Modern science has very many facts proving the existence of the evolutionary process. These are data from biochemistry, genetics, embryology, anatomy, taxonomy, biogeography, paleontology and many other disciplines.
Evidence of the unity of the origin of the organic world. All organisms, be they viruses, bacteria, plants, animals or fungi, have a surprisingly close elemental chemical composition. In all of them, proteins and nucleic acids play a particularly important role in life phenomena, which are built according to a single principle and from similar components. It is especially important to emphasize that a high degree of similarity is found not only in the structure of biological molecules, but also in the way they function. The principles of genetic coding, biosynthesis of proteins and nucleic acids (see § 14-16) are the same for all living things. In the vast majority of organisms, ATP is used as energy storage molecules, the mechanisms for the breakdown of sugars and the main energy cycle of the cell are also the same.
Most organisms have a cellular structure. The cell is the basic building block of life. Its structure and functioning are very similar in different organisms. Cell division - mitosis, and in germ cells - meiosis - is carried out in a fundamentally similar way in all eukaryotes.
It is extremely unlikely that such an amazing similarity in the structure and functioning of living organisms was the result of a random coincidence. It is the result of their common origin.
Embryological evidence for evolution. Embryological data speak in favor of the evolutionary origin of the organic world.
The Russian scientist Karl Baer (1792-1876) discovered a striking similarity between the embryos of various vertebrates. He wrote: “The embryos of mammals, birds, lizards and snakes are extremely similar to each other in the earliest stages, both in general and in the way of development of individual parts. I have two small germs in my alcohol that I forgot to label, and now I am completely unable to tell which class they belong to. Maybe these are lizards, maybe they are small birds, and maybe they are very small mammals, the similarity in the structure of the head and body of these animals is so great. However, these embryos do not yet have limbs. But even if they were at the earliest stages of their development, even then we would not know anything, because the legs of lizards and mammals, the wings and legs of birds, as well as the arms and legs of man, develop from the same basic form. .
Rice. 52. The similarity of the initial stages of the embryonic development of vertebrates
At later stages of development, the differences between embryos increase, signs of a class, order, family appear (Fig. 52). C. Darwin considered the similarity of the early stages of ontogenesis in different representatives of large taxa as an indication of their origin through evolution from common ancestors. Recent discoveries in developmental genetics have confirmed Darwin's hypothesis. It has been shown, for example, that the most important processes of early ontogeny in all vertebrates are controlled by the same genes. Moreover, many of these regulatory genes have also been found in invertebrates (worms, molluscs, and arthropods). Figure 53 shows the areas of activity of Hox family genes during the formation of the nervous system in Drosophila and mice. The last common ancestor of these two animal species existed more than 500 million years ago. Despite this, in mice and Drosophila, not only the regulatory genes themselves remained basically unchanged, but also the order of their arrangement in chromosomes, the sequence of their inclusion in ontogenesis, and the mutual position of the regions of the developing nervous system in which these genes are active.
Rice. 53. Comparison of regions of activity of genes that control the development of the nervous system in Drosophila and mice
Morphological evidence for evolution. Of particular value for proving the unity of the origin of the organic world are forms that combine the features of several large systematic units. The existence of such intermediate forms indicates that in the previous geological epochs there lived organisms that were the ancestors of several systematic groups. A good example of this is the unicellular organism Euglena green. It simultaneously has features typical for plants (chloroplasts, the ability to use carbon dioxide) and for protozoa (flagella, a light-sensitive eye, and even a semblance of a mouth opening).
Lamarck also introduced the division of animals into vertebrates and invertebrates. For a long time, no links were found between them, until the studies of the domestic scientist A. O. Kovalevsky established a connection between these groups of animals. A. O. Kovalevsky proved that a seemingly typical invertebrate - a sessile ascidian - develops from a free-swimming larva. It has a chord and is very similar to the lancelet, a representative, as it was then believed, of vertebrates. On the basis of such studies, the entire group of animals, to which ascidians belonged, was attached to vertebrates and this type was given the name chordates.
The connection between different classes of animals also well illustrates the commonality of their origin. Oviparous (for example, echidna and platypus) in a number of features of their organization are intermediate between reptiles and mammals.
The structure of the forelimbs of some vertebrates (Fig. 54), for example, the flippers of a whale, a dolphin, a mole's paws, a bat's wing, a crocodile's paw, a bird's wing, a human hand, despite the performance of completely different functions by these organs, is similar in principle. Some bones in the skeleton of the limbs may be absent, others may grow together, the relative sizes of the bones may change, but their homology, i.e., similarity based on a common origin, is quite obvious. Homologous organs are those that develop from the same embryonic primordia in a similar way.
Rice. 54. Homology of the forelimbs of vertebrates
Some organs or their parts do not function in adult animals and are superfluous for them - these are the so-called vestigial organs, or rudiments. The presence of rudiments, as well as homologous organs, is also evidence of a common origin. Rudimentary eyes are found in completely blind animals that lead an underground lifestyle. The whale's hind limb skeleton, hidden inside the body, is a vestige that testifies to the terrestrial origin of its ancestors. In humans, rudimentary organs are also known. Such are the muscles that move the auricle, the vestige of the third eyelid, or the so-called nictitating membrane, etc.
Paleontological evidence for evolution. The development of, for example, chordates was carried out in stages. At first, lower chordates arose, then fish, amphibians, and reptiles arose sequentially in time. Reptiles, in turn, give rise to mammals and birds. At the dawn of their evolutionary development, mammals were represented by a small number of species, while reptiles flourished. Later, the number of species of mammals and birds increases sharply, and most species of reptiles disappear. Thus, paleontological data indicate a change in the forms of animals and plants over time.
In some cases, paleontology points to the causes of evolutionary transformations. In this regard, the evolution of horses is interesting. Modern horses descended from small omnivorous ancestors who lived 60-70 million years ago in forests and had a five-fingered limb. Climate change on Earth, which entailed a reduction in forest areas and an increase in the size of the steppes, led to the fact that the ancestors of modern horses began to develop a new habitat - the steppes. The need for protection from predators and movement over long distances in search of good pastures led to the transformation of the limbs - a decrease in the number of phalanges down to one (Fig. 55). In parallel with the change in the limbs, the whole organism was transformed: an increase in the size of the body, a change in the shape of the skull and the complication of the structure of the teeth, the emergence of the digestive tract characteristic of herbivorous mammals, and much more.
Rice. 55. Historical series of changes in the structure of the forelimb of the horse
As a result of changes in external conditions under the influence of natural selection, a gradual transformation of small five-toed omnivores into large herbivores took place. The richest paleontological material is one of the most convincing evidence of the evolutionary process that has been going on on our planet for more than 3 billion years.
Biogeographic evidence for evolution. A striking evidence of the past and ongoing evolutionary changes is the spread of animals and plants on the surface of our planet. Even in the era of the Great geographical discoveries, travelers and naturalists were amazed by the diversity of animals in distant countries, the features of their distribution. However, only A. Wallace managed to bring all the information into the system and identify six biogeographic regions (Fig. 56): 1) Paleoarctic, 2) Neoarctic (Paleoarctic and Neoarctic zones are often combined into the Holarctic region), 3) Indo-Malayan, 4) Ethiopian , 5) Neotropical and 6) Australian.
Rice. 56. Map of biogeographic zones
Comparison of the animal and plant worlds of different zones provides the richest scientific material for proving the evolutionary process. The fauna and flora of the Paleoarctic (Eurasian) and Neoarctic (North American) regions, for example, have much in common. This is explained by the fact that in the past there was a land bridge between these areas - the Bering Isthmus. In contrast, the Neoarctic and Neotropical regions have little in common, although they are currently connected by the Isthmus of Panama. This is due to the isolation of South America for several tens of millions of years. After the emergence of the Panama Bridge, only a few South American species managed to penetrate north (porcupine, armadillo, opossum). North American species have succeeded somewhat more in the development of the South American region. Llamas, deer, foxes, otters, bears entered South America, but did not have a significant impact on its unique species composition.
The fauna of the Australian region is interesting and original. It is known that Australia separated itself from South Asia even before the emergence of higher mammals.
Thus, the distribution of animal and plant species over the surface of the planet and their grouping into biogeographic zones reflect the process of the historical development of the Earth and the evolution of living things.
Island fauna and flora. To understand the evolutionary process, the fauna and flora of the islands are of interest. The composition of their fauna and flora depends entirely on the history of the origin of the islands. Islands can be of continental origin, that is, they can be the result of the separation of a part of the mainland, or of oceanic origin (volcanic and coral).
The mainland islands are characterized by fauna and flora similar in composition to the mainland. However, the older the island and the more significant the water barrier, the more differences are found. The British Isles separated from Europe quite recently and have a fauna identical to that of Europe. On long isolated islands, the process of species divergence goes much further. In Madagascar, for example, there are no large ungulates typical of Africa: bulls, antelopes, rhinos, zebras. There are no large predators (lions, leopards, hyenas), higher monkeys (baboons, monkeys). However, many lower primates are lemurs, which are not found anywhere else.
A completely different picture is revealed when examining the faunas of oceanic islands. Their species composition is very poor. On most of these islands, there are no terrestrial mammals and amphibians that are unable to overcome significant water obstacles. The entire fauna of the oceanic islands is the result of the accidental introduction of some species, usually birds, reptiles, and insects, to them. Representatives of such species that have fallen on oceanic islands receive ample opportunities for reproduction. For example, on the Galapagos Islands, out of 108 bird species, 82 are endemic (that is, they are not found anywhere else) and all 8 species of reptiles are characteristic only for these islands. A wide variety of snails have been found in the Hawaiian Islands, of which 300 endemic species belong to the same genus.
A huge number of diverse biogeographical facts indicate that the features of the distribution of living beings on the planet are closely related to the transformation of the earth's crust and evolutionary changes in species.
Molecular evidence for evolution. At present, the complete decoding of the human genome (the totality of all genes) and the genomes of a number of animals, plants and microorganisms is almost completed. The complete sequence of nucleotides in DNA is known in a huge number of species of living organisms. Comparison of these sequences provides a new clue to the construction of the genealogy of life on Earth.
Many mutations are substitutions of one nucleotide for another. Mutations occur, as a rule, during DNA replication (see § 14). It follows that the more generations have passed since the divergence of two species from a common ancestor, the more random nucleotide substitutions should have accumulated in the genomes of these daughter species. The common ancestor of humans and chimpanzees existed about five million years ago, and the common ancestor of humans and mice more than 80 million years ago. When we compare the nucleotide sequences of genes, such as the beta-globin gene, we see that there are far fewer differences between human and chimpanzee genes than there are between human (or chimpanzee) and mouse genes.
A quantitative assessment of these differences makes it possible to build a genealogical tree showing the relationship of various taxa (species, orders, families, classes) and to determine the relative time of their divergence. Basically, this tree coincides with those that were built on the basis of morphological, embryological and paleontological data. However, in some cases startling things are revealed. It turned out that whales and artiodactyls are much closer relatives than artiodactyls and equids. The African golden mole is phylogenetically closer to the elephant than to our moles. Modern methods of molecular genetics make it possible to analyze the genes of not only living organisms, but also long-extinct species, using traces of DNA in fossil remains. This helps to trace the path of evolution of life on Earth.
- 0 as evidenced by the following facts: a similar organization of molecular processes in all organisms living on Earth; the presence of intermediate forms and rudimentary organs? Justify the answer.
- The fauna and flora of North America and Eurasia are similar to each other, while the flora and fauna of North and South America are very different. How do you explain these facts?
- Usually, endemic species are quite common on the islands (not found anywhere else on the globe). How can this be explained?
- The fossil animal - Archeopteryx had signs of a bird and a reptile. Evaluate this fact from a scientific point of view.
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Formal statistical tests confirm the origin of all living organisms from a single ancestor
The idea of the unity of the origin of all living things is generally accepted among biologists, but the arguments in its favor are mainly qualitative, not quantitative. Formal statistical tests based on "model selection theory" and not using the a priori assumption that the similarity of protein molecules indicates their relationship, have shown that the hypothesis of a single origin of all living things is much more plausible than alternative models, suggesting the independent origin of different groups of organisms from different ancestors.
Darwin thought that all living organisms originated either from one initial form or from several (see common descent). Darwin left the question of the number of first ancestors open, because in the 19th century science did not yet have the means to solve this problem. Today, most biologists believe that all living things came from the "last universal common ancestor" (last universal common ancestor, LUCA). This ancestor, however, was hardly a single organism or "species" in the modern sense of the word, but rather a polymorphic microbial community in which an active horizontal gene exchange took place.
Of course, LUCA was not the first living being in the world: its appearance was preceded by a long evolution (during which, in particular, the modern genetic code and protein synthesis apparatus were formed, see: Vetsigian, Woese, Goldenfeld. 2006. Collective evolution and the genetic code ). Other creatures most likely lived at the same time as LUCA, but their descendants died out. Most experts believe that LUCA already had DNA and RNA, replication and transcription enzymes, ribosomes, and other components of the protein synthesis apparatus. The strongest argument in favor of the reality of LUCA is the unity of the genetic code and the fundamental similarity of the molecular systems of DNA, RNA and protein synthesis in all living organisms (see: Molecular genetic evidence for evolution). But this argument, for all its persuasiveness, is not quantitative but qualitative. It is very difficult to estimate its strength numerically.
If life once originated on Earth or in space, then theoretically it could have originated several times. In principle, it can be assumed that modern life is descended from more than one ancestor. For example, bacteria could have descended from one, and archaea from another ancestor (this point of view is occasionally expressed, although it has few supporters).
Strict statistical procedures to resolve this dilemma have so far been practically not used. Standard techniques for comparing DNA nucleotide sequences and protein amino acid sequences involve calculating a series of scores that reflect the likelihood that the observed similarity is due to chance (see: The Statistics of Sequence Similarity Scores). The low values of these indicators indicate the statistical significance (non-randomness) of the similarity, but in principle they are not a strict proof of the relationship (unity of origin) of the compared molecules. The high similarity of two sequences can theoretically be explained not only by their common origin, but also by convergent evolution under the influence of similar selection factors.
Even more serious claims can be made against the majority of computer programs designed to build evolutionary trees. These programs, as a rule, are focused on building the “best” evolutionary tree based on any set of compared sequences, that is, having the maximum statistical support. These programs simply do not consider the possibility of multiple unrelated trees growing from multiple independent roots. These methods can quantify and compare the “likelihood” of different trees, but it is not possible to understand whether a model with one tree is more or less likely than models with two or three independent trees. In other words, the idea of a single common ancestor is built into these programs from the very beginning (which reflects the deep conviction of biologists that such an ancestor exists in any pair of living organisms).
Douglas L. Theobald of Brandeis University (USA) tried to overcome these limitations and develop independent statistical tests to test the LUCA hypothesis, which would not have the idea that the similarity of sequences is a measure of their relationship, and even less the idea of the unity of origin would have been initially laid down. Theobald did not try to find out how statistically significant the unity of the genetic code of all organisms is. His task was more narrow: he wanted to quantify how reliable (or unreliable) the evidence for LUCA is in the amino acid sequences of key proteins that all living things have.
Theobald's approach is based on tests developed within model selection theory(model selection theory). Three tests were used to compare competing evolutionary models: 1) log likelihood ratio, LLR (see Likelihood-ratiotest ; 2) Akaike information criterion (AIC); 3) log Bayes factor . These tests quantify the “likelihood” of the compared models (in this case, evolutionary reconstructions consisting of one or many trees) based on two main criteria: 1) the accuracy of the model’s correspondence to real facts, 2) the parsimonicity (parsimony) of the model. In other words, this technique allows you to choose from a variety of models the one that most accurately describes (explains) the observed facts, using the minimum number of assumptions (“free parameters”) for this.
Theobald analyzed the amino acid sequences of 23 proteins that all living organisms have (mainly proteins involved in the synthesis of the aminoacyl-tRNA synthetase protein, ribosomal proteins, elongation factors, etc.). Protein sequences were taken from 12 organisms: four bacteria, four archaea and four eukaryotes (yeast, Drosophila, worm C.elegans, human).
The compared evolutionary models were built on the basis of a number of generally accepted assumptions. It was assumed that amino acid sequences can gradually change in the course of evolution by replacing some amino acids with others. Previously developed 20 × 20 matrices were used, reflecting the empirical probability or frequency of substitution of each amino acid for any other. It was also assumed that amino acid substitutions occurring in different evolutionary lines and in different regions of the protein are not correlated with each other.
The hypothesis of a single common ancestor (LUCA) was compared with hypotheses about several common ancestors, and the question of a single or multiple origin of life was left behind the scenes. The fact is that the LUCA hypothesis is quite compatible with the multiple origin of life. In this case, either all other ancient life forms, except for LUCA, did not leave descendants that survived to this day, or representatives of several independently emerging populations acquired the ability to exchange genes with each other during evolution and actually merged into one species. The models considered by Theobald are compatible with both of these scenarios.
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The author considered two classes of models: in the first of them, horizontal genetic exchange was not taken into account, and organisms had to evolve in accordance with tree-like schemes. Models of the second class allowed horizontal exchange (including the symbiogenetic fusion of two organisms into one), so the schemes were not tree-like, but meshed, with jumpers between branches. Within each class, the most plausible models were compared with each other, built on the basis of various assumptions about the number of original ancestors. The single origin model (ABE, where A is archaea, B is bacteria, E is eukaryotes) was compared with a variety of multiple origin models: AE + B (archaea and eukaryotes had one common ancestor, but bacteria evolved from a different ancestor), AB + E , BE + A, A + B + E, etc. Even the possibility of an independent origin of multicellular animals or humans was considered.
All three tests used in all cases strongly supported the LUCA hypothesis as opposed to alternative multiple origin hypotheses. For example, for class 1 models, the “likelihood” of the ABE hypothesis turned out to be 10 2860 times higher than that of its closest competitor (the AE + B models). This number cannot even be called "astronomical", there are no such large numbers in astronomy. Approximately the same reliable support was received by class 2 hypotheses (with horizontal transfer) when compared with class 1 hypotheses. horizontal genetic exchange between evolving lines. This model, in particular, adequately reflects the symbiogenetic origin of eukaryotes: some of the 23 considered eukaryotic proteins clearly inherited from bacteria, while others from archaea.
Thus, the amino acid sequences of key proteins found in every living cell provide strong statistical support for the LUCA hypothesis. At the same time, the main evidence in favor of the unity of origin is not the magnitude of similarity as such (the real similarity of homologous proteins in humans, yeast and bacteria is actually not so great), but character(or structure) of this similarity, that is, the distribution of amino acids that are identical or similar in properties along a protein molecule in different organisms. The structure of the observed similarity is such that it ensures the "derivability" of some proteins from others, and therefore the hypothesis of a single origin explains the whole picture much better than other models. In supplementary materials (PDF, 352 Kb) to the article under discussion, Douglas Theobald provides fictitious examples of protein molecules that have a very high similarity, but for which a single origin is less likely than multiple. For example, this happens if protein A is similar to protein B in some amino acid positions, and to protein C in others. As for real proteins, the LUCA hypothesis explains the observed similarity in the most "parsimonious" way.
If we include proteins that not everyone has, but only some organisms (for example, only eukaryotes), the results remain the same, because new types of proteins somehow had to arise in different evolutionary lines - regardless of whether whether these lines had the same or different origins.
This work, of course, is not the final solution to the problem posed - rather, it should be considered as a first step. It is rather difficult to completely exclude all possible alternative interpretations of the obtained results. This will require a more detailed knowledge of the patterns of protein evolution and even more sophisticated statistical methods.
Sources:
1) Douglas L. Theobald. A formal test of the theory of universal common ancestry // Nature. 2010. V. 465. P. 219-222.
2) Mike Steel, David Penny. Common ancestry put to the test // Nature. 2010. V. 465. P. 168-169.
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Lesson form: frontal, individual.
Teaching methods: heuristic method, explanatory and illustrative, practical, visual.
Equipment: Presentation "Basic Evidence for Evolution", computer, multimedia projector, "Forms of Fossil Plants and Animals" collections.
The purpose of the lesson: to form and reveal the essence of the main evidence for evolution.
Lesson objectives:
- identify the main evidence for the development of the organic world;
- evaluate the biogenetic law of F. Müller and E. Haeckel as embryological evidence;
- to find out the significance for science of fossil transitional forms as paleontological evidence, to study comparative anatomical (morphological), biogeographic evidence of evolution.
- continue the formation of skills for independent work with text, with handouts, with a presentation.
During the classes
I. Testing knowledge.
Frontal conversation on key issues on the topic “Evolution”.
- Define the concept of evolution.
- Name the periods of development of evolution.
- Define creationism. What is the essence of the metaphysical worldview?
- Tell us about the main views and mistakes of K. Linnaeus, determine the role of his works in the development of biology.
- Tell us about the main views and mistakes of J. B. Lamarck, determine the role of his works in the development of biology.
- What prerequisites for the emergence of Darwinism do you know?
- Tell us about the main stages in the life of the great English naturalist Charles Darwin.
- What are the main provisions of Ch. Darwin's theory of evolution.
- Explain from the point of view of C. Linnaeus, J-B. Lamarck, C. Darwin, the formation of a long neck in a giraffe and the absence of organs of vision in a mole rat.
II. Learning new material (the topic of the lesson on slide 1).
Presentation - "Basic Evidence for Evolution".
The fact of evolution, that is, the historical development of living organisms from simple forms to more highly organized ones, which is based on the processes of the unique functioning of genetic information, was accepted and confirmed by the data of biochemistry, paleontology, genetics, embryology, anatomy, taxonomy and many other sciences that had facts proving the existence of an evolutionary process.
The main evidence for evolution is (slide 2):
1. Similar chemical composition of cells of all living organisms.
2. The general plan of the structure of the cells of all living organisms.
3. Universality of the genetic code.
4. Uniform principles of storage, implementation and transfer of genetic information.
5. Embryonic evidence for evolution.
6. Morphological evidence of evolution.
7. Paleontological evidence for evolution.
8. Biogeographic evidence for evolution.
(Frontal conversation with the definition of the main provisions of the evidence)
What is the chemical composition of organisms? (Similar elemental chemical composition of cells of all organisms) (slide 3);
What is the basic structural unit of all living organisms? (A cell is an elementary unit of a living thing, its structure and functioning are very similar in all organisms) (Slide 4);
What does the universality of the genetic code say? (Proteins and nucleic acids are always built according to the same principle and from similar components, they play a particularly important role in the life processes of all organisms) (slide 5);
The principles of genetic coding, biosynthesis of proteins and nucleic acids are the same for all living things. (slide 6) .
Embryological evidence
The fact of the unity of the origin of living organisms was established on the basis of embryological studies, which are based on the data of the science of embryology.
Embryology (from the Greek embryo - embryo and logos - doctrine) is a science that studies the embryonic development of organisms. All multicellular animals develop from a single fertilized egg. In the process of individual development, they go through the stages of crushing, the formation of two- and three-layer embryos, the formation of organs from the germ layers. The similarity of the embryonic development of animals testifies to the unity of their origin.
Embryology, depending on the tasks, is divided into: general, comparative, experimental, population and ecological.
Embryological data that are evidence of evolution include :
1. Karl Baer's law of germline similarity (slides 7, 8) , which reads: "Embryos show, already from the earliest stages, a known general resemblance within the phylum" . In all chordates, in the early stages of development, a notochord is laid, a neural tube appears, gills form in the anterior part of the pharynx, etc. The similarity of the embryos indicates the common origin of these organisms. As the embryos develop, the features of their differences become more and more pronounced. K. Baer was the first to discover that in the course of embryonic development, first, general signs of a type appear, then successively of a class, order, and, finally, of a species.
The divergence of signs of embryos in the process of development is called embryonic divergence, and it is explained by the history of this species.
2. Haeckel-Muller biogenetic law (slides 7, 9) indicating the relationship between individual (ontogeny) and historical (phylogenesis) development. This law was formulated in 1864-1866. German scientists F. Müller and E. Haeckel. In their development, multicellular organisms pass through a unicellular stage (zygote stage), which can be considered as a repetition of the phylogenetic stage of the primitive amoeba. In all vertebrates, the notochord is laid, which is then replaced by the spine, and in their ancestors the notochord remained all their lives. During the embryonic development of birds and mammals, gill slits appear in the pharynx. This fact can be explained by the origin of these land animals from fish-like ancestors. These and other facts led Haeckel and Müller to formulate the biogenetic law. It says: "Ontogeny is a short and quick repetition of phylogeny, each organism in its individual development repeats the stages of development of its ancestors." Figuratively speaking, every animal during its development climbs up its own genealogical tree. However, ontogeny does not exactly repeat phylogeny. Therefore, the repetition of the stages of the historical development of a species in embryonic development occurs in a compressed form, with the loss of a number of stages. In addition, embryos do not resemble adult forms of ancestors, but with their embryos.
Morphological evidence
Evidence for the evolution of this group includes:
1) Comparative anatomical studies have shown the presence in modern flora and fauna transitional forms of organisms (slide 10) , combining the features of several large systematic units. For example, green euglena combines the features of a plant (chloroplasts, photosynthesis) and animals (flagella, a photosensitive eye, a kind of mouth apparatus); echidna and platypus stand between reptiles and mammals (lay eggs and feed their young with milk). The existence of such intermediate forms indicates that in the previous geological epochs there lived organisms that were the ancestors of several systematic groups.
2) Availability within a class, type homologous bodies (slide 11) , formations similar to each other in terms of the general plan of the structure, position in the body and appearance in the process of ontogenesis. Homology is associated with the presence in different species of equally active hereditary factors (the so-called homologous genes) inherited from a common ancestor. For example, the flippers of a whale, the paws of a mole, a crocodile, the wings of a bird, a bat, a human hand, despite performing completely different functions, the structure is similar in principle. Homologous organs are the result of divergence - a divergence of traits within a population of a species that occurs under the influence of natural selection. The general pattern of evolution leading to the formation of new species, genera, classes, etc.
3) Availability vestiges(from lat. rudimentum - germ, fundamental principle) (slide 12, 13) - relatively simplified, underdeveloped, in comparison with the homologous structures of ancestors, organs that have lost their main significance in the body during evolutionary development (Slide 11-13). Rudiments are laid during the embryonic development of the organism, but do not fully develop. They are found in all individuals of this species. For example, the fibula in birds, the pelvic girdle in a whale, the eyes in burrowing animals, etc.; The presence of rudiments, as well as homologous organs, testifies to the common origin of living forms. The whale's hind limbs, hidden inside the body, are a vestige that proves the terrestrial origin of its ancestors. In humans, rudimentary organs are also known: muscles that move the auricle, a vestige of the third eyelid, etc. In some organisms, vestigial organs can develop to normal-sized organs. Such a return to the structure of the organ of ancestral forms is called atavism.
4) Availability atavisms(from lat. atavus - ancestor) (slide 14) , traits that appear in individual individuals of a given species that existed in distant ancestors, but were lost in the process of evolution. For example, hind limbs that occasionally appear in whales, among thousands of one-toed horses, individuals occasionally come across who have developed small hooves of II and IV fingers. There are known cases of the appearance of atavistic signs in humans: the birth of children with primary hairline, with a long tail, etc. The occurrence of atavisms indicates the possible structure of one or another organ in ancestral forms. Atavisms are manifestations of evolutionary memory of ancestors. The reasons for their appearance are that the genes responsible for a given trait are preserved in the evolution of a given species, but their action during normal development is blocked by repressor genes. After many generations in the ontogenesis of individual individuals, for specific reasons, the blocking is removed and the trait appears again.
paleontological evidence
Paleontological evidence is based on the science of paleontology.
Paleontology (from the Greek. paleo - ancient; ontos - a creature; logos - teaching) - a science that studies the remains of extinct organisms, revealing their similarities and differences with modern organisms. Founders of paleontology: J. Cuvier, J.-B. Lamarck, A. Brongniard. The term "paleontology" was proposed in 1822 by A. Blainville. The foundations of modern evolutionary paleontology were laid by V.O. Kovalevsky.
Paleontology solves the following tasks:
- the study of the flora and fauna of the past, because fossil remains provide a lot of material about successive relationships between various systematic groups;
- identification of the early stages of the evolution of life and events at the boundaries of the main divisions of the history of the Earth;
- identification of the isolation of the trunks of the organic world;
- identification of the main stages in the development of the organic world; comparing the fossil remains of the earth's layers from different geological eras, they conclude that the organic world has changed over time.
Paleontology provides the following data in favor of evolution:
1) Information about phylogenetic (evolutionary) series (slide 15), which are not only an excellent illustration of evolution, but also allow you to find out the reason for the evolution of individual groups of organisms. Works by V.O. Kovalevsky were the first paleontological studies that managed to show that some species are descended from others. Investigating the history of the development of horses, V.O. Kovalevsky showed that modern one-toed animals descend from small five-toed omnivorous ancestors that lived 60-70 million years ago in forests. The change in the climate of the Earth, which entailed a reduction in the area of \u200b\u200bforests and an increase in the size of the steppes, led to the fact that the ancestors of modern horses began to develop a new habitat - the steppes. The need for protection from predators and movement over long distances in search of good pastures led to the transformation of the limbs - a decrease in the number of phalanges down to one. In parallel with the change in the limbs, the whole organism was transformed: an increase in the size of the body, a change in the shape of the skull and the complication of the structure of the teeth, the emergence of the digestive tract characteristic of herbivorous mammals, and much more.
2) Information about fossil transitional forms (the definition of transitional forms was given above), which have not survived to this day and are present only in the form of fossil remains. The existence of transitional forms between different types and classes shows that the gradual nature of historical development is characteristic not only of the lower systematic categories (species, genera, families), but also of the higher categories, and that they are also a natural result of evolutionary development. Examples of fossil transitional forms are: ancient lobe-finned fish, linking fish with land-dwelling tetrapod amphibians; seed ferns - a transitional group between ferns and gymnosperms, psilophytes, animal-toothed lizard, Archeopteryx, etc. (Slides 16, 17).
Biogeographic evidence
Biogeography (from Greek bio - life, geo - earth, graph - I write) - the science of the patterns of distribution around the globe of communities of living organisms and their components - species, genera and other taxa. Biogeography includes zoogeography and botanical geography. The main sections of biogeography began to take shape at the end of the 18th and in the first half of the 19th centuries, thanks to numerous expeditions. At the origins of biogeography were A. Humboldt, A.R. Wallace, F. Sclater, P.S. Pallas, I.G. Borshov and others.
Biogeographical evidence for evolution includes the following:
1. Features of the distribution of animals and plants on different continents (slides 18, 19) , as clear evidence of the evolutionary process. A.R. Wallace, one of the outstanding predecessors of Charles Darwin, brought all the information about the distribution of animals and plants into the system and identified six zoogeographic regions (students work with a map of the zoogeographic regions of the world):
1) Paleoarctic (Europe, North Africa, North and Central Asia, Japan);
2) Neoarctic (North America);
3) Ethiopian (Sub-Saharan Africa);
4) Indomalayan (South Asia, Malay Archipelago);
5) Neotropical (South and Central America);
6) Australian (Australia, New Guinea, New Zealand, New Caledonia).
The degree of similarity and difference of floras and faunas between different biogeographic regions is not the same. Thus, the paleoarctic and neoarctic regions, despite the absence of a land connection between them, show a significant similarity of floras and faunas. The flora and fauna of the neoarctic and neotropical regions, although there is a land-based Isthmus of Panama between them, are very different from each other. How can this be explained? This can be explained by the fact that once Eurasia and North America were part of the single continent of Laurasia and their organic world developed together. The overland connection between North and South America, by contrast, is relatively recent, and their floras and faunas have long evolved separately. The organic world of Australia stands apart, which separated from South Asia more than 100 million years ago, and only during the Ice Age did a few placental animals - mice and dogs - move here through the Sunda archipelago. Thus, the closer the connection of the continents, the more related forms live there, the more ancient the isolation of parts of the world from each other, the greater the difference between their populations.
2. Features of the fauna and flora of the islands also testify in favor of evolution. The organic world of the mainland islands is close to the mainland if the separation of the island occurred recently (Sakhalin, Britain). The older the island and the greater the water barrier, the greater the differences in the organic world of this island and the nearby mainland (Madagascar). The organic world of the volcanic and coral islands is poor and is the result of the accidental introduction of some species capable of moving through the air.
mainland islands
The living world is close to the mainland. British, Sakhalin the islands separated from the land several thousand years ago, so the living world is very similar to the mainland. The older the island and the more significant the water barrier, the more differences are found.
Madagascar (slide 20). There are no large ungulates typical of Africa: bulls, antelopes, zebras. There are no large predators: lions, leopards, hyenas, higher monkeys. But this island is the last refuge of lemurs. Once upon a time, before the advent of monkeys, lemurs were the dominant primates. But they could not compete with their more advanced relatives and disappeared everywhere except Madagascar, which separated from the mainland before the apes evolved. There are 46 genera of birds in Madagascar that are not found anywhere else in the world. Chameleons– larger and more diverse than in Africa. Unlike Africa, there are no poisonous snakes on the island. But there are many pythons and non-venomous snakes. According to the history of the living world, snakes appeared quite late compared to other reptiles, and poisonous snakes are the youngest of them. Madagascar separated from the continent before snakes appeared there. There are about 150 species of frogs in Madagascar.
oceanic islands
The species composition of the fauna of the oceanic islands is poor and is the result of the accidental introduction of certain species, usually birds, reptiles, and insects. Terrestrial mammals, amphibians and other animals are not able to overcome significant water barriers; most of these islands are absent. Galapogos Islands (slide 21) - removed from the coast of South America by 700 km. This distance can only be overcome by well-flying forms. 15% of bird species are represented by South American species, and 85% are different from the mainland and are not found anywhere else.
III. Consolidation of knowledge.
1. List all evidence for evolution.
2. Do a test job.
Test “Evidence of Evolution”
1. What evidence for evolution is based on paleontological data?
- Morphological.
- Embryological.
- Paleontological.
- Biogeographic.
2. What organs of horses underwent the greatest changes?
- Limbs.
- Heart.
- Digestive tract.
- Body dimensions.
3. What are the homologous organs?
- Butterfly wing and bird wing.
- Polygamy in humans.
4. Name similar organs?
- Vertebrate forelimbs.
- Butterfly wing and bird wing.
- Muscles that move the auricle in humans.
- Polygamy in humans.
5. What are the vestigial organs?
- Vertebrate forelimbs.
- Butterfly wing and bird wing.
- Muscles that move the auricle in humans.
- Polygamy in humans
6. What evidence for evolution is based on comparative anatomy?
- Island fauna and flora.
- Unity of the origin of the organic world.
- Morphological.
- Embryological.
7. Who formulated the biogenetic law?
- Ch. Darwin.
- A.N. Severtsev.
- Müller and Haeckel.
- K. Linney.
8. How many zoogeographic regions did A. Wallace identify?
9. What determines the diversity of flora and fauna of the islands?
- From the history of origin.
- From the species composition of the mainland.
- from environmental conditions.
- From distance from the mainland.
10. What are the proofs of the unity of the origin of the organic world based on?
- Similarities in the chemical composition of cells.
- Similarities between the processes of mitosis and meiosis.
- Cellular structure of organisms.
- variety of living organisms.
IV. Homework: learn the lesson summary; prepare for a frontal poll about the evidence for evolution.
Why do organisms grow and reproduce?
what substances are found in the cells of living organisms and are absent in the bodies of inanimate nature?
What is evidence of the similarity of the composition and structure of the cells of all living organisms?
The next question is what organisms help turn waste products into food? Add the names of "professions" of living organisms to the scheme so that the circulation of substances becomes closed. The names of the professions are as follows: producers consumers food apartment waste, the next question is what role does the sun play for all the inhabitants of the earth? Add a phrase, the phrase is this: The sun is ........... the existence of all living organisms. next question. Check off the phenomenon in which energy storage does not occur, the phenomena themselves are as follows: Accumulation of nutrients in the root of a carrot. The formation of subcutaneous fat in a wild boar. Seed dispersal in dandelion. REMEMBER IF YOU ANSWER CORRECTLY 30 POINTS YOUR AND ONLY YOUR ASSIGNMENTS ARE GIVEN FOR 3 CLASSES ON THE SUBJECT DIVISIONS OF THE EARTH THERE IS NO SUCH THERE SO I CHOOSE BIOLOGY
1. We are surrounded by inanimate and ... nature - living organisms. 2. Living organisms differ from inanimate nature in that they: a) breathe, b) ..., c) ..., d) ...3. Living organisms live: a) on land, b) ..., c) ....
4. What cells make up living organisms.
5. In plants, animals and humans, body cells are distinguished by special sex cells - gametes:
♀ - ...,♂ - ... .
1. The term ecology was introduced by 2. the founder of biogeography 3. A branch of biology that studies the relationship of living organisms with each other and with inanimate nature.4. inas an independent science, ecology began to develop 5. the direction of movement dictates to natural selection 6. Environmental factors that affect the body 7. A group of environmental factors due to the influence of living organisms 8. A group of environmental factors due to the influence of living organisms 9. A group of environmental factors due to the influence of inanimate nature 10. A factor of inanimate nature that gives impetus to seasonal changes in the life of plants and animals. 11. the ability of living organisms to change their biological rhythms depending on the length of daylight hours 12. The most significant factor for survival 13. Light, the chemical composition of air, water and soil, atmospheric pressure and temperature are among the factors 14. construction of railways, plowing of land, the creation of mines is related to 15. Predation or symbiosis is related to factors 16. long-year plants live 17. short-day plants 18. tundra plants belong to 19. Plants of semi-deserts, steppes and deserts belong to 20. A characteristic indicator of a population. 21. The totality of all types of living organisms inhabiting a certain territory and interacting with each other 22. The ecosystem of our planet richest in species diversity 23. ecological group of living organisms that create organic substances 24. ecological group of living organisms that consume ready-made organic substances, but do not conduct mineralization 25. an ecological group of living organisms that consume ready-made organic substances and contribute to their complete transformation into mineral substances 26. useful energy goes to the next trophic (food) level 27. consumers of the 1st order 28. consumers of the 2nd or 3rd order 29. a measure of the sensitivity of communities of living organisms to changes in certain conditions 30. the ability of communities (ecosystems or biogeocenoses) to maintain their constancy and resist changing environmental conditions sources of energy and high productivity are characteristic of 32. artificial biocenosis with the highest metabolic rate per unit area. with the involvement of the circulation of new materials and the excretion of a large amount of non-utilizable waste are characteristic of 33. arable land is occupied by 34. cities occupy 35. the shell of the planet inhabited by living organisms 36. the author of the study of the biosphere 37. the upper boundary of the biosphere 38. the boundary of the biosphere in the depths of the ocean. 39 the lower boundary of the biosphere in the lithosphere. 40. an international non-governmental organization founded in 1971, which performs the most effective actions in defense of nature.
Cytology is the science of the cell (Greek "cytos" - cell, "logos" - science).
Cytology is the study of cells. Cells are the elementary units of a living system. And they are called elementary, because in nature there are no smaller systems that have all the signs and properties of the living.
It is known that in nature organisms are unicellular (for example, bacteria, protozoan algae) or multicellular.
The cell carries out the metabolism and energy exchange, grows, multiplies, transfers its properties by inheritance, reacts to the external environment, and moves. The above functions in the cell are performed by organelles - the nucleus, mitochondria, etc.
All this is studied by the complex science of cytology. This science is about 100 years old and is closely related to other sciences.
The cell itself is over 300 years old. And for the first time Robert Hooke saw them with a microscope in 1665 and he called the cells he saw on a thin section of cork "cells". After that, the microscope invented by Hooke began to be widely used in scientific research and discoveries. Single-celled organisms were discovered, and cells were found in the tissues of many animals and plants.
In the 30s of the XIX century. Scottish scientist Robert Brown, observing the structure of a leaf through a microscope, made a remarkable discovery: he discovered a round dense formation, which he called the core.
In 1838, the German scientist Schleiden summarized his observations and came to the conclusion that the nucleus is included in all plant cells.
Another German scientist Schwann, observing cells of animal origin and comparing them with plant cells, came to the conclusion that all the most diverse cells have nuclei and this is their similarity.
Summarizing all the disparate facts, experiments, observations, Schwann and Schleiden formulated one of the main provisions of the cell theory:
All plant and animal organisms are composed of cells that are similar in structure.
20 years later, in 1858, a significant contribution to cytology was made by the German scientist Rudolf Virchow, who argued that cells arise only by division. He formulated the most important principle: "Each cell from a cell."
The zoologist Schneider first described in 1873 the indirect division of animal cells - "mitosis".
In 1882, Fleming studied in detail the process of cell division and arranged its phases in a certain order.
Academician of the Russian Academy of Sciences Karl Baer discovered the mammalian egg and found that all multicellular organisms begin their development from one cell and this cell is a zygote. This discovery showed that the cell is not only a unit of structure, but also a unit of development of all living organisms.
F. Engels highly appreciated the cell theory, calling it one of the great discoveries of the 19th century and comparing its appearance with the discovery of the law of conservation of energy and the teachings of Charles Darwin on the evolution of the organic world.
The cell theory underlies the ideas about the unity of all living things, the commonality of its origin and evolutionary development.
The light microscope was constantly and very significantly improved, and so were the methods of staining cells, and thanks to this, scientific discoveries quickly succeeded each other. The nucleus, cytoplasm and other organelles of the cell were isolated and studied.
At present, when studying cells, they use the latest physical and chemical methods, as well as modern electron microscopes, giving an increase of 1,000,000. Special dyes are used, and the centrifugation method is used to study the chemical composition of the cell. It is based on the unequal density of different cellular organelles. During rapid rotation in the ultracentrifuge, various organelles of pre-crushed cells are arranged in layers. Dense layers settle faster and end up at the bottom, less dense layers at the top. The layers are separated and studied separately.
Such a modern and detailed study of the chemical organization of the cell led to the conclusion that it is chemical processes that underlie its life, that the cells of all organisms are similar in chemical composition, they have the same basic metabolic processes.
Data on the similarity of the chemical composition of cells once again confirmed the unity of the entire organic world.
Thanks to the most modern methods of physical and chemical research, the main provisions of the cell theory at the present stage of development of biology are formulated as follows:
1. The cell is the basic structural and functional unit of life. All organisms are made up of cells, the life of the organism as a whole is due to the interaction of its constituent cells.
2. Cells of all organisms are similar in their chemical composition, structure and functions.
3. All new cells are formed during the division of the original cells.
Based on the provisions of the cellular theory, it is clear that cells are characterized by the ability to grow, reproduce, respire, release, use and convert energy, they respond to irritation, i.e. cells have the properties necessary to sustain life, and only the totality of the structures that form the cell.
Using the achievements of biology, a science adjacent to medicine was formed - microbiology in the second half of the 19th century. Its founder L. Pasteur.
Early 50s of the XIX century. by studying beneficial microorganisms, a method of "pasterilization" was discovered. And then in the 70s and 80s, Pasteur, studying the pathogens of contagious diseases in humans and animals, developed a method of dealing with them through preventive vaccinations:
1879 - a prescription for vaccination against chicken cholera;
1881 - against anthrax;
1885 - against rabies;
Pasteur's studies of pathogenic microbes formed the basis of the doctrine of immunity.
1876 - in Russia, O. Motuchkovsky discovered the causative agent of typhus in the blood of a patient;
And the doctor Nicole proved that the body louse is the carrier of typhus.
1882 - German scientists R. Koch - the causative agent of turbuculosis;
1883 - the causative agent of cholera;
1884 - Gafke discovered typhoid fever sticks,
Leffer - diphtheria, glanders, foot-and-mouth disease and swine fever.
Studies of toxins - poisons secreted by microbes led to the discovery
antitoxic sera: antidiphtheria, tetanus, etc.
Cell studies are of great importance in unraveling diseases.
All the above facts testify to the importance of the commonality of the chemical composition and structure of the cell - the main structural and functional unit of living organisms - for biology, medicine and veterinary medicine, and also testifies to the unity of the origin of life on Earth.
