Development of evolutionary ideas. Evidence for evolution

Evolution is a process of development consisting of gradual change, without sharp jumps (as opposed to revolution). Most often, speaking of evolution, they mean biological evolution.

Biological evolution is an irreversible and directed historical development of living nature, accompanied by a change in the genetic composition of populations, the formation of adaptations, the formation and extinction of species, the transformation of ecosystems and the biosphere as a whole. Biological evolution is the study of evolutionary biology.

There are several evolutionary theories that have in common the claim that living forms of life are the descendants of other life forms that existed before. Evolutionary theories differ in explaining the mechanisms of evolution. AT this moment the most common is the so-called. synthetic theory evolution, which is the development of Darwin's theory.

Genes that are passed on to offspring, as a result of expression, form the sum of the characteristics of the organism (phenotype). When organisms reproduce, their descendants develop new or altered traits that arise as a result of mutation or when genes are transferred between populations or even species. In species that reproduce sexually, new combinations of genes arise through genetic recombination. Evolution occurs when hereditary differences become more frequent or rarer in a population.

Evolutionary biology studies evolutionary processes and puts forward theories to explain their causes. The study of fossils and species diversity by the middle of the 19th century convinced most scientists that species change over time. However, the mechanism of these changes remained unclear until the publication in 1859 of Charles Darwin's Origin of Species on natural selection as the driving force behind evolution. Darwin and Wallace's theory was eventually accepted scientific community. In the 1930s, the idea of ​​Darwinian natural selection was combined with Mendel's laws, which formed the basis of the synthetic theory of evolution (STE). STE made it possible to explain the relationship between the substrate of evolution (genes) and the mechanism of evolution ( natural selection).

Heredity

Heredity, the inherent property of all organisms to repeat the same signs and features of development in a number of generations; due to the transfer in the process of reproduction from one generation to another of the material structures of the cell, containing programs for the development of new individuals from them. Thus, heredity ensures the continuity of the morphological, physiological and biochemical organization of living beings, the nature of their individual development, or ontogenesis. As a general biological phenomenon, heredity is essential condition the existence of differentiated forms of life, impossible without the relative constancy of the characteristics of organisms, although it is violated by variability - the emergence of differences between organisms. Affecting a wide variety of traits at all stages of the ontogeny of organisms, heredity manifests itself in the patterns of inheritance of traits, that is, their transmission from parents to descendants.

Sometimes the term "Heredity" refers to the transfer from one generation to another of infectious principles (the so-called infectious heredity) or skills of training, education, traditions (the so-called social, or signal, heredity). Such an extension of the concept of heredity beyond its biological and evolutionary nature is debatable. Only in cases where infectious agents are able to interact with host cells up to inclusion in their genetic apparatus, it is difficult to separate infectious heredity from normal. Conditioned reflexes are not inherited, but are developed anew by each generation, but the role of heredity in the speed of fixing conditioned reflexes and behavioral patterns is indisputable. Therefore, the signal heredity includes a component of biological heredity.

Variability

Variability is a variety of features and properties in individuals and groups of individuals of any degree of kinship. Present in all living organisms. There are hereditary and non-hereditary variability, individual and group, qualitative and quantitative, directed and undirected. Hereditary variability is caused by the occurrence of mutations, non-hereditary - by the influence of environmental factors. The phenomena of heredity and variability underlie evolution.

Mutation

Mutation - randomly occurring, persistent changes in the genotype that affect whole chromosomes, their parts or individual genes. Mutations can be large, clearly visible, for example, the absence of pigment (albinism), lack of plumage in chickens, short fingers, etc. However, most often, mutational changes are small, barely noticeable deviations from the norm.

Mutations are rare events. The frequency of occurrence of individual spontaneous mutations is expressed as the number of gametes of one generation that carry a particular mutation, in relation to total number gametes.

Mutations arise mainly as a result of two causes: spontaneous replication errors in the nucleotide sequence and the action of various mutagenic factors that cause replication errors.

Mutations caused by the action of mutagens (irradiation, chemical substances, temperature, etc.) are called induced, in contrast to spontaneous mutations that occur due to random errors in the action of enzymes that ensure replication, or (and) as a result of thermal vibrations of atoms in nucleotides.

Mutation types. According to the nature of the change in the genetic apparatus, mutations are divided into genomic, chromosomal and gene, or point. Genomic mutations consist in changing the number of chromosomes in the cells of the body. These include: polyploidy - an increase in the number of sets of chromosomes, when instead of the usual 2 sets of chromosomes for diploid organisms, there can be 3, 4, etc.; haploidy - instead of 2 sets of chromosomes, there is only one; aneuploidy - one or more pairs of homologous chromosomes are absent (nullisomy) or are represented not by a pair, but by only one chromosome (monosomy) or, on the contrary, by 3 or more homologous partners (trisomy, tetrasomy, etc.). Chromosomal mutations, or chromosomal rearrangements, include: inversions - a section of the chromosome is turned 180 °, so that the genes contained in it are located in the reverse order compared to normal; translocations - exchange of parts of two or more non-homologous chromosomes; deletions - loss of a significant portion of the chromosome; shortages (small deletions) - loss small area chromosomes; duplications - doubling of a section of a chromosome; fragmentation - breakage of a chromosome into 2 parts or more. Gene mutations are permanent changes chemical structure individual genes and, as a rule, are not reflected in the chromosome morphology observed under a microscope. Mutations of genes localized not only in chromosomes, but also in some self-reproducing organelles of the cytoplasm (for example, in mitochondria, plastids) are also known.

Causes of mutations and their artificial induction. Polyploidy often occurs when the chromosomes at the beginning cell division- mitosis - divided, but for some reason, cell division did not occur. Polyploidy can be artificially induced by acting on a cell that has entered mitosis with substances that disrupt cytotomy. Less commonly, polyploidy is the result of a fusion of 2 somatic cells or participation in the fertilization of an egg by 2 sperm. Haploidy - for the most part a consequence of the development of the embryo without fertilization. It is artificially caused by pollinating plants with killed pollen or pollen of another species (remote). The main cause of aneuploidy is the accidental nondisjunction of a pair of homologous chromosomes during meiosis, as a result of which both chromosomes of this pair fall into the same germ cell or none of them enter it. Less commonly, aneuploids arise from the few viable germ cells formed by unbalanced polyploids.

The causes of chromosomal rearrangements and the most important category of mutation, genes, remained unknown for a long time. This gave rise to erroneous autogenetic concepts, according to which spontaneous gene mutations appear in nature, allegedly without the participation of influences. environment. Only after the development of methods for quantitative accounting of gene mutations did it become clear that they could be caused by various physical and chemical factors - mutagens.

Recombination

Recombination - redistribution of the genetic material of parents in the offspring, leading to hereditary combinative variability of living organisms. In the case of unlinked genes (located on different chromosomes), this redistribution can be carried out with the free combination of chromosomes in meiosis, and in the case of linked genes, usually by crossing over chromosomes. Recombination is a universal biological mechanism inherent in all living systems - from viruses to higher plants, animals and humans. At the same time, depending on the level of organization of a living system, the process of recombination (genetic) has a number of features. Recombination occurs most easily in viruses: when a cell is co-infected with related viruses that differ in one or more characteristics, after cell lysis, not only the original viral particles are detected, but also recombinant particles with new combinations of genes that arise with a certain average frequency. In bacteria, there are several processes that end in recombination: conjugation, i.e., the union of two bacterial cells with a protoplasmic bridge and the transfer of a chromosome from a donor cell to a recipient cell, after which individual sections of the recipient's chromosome are replaced by the corresponding fragments of the donor; transformation - the transfer of signs by DNA molecules penetrating from the environment through the cell membrane; transduction - the transfer of genetic material from a donor bacterium to a recipient bacterium, carried out by a bacteriophage. In higher organisms, recombination occurs during meiosis during the formation of gametes: homologous chromosomes approach and are installed side by side with great accuracy (the so-called synapsis), then the chromosomes break at strictly homologous points and the fragments are recombined crosswise (crossing over). The result of recombination is detected by new combinations of traits in the offspring. The probability of crossing over between two chromosome points is approximately proportional to the physical distance between these points. This makes it possible, on the basis of experimental data on recombination, to build genetic maps of chromosomes, i.e., graphically arrange genes in a linear order in accordance with their location in chromosomes, and, moreover, on a certain scale. The molecular mechanism of recombination has not been studied in detail, however, it has been established that the enzymatic systems that ensure recombination are also involved in this process. critical process, as a correction of damage that occurs in the genetic material. After synapsis, endonuclease, an enzyme that carries out primary breaks in DNA chains, comes into action. Apparently, these breaks in many organisms occur in structurally determined areas - recombinators. Next, there is an exchange of double or single strands of DNA and, finally, special synthetic enzymes - DNA polymerases - fill in the gaps in the chains, and the ligase enzyme closes the last covalent bonds. These enzymes have been isolated and studied only in some bacteria, which made it possible to approach the creation of an in vitro recombination model (in vitro). One of the most important consequences of recombination is the formation of reciprocal offspring (i.e., in the presence of two allelic forms of the genes AB and av, two recombination products should be obtained - AB and aB in equal amounts). The principle of reciprocity is observed when recombination occurs between sufficiently distant points on the chromosome. In intragenic recombination, this rule is often violated. The last phenomenon, studied mainly in lower fungi, is called gene conversion. The evolutionary significance of recombination lies in the fact that it is often not individual mutations that are favorable for the organism, but their combinations. However, the simultaneous occurrence of a favorable combination of two mutations in one cell is unlikely. As a result of recombination, a combination of mutations belonging to two independent organisms is carried out, and thereby the evolutionary process is accelerated.

Mechanisms of evolution

Natural selection

There are two main evolutionary mechanisms. The first is natural selection, that is, the process by which hereditary traits favorable for survival and reproduction are distributed in a population, and unfavorable ones become rarer. This is because individuals with favorable traits are more likely to reproduce, so more individuals in the next generation have the same traits. Adaptations to the environment arise as a result of the accumulation of successive, small, random changes and the natural selection of the variant that is most adapted to the environment.

genetic drift

The second major mechanism is genetic drift, an independent process of random variation in the frequency of traits. Genetic drift occurs as a result of probabilistic processes that cause random changes in the frequency of traits in a population. Although the changes due to drift and selection during one generation are quite small, the differences in frequencies accumulate in each subsequent generation and eventually lead to significant changes in living organisms. This process may culminate in the formation of a new species. Moreover, the biochemical unity of life indicates the origin of all known species from a common ancestor (or pool of genes) through a process of gradual divergence.

The historical development of wildlife occurs according to certain laws and is characterized by a combination of individual features. The successes of biology in the first half of the 19th century served as a prerequisite for the creation of a new science - evolutionary biology. She immediately became popular. And she proved that evolution in biology is a deterministic and irreversible process of development as certain types, and their entire communities - populations. It occurs in the biosphere of the Earth, affecting all its shells. This article will be devoted to both the study of the concepts of a biological species, and

History of development of evolutionary views

science passed hard way formation of worldview ideas about the mechanisms underlying the nature of our planet. It began with the ideas of creationism expressed by C. Linnaeus, J. Cuvier, C. Lyell. The first evolutionary hypothesis was presented by the French scientist Lamarck in his work "Philosophy of Zoology". The English researcher Charles Darwin was the first in science to suggest that evolution in biology is a process based on hereditary variability and natural selection. Its basis is the struggle for existence.

Darwin believed that the appearance of continuous changes in biological species is the result of their adaptation to the constant change of environmental factors. The struggle for existence, according to the scientist, is a combination of the relationship of the organism with the surrounding nature. And its reason lies in the desire of living beings to increase their numbers and expand their habitats. All of the above factors and includes evolution. Biology, which grade 9 studies in the classroom, considers the processes of hereditary variability and natural selection in the section "Evolutionary Teaching".

Synthetic hypothesis of the development of the organic world

Even during the lifetime of Charles Darwin, his ideas were criticized by a number of such famous scientists as F. Jenkin and G. Spencer. In the 20th century, in connection with the rapid genetic research and the postulation of Mendel's laws of heredity, it became possible to create a synthetic hypothesis of evolution. In their writings, it was described by such as S. Chetverikov, D. Haldane and S. Ride. They argued that evolution in biology is a phenomenon of biological progress, which has the form of aromorphoses, idioadaptations affecting populations various kinds.

According to this hypothesis, the evolutionary factors are the waves of life, and isolation. Forms historical development nature are manifested in such processes as speciation, microevolution and macroevolution. The above scientific views can be represented as a summation of knowledge about mutations, which are the source of hereditary variability. As well as ideas about the population as a structural unit of the historical development of a biological species.

What is an evolutionary environment?

This term is understood as biogeocenotic. Microevolutionary processes occur in it, affecting populations of one species. As a result, the emergence of subspecies and new biological species becomes possible. Processes leading to the appearance of taxa - genera, families, classes - are also observed here. They belong to macroevolution. Scientific research V. Vernadsky, proving the close relationship of all levels of organization of living matter in the biosphere, confirm the fact that biogeocenosis is an environment for evolutionary processes.

In climax, that is, stable ecosystems, in which there is a large diversity of populations of many classes, changes occur as a result of coherent evolution. in such stable biogeocenoses are called coenophilic. And in systems with unstable conditions, uncoordinated evolution occurs among ecologically plastic, so-called cenophobic species. Migrations of individuals of different populations of the same species change their gene pools, disrupting the frequency of occurrence of different genes. So says modern biology. The evolution of the organic world, which we will consider below, confirms this fact.

Stages of development of nature

Scientists such as S. Razumovsky and V. Krasilov proved that the pace of evolution underlying the development of nature is uneven. They represent slow and almost imperceptible changes in stable biogeocenoses. They accelerate sharply during periods environmental crises: man-made disasters, melting glaciers, etc. About 3 million species of living beings live in the modern biosphere. The most important of them for human life is studied by biology (Grade 7). The evolution of Protozoa, Coelenterates, Arthropods, Chordates is a gradual complication of the circulatory, respiratory, nervous systems these animals.

The first remains of living organisms are found in the Archean sedimentary rocks. Their age is about 2.5 billion years. The first eukaryotes appeared at the beginning Possible options The origin of multicellular organisms is explained by the scientific hypotheses of I. Mechnikov's phagocytella and E. Getell's gastrea. Evolution in biology is the path of development of wildlife from the first Archean life forms to the diversity of flora and fauna of the modern Cenozoic era.

Modern ideas about the factors of evolution

They are conditions that cause adaptive changes in organisms. Their genotype is the most protected from external influences (the conservation of the gene pool of a biological species). Hereditary information can still change under the influence of genes. It was in this way - by acquiring new signs and properties - that the evolution of animals took place. Biology studies it in such sections as comparative anatomy, biogeography and genetics. Reproduction, as a factor in evolution, is of exceptional importance. It ensures the change of generations and the continuity of life.

Man and the biosphere

Biology studies the processes of the formation of the Earth's shells and the geochemical activity of living organisms. The evolution of the biosphere of our planet has a long geological history. It was developed by V. Vernadsky in his teachings. He also introduced the term "noosphere", meaning by it the influence of conscious (mental) human activity on nature. Living matter, which enters into all the shells of the planet, changes them and determines the circulation of substances and energy.

Evolution is the process of historical development of the organic world. The essence of this process consists in the continuous adaptation of living things to diverse and constantly changing environmental conditions, in the increasing complexity of the organization of living beings over time. In the course of evolution, one species is transformed into another.

Major in evolutionary theory- the idea of ​​historical development from relatively simple forms of life to more highly organized ones. The foundations of the scientific materialistic theory of evolution were laid by the great English naturalist Charles Darwin. Before Darwin, biology was largely dominated by the misconception that species are historically immutable, that there are as many of them as God created them. Even before Darwin, however, the most astute biologists understood the inconsistency of religious views on nature, and some of them speculatively came to evolutionary ideas.

The most prominent naturalist, Charles Darwin's predecessor was the famous French scientist Jean-Baptiste Lamarck. In his famous book"Philosophy of Zoology" he proved the variability of species. Lamarck emphasized that the constancy of species is only an apparent phenomenon, it is associated with the short duration of observations of species. higher forms life, according to Lamarck, originated from the lower in the process of evolution. The evolutionary doctrine of Lamarck was not sufficiently demonstrative and did not receive wide recognition among his contemporaries. Only after the outstanding works of Charles Darwin did the evolutionary idea become generally accepted.

Modern science has very many facts proving the existence of the evolutionary process. These are data from biochemistry, embryology, anatomy, taxonomy, biography, paleontology and many other disciplines.

Embryological evidence- similarity initial stages embryonic development of animals. studying embryonic period development in various groups, K. M. Baer discovered the similarity of these processes in various groups of organisms, especially in the early stages of development. Later, based on these conclusions, E. Haeckel suggests that this similarity has an evolutionary significance and on its basis a "biogenetic law" is formulated - ontogenesis is a brief reflection of phylogeny. Each individual in its individual development(ontogenesis) passes through the embryonic stages of ancestral forms. The study of only the early stages of development of the embryo of any vertebrate does not allow us to determine with accuracy which group they belong to. Differences are formed at later stages of development. The closer the groups to which the studied organisms belong, the longer the common features will remain in embryogenesis.?

Morphological- many forms combine the features of several large systematic units. When studying various groups of organisms, it becomes obvious that they are fundamentally similar in a number of features. For example, the structure of the limb in all four-legged animals is based on a five-fingered limb. This basic structure in different species has been transformed due to different conditions of existence: this is the limb of an equid-hoofed animal, which, when walking, relies on just one finger, and the flippers of a marine mammal, and the burrowing limb of a mole, and the wing of a bat.

Organs built according to a single plan and developing from single primordia are called homologous. Homologous organs cannot in themselves serve as evidence of evolution, but their presence indicates the origin of similar groups of organisms from a common ancestor. A prime example evolution is served by the presence of rudimentary organs and atavisms. Rudimentary organs are organs that have lost their original function, but remain in the body. Examples of rudiments are: in humans, which performs a digestive function in ruminant mammals; pelvic bones of snakes and whales, which perform no function in them; coccygeal vertebrae in humans, which are considered vestiges of the tail that our distant ancestors had. called the manifestation in organisms of structures and organs characteristic of ancestral forms. classic examples atavisms are multi-nipple and caudate in humans.

paleontological- the fossil remains of many animals can be compared with each other and find similarities. Based on the study of fossil remains of organisms and comparison with living forms. They have their advantages and disadvantages. The advantages include the opportunity to see firsthand how a given group of organisms changed in different periods. The disadvantages include that the paleontological data are very incomplete due to a variety of reasons. These include such as the rapid reproduction of dead organisms by animals that feed on carrion; soft-bodied organisms are extremely poorly preserved; and, finally, that only a small part of the fossil remains are found. In view of this, there are many gaps in paleontological data, which are the main object of criticism of opponents of the theory of evolution.

General concept of evolution

We often find the term "evolution" in the literature. But we can not always clearly explain its meaning. Therefore, in this article we will consider the question of evolution in general and the evolution of living organisms in more detail. The explanatory dictionary gives the following explanation of this term:

The key points in this definition are the theses about the irreversibility of changes and the gradual (step by step) transition from one state to another.

In a broad sense, we can talk about the evolution of morals, the evolution of fashion, implying any development. Now let's take a closer look at biological evolution.

biological evolution

Remembering the well-known phase: "Everything flows, everything changes", we can successfully apply it to living organisms. They are also undergoing changes. The process of evolution is also characteristic of them. modern biology gives the following interpretation of the concept of evolution:

Definition 2

"Biological evolution is a natural irreversible process of the development of wildlife, which is accompanied by a change in the genetic composition of populations, the formation of adaptations, speciation and extinction of species, the transformation of ecosystems and the biosphere as a whole."

During the development of science, a large number of theories trying to explain the mechanism of evolutionary transformations.

Development of evolutionary views in science

From the very beginning of the development of human knowledge, a complex of closely interconnected sciences was formed that studied nature. This complex was called natural science.

Already in ancient times, natural scientists (then they were called natural philosophers) were engaged in describing plants and animals. For a long time, the descriptive method of cognition prevailed in science. But often it only led to an unsystematic, chaotic accumulation scientific facts. Even Aristotle and Theophrastus tried to systematize knowledge about living organisms, dividing them into plants and animals. Carl Linnaeus tried to create a coherent system of the organic world. But long time scientists could not explain the reasons species diversity living organisms, the mechanism of occurrence of changes in living organisms.

Metaphysical views deny changes in organic world. And creationism involves the intervention of some force - the "Creator" in the creation of life and living organisms. Both theories cannot explain the presence of fossil forms and the reasons for their extinction.

The theory of transformism, which arose on the crest of the industrial revolution and social transformations of the $18th-19th centuries, already recognized the possibility of changing species and tried to explain the mechanism of these changes.

The ideas of transformism found their further development in the works of the famous French scientist Jean-Baptiste Lamarck. He was the first to create a holistic theory of the historical development of flora and fauna. He actively opposed the metaphysical postulate of the immutability of the forms of the living.

Lamarck admitted the possibility of spontaneous generation of life from inanimate nature. Lamarck called the complication of the organization of living organisms from the lowest to the highest level in the process of evolution gradation. But Lamarck's views also reflected an idealistic worldview. So, for example, he explained the evolution of higher animals by the desire for improvement.

Remark 1

The ideas of Lamarckism, discoveries in cytology, the achievements of paleontology and personal observations allowed the outstanding British researcher Charles Darwin to develop his evolutionary theory. Darwin's theory of the origin of species long years provided biological science reliable theoretical foundation for further research.

But human knowledge does not stand still. Darwin's theory can no longer explain the new facts. Therefore, at present, the synthetic theory of evolution (STE) is generally recognized. It is a synthesis of classical Darwinism and population genetics. STE makes it possible to explain the connection between the material of evolution (genetic mutations) and the mechanism of evolution (natural selection).

The offspring of living beings are very similar to their parents. However, if the habitat of living organisms changes, they too can change significantly. For example, if the climate gradually becomes colder, then some species may acquire more and more dense wool from generation to generation. This process is called evolution. Over millions of years of evolution, small changes, accumulating, can lead to the emergence of new plant and animal species that differ sharply from their ancestors.

How does evolution take place?

Evolution is based on natural selection. It happens like this. All animals or plants belonging to the same species are still slightly different from each other. Some of these differences allow their owners to better adapt to the conditions of life than their relatives. For example, some deer especially quick legs, and every time he manages to escape from the predator. Such a deer is more likely to survive and have offspring, and the ability to run fast can be passed on to its cubs, or, as they say, be inherited by them.

Evolution has created countless ways to adapt to the difficulties and dangers of life on Earth. For example, seeds horse chestnut over time, they acquired a shell covered with sharp spines. The thorns protect the seed as it falls from the tree to the ground.

What is the rate of evolution?

Previously, these butterflies had light wings. They hid from enemies on tree trunks with the same light bark. However, about 1% of these butterflies had dark wings. Naturally, the birds immediately noticed them and, as a rule, ate them before others.

Usually evolution proceeds very slowly. But there are times when a species of animal undergoes rapid changes and spends not thousands and millions of years on it, but much less. For example, some butterflies have changed their color over the past two hundred years in order to adapt to new living conditions in those parts of Europe where many industrial enterprises have arisen.

About two hundred years ago in Western Europe began to build coal-fired factories. The smoke from the factory chimneys contained soot, which settled on the trunks of the trees, and they turned black. Now the bright butterflies are more noticeable. And a few previously dark-winged butterflies survived, because the birds no longer noticed them. From them came other butterflies with the same dark wings. And now most of the butterflies of this species that live in industrial areas have dark wings.

Why are some animal species going extinct?

Some living beings are unable to evolve when their environment changes drastically and die out as a result. For example, huge hairy animals that look like elephants - mammoths, most likely died out because the climate on Earth at that time became more contrasting: it was too hot in summer and too cold in winter. In addition, their numbers have declined due to increased hunting for them by primitive man. And after the mammoths, the saber-toothed tigers also died out - after all, their huge fangs were adapted to hunt only large animals like mammoths. Smaller animals were not available for saber-toothed tigers, and, left without prey, they disappeared from the face of our planet.

How do we know that man also evolved?

Most scientists believe that humans evolved from tree-dwelling animals similar to modern apes. The proof of this theory are some features of the structure of our bodies, allowing, in particular, to suggest that once our ancestors were vegetarians and ate only the fruits, roots and stems of plants.

At the base of your spine there is a bone formation called the coccyx. This is all that's left of the tail. Most of the hair that covers your body is just soft fluff, but our ancestors had much thicker hair. Each hair is equipped with a special muscle and stands on end when you get cold. So it is with all mammals with hairy skin: it retains air, which does not allow the heat of the animal to escape.

Many adults have wide outer teeth - they are called "wisdom teeth". Now there is no need for these teeth, but at one time our ancestors chewed with them the hard plant food they ate. The appendix is ​​a small tube attached to the intestines. Our distant ancestors, with its help, digested plant foods that were poorly absorbed by the body. Now it is no longer needed and is gradually getting smaller and smaller. In many herbivores - for example, rabbits - the appendix is ​​​​very well developed.

Can humans control evolution?

Humans drive evolution some animals are over 10,000 years old. For example, many modern breeds of dogs, in all likelihood, descended from wolves, packs of which roamed near the camps of ancient people. Gradually, those of them that began to live with people evolved into the new kind animals, that is, became dogs. Then people began to specially raise dogs for certain purposes. This is called selection. As a result, today there are more than 150 various breeds dogs.

• Dogs that could be taught different commands, like this English Sheepdog, were bred to herd cattle.
• Dogs that could run fast were used to chase game. This greyhound has powerful legs and runs with huge leaps.
• Dogs with a good sense of smell were bred specifically for tracking down game. This smooth-coated dachshund can rip rabbit holes.

Through natural selection, as a rule, proceeds very slowly. Selective selection allows you to dramatically accelerate it.

What is genetic engineering?

In the 70s. 20th century scientists have invented a way to change the properties of living organisms by interfering with their genetic code. This technology is called genetic engineering. Genes carry a kind of biological cipher contained in every living cell. It determines the size and appearance every living being. Via genetic engineering you can breed plants and animals that, say, grow faster or are less susceptible to any disease