Evolution of the organic world.
Definition of evolution.
Theories of evolution.
Biological species, its population structure.
The effect of elementary factors on the population.
Biological evolution is based on the processes of self-reproduction of macromolecules and organisms.
Biological evolution is the irreversible and directed historical development of living nature.
Biological evolution is accompanied by:
Changes in the genetic composition of the population;
Formation of adaptations;
Formation and extinction of species;
Transformation of ecosystems and the biosphere as a whole.
There is a correspondence between organisms and the external environment. Everyone can exist and reproduce their own kind only in an environment appropriate to them.
1809 - Jean Baptiste Lamarck focused on the progressive development of organisms.
Principles of evolution (according to Lamarck)
The existence of an internal desire for self-improvement in organisms.
The ability of organisms to adapt to circumstances, i.e. external environment.
Frequent acts of spontaneous generation.
Inheritance of acquired characteristics and traits.
An important merit is position 2. Lamarck could not prove his theory, and there were no empirical facts to support his point of view. Neo-Lamarckism arose later.
C. Rouvier developed the concept of the emergence of the organic world from the inorganic, of the gradual natural change of organisms, of the formation of the diversity of living beings under the influence of changing external conditions, of heredity and variability as the main properties of living organisms.
Beketov in 1854 he conducted a study of changes in plants.
1858 - Darwin made a preliminary report on the theory to the Linnaean Society. A.Walres made the same conclusions and wrote a letter to Charles Darwin, because By the time Walres wrote the manuscript, Darwin had already published part of the works. Darwin was not the first to propose the theory of universal evolution, but he proved that evolution exists, and in addition, there are driving forces of evolution in nature.
On November 24, 1859, Darwin's work "The Origin of Species by Means of Natural Selection" was published in full.
Postulates of Darwin's theory.
The world around us is not static, but constantly evolving. Species are constantly changing, some species arise, others die out.
The evolutionary process occurs gradually and continuously. The evolutionary process is not a collection of individual leaps or sudden changes.
Similar organisms descend from a common ancestor and are related by kinship.
The theory of natural selection.
Until the 1930s, when the theory of synthetic evolution appeared, there were many discrepancies. All theories can be divided into 4 groups:
Monistic;
Synthetic;
The theory of punctuated equilibrium;
The theory of neutral mutations.
Monistic theories explain evolutionary changes by the action of a single factor.
Ectogenetic – changes are caused directly by the environment.
Endogenetic - changes are controlled by internal forces, true Lamarckism.
Random events (“accidents”) – spontaneous mutations, recombinations.
Natural selection.
Synthetic theories explain evolutionary changes by the action of many factors.
Most theories are Lamarckian;
Later views of Charles Darwin;
Early stage of the "modern synthesis";
Modern stage.
1926 - Chetverikov published an article in “Experimental Biology” “On some aspects of the evolutionary process from the point of view of modern genetics.” Connected some Darwin facts.
1935 – I.I. Vorontsov formulated the main provisions of the synthetic theory of evolution (11 postulates).
Synthetic theory of evolution.
The smallest unit of evolution is the local population.
The main factor in evolution is natural selection.
Evolution is divergent in nature (convergent, parallel).
Evolution is gradual, step-by-step (sometimes spasmodic).
The exchange of alleles and gene flow occurs only within one biological species.
Macroevolution follows the path of microevolution.
A species consists of many subordinate units.
The concept of species is unacceptable for forms that do not have sexual reproduction.
Evolution is carried out on the basis of variability (so-called tychogenesis).
The taxon has monophylithic potential (descends from a single ancestor).
Evolution is unpredictable.
It became clear that the elementary unit of evolution is not one organism, but a population. It has been established that the cause of evolution is not a single factor, but an interaction between many factors that are realized as a result of natural selection.
The synthetic theory of evolution is accepted by most scientists. All provisions at the level of microevolution have been proven; at the level of macroevolution they have not yet been sufficiently confirmed, which is why new evolutionary theories are being created.
In addition to the synthetic theory, the concept of punctuated equilibrium is interesting. In evolution, periods of stability of species alternate with short periods of rapid speciation. The appearance of sudden mutations is associated with regulatory genes. However, no regulatory genes have been found in plants.
The theory of neutral mutations. Authors – King, Kimura – 1970 Appeared after the discovery of patterns in molecular biology. The main factor at the molecular level is not natural selection, but chance events that lead to the fixation of neutral or almost neutral mutations. Changes occur in the sequence of DNA triplets, and proteins change accordingly. DNA changes are caused by random genetic drift. The theory does not deny the role of natural selection, but believes that only a small part of DNA changes is adaptive. Most changes have no phylogenetic influence, they are not selective, neutral and do not have any role in evolution. The theory has evidence: leucine is co-regulated by 6 triplets, with preferred ones in different animal species. Changing the triplet in this case does not change anything, however, different triplets in different animals perform the “key” function.
Zavatsky - “General characteristics of a biological species.”
number;
type of organization/specific set of chromosomes;
reproduction (in the process of reproduction, the species preserves itself);
discreteness (a species exists and evolves as a separate entity);
environmental certainty. The species is adapted to certain conditions, where it is competitive;
geographical definition/range of the species;
diversity of forms – internal structure of the species – population;
historicity. A species is a system capable of evolutionary development;
sustainability;
integrity. A species is a tribal community united by certain adaptations and intraspecific relationships.
The question of what a biological species is has not been resolved. Basic Concepts:
Philosophical and logical concept;
Biological concept;
Morphological concept.
According to the philosophical and logical concept, view is a category of thinking. General properties are characteristic of all representatives.
The morphological criterion is the application of a philosophical and logical concept to living organisms. Species are defined strictly by the presence of certain characteristics in a population (Linnaeus, most naturalists and taxonomists of the 18th – 19th centuries).
The biological concept is based on the fact that all species are composed of populations. Individuals are potentially capable of interbreeding with each other, species actually exist, individuals have a common genetic program that has developed in the process of evolution. It is a reproductive community, an ecological unit, a genetic unit. The species is genetically closed and reproductively isolated. The genetic structure reflects the essence of the species. The species is characterized by genetic diversity.
View- a group of morphologically similar organisms that have a common origin and are potentially capable of interbreeding with each other under natural conditions.
Individuals do not always live in close relation to each other (immediate proximity); they live in populations.
Signs of a population.
A population is a freely interbreeding group.
The panmix group is a reproductive unit.
A population is an ecological unit. Individuals are genetically similar in environmental requirements.
Population- a group of individuals of the same species that inhabit a certain territory for a sufficiently long time, freely interbreed with each other under natural conditions and produce fertile offspring.
The population size is unstable. Real populations vary in shape and number of individuals.
Population structure.
Spatial configuration;
Reproduction system;
Migration speed.
Depending on the spatial configuration, there are:
Large continuous populations (tens and hundreds of kilometers).
Small colonial populations (corresponding to the island type).
There are large ranges of values in the breeding system.
Autogamous populations - reproduce by self-fertilization.
Allogamous populations - reproduce by cross-fertilization.
In autogamous organisms, homozygous organisms predominate, the proportion of heterozygotes is small.
Allogamous populations are characteristic of all animals and some plants. The composition of alleles is determined by mutations and, for the most part, recombinations of genes. Because the offspring occurs due to crossing, the proportion of heterozygotes is large. The numbers of genotypes reach values characteristic of the Hardy–Weinberg law. Until evolutionary factors take effect, the relationships remain the same. Microevolution factors cause chromosomal aberrations, mutations and other changes - this is the main factor of evolution.
Factors of evolution.
Mutation process.
Gene flow.
Genetic drift.
Natural selection.
The mutation process and gene flow create variation. Genetic drift and natural selection sort it, work on it and determine its fate.
Mutation process. Each mutant allele first appears very rarely. If it is neutral, elimination occurs. If useful, it accumulates in the population.
Gene flow. A new gene can appear only as a result of mutation, but a population can receive it when a carrier of this gene immigrates from another population. Gene flow is the transfer of genes from one population to another. Gene flow can be considered a lagging effect of the evolutionary process. The carriers of gene flow are different.
Natural selection consists of different processes:
Driving (directed, progressive) selection - established by Charles Darwin.
Stabilizing.
Disruptive (tearing) Mauer.
Driving selection– directional selection, in which the population changes along with its environment. Occurs when the population gradually changes along with the environment.
Stabilizing selection– selection that occurs when the environment does not change, but the population is well adapted, extreme forms are eliminated, and the population grows.
Disruptive selection– selection in which middle forms are eliminated, and extreme variants are retained. Genetic polymorphism. The more polymorphic the population, the easier the process of speciation occurs.
Genetic drift. The implementation of the Hardy–Weinberg law is possible only in ideal populations. In small populations there are deviations from this distribution. Random changes in genotypes and allele frequencies during the transition from one generation to another generation - genetic drift, which is characteristic of a small population.
the population system consists of a number of isolated colonies;
the population is large, then declines and is restored again due to surviving individuals;
a large population gives rise to several colonies. The ancestral individuals form colonies.
Theory evolution organic peace
Abstract >> BiologyFormation of an idea evolution organic peace taxonomy played a significant role - biological science... in material germ cells structures, predetermining the development of the embryo and... population-genetic research, which was implemented his ...
Biological map peace
Abstract >> Biology... evolution organic peace taxonomy played a significant role - biological...material structures, ... species to the idea evolution, historical development species assumed, firstly, consideration of the process of education species V his ... population waves...
Theory evolution (4)
Cheat sheet >> BiologyPattern evolution organic peace. Theory... view and opportunities his further evolution. With the emergence of man as a social being biological factors
7.2.1. Evidence for the evolution of the organic world
Evidence of evolution - evidence of the common origin of all organisms from common ancestors, the variability of species and the emergence of some species from others
Evidence for evolution is divided into groups.
1. Cytological. All organisms (except viruses) are composed of cells that have a common structure and function.
2. Biochemical. All organisms are made of the same chemicals: proteins, nucleic acids, etc.
3. Comparative anatomical:
unity of structure of organisms within a type, class, genus, etc. For example, all representatives of the class of mammals are characterized by a highly developed cortex of the cerebral hemispheres of the forebrain, intrauterine development, feeding the young with milk, hair, a four-chambered heart and complete separation of arterial and venous blood, warm-bloodedness, lungs of an alveolar structure:
homologous organs are organs that have the same origin, regardless of the functions they perform. For example, limbs of vertebrates, modifications of roots, stems and leaves in plants;
rudiments - remnants of organs (characteristics) present in the ancestors. For example, a person has such rudiments as the coccyx, appendix, third eyelid, wisdom teeth, muscles that move the auricle, etc.;
atavisms - the sudden appearance in individual individuals of the organs (characters) of their ancestors. For example, the birth of people with a tail, thick body hair, extra nipples, highly developed fangs, etc.
4. Embryological evidence. These include: the similarity of gametogenesis, the presence of a single-cell stage in development - the zygote; similarity of embryos at early stages of development; connection between ontogeny and phylogeny.
The embryos of organisms of many systematic groups are similar to each other, and the closer the organisms are, the more until the later stage of development of the embryo this similarity is maintained (Fig. 7.8). Based on these observations, E. Haeckel and F. Müller formulated the biogenetic law - each individual in the early stages of ontogenesis repeats some of the basic structural features of its ancestors. Thus, ontogeny (individual development) is a brief repetition of phylogeny (evolutionary development).
6. Relic evidence. Currently, there are descendants of transitional forms (Fig. 7.11), for example, the lobe-finned fish coelacanth is a descendant of a transitional form between fish and amphibians, tuateria is a descendant of a transitional form between amphibians and reptiles; platypus - a descendant of a transitional form between reptiles and mammals
7. Biogeographical evidence. Similarities and differences between organisms living in different biogeographical zones. For example, marsupial mammals survive only in Australia.
7.2.2. Origin of life
Development of views on the origin of life. From ancient times to this day, humanity has been looking for an answer to the question of the origin of life on Earth. Previously it was believed that spontaneous generation of life from inanimate matter was possible. According to scientists of the Middle Ages, fish could be born from silt, worms from soil, mice from dirty rags, flies from rotten
meat. In the 17th century Italian scientist F. Redi conducted an original experiment: he placed pieces of meat in glass vessels, some of them he left open, and some he covered with muslin. Fly larvae appeared only in open vessels (Fig. 7.12). In the middle of the 19th century. French microbiologist L. Pasteur placed sterilized broth in a flask with a long, narrow B-shaped neck. Bacteria and other airborne organisms settled under the influence of gravity in the lower curved part of the neck and did not reach the broth, while air entered the flask itself (Fig. 7.13).
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These and other similar experiments convincingly proved that in the modern era living organisms descend only from other living organisms. The impossibility of spontaneous generation of life from non-living things was called the Redi principle. As a result, the question of the origin of the first living organisms is logical.
Diversity of approaches to the question of the origin of life. There is no consensus among scientists on the question of the origin of life, as well as on the question of the essence of life. There are several approaches to solving the question of the origin of life, which are closely intertwined. They can be classified as follows.
1) according to the principle that the idea, mind are primary, and matter is secondary (idealistic hypotheses) or matter is primary, and the idea, mind are secondary (materialistic hypotheses);
2) according to the principle that life has always existed and will exist forever (stationary state hypotheses) or life arises at a certain stage in the development of the world;
3) according to the principle that living things only come from living things (biogenesis hypotheses) or the spontaneous generation of living things from non-living things is possible (abiogenesis hypotheses)",
4) according to the principle that life originated on Earth or was brought from space (panspermia hypothesis).
Let's consider the most significant of the hypotheses.
Creationism. According to this hypothesis, life was created by a Creator. The Creator is God, Idea, Supreme Intelligence, etc.
Stationary state pshotosis. Life, like the Universe itself, has always existed and will exist forever, for what has no beginning has no end. At the same time, the existence of individual bodies and formations (stars, planets, organisms) is limited in time: they arise, are born and die. Currently, this hypothesis has mainly historical significance, since the “Big Bang theory” is generally accepted, according to which the Universe exists for a limited time; it formed from a single point about 15 billion years ago.
Photosis of panspermia. Life was brought to Earth from space and took root here after conditions favorable for this developed on Earth. This assumption was made by the German scientist G. Rihyur in 1865, and finally formulated by the Swedish scientist S. Arrhenius in 1895. Bacterial spores, which are largely resistant to radiation, vacuum, and low temperatures, could have reached the Earth with meteorites and cosmic dust. Solution of the issue about how life arose in space, due to objective difficulties, is postponed for an indefinite period. It could have been created by the Creator, existed forever, or arisen from inanimate matter. Recently, more and more supporters of the panspermia hypothesis have appeared among scientists.
Photic abiogenesis (spontaneous generation of living things from non-living things and subsequent biochemical evolution). In 1924, the Russian biochemist A.I. Oparin, and later in 1929, the English scientist J. Haldane, suggested that living things arose on Earth from inanimate matter as a result of chemical evolution - complex chemical transformations of molecules. This event was favored by the conditions prevailing on Earth at that time.
According to this hypothesis, four stages can be distinguished in the process of the formation of life on Earth -
1) synthesis of low molecular weight organic compounds from gases of the primary atmosphere;
2) polymerization of monomers to form chains of proteins and nucleic acids;
3) the formation of phase-separated systems of organic substances, separated from the external environment by membranes;
4) the emergence of simple cells with the properties of living things, including the reproductive apparatus that carries out transformation
giving daughter cells all the chemical and metabolic properties of parent cells.
The first three stages belong to the period of chemical evolution; from the fourth, biological evolution begins.
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Ideas about the possible chemical evolution of matter are confirmed by a number of model experiments. In 1953, the American chemist S. Miller and physicist G. Urey, in laboratory conditions, imitated the composition of the Earth’s primary atmosphere, consisting of methane, ammonia and water vapor, and, by exposing it to a spark discharge, they obtained simple organic substances - the amino acids glycine, alanine and etc. (Fig. 7.14). Thus, the fundamental possibility of abiogenic synthesis of organic compounds (but not living organisms) from inorganic substances was proven
Thus, organic substances could be created in the primordial ocean from simple inorganic compounds. As a result of the accumulation of organic substances in the ocean, the so-called “primary broth” was formed. Then, combining, proteins and other organic molecules formed droplets of coacervates, which served as a prototype
Cells Droplets of coacervates were subject to natural selection and evolved. The first organisms were heterotrophic. As the reserves of the “primary broth” were consumed, autotrophs arose.
It should be noted that from the point of view of probability theory, the probability of synthesizing highly complex biomolecules under the condition of random combinations of their constituent parts is extremely low.
IN AND. Vernadsky on the origin and essence of life and the biosphere. IN AND. Vernadsky outlined his views on the origin of life in the following theses.
1. There was no beginning of life in the cosmos that we observe, since there was no beginning of this cosmos. Life is eternal, since the cosmos is eternal, and has always been transmitted through biogenesis.
2. Life, eternally inherent in the Universe, appeared new on Earth, its embryos were constantly brought from outside, but took hold on Earth only when opportunities were favorable for this.
3. Life on Earth has always existed. The lifetime of a planet is only the lifetime of life on it. Life is geologically (planetarily) eternal. The age of the planet is indeterminable.
4. Life has never been something random, huddled in some separate oases. It was distributed everywhere and living matter always existed in the form of a biosphere.
5. The most ancient forms of life - crushers - are capable of performing all functions in the biosphere. This means that a biosphere consisting of only prokaryotes is possible. It is likely that she was like this in the past.
6. Living matter could not come from inert matter. There are no intermediate steps between these two states of matter. On the contrary, as a result of the influence of life, the evolution of the earth's crust occurred.
Thus, it must be recognized that to date, none of the existing hypotheses about the origin of life has direct evidence, and modern science does not have an unambiguous answer to the question of the origin of life.
7.2.3. A Brief History of the Development of the Organic World
The age of the Earth is about 4.6 billion years. Life on Earth originated in the ocean more than 3.5 billion years ago.
A brief history of the development of the organic world is given in Table. 7.2. Phylogeny of the main groups of organisms is shown in Fig. 7.15. The organic world of bygone eras is recreated in Fig. 7.16-7.21.
Geochronological scale and history of the development of living organisms
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| Era, age, million years | Climate and geological processes | Animal world | World of plants | The most important aromorphoses | |
| Mesozoic, 240 | Archeopteryx; ancient cartilaginous fish are dying out | gymnosperms | |||
| Triassic | Weakening of climatic zonality The beginning of continental movement | Amphibians, cephalopods, herbivores and predatory reptiles predominate; teleost fish, oviparous and marsupial mammals appear | Ancient gymnosperms predominate; modern gymnosperms appear, seed ferns die out | The appearance of a four-chambered heart; complete separation of arterial and venous blood flow, the appearance of warm-bloodedness, the appearance of mammary glands | |
| Paleozoic | Perm (Perm), 50± 10 | Sharp climate zonation, completion of mountain-building processes | Marine invertebrates and sharks dominate; reptiles and insects develop rapidly; animal-toothed and herbivorous reptiles appear; Stegocephalians and trilobites become extinct | Rich flora of seed and herbaceous ferns; ancient gymnosperms appear; tree-like horsetails, mosses and ferns are dying out | Pollen tube and seed formation |
| Carboniferous (Carbon), b5± 10 | Distribution of forest swamps. Evenly moist te- | Amphibians, mollusks, sharks, lungfishes dominate, and | Abundance of tree-like | The appearance of internal fertilization 1st |
| Era, age, million years | Period, duration, million years | Climate and geological processes | Animal world | World of plants | The most important aromorphoses |
| the warm climate is replaced by arid climate at the end of the period | Winged forms of insects, spiders, scorpions quickly develop, and the first reptiles appear; trilobites and stegocephals noticeably decrease | pteridophytes forming “coal forests”, seed ferns appear, lsilophytes disappear | the phenomenon of dense egg shells; keratinization of the skin | ||
| Devonian (Devonian). | Change of dry and rainy seasons, glaciation in the territory of modern South Africa and America | Armored shellfish, mollusks, trilobites, and corals predominate; cysteleres, lungfishes and ray-finned fishes, stegocephals appear | Rich flora and ophyte forces, mosses, ferns, and mushrooms appear | Dismemberment of the plant body into organs; transformation of fins into terrestrial limbs; appearance of air breathing organs | |
| Silurian | First dry, then humid climate, mountain building | Rich fauna of trilobites, mollusks, crustaceans, corals, armored fish appear, the first terrestrial invertebrates: centipedes, scorpions, wingless insects | Abundance of algae; plants come to land - PS or ophites appear | Differentiation of the plant body into tissues, division of the animal body into sections, formation of jaws and limb girdles in vertebrates |
| Era, age, million years | Period, duration, million years | Climate and geological processes | Animal world | World of plants | The most important aromorphoses |
| Paleozoic | Ordovician (Ordovician), \ 55± 10 | Cambrian) (Cambrian), I 80±20) | Glaciation gives way to a moderately humid, then dry climate. Most of the land is occupied by the sea, mountain building | Sponges, coelenterates, worms, echinoderms, and trilobites predominate; jawless vertebrates (scutellates), mollusks appear | Prosperity of all departments of algae | |
| Prothero | The surface of the planet is bare desert. Frequent glaciations, active formation of rocks | Protozoa are widespread; all types of invertebrates, echinoderms appear: primary chordates - subtype Cranial | Bacteria, blue-green and green algae are widespread; red algae appears | The emergence of bilateral symmetry | |
| Archeyskaya, 3 500 (3 800) | Active volcanic activity Anaerobic living conditions in shallow waters | The emergence of life, prokaryotes (bacteria, blue-green algae), eukaryotes (green algae, protozoa), primitive multicellular organisms | Emergence of photosynthesis, aerobic respiration, eukaryotic cells, sexual process, multicellularity™ | ||
The history of the development of life on Earth is studied from the fossil remains of organisms or traces of their vital activity. They are found in rocks of different ages.
The geochronological scale of the history of the development of the organic world of the Earth includes eras and periods (see Table 7.2). The following eras are distinguished: Archean (Archaean) - the era of ancient life, Proterozoic (Proterozoic) - the era of primary life, Paleozoic (Paleozoic) - the era of ancient life, Mesozoic (Mesozoic) - the era of middle life, Cenozoic (Cenozoic) - the era of new life. The names of the periods are formed either from the names of the places where the corresponding deposits were first found (the city of Perm, Devon County), or from the processes that took place at that time (during the Coal period - the Carboniferous - the laying of coal deposits took place, in the Cretaceous - chalk, etc. .).
Archean era (era of ancient life: 3500 (3800 2600 million years ago). The first living organisms on Earth appeared, according to various sources, 3.8-3.2 billion years ago. These were prokaryotic heterotrophic anaerobes (prenuclear, feeding on ready-made organic substances, not needing oxygen).They lived in the primary ocean and fed on organic substances dissolved in its water, created abiogenically from inorganic substances under the influence of the energy of ultraviolet rays of the Sun and lightning discharges.
The Earth's atmosphere consisted mainly of C0 2, CO, H 2, N7, water vapor, small amounts of N113, H 2 5, CH 4 and contained almost no free oxygen 0 2. The absence of free oxygen provided the opportunity for the accumulation of abiogenically created organic substances in the ocean, otherwise they would be immediately broken down by oxygen.
The first heterotrophs carried out the oxidation of organic substances anaerobically - without the participation of oxygen through fermentation. During fermentation, organic substances are not completely broken down, and little energy is produced. For this reason, evolution in the early stages of life was very slow.
Over time, heterotrophs multiplied greatly and they began to lack abiogenically created organic matter. Then prokaryotic autotrophic anaerobes arose. They could synthesize organic substances from inorganic ones on their own, first through chemosynthesis and then through photosynthesis.
The first was anaerobic photosynthesis, which was not accompanied by the release of oxygen:
6С0 2 + 12Н 2 5 -> С(,Н 12 0 6 + 125 + 6 Н,0
Then aerobic photosynthesis appeared:
6С0 2 + 6Н 2 0 -> СБН, 2 0 6 + 60,
Aerobic photosynthesis was characteristic of creatures similar to modern cyanobacteria.
Free oxygen released during photosynthesis began to oxidize divalent iron and sulfur and manganese compounds dissolved in ocean water. These substances turned into insoluble forms and settled on the ocean floor, where they formed deposits of iron, sulfur and manganese ores, which are currently used by people.
The oxidation of dissolved substances in the ocean occurred over hundreds of millions of years, and only when their reserves in the ocean were exhausted did oxygen begin to accumulate in the water and diffuse into the atmosphere.
It should be noted that a prerequisite for the accumulation of oxygen in the ocean and atmosphere was the burial of some of the organic matter synthesized by organisms at the bottom of the ocean. Otherwise, if all organic matter was broken down with the participation of oxygen, there would be no excess left and oxygen would not be able to accumulate. The undecomposed bodies of organisms settled on the ocean floor, where they formed deposits of fossil fuels - oil and gas.
The accumulation of free oxygen in the ocean made possible the emergence of autotrophic and heterotrophic aerobes. This happened when the concentration of 0 2 in the atmosphere reached 1% of the current level (and it is equal to 21 6C0 2 + 6H 2 0 + 38ATP.
Since aerobic processes began to release much more energy, the evolution of organisms accelerated significantly.
As a result of the symbiosis of various prokaryotic cells, the first eukaryotes (nuclear) appeared.
As a result of the evolution of eukaryotes, the sexual process arose - the exchange of genetic material between organisms - DNA. Thanks to the sexual process, evolution went even faster, since combinative variability was added to mutational variability.
At first, eukaryotes were unicellular, and then the first multicellular organisms appeared. The transition to multicellularity™ in plants, animals and fungi occurred independently of each other.
Multicellular organisms have received a number of advantages over unicellular ones:
1) a long duration of ontogenesis, since during the individual development of the organism some cells are replaced by others;
2) numerous offspring, since the organism can allocate more cells for reproduction;
3) significant size and varied body structure, which provides greater resistance to external environmental factors due to the stability of the internal environment of the body.
Scientists do not have a consensus on the issue of when the sexual process and multicellularity arose - in the Archean or Proterozoic era.
Proterozoic era (era of primary life: 2600-570 million years ago). The appearance of multicellular organisms further accelerated evolution, and in a relatively short period (on a geological time scale), various types of living organisms appeared, adapted to different living conditions. New forms of life occupied and formed ever new ecological niches in different areas and depths of the ocean. Rocks 580 million years old already contain imprints of creatures with hard skeletons, making it much easier to study evolution from this period. Hard skeletons serve as support for the bodies of organisms and help increase their size.
By the end of the Proterozoic era (570 million years ago), a producer-consumer system had developed and an oxygen-carbon biogeochemical cycle of substances had formed.
Paleozoic era (era of ancient life: 570-240 million years ago).
In the first period of the Paleozoic era - the Cambrian (570-505 million years ago) - a so-called “evolutionary explosion” occurred: in a short time, almost all currently known types of animals were formed. The entire evolutionary time preceding this period was called the Precambrian, or cryptozoic (“era of hidden life”) - this is 7/jj of the history of the Earth. The time after the Cambrian was called the Phanerozoan (“era of manifest life”).
As more and more oxygen was formed, the atmosphere gradually acquired oxidizing properties. When did the concentration of 0 2 in the atmosphere reach lOfS? from the modern level (at the Silurian-Devonian boundary), at an altitude of 20-25 km, the ozone layer began to form in the atmosphere. It was formed from 0 2 molecules under the influence of the energy of ultraviolet rays of the Sun:
o 2 + o -> o,
Ozone molecules (0 3) have the ability to reflect ultraviolet rays. As a result, the ozone screen became a protection for living organisms from harmful ultraviolet rays in large doses. Before this, the ox served as protection. Now life has the opportunity to emerge from the ocean onto land.
The emergence of living creatures on land began in the Cambrian period: bacteria were the first to reach it, and then fungi and lower plants. As a result, soil was formed on land and in the Silurian period (435-400 million years ago) the first vascular plants - psilophytes - appeared on land. Access to land contributed to the appearance of plant tissues (integumentary, conductive, mechanical, etc.) and organs (roots, stems, leaves). As a result, higher plants appeared. The first land animals were arthropods, descended from sea crustaceans.
At this time, chordates evolved in the marine environment: vertebrate fish evolved from invertebrate chordates, and in the Devonian, amphibians evolved from lobe-finned fish. They dominated the land for 75 million years and were represented by very large forms. During the Permian period, when the climate became colder and drier, reptiles gained superiority over amphibians.
Mesozoic era (era of middle life: 240-66 million years ago). In the Mesozoic era - the “era of dinosaurs”, reptiles reached their heyday (their numerous forms were formed) and decline. In the Triassic, crocodiles and turtles appeared, and the class Mammals arose from beast-toothed reptiles. Throughout the Mesozoic era, mammals were small and not widespread. At the end of the Cretaceous period, a cold snap occurred and a mass extinction of reptiles occurred, the final causes of which are not fully understood. Angiosperms (flowering plants) appeared in the Cretaceous period.
Cenozoic era (era of new life: 66 million years ago - present). In the Cenozoic era, mammals, birds, arthropods, and flowering plants became widespread. A man appeared.
Currently, human activity has become an important factor in the development of the biosphere.
Until the end of the 17th century. Most Europeans believed that everything in nature has remained unchanged since the day of creation, that all types of plants and animals today are the same as God created them. However, in the 18th century. New scientific data has cast doubt on this. People began to find evidence that plant and animal species change over long periods of time. This process is called evolution.
First theories of evolution
Jean-Baptiste de Monnet (1744-1829), Chevalier de Lamarck, was born in France. He was the eleventh child in an impoverished aristocratic family. Lamarck lived a difficult life, died a poor blind man, and his works were forgotten. At age 16, he joined the army, but soon resigned due to poor health. Need forced him to work in a bank instead of doing what he loved - medicine.
Royal Botanist
In his free time, Lamarck studied plants and acquired such extensive knowledge that in 1781 he was appointed chief botanist to the French king. Ten years later, after Lamarck was elected professor of zoology at the Natural History Museum in Paris. Here he gave lectures and organized exhibitions. Noticing the differences between fossils and modern animal species, Lamarck came to the conclusion that the types and characteristics of animals and plants are not constant, but, on the contrary, change from generation to generation. This conclusion was suggested to him not only by fossils, but also by geological evidence of changes in the landscape over many millions of years.
Lamarck came to the conclusion that throughout the life of an animal, the characteristics of an animal can change depending on external conditions. He proved that these changes are inherited. Thus, the giraffe's neck may have lengthened during its life due to the fact that it had to reach for tree leaves, and this change was passed on to its offspring. Nowadays, this theory is recognized as erroneous, although it was used in the theory of evolution of Darwin and Wallace that appeared 50 years later.
Expedition to South America
Charles Darwin (1809-1882) was born in Shrewsbury in England. He was the son of a doctor. After leaving school, Darwin went to study medicine at the University of Edinburgh, but soon became disillusioned with the subject and, at the insistence of his father, went to Cambridge University to prepare for the priesthood. And although the preparations were successful, Darwin was again disappointed in the career ahead of him. At the same time, he became interested in botany and entomology (the study of insects). In 1831, botany professor John Henslowe noticed Darwin's abilities and offered him a position as a naturalist on an expedition to South America. Before sailing, Darwin read the works of geologist Charles Lyell (see article “”). They amazed the young scientist and influenced his own views.
Darwin's discoveries
The expedition sailed on the Beagle and lasted 5 years. During this time, the researchers visited Brazil, Argentina, Chile, Peru and the Galapagos Islands - ten rocky islands off the coast of Ecuador in the Pacific Ocean, each of which has its own fauna. On this expedition, Darwin collected a huge collection of rock fossils, compiled herbariums and a collection of stuffed animals. He kept a detailed diary of the expedition and subsequently used many materials made on the Galapagos Islands when presenting his theory of evolution.
In October 1836, the Beagle returned to England. Darwin devoted the next 20 years to processing the collected materials. In 1858, he received a manuscript by Alfred Wallace (1823-1913) with ideas very close to him. And although both naturalists were co-authors, Darwin's role in putting forward the new theory was much more significant. In 1859, Darwin published On the Origin of Species by Means of Natural Selection, in which he outlined the theory of evolution. The book was a huge success and caused a lot of noise, as it contradicted traditional ideas about the origin of life on Earth. One of the boldest ideas was the assertion that evolution lasted many millions of years. This contradicted the teaching of the Bible that the world was created in 6 days and has not changed since then. Nowadays, most scientists use a modernized version of Darwin's theory to explain changes in living organisms. Some reject his theory for religious reasons.
Natural selection
Darwin discovered that organisms fight each other for food and habitat. He noticed that even within the same species there are individuals with special characteristics that increase their chances of survival. The offspring of such individuals inherits these characteristics, and they gradually become common. Individuals that do not have these characteristics die out. Thus, after many generations, the entire species acquires useful characteristics. This process is called natural selection. Let's look, for example, at how a moth adapted to changes in its environment. At first, all the moths were silver in color and were invisible on tree branches. But the trees darkened from the smoke - and the moths became more noticeable, the birds more actively ate them. The darker-colored moths survived. This dark coloring was passed on to their offspring and subsequently spread throughout the species.
The role of Charles Darwin's works in the creation of scientific evolutionary theory
By the middle of the 19th century. Objective conditions arose for the creation of a scientific evolutionary theory. They boil down to the following.
1. By this time, a lot of factual material had accumulated in biology proving the ability of organisms to change, and the first evolutionary theory was created.
2. All the most important geographical discoveries were made, as a result of which the most important representatives of the organic world were described in more or less detail; a wide variety of animal and plant species were discovered, and some intermediate forms of organisms were identified.
3. The rapid development of capitalism required the study of sources of raw materials (including biological) and sales markets, which intensified the development of biological research.
4. Great strides have been made in the selection of plants and animals, which has helped to identify the causes of variability and the consolidation of emerging traits in organisms.
5. Intensive mining made it possible to discover cemeteries of prehistoric animals, imprints of ancient plants and animals, which confirmed evolutionary ideas.
The founder of the scientific evolutionary theory was Charles Darwin (1809-1882). Its main provisions were published in 1859 in the book “The Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life.” Charles Darwin continued to work on the development of evolutionary theory and published the books “Change in Domestic Animals and Cultivated Plants” (1868) and “The Descent of Man and Sexual Selection” (1871). Evolutionary theory is constantly developing and being supplemented, but its foundations were outlined in the above-mentioned books.
The creation of Darwin's theory was facilitated by the situation that had developed in biology at the time the scientist began his scientific activity, the fact that he lived in the most developed (at that time) capitalist country - England, and the opportunity to travel (Charles Darwin traveled around the world on the Beagle ship) , as well as the personal qualities of the scientist.
When developing the scientific evolutionary theory, Charles Darwin created his own definition of “species” and put forward new principles for systematizing the organic world, which consisted in finding related (genetic) connections that arose due to the same origin of the entire organic world; gave a definition of evolution as the ability of species to slowly, gradually develop in the process of their historical existence. He correctly revealed the cause of evolution, which consists in the manifestation of hereditary variability, and also correctly revealed the factors (driving forces) of evolution, including natural selection and the struggle for existence, through which natural selection is realized.
The theory of evolution of the organic world, developed in the works of Charles Darwin, was the foundation for the creation of a modern synthetic evolutionary theory.
The synthetic theory of evolution of the organic world is a set of scientifically based provisions and principles that explain the emergence of the modern organic world of the Earth. When developing this theory, the results of research in the field of genetics, breeding, molecular biology and other biological sciences obtained in the second half of the 19th century and throughout the 20th century were used.
Carl Linnaeus and the role of his work in the development of evolutionary theory
Man has always been interested in where such a wonderful world of animals and plants came from, whether it has always been the same as it is now, whether organisms existing in nature change. Through the eyes of one generation, it is difficult, and sometimes impossible, to detect significant changes in the surrounding world, so a person initially formed the idea of the immutability of the surrounding world, especially the world of animals (fauna) and plants (flora).
Ideas about the immutability of the organic world are called metaphysical, and people (including scientists) who share these views are called metaphysicians.
The most ardent metaphysicians who believe that all living things are created by God and do not change from the day of creation are called creationists, and the pseudo-teaching about the divine creation of living things and its immutability is called creationism. This is an extremely reactionary doctrine, it slows down the development of science, interferes with normal human activity both in the development of civilization and in ordinary life.
Creationism was widespread in the Middle Ages, but even today believers and church leaders adhere to this teaching, however, even now the church recognizes the changeability of living things and believes that only the soul was created by God.
As knowledge about nature accumulated and knowledge was systematized, it was revealed that the world is changeable, and this subsequently led to the creation and development of evolutionary theory.
An outstanding biologist, who was a metaphysician and creationist, but whose work paved the way for the development of evolutionary theory, was the Swedish naturalist Carl Linnaeus (1707-1778).
C. Linnaeus created the most perfect artificial system of the organic world. It was artificial because Linnaeus based it on characteristics that often did not reflect the relationship between organisms (which was impossible at that time due to incomplete knowledge about organisms). Thus, he classified lilac and fragrant spikelet (plants of completely different classes and families) into one group because both of these plants have two stamens (fragrant spikelet belongs to the class of monocotyledons, the family of cereals, and lilac - to the class of dicotyledons, the family of Olives) .
The system proposed by K. Linnaeus was practical and convenient. It used binary nomenclature, which was introduced by Linnaeus and which is still used today because of its rationality. In this system, the highest taxon was a class. Plants were divided into 24 classes, and animals into six. The scientific feat of C. Linnaeus was the inclusion of man in the kingdom of Animals, which during the undivided dominance of religion was far from safe for the scientist. The significance of K. Linnaeus’ system for the further development of biology is as follows:
1) it created the basis for scientific systematization, since it was clearly visible that there is an interconnection and family relationships between organizations;
2) this system set the task of clarifying the reasons for the similarity between organisms, which was an incentive to study the underlying features of similarity and explain the reasons for such similarity.
Towards the end of his life, C. Linnaeus abandoned the idea of the immutability of species, since the system of the organic world he proposed did not fit into the framework of metaphysical and creationist ideas.
General characteristics of the evolutionary theory developed by J. B. Lamarck
At the end of the 18th - beginning of the 19th centuries. The idea of the variability of the organic world is increasingly conquering the minds of scientists. The first evolutionary theories appear.
Evolution is the gradual long-term development of the organic world, accompanied by its change and the emergence of new forms of organisms.
The first, more or less substantiated evolutionary theory was created by the French naturalist Jean Baptiste Lamarck (1744-1829). He was a prominent representative of transformism. Transformists were also J. Buffon (France), Erasmus Darwin - the grandfather of Charles Darwin (England), J. V. Goethe (Germany), C. F. Roulier (Russia).
Transformism is the doctrine of the variability of species of various organisms, including animals, plants and humans.
J. B. Lamarck outlined the foundations of his theory of evolution in the book “Philosophy of Zoology”. The essence of this theory is that organisms change in the process of historical existence. Changes in plants occur under the direct influence of environmental conditions; animals are affected indirectly by these conditions.
The reason for the appearance of new forms of organisms (especially animals) is the body’s internal desire for perfection, and the resulting changes are consolidated due to the exercise or lack of exercise of the organs. The changes that occur are inherited by the body when exposed to successive conditions that caused these changes, if these conditions last for several generations.
The central tenet of Lamarck's evolutionary theory is the idea of the types of organisms, their gradation and the desire of the species to move from a lower level (gradation) to a higher one (hence the desire for perfection).
An example illustrating the exercise of organs is the stretching of the neck of a giraffe to get food, which leads to its lengthening. If a giraffe does not stretch its neck, it will become shorter.
The factors of evolution (according to Lamarck) are:
1) adaptation to environmental conditions, due to which various changes occur in organisms;
2) inheritance of acquired characteristics.
The driving forces of evolution (according to Lamarck) consist in the desire of organisms to improve.
The main achievement of Lamarck's theory was that for the first time an attempt was made to prove the presence of evolution in the organic world in the process of historical existence, but the scientist was unable to correctly reveal the causes and driving forces of evolution (at that stage of the development of scientific thought this was impossible due to the lack of scientific ).
Similar views on the development of the organic world were expressed by Moscow University professor K. F. Roulier. In his theoretical positions, he went further than J.B. Lamarck, since he denied the idea of organisms striving for improvement. But he published his theory later than Lamarck and was unable to create an evolutionary theory in the form in which Charles Darwin developed it.
General characteristics of evidence for the evolution of the organic world
The study of organisms over a long historical period of human development has shown that organisms underwent changes and were in a state of constant development, that is, they evolved. There are four groups of evidence for the evolutionary theory: cytological, paleontological, comparative anatomical and embryological. In this subsection we will consider this evidence in general form.
General characteristics of cytological evidence of the evolution of organisms
The essence of cytological evidence is that almost all organisms (except viruses) have a cellular structure. Animal and plant cells are characterized by a general structural plan and organelles that are common in form and function (cytoplasm, endoplasmic reticulum, cell center, etc.). However, plant cells differ from animal cells in different ways of nutrition and different adaptability to the environment compared to animals.
Cells have the same chemical and elemental composition, regardless of their belonging to any organism, having specificity associated with the characteristics of the organism.
The existence in nature of an intermediate type of unicellular organisms - flagellates, which combine the characteristics of plant and animal organisms (they, like plants, are capable of photosynthesis, and like animals, they are capable of a heterotrophic mode of nutrition), indicates the unity of origin of animals and plants.
Review of embryological evidence for evolution
It is known that in individual development (ontogenesis) all organisms go through the stage of embryonic (intrauterine - for viviparous organisms) development. The study of the embryonic period of different organisms shows the common origin of all multicellular organisms and their ability to evolve.
The first embryological evidence is that the development of all (both animal and plant) organisms begins with one cell - the zygote.
The second most important evidence is the biogenetic law discovered by F. Muller and E. Haeckel, supplemented by A. N. Severtsov, A. O. Kovalevsky and I. I. Shmalhausen. This law states: “In the embryonic development of ontogenesis, organisms go through the main embryonic stages of the phylogenetic (historical) development of the species.” Thus, individual individuals of a species, regardless of the level of its organization, go through the stage of zygote, morula, blastula, gastrula, three germ layers, and organogenesis; Moreover, both fish and humans have a larval fish-like stage and the human embryo has gills and gill slits (this applies to animals).
The clarification of the biogenetic law by Russian scientists refers to the fact that organisms go through the main stages of phylogenetic development, repeating the stages characteristic of the embryonic period of development, and not for the adult states of organisms.
Comparative anatomical evidence of evolution
This evidence relates to the evolution of animals and is based on information obtained from comparative anatomy.
Comparative anatomy is a science that studies the internal structure of various organisms in comparison with each other (this science is of greatest importance for animals and humans).
As a result of studying the structural features of chordates, it was discovered that these organisms have bilateral (bilateral) symmetry. They have a musculoskeletal system that has a single structural plan, common to all (compare the human skeleton and the skeleton of a lizard or frog). This indicates the common origin of humans, reptiles and amphibians.
Different organisms have homologous and similar organs.
Homologous are organs that are characterized by a general structural plan and unity of origin, but they may have a different structure due to the performance of different functions.
Examples of homologous organs are the pectoral fin of a fish, the forelimb of a frog, the wing of a bird, and the human hand.
Analogous are those organs that have approximately the same structure (external shape) due to the performance of similar functions, but have a different structural plan and different origin.
Similar organs include the burrowing limb of a mole and mole cricket (an insect that leads an underground lifestyle), the wing of a bird and the wing of a butterfly, etc.
Comparative anatomical evidence also includes the presence of rudiments and atavisms in organisms.
Rudiments are residual organs that are not used by these organisms. Examples of rudiments are the appendix (the blind process of the intestine), coccygeal vertebrae, etc. Rudiments are the remains of those organs that were once necessary, but at this stage of phylogenesis have lost their importance.
Atavisms are signs that were previously inherent and characteristic of a given organism, but at this stage of evolution have lost their meaning for most individuals, but manifested themselves in this particular individual in its ontogenesis. Atavisms include tailedness in some people, human polymastia (multi-nipple), and excessive development of hair. Superstitious people attach some religious meaning to tails and increased hair development; they consider such people to be close to the devil, and in the Middle Ages they were even burned at the stake.
Paleontological evidence of evolution
Paleontology is the science of the organic world of past geological eras, that is, of organisms that once lived on Earth and are now extinct. Paleontology includes paleozoology and paleobotany.
Paleozoology studies the remains of fossil animals, and paleobotany studies the remains of fossil plants.
Paleontology directly proves that the organic world of the Earth was different in different geological eras, it changed and developed from primitive forms of organisms to more highly organized forms.
Paleontological research makes it possible to establish the history of the development of different forms of organisms on Earth, to identify related (genetic) connections between individual organisms, which contributes to the creation of a natural system of the organic world of the Earth.
In conclusion, we can conclude that the briefly discussed phenomena prove that the organic world of the Earth is in a state of constant slow gradual development, i.e. evolution, while development has proceeded and continues to progress from simple to complex.
The role of heredity and variability in the evolution of the organic world
The most important factors in evolution are variability and heredity. The role of heredity in evolution is the transmission of traits, including those that arose in ontogenesis, from parents to descendants.
The variability of organisms leads to the emergence of individuals that have different levels of differences from each other. Is every change that occurs during ontogenesis inherited? Probably not. Modification changes that do not affect the genome are not inherited. Their role in evolution is that such changes allow the organism to survive in complex, sometimes extreme environmental conditions. Thus, small leaves help reduce transpiration (evaporation), which allows the plant to survive in conditions of lack of moisture.
A major role in the processes of evolution is played by hereditary (mutational) variability affecting the genome of gametes. In this case, the resulting changes are passed on from parents to descendants, and the new trait is either fixed in the offspring (if it is useful to the organism), or the organism dies if this trait worsens its adaptability to the environment.
Thus, hereditary variability “creates” material for natural selection, and heredity consolidates the changes that have arisen and leads to their accumulation.
Concept of evolutionism 1. The concept of "evolution". 2. Basic postulates of the concept of evolution of the organic world. 3. Principles of global evolutionism.
The concept of “evolution” 1. Evolutionary theory is now not considered as a single description of an unambiguous path of development, which is fully understood by science; rather, evolutionism in modern science is a spectrum of concepts that are substantiated to varying degrees. 2. Evolution implies universal gradual development, orderly and consistent.
The concept of “evolution” By the second half of the 18th century, objective prerequisites had developed for the emergence of scientifically based evolutionist views: descriptions of many new species as a result of geographical discoveries; the unity of the structural plan of many previously known groups of organisms was established; the emergence of a special biological discipline - paleontology; the emergence of scientifically based theories of the origin of the Earth and the solar system
The concept of "evolution". At the turn of the 18th and 19th centuries, revealing the patterns of historical development of the flora and fauna became a priority task.
Basic postulates of the concept of evolution of the organic world. French biologist Jean-Baptiste Lamarck (1744 – 1829) hypothesized the mechanism of evolution. He published his views, now considered the essence of Lamarckism, in Philosophy of Zoology in 1809. The implementation of the principle of gradation, according to Lamarck, becomes possible due to the presence in organisms of an internal desire for improvement.
Basic postulates of the concept of evolution of the organic world. The main generalization of Lamarck's views are two provisions that entered the history of science under the name "Lamarck's laws." 1. In all animals that have not reached the limit of their development, organs and organ systems that have been subjected to prolonged intensive exercise gradually increase in size and become more complex, while those not exercised become simpler and disappear. 2. Traits and properties acquired as a result of long-term and stable exposure to the external environment are inherited and preserved in the offspring, provided they are present in both parent organisms.
Basic postulates of the concept of evolution of the organic world. Lamarck's concept represented the first complete system of evolutionary views and at the same time the first attempt to substantiate these views. Lamarck, in general, correctly characterized evolution as a progressive process moving in the direction of increasing the complexity of the structure of organisms. Lamarck's views on the adaptive nature of the evolutionary process were advanced for his time. Lamarck's concept contained a number of erroneous provisions: 1. explanation of the evolutionary process as the result of an internal desire for improvement. 2. assumption of the possibility of the emergence of heritable adaptive traits in response to environmental influences. 3. denial of the reality of the species.
Basic postulates of the concept of evolution of the organic world. The theory of evolution by Charles Darwin (English Charles Robert Darwin;) is considered one of the main scientific revolutions, since in addition to its purely scientific significance, it led to a revision of a wide range of ideological, ethical, and social problems.
Basic postulates of the concept of evolution of the organic world. Charles Darwin's theory of evolution has several scientific components. 1. The idea of evolution as a reality, which means defining life as a dynamic structure of the natural world, and not a static system. 2. As a result of excess fertility, competition for habitat and food arises between organisms in nature - the “struggle for existence.” It is customary to distinguish three forms: fight against factors of non-biological (abiotic) origin, interspecific and intraspecific fight.
Basic postulates of the concept of evolution of the organic world. Due to the presence of variability, different individuals in the process of struggle for existence find themselves in an unequal position. Individual changes that facilitate survival provide their carriers with an advantage, as a result of which individuals more adapted to the given conditions more often survive and produce offspring, while the weakest are more likely to die or are eliminated from crossing. Darwin called this phenomenon natural selection.
Basic postulates of the concept of evolution of the organic world. The adaptive nature of evolution is achieved by selecting from many random changes those that facilitate survival in given, specific environmental conditions. The adaptability of organisms is, as a rule, relative.
Basic postulates of the concept of evolution of the organic world. Darwin derived the idea that species arose through natural selection based on five basic postulates: 1. All species have the biological potential to increase the number of individuals to large populations. 2. Populations in nature demonstrate relative constancy in the number of individuals over time. 3. The resources necessary for the existence of species are limited, so the number of individuals in populations is approximately constant over time. Conclusion 1. Between representatives of the same species there is a struggle for resources necessary for survival and reproduction. Only a small portion of individuals survive and produce offspring.
Basic postulates of the concept of evolution of the organic world. 4. There are no two individuals of the same species that would have the same properties. Members of the same species exhibit greater variability. 5. Most variability is determined genetically and is therefore inherited. Conclusion 2. Competition between representatives of the same species depends on the unique hereditary properties of individuals, which provide advantages in the struggle for resources for survival and reproduction. This unequal ability to survive is natural selection. Conclusion 3. The accumulation of more favorable properties as a result of natural selection leads to constant change in species. This is how evolution happens.
Evidence for the Evolutionary Concept Evidence supporting modern ideas about evolution comes from a variety of sources. Some of the events cited as evidence for evolutionary theory can be reproduced in the laboratory, however, this does not mean that they actually occurred in the past, they simply indicate the possibility of such events.
Evidence for an evolutionary concept. Taxonomy Natural classification can be phylogenetic or phenotypic. Phylogenetic classification is used more often because it reflects evolutionary relationships based on the origin of organisms and their inheritance of certain characteristics. Similarities and differences between organisms can be explained as the result of progressive adaptation of organisms within each taxonomic group to certain environmental conditions over a period of time.
Evidence for an evolutionary concept. The taxonomy uses the following basic hierarchical units: Kingdom; Type (division in plants); Class; Order (order in plants); Family; Genus; View. Each taxon may contain several lower-ranking taxonomic units. But at the same time, a taxon can belong to only one taxon located directly above it. There may be several taxa at each hierarchical level, but they are all distinct from each other.
Evidence for an evolutionary concept. Comparative anatomy The presence of homologous and rudimentary organs is considered as evidence of the origin of animals from a common ancestor. The nictitating membrane is a “rudiment” of humans.
The concept of catastrophism The hypotheses of catastrophists can be divided into two main groups. 1. Earthly catastrophism: disasters are associated with geological processes (the revival of volcanism leading to global cooling and the release of large volumes of toxic substances into the atmosphere, mountain-building processes associated with climate change).
concept of catastrophism 2. Cosmic catastrophism: disasters have a cosmic origin: a catastrophic increase in radiation caused by a supernova explosion; fluctuations in solar activity; b bombardment of the Earth by comets and giant asteroids, associated with fluctuations in the position of the Solar system relative to the plane of the galaxy; the passage of a large celestial body through the comet cloud surrounding the Solar System.
The concept of catastrophism In 1980, the American physicist, Nobel Prize laureate L. Alvarez and his son geologist W. Alvarez suggested that the iridium anomaly was a consequence of the impact of a large asteroid on the Earth, the substance of which was scattered across the entire earth's surface. Which led to a complete short-term suspension of photosynthesis and the massive death of green plants, and after the green plants the death of herbivores, animals, and then predators.
The concept of catastrophism None of the catastrophic models explains the meaning of the processes that took place on Earth during critical epochs, but rather raise new questions. Psychological factors (the novelty of the idea of asteroids) play a large role in the spread of alternative, anti-Darwinian concepts of evolution.
The relationship between micro- and macroevolution. Microevolution is a set of evolutionary processes occurring in populations of a species and leading to changes in the gene pool of these populations and the formation of new species. Macroevolution is evolutionary transformations leading to the formation of taxa of a higher rank than the species.
The evolution of the organic world of the Earth is inextricably linked with the evolution of the lithosphere. The history of the development of the Earth's lithosphere is divided into geological eras: Katarchean, Archean, Proterozoic, Paleozoic, Mesozoic, Cenozoic. Each era is divided into periods and epochs. Geological eras, periods and epochs correspond to certain stages in the development of life on Earth.
Katarchean, Archean and Proterozoic are combined into cryptozoic- “the era of hidden life.” Fossil remains of the Cryptozoic are represented by individual fragments that are not always identifiable. Paleozoic, Mesozoic and Cenozoic are combined into Phanerozoic- “the era of obvious life.” The beginning of the Phanerozoic is characterized by the appearance of skeletal-forming animals that are well preserved in fossil form: foraminifera, shell mollusks, and ancient arthropods.
Early stages of development of the organic world
In conditions of excess of ready-made organic substances, the heterotrophic (saprotrophic) method of nutrition is primary. B O Most of the archaebionts specialized specifically in heterotrophic saprotrophic nutrition. They develop complex enzyme systems. This led to an increase in the volume of genetic information, the appearance of a nuclear membrane, various intracellular membranes and organelles of movement. Some heterotrophs undergo a transition from saprotrophic supply to holozoic. Subsequently, histone proteins appeared, which made possible the appearance of real chromosomes and perfect methods of cell division: mitosis and meiosis. Thus, there is a transition from prokaryotic type of cell organization To eukaryotic.
Another part of the archaebionts specialized in autotrophic nutrition. The oldest method of autotrophic nutrition is chemosynthesis. Based on enzyme-transport systems of chemosynthesis, it arises photosynthesis– a set of metabolic processes based on the absorption of light energy with the help of various photosynthetic pigments (bacteriochlorophyll, chlorophylls a, b, c, d and others). The excess of carbohydrates formed during CO 2 fixation made it possible to synthesize a variety of polysaccharides.
All of the listed characters in heterotrophs and autotrophs are large aromorphoses.
Probably, in the early stages of the evolution of the organic world of the Earth, the exchange of genes between completely different organisms (gene transfer through transduction, interspecific hybridization and intracellular symbiosis) was widespread. During synthesis, the properties of heterotrophic and photoautotrophic organisms were combined in one cell. This led to the formation of various divisions of algae - the first true plants.
Main stages of plant evolution
Algae are a large heterogeneous group of primary aquatic photoautotrophic organisms. In the fossil state, algae have been known since the Precambrian (over 570 million years ago), and in the Proterozoic and early Mesozoic all the currently known divisions already existed. None of the modern divisions of algae can be considered the ancestor of another division, which indicates mesh character evolution of algae.
At the end of the Silurian (≈ 400 million years ago) Higher(ground) plants.
In the Silurian, the ocean shallowed and water desalinated. This created the prerequisites for the settlement of the littoral and supralittoral zones ( littoral– part of the coast that is flooded during high tides; the littoral zone occupies an intermediate position between aquatic and terrestrial-air habitats; supralittoral– part of the coast above the tide level, moistened by spray; in essence, the supralittoral is part of the terrestrial-air habitat).
The oxygen content in the atmosphere before the appearance of land plants was significantly lower than today: Proterozoic - 0.001 from the modern level, Cambrian - 0.01, Silurian - 0.1. When there is a deficiency of oxygen, the limiting factor in the atmosphere is ultraviolet radiation. The emergence of plants onto land was accompanied by the development of the metabolism of phenolic compounds (tannins, flavonoids, anthocyanins), which are involved in protective reactions, including those against mutagenic factors (ultraviolet, ionizing radiation, some chemicals).
The movement of plants onto land is associated with the appearance of a number of aromorphoses:
1) The appearance of differentiated tissues: integumentary, conductive, mechanical, photosynthetic. The appearance of differentiated tissues is inextricably linked with the appearance of meristems and main parenchyma.
2) The appearance of differentiated organs: shoot (organ of carbon nutrition) and root (organ of mineral nutrition).
3) Multicellular gametangia appear: antheridia and archegonia.
4) Significant changes occur in metabolism.
The ancestors of Higher plants are considered to be organisms similar to modern Characeae algae. The oldest known land plant is Cooksonia. Cooksonia was discovered in 1937 (W. Lang) in the Silurian sandstones of Scotland (age about 415 million years). This plant was an algae-like bush of twigs bearing sporangia. Attached to the substrate using rhizoids.
The further evolution of higher plants was divided into two lines: gametophytic and sporophytic
Representatives of the gametophytic line are modern Bryophytes. This avascular plants, which lack specialized conductive and mechanical tissues.
Another line of evolution led to the appearance vascular plants, in which the sporophyte dominates in the life cycle, and all the tissues of higher plants are present (educational, integumentary, conductive, main parenchyma and its derivatives). Thanks to the appearance of all types of tissues, the plant body differentiates into roots and shoots. The oldest vascular plants are now extinct Rhineaceae(psilophytes). During the Devonian, modern groups formed spore plants(Mosses, Horsetails, Ferns). However, in spore plants missing seed, and the sporophyte develops from an undifferentiated embryo.
At the beginning of the Mesozoic (≈ 220 million years ago), the first Gymnosperms, which dominated the Mesozoic era. The largest aromorphoses of Gymnosperms:
1) Appearance ovules; The female gametophyte (endosperm) develops in the ovule.
2) Appearance pollen grains; In most species, the pollen grain, when germinated, forms a pollen tube, forming a male gametophyte.
3) Appearance seed, which includes a differentiated embryo.
However, gymnosperms retain a number of primitive characteristics: the ovules are located openly on the seed scales (megasporangiophores), pollination occurs only with the help of the wind (anemophily), the endosperm is haploid (female gametophyte), primitive conducting tissues (xylem includes tracheids).
First Angiosperms(Flowering)plants probably appeared in the Jurassic period, and in the Cretaceous period they began adaptive radiation. Currently, angiosperms are in a state of biological progress, which is facilitated by a number of aromorphoses:
1)Appearance pestle– closed carpel with ovules.
2) Appearance perianth, which made possible the transition to entomophily (pollination by insects).
3) Appearance embryo sac And double fertilization.
Currently, angiosperms are represented by many life forms: trees, shrubs, vines, annual and perennial grasses, and aquatic plants. The structure of the flower achieves particular diversity, which contributes to the accuracy of pollination and ensures intensive speciation - about 250 thousand plant species belong to Angiosperms.
Main stages of animal evolution
Eukaryotic organisms specializing in heterotrophic nutrition gave rise to Animals And Mushrooms.
All known types arise in the Proterozoic era Multicellular invertebrate animals. There are two main theories about the origin of multicellular animals. According to theory gastrea(E. Haeckel), the initial method of forming a two-layer embryo is invagination (invagination of the wall of the blastula). According to theory phagocytella(I.I. Mechnikov), the initial method of formation of a two-layer embryo is immigration (movement of individual blastomeres into the cavity of the blastula). Perhaps these two theories complement each other.
Coelenterates- representatives of the most primitive (two-layer) multicellular organisms: their body consists of only two layers of cells: ectoderm and endoderm. The level of tissue differentiation is very low.
In the Lower Worms ( Flat And Roundworms) the third germ layer appears - the mesoderm. This is a major aromorphosis, due to which differentiated tissues and organ systems appear.
Then the evolutionary tree of animals branches into Protostomes and Deuterostomes. Among the Protostomes Annelids a secondary body cavity is formed ( in general). This is a major aromorphosis, thanks to which it becomes possible to divide the body into sections.
Annelids have primitive limbs (parapodia) and homonomic (equivalent) body segmentation. But at the beginning of the Cambrian they appear Arthropods, in which parapodia are transformed into articulated limbs. In Arthropods, heteronomous (unequal) segmentation of the body appears. They have a chitinous exoskeleton, which contributes to the appearance of differentiated muscle bundles. The listed features of Arthropods are aromorphoses.
The most primitive arthropods are Trilobitiformes- dominated the Paleozoic seas. Modern Gill-breathing primary aquatic arthropods are represented Crustaceans. However, at the beginning of the Devonian (after plants reached land and the formation of terrestrial ecosystems), landfall occurred Arachnids And Insects.
Arachnids came to land thanks to numerous allomorphoses (idioadaptations):
1) Impermeability of covers to water.
2) Loss of larval stages of development (with the exception of ticks, but the nymph of ticks is not fundamentally different from adult animals).
3) Formation of a compact, weakly dissected body.
4) Formation of respiratory and excretory organs corresponding to new living conditions.
Insects are most adapted to life on land, thanks to the appearance of large aromorphoses:
1) The presence of germinal membranes - serous and amniotic.
2) The presence of wings.
3) Plasticity of the oral apparatus.
With the appearance of flowering plants in the Cretaceous period, the joint evolution of Insects and Flowering plants begins ( coevolution), and they form joint adaptations ( co-adaptation). In the Cenozoic era, insects, like flowering plants, are in a state of biological progress.
Among Deuterostome animals, the highest flourishing is achieved by Chordates, in which a number of large aromorphoses appear: notochord, neural tube, abdominal aorta (and then the heart).
The origin of the notochord has not yet been precisely established. It is known that strands of vacuolated cells are present in lower invertebrates. For example, in the eyelash worm Coelogynopora the branch of the intestine, located above the nerve ganglia at the anterior end of the body, consists of vacuolated cells, so that an elastic rod appears inside the body, which helps to dig into the sandy soil. In the North American eyelash worm Nematoplana nigrocapitula in addition to the described foregut, the entire dorsal side of the intestine is transformed into a cord consisting of vacuolated cells. This organ was called the intestinal chord (chordaintestinalis). It is possible that the dorsal chord (chordadorsalis) of endomesodermal origin arose directly from the vacuolated cells of the dorsal side of the intestine.
From primitive Chordates the first occur in Silurian Vertebrates(Jawless). In vertebrates, the axial and visceral skeleton is formed, in particular, the braincase and jaw region of the skull, which is also an aromorphosis. Inferior Ghostostomes vertebrates are represented by a variety Pisces. Modern classes of fish (Cartilaginous and Bony) were formed at the end of the Paleozoic - beginning of the Mesozoic).
Some of the Bony fishes (Fleshy-lobed fishes), thanks to two aromorphoses - pulmonary respiration and the appearance of true limbs - gave rise to the first Four-legged–Amphibians(Amphibians). The first amphibians came onto land in the Devonian period, but their heyday occurred in the Carboniferous period (numerous stegocephali). Modern amphibians appear at the end of the Jurassic period.
In parallel, among the Quadrupeds, organisms with embryonic membranes appear - Amniotes. The presence of embryonic membranes is a large aromorphosis that first appears in Reptiles. Thanks to the embryonic membranes, as well as a number of other features (keratinizing epithelium, pelvic buds, appearance of the cerebral cortex), Reptiles have completely lost their dependence on water. The appearance of the first primitive reptiles - cotylosaurs- dates back to the end of the Carboniferous period. In the Permian, various groups of reptiles appeared: beast-toothed, proto-lizards and others. At the beginning of the Mesozoic, branches of turtles, plesiosaurs, and ichthyosaurs were formed. Reptiles begin to flourish.
Two branches of evolutionary development are separated from groups close to the proto-lizards. One branch at the beginning of the Mesozoic gave rise to a large group pseudosuchian. Pseudosuchia gave rise to several groups: crocodiles, pterosaurs, ancestors of birds and dinosaurs, represented by two branches: lizards (Brontosaurus, Diplodocus) and ornithischians (only herbivorous species - Stegosaurus, Triceratops). The second branch at the beginning of the Cretaceous period led to the emergence of a subclass scaly(lizards, chameleons and snakes).
However, Reptiles could not lose their dependence on low temperatures: warm-bloodedness is impossible for them due to incomplete separation of the blood circulation. At the end of the Mesozoic, with climate change, a mass extinction of reptiles occurred.
Only in some pseudosuchians in the Jurassic period does a complete septum between the ventricles appear, the left aortic arch is reduced, a complete separation of the circulatory circles occurs, and warm-bloodedness becomes possible. Subsequently, these animals acquired a number of adaptations to flight and gave rise to the class Birds.
In the Jurassic deposits of the Mesozoic era (≈ 150 million years ago), prints of the First Birds were discovered: Archeopteryx and Archaeornis (three skeletons and one feather). They were probably arboreal climbing animals that could glide but were not capable of active flight. Even earlier (at the end of the Triassic, ≈ 225 million years ago) protoavis existed (two skeletons were discovered in 1986 in Texas). The skeleton of Protoavis was significantly different from the skeleton of reptiles; the cerebral hemispheres and cerebellum were increased in size. During the Cretaceous period, there were two groups of fossil birds: Ichthyornis and Hesperornis. Modern groups of birds appear only at the beginning of the Cenozoic era.
A significant aromorphosis in the evolution of birds can be considered the appearance of a four-chambered heart in combination with a reduction of the left aortic arch. There was a complete separation of arterial and venous blood, which made possible further development of the brain and a sharp increase in the level of metabolism. The flourishing of Birds in the Cenozoic era is associated with a number of major idioadaptations (the appearance of feathers, specialization of the musculoskeletal system, development of the nervous system, caring for offspring and the ability to fly), as well as with a number of signs of partial degeneration (for example, loss of teeth).
At the beginning of the Mesozoic era, the first Mammals, which arose due to a number of aromorphoses: enlarged forebrain hemispheres with a developed cortex, a four-chambered heart, reduction of the right aortic arch, transformation of the suspension, quadrate and articular bones into auditory ossicles, the appearance of fur, mammary glands, differentiated teeth in the alveoli, pre-oral cavity. The ancestors of Mammals were primitive Permian Reptiles, which retained a number of characteristics of Amphibians (for example, skin glands were well developed).
In the Jurassic period of the Mesozoic era, Mammals were represented by at least five classes (Multitubercles, Tritubercles, Tricodonts, Symmetrodonts, Panthotheriums). One of these classes probably gave rise to the modern Protobeasts, and the other to the Marsupials and Placentals. Placental mammals, thanks to the appearance of the placenta and true viviparity, enter a state of biological progress in the Cenozoic era.
The original order of Placentals are Insectivores. Early on, the Insectivores were separated from the Incomplete Teeth, Rodents, Primates and the now extinct group of Creodonts - primitive predators. Two branches separated from the Creodonts. One of these branches gave rise to modern Carnivores, from which Pinnipeds and Cetaceans separated. Another branch gave rise to primitive ungulates (Condylarthra), and then to the Odd-toed, Artiodactyl and related orders.
The final differentiation of modern groups of Mammals was completed during the era of great glaciations - in the Pleistocene. The modern species composition of Mammals is significantly influenced by the anthropogenic factor. In historical times, the following species were exterminated: aurochs, Steller's cow, tarpan and other species.
At the end of the Cenozoic era, some Primates A special type of aromorphosis occurs - overdevelopment of the cerebral cortex. As a result, a completely new species of organisms arises - Homo sapiens.
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Plants |
Animals |
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cryptozoic |
Archean |
Restored atmosphere, primordial ocean, high pressure and temperature |
Prokaryotic biosphere, chemo and photosynthesis, fertilization, appearance of eukaryotes at the border with the Proterozoic |
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Proterozoic |
2.6 billion-650 million |
Eukaryotes, cellular, tissues, 2 layers |
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Phanerozoic |
Paleozoic |
Dry climate of the sea |
60% trilobites, skeleton, all types of animals. |
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Mountain and seas |
Cephalopods, brachiopods flowering mollusks |
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Arthropods, jawless vertebrates |
Plants came to land - rhiniophytes |
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Amphibians and fish |
spores |
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warming |
reptiles | |||||
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Cooling, ice age | ||||||
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Triassic |
Pangea split |
Milks and birds | ||||
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Continental split |
The appearance of placentals | |||||
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Ice Age, continental breakup |
extinction |
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