All types 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 characteristics 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, are inhabited by fish that can breathe not only with gills, but also through swim bladder, not much different from real lungs. They have adapted perfectly to drought, which lasts in those places from 6 to 9 months a year. When reservoirs dry up, these fish (protoptera) go into hibernation - they fall asleep with their nose up in peculiar burrows dug in the muddy bottom, until the rainy season wakes them up. However, in a laboratory experiment, the experimental fish slept for more than 3 years without water or food... The mysteries of the appearance of such amazing natural phenomena are explained by the modern theory of evolution.
The topic 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 things have happened. most important discoveries population ecology, genetics, molecular biology. The most important of them were: the rediscovery of G. Mendel’s laws at the beginning of the twentieth century, the introduction of the concept of the gene by V. Johansen, the formulation of T. Morgan’s chromosomal theory of inheritance, the mutation theory of G. Friese, the population ideas of S. S. Chetverikov and many others () ( see Fig. 1, 2).
Rice. 1
Rice. 2
The first discoveries of genetics, namely the genetic nature of heredity and mutation theory, caused a crisis in evolutionary theory. Scientists of that time were unable to correctly combine these discoveries and the principles 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 the 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 arises against the background of the struggle for survival.
Overabundance is no longer the driving force behind evolution, as Darwin previously assumed.
3. Smallest unit evolution is the population.
One individual is not capable of reproduction and transmission of its characteristics to offspring, therefore the 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-term.
Speciation is a continuous sequence of changes in different characters. It is impossible to distinguish the beginning and end of speciation.
6. A species is a collection of populations.
Gene flow is possible between populations as a result of interbreeding. When gene flow is interrupted for some reason, we speak 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 paths of macroevolution that would not be characteristic of microevolution.
8. All taxa are of monophyletic origin.
This means that all species of the same taxon have a common ancestor.
9. Evolution has an undirected course, that is, its movement is not subject to any logic.
Indeed, completely identical populations that have undergone isolation will, as a rule, develop in completely independent directions.
These provisions of modern evolutionary theory help explain the diversity of species on Earth. However, there is still a lot of experimental data that contradicts these theses. But let's hope that further discoveries can 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 was able to 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 living nature.
Preventing the Collapse of Darwinism
Huxley's work - "Evolution - a 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 do not contradict Darwinism, but, moreover, confirm it.
Rice. 3
Experiment confirming microevolution
Evolution is practically inaccessible to 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 evolution experiments has been the observation of microorganisms. The fact is that a new generation of E. coli is formed in 10 - 20 minutes, so within a few days, weeks or months a huge number of generations can be accumulated (see Fig. 4). At this scale, mutations will be sufficiently pronounced to allow their role in natural selection to be assessed. These experiments brilliantly confirmed Darwin's theory of evolution.
Rice. 4
Bibliography
- Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - M.: Bustard, 2009.
- Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology. Textbook for 9th grade. 3rd ed., stereotype. - M.: Bustard, 2002.
- Ponomareva I.N., Kornilova O.A., Chernova N.M. Basics general biology. 9th grade: Textbook for 9th grade students. educational institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.
Homework
- What discoveries were associated with the crisis of Darwinism at the beginning of the twentieth century?
- Why does classical genetics contradict Darwinism?
- Are you convinced by the evolutionary evidence?
- 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. Charles Darwin’s teaching about selection and the struggle for existence), but also data from genetics, systematics, morphology, biochemistry, physiology, ecology and other sciences . The discoveries made in genetics and molecular biology turned out to be especially valuable for understanding the essence of evolution.
Chromosomal theory and gene theory revealed the nature of mutations and the laws of transmission of heredity, and molecular biology and molecular genetics established methods for storing, implementing and transmitting genetic information using DNA. It was determined that the elementary evolutionary unit capable of responding to environmental changes by restructuring its gene pool is a population. Therefore, it is not the species, but its populations that are saturated with mutations and serve as the main material for the evolutionary process, which occurs under the influence of natural selection.
Gradually, 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 parent species. If the differences that appear ensure that individuals of one population do not interbreed with individuals of other populations of the original species, then the isolated population becomes an independent new species, isolated through divergence from the original species.
In modern evolutionary teaching, a distinction is made between elementary units of evolution, elementary material and elementary factors of evolution. The elementary unit of evolution is the population. Each population is characterized by such properties as area, number and density, genetic heterogeneity of individuals, age and sex structure, special functioning in nature (intra-population and inter-population contacts, relationships with other species and with the external environment).
Therefore, changes that accumulate in one population through 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 heritable traits is required, and this is only available to an integral group of individuals, such as a population.
Under certain conditions and over a period of time, new heritable traits that have arisen can reach fairly high concentrations in one or more adjacent populations of the species. Groups with special characteristics that have arisen in this way can be found in some territory within the species' range. Finches. Different types.
The elementary factors of evolution are natural selection, the mutation process, population waves and isolation. Natural selection eliminates from the population individuals with unsuccessful combinations of genes and preserves individuals with genotypes that do not disrupt the process of adaptive morphogenesis. Natural selection guides evolution. The mutation process maintains the genetic heterogeneity of natural populations.
Population waves supply mass quantities of elementary evolutionary material for natural selection. Each population is characterized by a certain fluctuation in the number of individuals, either increasing or decreasing. In 1905, the Russian geneticist Sergei Sergeevich Chetverikov called these fluctuations waves of life.
Isolation provides barriers that prevent free interbreeding of organisms. It can be caused by territorial-mechanical (spatial, geographic) or biological (behavioral, physiological, environmental, chemical and genetic) incompatibility.
Modern evolutionary teaching 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, systematics, morphology, biochemistry, physiology, ecology and other sciences. The discoveries made in genetics and molecular biology turned out to be especially valuable for understanding the essence of evolution.
Chromosomal theory and gene theory revealed the nature of mutations and the laws of transmission of heredity, and molecular biology and molecular genetics established methods for storing, implementing and transmitting genetic information using DNA. It was determined that The elementary evolutionary unit capable of responding to environmental changes by rearranging its gene pool is a population. Therefore, it is not the species, but its populations that are saturated with mutations and serve as the main material of the evolutionary process, which occurs under the influence of natural selection.
The modern doctrine of evolution is based on the population idea .
Population is structural unit kind. 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 occurs between such populations ( divergence ) according to a number of genetic characteristics that accumulate through combinations and mutations. Gradually, individuals of populations acquire noticeable differences from the original parent species. If the differences that appear ensure that individuals of one population do not interbreed with individuals of other populations of the original species, then the isolated population becomes an independent new species, isolated by divergence from the original view.
In modern evolutionary teaching, a distinction is made between elementary units of evolution, elementary material and elementary factors of evolution.
- Elementary unit evolution serves population. Each population is characterized by such properties as area, number and density, genetic heterogeneity of individuals, age and sex structure, special functioning in nature (intra-population and inter-population contacts, relationships with other species and with the external environment).
Elementary material evolution is served by hereditary variability - combinative and mutational.
These two types of hereditary variability lead to the emergence of both qualitative and quantitative phenotypic differences between organisms.
Under certain conditions and over a period of time, new heritable traits that have arisen can reach fairly high concentrations in one or more adjacent populations of the species. Groups with special characteristics that have arisen in this way can be found in some territory within the species' range.
Different types.
Elementary factors of evolution- this is natural selection, mutation process, population waves and isolation.
Natural selection eliminates from the population individuals with unsuccessful combinations of genes and preserves individuals with genotypes that do not disrupt the process of adaptive morphogenesis. Natural selection guides evolution.
Mutation process maintains genetic heterogeneity of natural populations.
Population waves supply mass quantities of elementary evolutionary material for natural selection. Each population is characterized by a certain fluctuation in the number of individuals, either increasing or decreasing. In 1905, the Russian geneticist Sergei Sergeevich Chetverikov called these fluctuations waves of life.
Insulation provides barriers to prevent free interbreeding of organisms . It can be caused by territorial-mechanical (spatial, geographic) or biological (behavioral, physiological, environmental, chemical and genetic) incompatibility.
Breaking the crossbreeding insulation divides the original population into two or more, different from each other, and fixes the differences in their genotypes. The separated parts of the population are already independently subject to the action of natural selection.
Isolation, mutation process and population waves, being factors of evolution, influence its course, but do not direct evolution.
The direction of evolution is provided by natural selection.
Modern evolutionary teaching is often called synthetic because it includes not only Darwinism (i.e. Charles Darwin’s teaching about selection and the struggle for existence), but also data from genetics, systematics, morphology, biochemistry, physiology, ecology and other sciences . The discoveries made in genetics and molecular biology turned out to be especially valuable for understanding the essence of evolution.
Chromosomal theory and gene theory revealed the nature of mutations and the laws of transmission of heredity, and molecular biology and molecular genetics established methods for storing, implementing and transmitting genetic information using DNA. It was determined that the elementary evolutionary unit capable of responding to environmental changes by restructuring its gene pool is a population. Therefore, it is not the species, but its populations that are saturated with mutations and serve as the main material for the evolutionary process, which occurs under the influence of natural selection.
The modern doctrine of evolution is based on the population idea. A population is a 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, 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 parent species. If the differences that appear ensure that individuals of one population do not interbreed with individuals of other populations of the original species, then the isolated population becomes an independent new species, isolated through divergence from the original species.
In modern evolutionary teaching, a distinction is made between elementary units of evolution, elementary material and elementary factors of evolution. The elementary unit of evolution is the population. Each population is characterized by such properties as area, number and density, genetic heterogeneity of individuals, age and sex structure, special functioning in nature (intrapopulation and sexual contacts between individuals within the same population are carried out much easier and more often than with individuals of different populations of the same species. Therefore, changes that accumulate in one population through 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 heritable characteristics is required. this is available only to an integral group of individuals, which is a population.
Elementary materialevolution is served by hereditary variability - combinative and mutational. These two types of hereditary variability lead to the emergence of both qualitative and quantitative phenotypic differences between organisms.
Elementary factors of evolution- this is natural selection, mutation process, population waves and isolation. Natural selection eliminates from the population individuals with unsuccessful combinations of genes and preserves individuals with genotypes that do not disrupt the process of adaptive morphogenesis. Natural selection guides evolution. The mutation process maintains the genetic heterogeneity of natural populations.
Population wavessupply mass quantities of elementary evolutionary material for natural selection. Each population is characterized by a certain fluctuation in the number of individuals, either increasing or decreasing. In 1905, the Russian geneticist Sergei Sergeevich Chetverikov called these fluctuations waves of life.
Insulation provides barriers that prevent free interbreeding of organisms. It can be caused by territorial-mechanical (spatial, geographic) or biological (behavioral, physiological, environmental, chemical and genetic) incompatibility.
By disrupting crossing, isolation divides the original population into two or more that differ from each other, and perpetuates the differences in their genotypes. The separated parts of the population are already independently subject to the action of natural selection.
Isolation, mutation process and population waves, being factors of evolution, influence its course, but do not direct evolution.The direction of evolution is provided by natural selection.