§38. The main methods of plant and animal breeding. Classification of garden plants
Introduction
1. The concept of the variety and breed
2. Centers of diversity and origin of cultivated plants
3. The concept of growth and development
4. Age periods of growth and development
Fruit tree
Conclusion
References
Introduction
Fruit growing is a branch of agriculture whose cultural objects are perennial plantsforming edible fruits.
Of the more than a thousand varieties of bananas in the world - with different colors and sizes - about half of world production, and almost all the varieties that are sold correspond to the numerous descendants of the same variety, the Cavendish, a typical dessert or a sweet banana.
The other half is “cooking bananas”, whose high content of complex carbohydrates makes them cook as if they were potatoes or similar vegetables: cooked, fried, fried, baked, etc. In the “first world,” a banana is a very popular fruit, given its properties and its ease for its consumption; however, in some countries they are vital for population accumulation.
The value of fruit growing in human life is great. Fruits are great foods. They contain, in easily digestible forms, many sugars, organic acids. The composition of fruits and berries include proteins, fats, mineral salts, tannic, pectin, aromatic and other substances.
Fruits are rich in biologically active compounds, primarily vitamins. They contain vitamins A, B1, B2, B6, C, PP and others.
Did you know that tropical and subtropical regions make up 85% of banana consumption and are staple food for at least 400 million people? The largest exporters of bananas in the world are Ecuador, Colombia, Costa Rica, Guatemala and the Philippines. In Europe, the main producers are the Canary Islands, which mainly supply the rest of Spain and are trying to find a place in other countries where competition with the American banana is greater.
Banana, banana and its wanderings. Although it may not seem like this, banana trees are not trees or shrubs, they are herbs, but gigantic. In fact, its leaves are among the largest plants in the world. Banana trees belong to the musk family, and among their relatives there are species that are used as a food source or plant fiber, and even as ornamental plants.
The minimum total human need for fruits and berries at medical standards is 100 kg per year.
Great therapeutic value of the fruit. Biologically active substances can have a direct therapeutic effect on the human body.
The systematic use of fruit helps to prevent diseases such as cardiovascular (atherosclerosis, hypertension, hypotension), blood diseases, hypo-and avitaminosis, gastrointestinal (gastritis, peptic ulcer), as well as infectious diseases (dysentery).
To determine the exact origin of the banana, which we eat regularly, was not easy. It is clear that one of the most important Tataratatapatepulos, a wild banana tree, is native to the islands of Southeast Asia. Living on the islands, there were different populations of wild banana trees scattered and isolated from each other.
Each population accumulated genetic changes that eventually led to the emergence of “subspecies” or even different species. In this plant orgy, extended in time, banana plants were connected to each other, sometimes bringing their chromosomes generously, cloning was the order of the day and dressed with mutations. The first settlers of these islands, moving from one to another in search of better life, took their banana bananas in their luggage. These banana trees found their distant cousins there and could not escape the temptation to mate.
The importance of fruit in the processing industry. Of them prepare a variety of wines, jams, compotes, jams, jellies, marmalades, syrups, dried fruits and other products.
Fruit crops play an essential role in the ecological system. Large arrays of industrial plantations, a significant number of fruit plants in home gardens help to improve the atmosphere, reduce wind strength, and have an aesthetic effect on people. Many fruit crops are good honey plants.
Just as when you cross animals that resemble each other, but different species, such as a horse and a donkey, you get a hybrid, a mule, which is a new person with intermediate characteristics, but sterile. You have the first answer: hybrid banana trees produce unviable seeds or do not directly produce them.
A curious consequence of hybridization was an increase in chromosomes, the appearance of a banana with three sets of chromosomes instead of two. In many species with chromosomes, most often there are big inconveniences, but it seems that banana trees come to them big and more vigorous plants appear with large fruits. Another tasty fruit with more chromosomes.
1. The concept of the variety and breed
An outstanding domestic geneticist and breeder, academician N.I. Vavilov, determining the content and tasks of modern breeding, indicated that for successful work on the creation of varieties and breeds, it is necessary to study and take into account: the initial variety and species diversity of plants and animals, hereditary variability , the role of the environment in the development and manifestation of the traits studied, the patterns of inheritance during hybridization, the forms of artificial selection, aimed at isolating and securing the desired traits.
Worse, parthenocarpy was attached to a plant orgy. This is another process that is not very often found in nature, which consists in the formation of fruits, without which the flower was fertilized. While this may seem a bit silly, the fact is that the banana worked perfectly to communicate with the person. She gives him a sweet, seedless fruit that is very easy to eat, and he is responsible for planting him along the tropical borders of the land.
Finally, we have cloning — the process by which, without resorting to sex, copies identical to an already developed organism is a resource that many living things use to reproduce, and the result becomes more or less the same as Dolly sheep, a clone .
What is the grade or breed.
Breed of animals or plant variety is called such a collection of individuals (population), artificially created by man, which is characterized by certain hereditary features: productivity, morphological, physiological signs.
Each breed or variety is characterized by a specific reaction to the environment. The positive qualities of the breed and variety are most fully manifested only under certain conditions of detention, feeding, agricultural technology, and when there is a complex of certain climatic factors. Therefore, rocks and varieties bred in one country are not always suitable for another soil-climatic zone.
Banana trees in concrete produce side shoots or shoots at the base of the stems, clonic versions of the mother plant, which will grow and grow until they replace their progenitor. Since banana fruits are unable to produce offspring because they do not have seeds, farmers use both side shoots and root pieces to produce new banana trees.
In principle, a clone is an individual, identical to its parents, because it has the same genes. However, the cloned equivalent is not always 100% identical. Sometimes called "somatic mutations", which are found only in the cells responsible for the formation of lateral shoots. These cells have some genes that have been altered due to mutation and therefore develop mutant shoots with small differences in relation to their predecessors.
In all countries there is an extensive system of scientific and scientific-practical institutions: institutions, breeding stations, breeding farms, which systematically engage in this complex work on a national scale. To check the newly created plant varieties in our country there is a large network of variety testing sites.
To compensate for sterility by hybridization and parthenocarpy, somatic mutations were the only source of genetic variation for the development of new banana varieties with different properties and properties. For example, “Cavendish” by means of somatic mutations gave rise to many subvarieties: “Lakatan”, “Robusta”, “Giant Cavendish”, “Gnome Cavendish” and others.
Mushrooms against banana trees: a struggle that repeats. By that time, one variety, Gros Michel, was dominant in many banana groves of the world. This plague was called the evil of Panama, and Gros Michel did not protect it. Banana banana bananas, which are clones, were equally susceptible to disease and eventually fell on the fungus. The damage to the banana industry and the trade was huge, farmers and producers had to choose: forget bananas or look for a “savior”. It would be logical to grow more varieties and not throw everything at the letter, but the laws of the market and distribution prevailed.
2. Centers of diversity and origin of cultivated plants
The more diverse the source material used for breeding, the more opportunities it gives for the successful creation of varieties and the more effective the results of breeding will be. But where in nature to search for this diversity.
N.I. Vavilov and his colleagues as a result of numerous expeditions studied the diversity and geographical distribution of cultivated plants. Expeditions covered the entire territory of the former Soviet Union and many foreign countries: Iran, Afghanistan, the Mediterranean countries, Ethiopia, Central Asia, Japan, Northern, Central and South America, etc.
And the fact is that on the market of one variety you can achieve greater profitability in harvest, packaging and transport, in addition, by offering a more uniform product. Scientists have discovered that the famous Cavendish is not protected from the fungus, but at least if it is able to stop its feet, highlighting a kind of gelatin, which traps the fungus and prevents its spread.
Did you know that 95% of all bananas sold in the world belong to the Cavendish variety? The problem is that history repeats itself. This time with another protagonist of fungi, Black Sigatoka, against which Cavendish has nothing to do. And again the same problem: thousands and thousands of hectares of banana trees, all the same, and none of them can find a new way to get rid of the new fungus.
During these trips about 1600 species of cultivated plants were studied. From the expeditions thousands of seed samples were brought, which were sown in the nurseries of the All-Union Institute of Plant Industry, located in different geographical areas of the former USSR. Work on the study of the world diversity of cultivated plants continues at the present time. These most valuable, constantly replenished unique collections serve as material for selection work.
Adopting another variety of bananas that are resistant to this new disease would mean the need to reorganize the entire banana processing infrastructure from scratch, which is a serious and unthinkable measure for its value. Thus, until a solution is found, fumigation is used from time to time with products that appear to affect the health of banana workers.
In the fight with the clock, to curb the progression of the fungus and avoid overuse of fungicides, scientists are looking for new varieties that have resistant genes for this new fungus. Benefits of Canary Bananas. The last question was required, and the answer is answered. The use of both names and the differences between them are as complex as the plant’s own origin. Descendants of the Cavendish variety grew on the Canary Islands: “Giant Cavendish”, “Gnome Cavendish” and a new race born on an archipelago called “Cargo Palmer” and others.
As a result of studying all this colossal material N.I. Vavilov established important regularities, showing that not all geographical areas cultivated plants have the same diversity.
For different cultures, there are centers of diversity where the largest number of varieties, varieties, and various hereditary deviations are concentrated. These centers of diversity are also the areas of origin of varieties of a given culture. Most centers coincide with the ancient foci of agriculture. These are mostly not flat, but mountainous areas.
This particular new variety arose thanks to the somatic mutation of the “Gnome Cavendish”, and now it belongs to our islands. The climate of the Canary Islands is more variable than in other tropical areas where bananas are grown. This requires the banana to stay longer on the plant in order to ripen well compared to the banana. Since the vast majority of bananas leave for the peninsula, that is, in a few days on the boat of the end consumer, this allows it to ripen longer in the banana tree, which helps it to reach a higher degree of maturity, flavor and aroma than the banana.
Such centers of diversity N.I. Vavilov counted first 8. In later works, he distinguishes 7 main centers.
1. South Asian Tropical Center. Tropical India, Indochina, South China, the islands of Southeast Asia. Exceptionally rich in cultivated plants (about half of the known species of cultivated plants). Homeland of rice, sugarcane, many fruit and vegetable plants.
Another advantage is the lack of pests and diseases affecting banana plantations in the Canary Islands, compared with tropical crops. Pikudo does its job, but it is treated with a complex struggle, because care for the environment is a priority.
Add that the salary and social conditions of farmers in the Canary Islands are better than the salary among bananas. Did you know that Canary Plantain's distinctive black pints are because they are especially sensitive to shocks? They appear only in mature fruits and appear during transport, with any minimal impact or friction activating the enzymes responsible for frying. Fortunately, they do not affect the quality of fruit at all.
2. East Asian Center. Central and Eastern China, Japan, the island of Taiwan, Korea. Homeland of soybean, several types of millet, a variety of fruit and vegetable crops. This center is also rich in species of cultivated plants - about 20% of the world's diversity.
3. South-West Asian Center. Asia Minor, Central Asia, Iran, Afghanistan, North-West India. Homeland of several forms of wheat, rye, many grains, legumes, grapes, fruit. It produced 14% of the world's cultural flora.
Determine the variety of avocados before planting. There are differences!
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Origin of different varieties
The first classification is carried out by the behavior of colors. The flowers open in two well-differentiated periods, making the alternating functionality of the female and male organs depending on the period.In both cases, the female organ becomes functional in the first hole. Although there is disagreement regarding the classification of races or avocado varieties, it more or less generalizes the classification into 3 types. Mexican breed Mexican breed Guatemala. . Each of these varieties has a number of well-defined agronomic characteristics, which are listed in the following table.
4. Mediterranean Center. Srany, located on the shores of the Mediterranean Sea. This center, where the greatest ancient civilizations were located, gave about 11% of species of cultivated plants. Among them are olives, many fodder plants (clover, lentils), many vegetable (cabbage) and fodder crops.
5. Abyssinian center. A small area of the African continent (the territory of Ethiopia) with a very peculiar flora of cultivated plants. Obviously, a very ancient center of original agricultural culture. Homeland grain sorghum, one type of banana, chickpea oilseed plant, a number of special forms of wheat and barley.
Avocado varieties cultivated in Spain
With this classification, depending on climatic and soil characteristics, we can determine the most suitable option for us. The most limiting is cold resistance, and then resistance to salinity and chlorosis. This is one of the varieties of avocados in our country and almost the most common in the world. Usually we usually buy. From skin cream and dark green, which becomes almost black when it reaches a state of maturation.
His cellulose has a very good quality and slightly fibrous, with a touch of nutty flavor. Being a Guatemalan race, its tolerance for cold is not very strong. The reason why this variety has become the most consumed and cultivated is its wide collection period, its quality and taste, the use of cellulose and great resistance in the tree and after collection.
6. Central American Center. South Mexico. Homeland of corn, cotton, cocoa, a number of pumpkin, beans.
7. Andean (South American) Center. It includes part of the Andean mountain range along the west coast of South America. The homeland of many tubers, including potatoes, some medicinal plants (coca bush, quinine tree, etc.).
Thus, in animal breeding, self-fertilization and vegetative reproduction are not used. Breeding animals is always associated with the selection of breeding producers for the desired human characteristics. In the selection of individuals for crossing, their genotype by pedigree is necessarily taken into account, in which all signs of producers' ancestors are noted that are of interest to the breeder. The number of individuals in the offspring of animals is small, so each hybrid individual is of great value for identifying new traits and properties. It is also important to take into account the totality of the external forms of the animal - its exterior, because many signs, such as productivity (milkiness, fleshiness), are associated with a particular body structure. This circumstance makes it necessary in the selection of animals to pay special attention to the correlation (interrelated) relationship between individual traits, that is, to take into account the linked inheritance of traits.
AT poultry breeders are trying to identify and consolidate sex-linked traits, which are already manifested in day-old chicks. It is very important to select future ones at a very early age. laying hens
and extinguish from them cockerels for growing on the tribe or for fattening for meat. Therefore, to identify the sex of chickens, a gene of slow feathering is used - chickens acquire a feather more quickly than cocks, and this is already noticeable in the first days after hatching. In egg poultry farming, floor-linked feathering is often used.
AT hybridization of animals is especially widely used two types of
chivaniya: closely related (inbreeding) and unrelated (outbreeding). Inbreeding (from the English .in - "inside" and breeding- "breeding") - crossing
individuals with common ancestors. The common origin, relationship of crossed organisms increase the likelihood of the presence of the same alleles of any genes. This leads to an increase in the number of homozygous organisms, which is important for the preservation of traits that are valuable from an economic point of view.
Outbreeding (eng. Out - "out") - crossing of unrelated individuals of the same species. Unrelatedness implies the absence of common ancestors in the next 4-6 generations. Outbreeding is contrasted with inbreeding, since, due to the unrelated nature of individuals, when crossed, the likelihood of the presence of different alleles of certain genes increases. Outbreeding is used to increase or maintain a certain degree of heterozygosity of individuals.
Modern methods of animal breeding. AT in recent years, animal breeding has been enriched with new methods for improving breeds.
1. In the method of crossing began to applyartificial insemination.
2. When breeding farm animals and fish farming, the increase in offspring of valuable animal producers is achieved by creating the conditions for the simultaneous maturation of several eggs. Ovules are removed after fertilization and transplanted to adoptive mothers of less valuable breeds or to less productive female individuals of the same breed.
3. Currently, breeding methods are being actively implemented.cloning - growing organisms from a single cell.
4. With the help of mutagens, mutations that cause male sterility (used later in breeding programs) are obtained, or chromosomes are labeled (marked) with recessive lethal genes, which makes it possible to control the preservation of the offspring of one desired sex.
For example, gamma-induced chromosome rearrangements have been successfully used in silkworm breeding. It is known that cocoons of males of this silkworm are 25-30% more productive
cocoons of females (the length of the thread, the integrity of the cocoon, the layiness of the thread in the cocoon, etc.). Therefore, silkworms tend to feed and breed mainly males. Males treated with gamma rays when crossed with any healthy female of silkworm ensure the death of all female offspring and the preservation of male. Males of some insect pests of agricultural crops and forest plants are processed in the same way for biological control.
Modern methods of practical breeding, based on the knowledge of genetics, pushed the limits of the possibilities of creating new, necessary to man signs and properties in domestic animals.
1. Why do livestock farms keep strict records of descendants for a number of generations?
2 *. Why do animal domestication centers coincide with centers of origin of cultivated plants?
3. Replace the highlighted words in each statement with one term.
The transformation of wild animals into domestic animals through taming, housing and breeding led to the development of animal husbandry as a branch of agriculture.
Inbreeding of individuals with common ancestors is widely used in hybridization of animals.
4. Complete the statement.
To increase or maintain a certain degree
heterozygosity of individuals in animal breeding is used ...
§ 31 The main directions of the selection of microorganisms
Microorganisms (microbes) - bacteria, microscopic fungi and protozoa - play an important role in the life of nature and man. They are used in various areas of industry (in bakery and winemaking, in the production of feed protein, lactic acid products, antibiotics, vitamins, hormones, amino acids, enzymes), in agriculture (in the production of silage), for biological plant protection and wastewater treatment. In this regard, industrial microbiology is being developed and intensive selection work is underway to develop new strains of microorganisms with increased productivity of substances needed by man.
Microorganisms are characterized by hereditary variability - mutations. Through the selection of mutations, active strains of microorganisms that are valuable to humans are created. Artificial (induced) mutagenesis is used especially extensively and successfully in the creation of new strains.
By treating mold fungi with actinomycetes with mutagens, various antibiotics are used in medicine to save lives in a wide variety of diseases. Artificial mutagenesis has provided the creation of a number of highly productive strains of microorganisms that produce vitamins (for example, vitamins B2, B12), proteins and amino acids are much more efficient than their original forms do.
Mutational selection of microorganisms played a large role in the development of the microbiological industry. Industrially, on the basis of mass cultivation of lower fungi and bacteria, when producing producer strains, protein-vitamin concentrates, antibiotics, vitamins, hormones, amino acids and other biologically active substances are produced.
Methods of selection of microorganisms.Basically, these are the same methods that are used in the breeding of other organisms. But the microscopic size and enormous speed of reproduction of microorganisms determine the development
special methods that accelerate the process of obtaining new highly productive strains.
Genetic Engineeringis a targeted manipulation of genetic material in the cells of microorganisms - a set of methods of influencing DNA, allowing to transfer hereditary information from one organism to another. In particular, new combinations of genetic material are being created that can multiply in a host cell to synthesize substances that a person uses for his or her needs. New combinations of genetic material are first carried out in vitro, i.e. in vitro. By hybridization of DNA molecules from different unicellular organisms, molecules are obtained that contain new genes that were previously absent in it. The hybrid DNA molecule created in this way is then introduced into
a host cell (usually bacteria or yeast), which, after administration, begins to synthesize the protein encoded by these genes. Since bacteria multiply very quickly, in this way it is possible to obtain many identical copies at once from the desired gene and, therefore, by means of biosynthesis, to create many substances that a person needs.
One of the methods of genetic engineering, which has developed in our time, is the creation of hybrid (recombinant) DNA. For this, the DNA of one organism is introduced into the cells of another organism. For example, genes of higher organisms are introduced into bacterial cells. First, the gene to be transferred is introduced into the circular DNA molecule and spliced with it. Then this hybrid DNA is placed in a bacterial cell, where it behaves the same way as a chromosome. A new gene in the hybrid DNA before cell division is replicated (doubled) along with bacterial DNA, and the bacterium itself is able to produce a protein encoded by its new DNA (Fig. 44).
In this way, insulin protein is obtained, which is necessary for patients with diabetes; interferon, which suppresses the multiplication of viruses; Hepatitis virus antigen, necessary to combat this infectious disease; human growth hormones and other important biological substances.
Many of these therapeutic agents used to receive only one, very laborious way - by extracting (drawing) from human cells. But in the mid-80s. XX century. by means of genetic engineering, it was possible to introduce into the bacterial cells three human genes responsible for the synthesis of interferon. This made it possible to adjust its industrial production, to produce in sufficient quantities and to sell at an affordable price. Similar manipulations were made with other genes that control the synthesis of biologically valuable substances necessary for humans.
Cell Engineering -this method of constructing cells of a new type by hybridization of their contents. During hybridization, whole cells of different organisms are artificially combined, creating a new hybrid genome (a set of genes in the haploid set of species chromosomes). Also, by manipulation (reconstruction), a new viable cell is created from separate fragments of different cells (nucleus, cytoplasm, chromosomes, etc.) by transplanting nuclei, by fusing protoplasts (i.e., the entire cell contents without a nucleus and cell wall) of different types of cells.
Cellular engineering allows to combine in one cage hereditary materials of very distant species, even belonging to different kingdoms.
The use of living cells and biological processes for the production of substances necessary for a person is called biotechnology (from the Greek bios - “life”, techne- “skill” and logos - “teaching”).
Genetic and cellular engineering are two areas of biotechnology. They are of practical importance in the microbiological industry for the synthesis of biologically active substances needed by man.
The selection of microorganisms is important for solving many problems of the microbiological industry, as well as for medicine, the production of medicines, the agricultural industry, for the development of methods and means for cleaning the environment from pollution.
1. What methods are used in the selection of microorganisms?
2. What is the difference between genetic engineering and cellular engineering?
3 *. Compare breeding methods for plant hybrids
and microorganisms.
4. What is the value of biotechnology in the national economy?
Breeding is the science and practice of creating new breeds, varieties and strains of organisms. The theoretical basis of breeding is genetics. In the selection found the practical embodiment of the laws of heredity and variability of organisms.
All cultivated plants and pets come from wild ancestors. The domestication of plants and animals began on Earth in the centers of origin of cultural species that coincide with the centers of the development of civilization. The study of the centers of origin of cultivated species was created by the Russian scientist N.I. Vavilov.
The domestication of plants and animals took place by artificial selection, initially unconscious, but later people began to apply selection to improve the qualities of cultivated plants and domestic animals. The main methods in breeding cultivated species of plants and animals are artificial selection, mutagenesis, hybridization and polyploidy.
In recent years, microbial selection has begun to actively develop. It is conducted by the same basic methods of selection, but the ability of microorganisms to multiply very quickly allowed them to widely introduce in their selection methods of genetic and cellular engineering, representing a new direction in industrial production - biotechnology. Biotechnology using
advances in biology, genetics, ecology, microbiology, molecular biology, biochemistry, immunology, are widely developed nowadays in all countries.
Check yourself
1. What is called grade, breed, strain?
2. What features are characteristic of heterotic organisms?
3. What is the relationship between artificial selection and selection?
4. What role in the national economy does the selection of microorganisms
5. What are the main methods of breeding.
6. What are the known varieties of fruit or vegetable plants, breeds
animals.
Issues for discussion
1. Describe the positive and negative sides of inbreeding in animals.
2. Why is male sterility helpful in breeding some crops?
3. Expand the role of spontaneous and artificial mutations in the selection of a) plants; b) animals; c) microorganisms.
4. Why, out of a wide variety of animal species on Earth, has man selected very few species for domestication?
Basic concepts
Selection. Center of origin. Artificial selection. Hybridization Crossing. Mutagenesis. Polyploidy. Heterosis. Genetic Engineering. Cell Engineering. Biotechnology.
Chapter 6 The Origin of Life and the Development of the Organic World
Having studied the chapter, you will be able to:
to characterize modern ideas about the origin of life
and its development;
name the two main stages of the origin and development of life;
explain the conditions that ensured the emergence of life on the ancient
describe the stages of the formation of the first organisms on Earth.
§ 32 Concepts of the emergence of life on Earth in the history of science
The problems of the origin and development of life on Earth are central to natural science, have long attracted the attention of all philosophers and naturalists and cause controversy and controversy.
When discussing the question of the origin of life, scientists put forward many hypotheses that still require reliable evidence, despite the persuasiveness of the arguments. Most of the assumptions on which these hypotheses are based are speculative. After all, the history of the Earth did not preserve material evidence of the appearance of the first organisms of our planet. It is impossible to reproduce experimentally those very old (most ancient) processes in modern conditions, since the Earth itself, its general appearance and condition, its atmosphere and living conditions on it have changed.
All the variety of points of view on the origin of life on Earth is reduced to two main mutually exclusive hypotheses: biogenesis and abiogenesis.
Supporters of biogenesis (from the Greek bios - "life" and genesis - "origin", "occurrence") argue that all life comes only from the living, while supporters of biogenesis (Greek - a particle of negation) consider possible the origin of the living from the nonliving.
The idea of abiogenesis (the birth of organisms from inanimate nature) was actively developed by the philosophers of ancient Greece: Empedocles, Democritus (V century BC), and especially
Aristotle (IV century. BC. E.). This idea was also widely spread in ancient China, Babylon and Egypt.
Empedocles claimed that the first living creatures arose from the four elements of matter: fire, air, water and earth.
Democritus is flat that living creatures, such as fish, can spontaneously arise out of silt and water with the participation of fire. He considered life itself as a consequence of the mechanical forces of nature: bodies are formed from the union of many atoms, and the disintegration of atoms leads to their death. In the process of the vortex motion of atoms, a multitude of both separate bodies and worlds appear, which arise and are destroyed naturally.
Aristotle also believed that some plants and animals can spawn from nonliving matter. This occurs in cases where there is a kind of “active principle” in the non-living material. It is just like energy that, under favorable conditions, can lead to the emergence of living matter from inanimate matter. For example, from a piece of rotting meat under the influence of this "active principle" can
worms originate, and from worms - flies. Here is another statement of his: "The living can arise not only as a result of mating animals, but also from the decomposition of the soil." The ideas of Aristotle on the spontaneous generation of life retained power over the minds of many prominent scientists for a very long time, until the XIX century. For example, in the XVI century. the famous physician Paracelsus tried to empirically prove the spontaneous generation of frogs, mice, turtles, eels from water, air, straw, rotting wood and other non-living objects. Even J. B. Lamarck already in the XIX century. wrote about the spontaneous generation of some mushrooms.
Theories of spontaneous generation of life from inanimate matter began to be questioned only in the 17th century. Italian biologist and physician Francesco Redi in the middle of the XVII century. made a discovery that marked the beginning of biogenesis research. Redy suggested and confirmed it by a series of experiments that the living does not arise spontaneously, but appears from living organisms.
F. Redi conducted such experiments. In the vessels put pieces of meat of various animals. Some vessels are tightly sealed so that the air does not have access to pieces of meat. Other vessels left open. After some time, “worms” (the larvae of flies) appeared in the open banks, but they were not in the blocked ones. In his work “Experiments on the birth of insects” in 1668, he, summarizing his observations, suggested that the “worms” appeared as a result of the sexual reproduction of flies in rotting meat, and the most rotten meat has no other function than to serve as food for flies and be the place of laying their eggs.
However, one or two series of experiments was not enough to refute ideas about the spontaneous generation of the living, for there were too many phenomena in nature that scientists of that time could not explain. Wonderful seemed the very emergence from the soil of plants, animals or fungi, where they were not there before. How this happens is unclear. After all, the science of those times did not have a microscope, did not know many of the processes and patterns of development of organisms, which in our days are known even to younger students.
A few years after the experiments of F. Redi, the Dutchman A. van Leeuwenhoek, using a microscope, discovered the previously invisible world of living nature: the simplest and bacteria, whose existence was not even suspected. But this did not destroy the idea of the spontaneous generation of life. Only in the late 70s. XIX century. experiments, brilliantly posed by the great French biologist L. Pasteur, have been able to prove that “inanimate matter”, such as meat, is easily infected by living - omnipresent bacteria, eggs, flies, mold fungi and other microorganisms. In his experiments, Pasteur used flasks with a long, curved neck. This neck freely passed air into the flask, but served as a trap for dust particles and microorganisms. Bacteria could penetrate the flask and cause decomposition of the broth in it only when the neck in the flask was broken off (Fig. 45). The experiments of L. Pasteur proved the inconsistency of the position
abiogenesis, adopting the idea of biogenesis.
However, the recognition of biogenesis has caused a series of new questions: how and when did life arise on Earth? What were the first creatures of our planet? Where did they come from? In search of the answer to the first and main question - “How did life originate on our Earth?” - the following main hypotheses were formed:
1. Life on our planet is brought from outside, from the universe -panspermia theory(from the Greek .pan - "all" and superma- "seed").
2. Life on Earth has always existed, but it has undergone various cataclysms -stationary theory.
3. Life originated on Earth as a result of biochemical processes in a still very young planet. This modern hypothesis is calledtheory of biochemical evolution.
Discussion and criticism of various theories of biogenesis led to the development, on the one hand, of modern scientific ideas about the evolution of the organic world, and on the other, the teachings on the origin of life (the theory of biochemical evolution) on Earth, convincingly revealing the conditions for the origin of life on planet Earth.
§ 33 Modern ideas about the origin of life on Earth
In 1924, the domestic biochemist scientist A.I. Oparin published the work "The Origin of Life", forcing the whole world to take a fresh look at the question of the origin of life on Earth.
According to the hypothesis put forward by Oparin, life originated on Earth, and not introduced from space.
In his work, Oparin emphasized that the first precursors of organisms (protobionts) in a series of chemical and physical processes (stage chemical evolution)occurred over a long time in the conditions of a young planet, acquired the properties of organisms. After that, the stage of the struggle for existence and the selection of living beings began in accordance with the laws revealed by C. Darwin (stage
biological evolution).
Great merit A.I. Oparin is the creation of a theory evolution of living matter.Its main ideas are: life originally originated in the World Ocean as a result of chemical evolution (i.e. abiogenically);
the development of living matter and the emergence of a large variety of life forms occurred in the process of biological evolution (that is, biogenically), which became the second, which began after chemical evolution, the most important stage in the development of life in the history of the Earth. Further A.I. Oparin repeatedly clarified and deepened his ideas, backing them up with new research materials.
A similar opinion from Oparinsky in 1929 was expressed by the English scientist J. Haldane. In the late 50s. XX century. it was developed by the English physicist J. Bernal, who believed that the accumulation of organic molecules occurred through the crystallization of the first polymer molecules on mineral particles. Domestic botanist and microbiologist NG Cold believed that initially there were not proteins, but hydrocarbons, and life did not originate in the World Ocean, but in shallow waters after the formation of land. There were other hypotheses, but they all do not contradict each other in the main, but only show the possibility of different ways for the emergence of primary organisms on our planet.
Which same conditions were on earth inthe time when the first organisms arose? According to modern scientific data, the Earth was formed approximately 4.5-7
billion years ago from the accumulation of gases and cold (frozen) dust particles, consisting of metals and other chemical elements that surround the emerging young star - the Sun. Initially, the Earth was gaseous and cold, but as the dust clouds compressed, under the influence of gravity and under the influence of heat from the decay of radioactive elements, its bowels were thickened, warmed and melted. At the same time, the gases buried inside the planet emitted out and formed the primary gas atmosphere of the forming Earth.
The primary atmosphere in its composition was very different from the modern one: a significant amount of hydrogen was present in it, there were water molecules (in the form of steam), carbon dioxide, methane and ammonia. There was no free oxygen in the earth's atmosphere. The formed Earth had a sufficiently large mass, which allowed it to keep gases in its environment. At the same time, it was at such a distance from the Sun that the amount of energy received was enough to keep the water in a liquid state.
AT as a result of warming up, the Earth became very hot, and the water, evaporating from its surface, formed an accumulation of thick clouds of vapor that enveloped the young planet. Water vapor, cooled at altitudes, turned into liquid and fell on the hot surface of the Earth in the form of showers. Such showers have been going on for thousands of years, filling all the depressions and cracks of the earth’s surface with water, forming the World Ocean.
and simultaneously causing cooling of the upper layers of the planet.
AT rainwater dissolved chemicals from the atmosphere and the earth's crust: methane, ammonia, hydrogen cyanide, carbon dioxide, and many others. The water that flowed into the oceans brought inorganic substances with them, and various salts were formed from their compounds with water. With torrential rains, molecules of the simplest organic substances, which appeared in the atmosphere under the influence of ultraviolet rays and electric discharges of lightning, fell into the ponds.
The accumulation of organic matter has turned the waters of the World Ocean into a kind of broth containing a mixture of various organic molecules. These molecules, being close to each other and engaging in various interactions with each other, created more complex compounds. This happened countless times over a very long time, measured in billions of years. Among the multitude of compounds formed, separate complex molecules arose, in
including proteins, lipids, nucleic acids, sugars, etc., which could then become a “living” molecular system in the form of a cell that exists in an aqueous medium.
The assumption that a large amount of organic matter was dissolved in the waters of the World Ocean has been confirmed in a number of experiments conducted by scientists in our time.
In 1953, the American biochemist S. Miller created an installation that allowed him to model the most ancient conditions of the primitive Earth. As a result of the experiment, they were synthesized from inorganic organic substances, including compounds with complex molecules: a number of amino acids, adenine, various carbohydrates - sugars, and among them ribose. Other researchers in similar experiments synthesized simple nucleic acid molecules in the form of small chains of six-monomer units.
A.I. Oparin believed that the main role in the transformation of organic substances into the body belongs to proteins, since they are capable of forming colloidal complexes that attract water to themselves and thereby create a kind of shell around themselves. Other scientists believe that in addition to proteins, nucleic acids played an important role in the creation of complexes. Due to diffusion, such complexes could stick together and merge with each other, removing excess water. This process was called a coacervation scientist, and the protein complexes themselves - coacervate dropsor koservservatami. Over time, the coacervates appeared shell and they were able to absorb substances rich in energy, and because of this
To an increase in weight and size. However, experiments carried out by a number of scientists confirm only the very possibility of such processes in those days.
Coacervates were the first "organizations" of molecules.
Increasing in size, coacervates were divided into smaller particles - this was the way of reproduction of primary living organisms. To maintain stability, the coacervate needed energy, which, apparently, was represented by various chemical bonds. The stability of some coacervates ensured their preservation and existence. It is possible that such stable structures with time (and this process lasted millions of years) gave rise to the first living organisms in the form of a living cell, where nucleic acids established primary control over the main intracellular processes, including such as nutrition, growth and reproduction . Scientists believe that these first life forms on Earth appeared about 3500-3900 million years ago.
So, the idea put forward by A.I. Oparin, can be briefly expressed as follows.
Life on Earth has gone a long way in the evolution of chemicals: from inorganic substances formed complex organic matter. Their accumulation over the billions of years in the oceans has made it possible for complex molecules to concentrate on coacervates, which became the basis for the emergence of elementary primary organisms.
It is not yet clear at the very moment of the transition from complex organic substances in a coacervate drop to a living cell, but it is clear that this evolution has continued for several million years. Experimentally, the moment when the complex molecular system becomes a “living system” has not yet been reproduced. Therefore, the ideas expressed by Oparin, Haldane, Bernal and other scientists are called a hypothesis, not a theory, since it still requires its proof.
1. What is the coacervation process?
