently to allow their role in natural selection to be assessed. These experiments brilliantly confirmed Darwin's theory of evolution.

Rice. 4

Bibliography

1. Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - M.: Bustard, 2009.
2. Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology. Textbook for 9 cells. 3rd ed., stereotype. - M.: Bustard, 2002.
3. Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of General Biology. Grade 9: Textbook for students in grade 9. educational institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.

Homework

1. What discoveries were associated with the crisis of Darwinism at the beginning of the 20th century?
2. Why does classical genetics contradict Darwinism?
3. Are you convinced by the evolutionist evidence?
4. What particular theories were united by J. Huxley's synthetic theory of evolution?

Modern evolutionary teaching is often
called synthetic because it
includes not only Darwinism (i.e. the teaching
Ch. Darwin on selection and struggle for existence),
but also the data of genetics, taxonomy, morphology,
biochemistry, physiology, ecology and other sciences.
Especially valuable for understanding the essence
evolution turned out to be discoveries made in
genetics and molecular biology.

The modern doctrine of evolution is based on the population idea.

In modern evolutionary teaching, elementary units of evolution, elementary material and elementary factors are distinguished.

The elementary material of evolution is hereditary variability - combinative and mutational.

The elementary factors of evolution are natural selection, the mutation process, population waves, and isolation.

Types of population waves:

Thus, genetic drift can lead to:

“Only spring waters will rush in, and without that they are dying in hundreds ...” Nekrasov

The founder effect is another cause of genetic drift. At the same time, several individuals (or even one, but pregnant) populate a new place

An example of the founder effect in humans: