Preparation for oge in biology. Biology as a science. Methods of biology: theory and practice. Cheat sheet basics of biology Biology in the practical activities of people
Biology as a science
Biology(from Greek. bios- life, logos- word, science) is a complex of sciences about wildlife.
The subject of biology is all manifestations of life: the structure and functions of living beings, their diversity, origin and development, as well as interaction with the environment. The main task of biology as a science is to interpret all the phenomena of living nature on a scientific basis, while taking into account that the whole organism has properties that are fundamentally different from its components.
The term "biology" is found in the works of the German anatomists T. Roose (1779) and K. F. Burdach (1800), but it was not until 1802 that it was first used independently by J. B. Lamarck and G. R. Treviranus to refer to the science that studies living organisms.
Biological Sciences
At present, biology includes a number of sciences that can be systematized according to the following criteria: by subject and prevailing research methods and by the studied level of organization of wildlife. According to the subject of study, biological sciences are divided into bacteriology, botany, virology, zoology, mycology.
Botany is a biological science that comprehensively studies plants and the vegetation cover of the Earth. Zoology- a branch of biology, the science of diversity, structure, life, distribution and relationship of animals with the environment, their origin and development. Bacteriology- biological science that studies the structure and vital activity of bacteria, as well as their role in nature. Virology is the biological science that studies viruses. The main object of mycology are fungi, their structure and features of life. Lichenology- biological science that studies lichens. Bacteriology, virology and some aspects of mycology are often considered as part of microbiology - a branch of biology, the science of microorganisms (bacteria, viruses and microscopic fungi). Systematics, or taxonomy, is a biological science that describes and classifies into groups all living and extinct creatures.
In turn, each of the listed biological sciences is subdivided into biochemistry, morphology, anatomy, physiology, embryology, genetics and taxonomy (of plants, animals or microorganisms). Biochemistry- this is the science of the chemical composition of living matter, chemical processes occurring in living organisms and underlying their vital activity. Morphology- biological science that studies the shape and structure of organisms, as well as the patterns of their development. In a broad sense, it includes cytology, anatomy, histology and embryology. Distinguish the morphology of animals and plants. Anatomy is a branch of biology (more precisely, morphology), a science that studies internal structure and the shape of individual organs, systems and the organism as a whole. Plant anatomy is considered as part of botany, animal anatomy is considered as part of zoology, and human anatomy is a separate science. Physiology- biological science that studies the processes of vital activity of plant and animal organisms, their individual systems, organs, tissues and cells. There are physiology of plants, animals and humans. Embryology (developmental biology)- a branch of biology, the science of the individual development of the organism, including the development of the embryo.
object genetics are patterns of heredity and variability. Currently, it is one of the most dynamically developing biological sciences.
According to the level of organization of living nature studied, molecular biology, cytology, histology, organology, biology of organisms and supraorganismal systems are distinguished. Molecular biology is one of the youngest branches of biology, a science that studies, in particular, the organization of hereditary information and protein biosynthesis. Cytology, or cell biology, is a biological science, the object of study of which are the cells of both unicellular and multicellular organisms. Histology- biological science, a section of morphology, the object of which is the structure of tissues of plants and animals. The field of organology includes morphology, anatomy and physiology. various bodies and their systems.
Biology of organisms includes all sciences that deal with living organisms, for example, ethology the science of the behavior of organisms.
The biology of supraorganismal systems is subdivided into biogeography and ecology. The distribution of living organisms studies biogeography, whereas ecology- organization and functioning of supraorganismal systems at various levels: populations, biocenoses (communities), biogeocenoses (ecosystems) and the biosphere.
According to the prevailing research methods, one can single out descriptive (for example, morphology), experimental (for example, physiology) and theoretical biology.
Revealing and explaining the regularities of the structure, functioning and development of living nature at various levels of its organization is a task general biology . It includes biochemistry, molecular biology, cytology, embryology, genetics, ecology, evolutionary science and anthropology. evolutionary doctrine studies the causes, driving forces, mechanisms and general patterns of evolution of living organisms. One of its sections is paleontology- science, the subject of which are the fossil remains of living organisms. Anthropology- a section of general biology, the science of the origin and development of man as a biological species, as well as the diversity of populations of modern man and the patterns of their interaction.
Applied aspects of biology are assigned to the field of biotechnology, breeding and other rapidly developing sciences. Biotechnology called the biological science that studies the use of living organisms and biological processes in production. It is widely used in food (baking, cheese-making, brewing, etc.) and pharmaceutical industries (obtaining antibiotics, vitamins), for water purification, etc. Selection- the science of methods for creating breeds of domestic animals, varieties of cultivated plants and strains of microorganisms with the properties necessary for a person. Selection is also understood as the process of changing living organisms, carried out by man for his needs.
The progress of biology is closely related to the success of other natural and exact sciences, such as physics, chemistry, mathematics, computer science, etc. For example, microscopy, ultrasound (ultrasound), tomography and other processes occurring in living systems would be impossible without the use of chemical and physical methods. The use of mathematical methods allows, on the one hand, to identify the presence of a regular connection between objects or phenomena, to confirm the reliability of the results obtained, and on the other hand, to model a phenomenon or process. Recently, computer methods, such as modeling, have become increasingly important in biology. At the intersection of biology and other sciences, a number of new sciences have arisen, such as biophysics, biochemistry, bionics, etc.
Achievements in biology
The most important events in the field of biology that influenced the entire course of its further development are: the establishment of the molecular structure of DNA and its role in the transmission of information in living matter (F. Crick, J. Watson, M. Wilkins); deciphering the genetic code (R. Holly, H. G. Koran, M. Nirenberg); the discovery of the structure of the gene and the genetic regulation of protein synthesis (A. M. Lvov, F. Jacob, J. L. Monod, and others); formulation of the cell theory (M. Schleiden, T. Schwann, R. Virchow, K. Baer); study of the patterns of heredity and variability (G. Mendel, H. de Vries, T. Morgan, and others); formulation of the principles of modern systematics (C. Linnaeus), evolutionary theory (C. Darwin) and the doctrine of the biosphere (V. I. Vernadsky).
The significance of the discoveries of the last decades has yet to be assessed, however, the most significant achievements of biology have been recognized as: deciphering the genome of humans and other organisms, determining the mechanisms for controlling the flow of genetic information in the cell and the developing organism, the mechanisms for regulating cell division and death, cloning of mammals, and the discovery of pathogens " mad cow disease (prions).
The work on the "Human Genome" program, which was carried out simultaneously in several countries and was completed at the beginning of this century, led us to understand that a person has about 25-30 thousand genes, but information from most of our DNA is never read , since it contains a huge number of sections and genes encoding features that have lost their significance for humans (tail, body hair, etc.). In addition, a number of genes responsible for the development of hereditary diseases, as well as drug target genes, have been deciphered. However, the practical application of the results obtained during the implementation of this program is postponed until the genomes of a significant number of people are decoded, and then it becomes clear what is their difference. These goals are set for a number of leading laboratories around the world working on the implementation of the ENCODE program.
Biological research is the foundation of medicine, pharmacy, widely used in agriculture and forestry, Food Industry and other branches of human activity.
It is well known that only the "green revolution" of the 1950s made it possible to at least partially solve the problem of providing the rapidly growing population of the Earth with food, and animal husbandry - with feed through the introduction of new plant varieties and advanced technologies for their cultivation. Due to the fact that the genetically programmed properties of agricultural crops have almost been exhausted, the further solution of the food problem is associated with the widespread introduction of genetically modified organisms into production.
The production of many food products, such as cheeses, yogurts, sausages, bakery products, etc., is also impossible without the use of bacteria and fungi, which is the subject of biotechnology.
Knowledge of the nature of pathogens, the processes of the course of many diseases, the mechanisms of immunity, the laws of heredity and variability made it possible to significantly reduce mortality and even completely eradicate a number of diseases, such as smallpox. With the help of the latest achievements of biological science, the problem of human reproduction is also being solved.
A significant part of modern medicines is produced on the basis of natural raw materials, and also thanks to the success of genetic engineering, such as insulin, which is so necessary for patients with diabetes mellitus, is mainly synthesized by bacteria that have transferred the corresponding gene.
Biological research is no less significant for the preservation of the environment and the diversity of living organisms, the threat of extinction of which casts doubt on the existence of mankind.
Of greatest importance among the achievements of biology is the fact that they even underlie the construction of neural networks and the genetic code in computer technology and are also widely used in architecture and other industries. Without a doubt, the 21st century is the century of biology.
Methods of knowledge of wildlife
Like any other science, biology has its own arsenal of methods. In addition to the scientific method of cognition, which is used in other branches, such methods as historical, comparative descriptive, etc. are widely used in biology.
The scientific method of cognition includes observation, formulation of hypotheses, experiment, modeling, analysis of results and derivation of general patterns.
Observation- this is a purposeful perception of objects and phenomena with the help of sensory organs or instruments, due to the task of activity. The main condition for scientific observation is its objectivity, that is, the possibility of verifying the data obtained by repeated observation or the use of other research methods, such as experiment. The facts obtained as a result of observation are called data. They can be like quality(describing smell, taste, color, shape, etc.), and quantitative, and quantitative data are more accurate than qualitative ones.
Based on the observational data, we formulate hypothesis- a hypothetical judgment about the regular connection of phenomena. The hypothesis is tested in a series of experiments. experiment called scientifically staged experience, the observation of the phenomenon under study under controlled conditions, allowing to identify the characteristics of this object or phenomenon. The highest form of experimentation is modeling- study of any phenomena, processes or systems of objects by building and studying their models. In essence, this is one of the main categories of the theory of knowledge: any method of scientific research, both theoretical and experimental, is based on the idea of modeling.
The results of the experiment and simulation are subjected to a thorough analysis. Analysis called the method of scientific research by decomposing an object into its component parts or mental dismemberment of an object by logical abstraction. Analysis is inextricably linked with synthesis. Synthesis- this is a method of studying the subject in its integrity, in the unity and interconnection of its parts. As a result of analysis and synthesis, the most successful research hypothesis becomes working hypothesis, and if it can resist attempts to refute it and still successfully predict previously unexplained facts and relationships, then it can become a theory.
Under theory understand such a form of scientific knowledge, which gives a holistic view of the patterns and essential connections of reality. The general direction of scientific research is to achieve higher levels of predictability. If no facts can change a theory, and the deviations from it that occur are regular and predictable, then it can be elevated to the rank law- a necessary, essential, stable, recurring relationship between phenomena in nature.
As the body of knowledge increases and research methods improve, hypotheses and well-established theories can be challenged, modified, and even rejected, since scientific knowledge itself is dynamic in nature and is constantly subject to critical rethinking.
historical method reveals patterns of appearance and development of organisms, formation of their structure and function. In a number of cases, with the help of this method, hypotheses and theories that were previously considered false acquire new life. So, for example, it happened with Charles Darwin's assumptions about the nature of signal transmission through the plant in response to environmental influences.
Comparative descriptive method provides for an anatomical and morphological analysis of the objects of study. It underlies the classification of organisms, identifying patterns of emergence and development of various forms of life.
Monitoring- this is a system of measures for monitoring, evaluating and predicting changes in the state of the object under study, in particular the biosphere.
Conducting observations and experiments often requires the use of special equipment such as microscopes, centrifuges, spectrophotometers, etc.
Microscopy is widely used in zoology, botany, human anatomy, histology, cytology, genetics, embryology, paleontology, ecology and other branches of biology. It allows you to study the fine structure of objects using light, electron, X-ray and other types of microscopes.
Light microscope device. The light microscope consists of optical and mechanical parts. The first includes the eyepiece, objectives and mirror, and the second includes the tube, tripod, base, stage and screw.
The total magnification of the microscope is determined by the formula:
lens magnification $×$ eyepiece magnification $-$ microscope magnification.
For example, if the lens magnifies the object by $8$ and the eyepiece by $7$, then the total magnification of the microscope is $56$.
Differential centrifugation, or fractionation, allows to separate particles according to their size and density under the action of centrifugal force, which is actively used in the study of the structure of biological molecules and cells.
The arsenal of biology methods is constantly updated, and at present it is practically impossible to cover it completely. Therefore, some of the methods used in individual biological sciences will be discussed further.
The role of biology in the formation of the modern natural-science picture of the world
At the stage of formation, biology did not yet exist separately from other natural sciences and was limited only to the observation, study, description and classification of representatives of the animal and flora, i.e., was a descriptive science. However, this did not prevent the ancient naturalists Hippocrates (c. 460-377 BC), Aristotle (384-322 BC) and Theophrastus (real name Tirtham, 372-287 BC). e.) to make a significant contribution to the development of ideas about the structure of the human and animal body, as well as the biological diversity of animals and plants, thereby laying the foundations of human anatomy and physiology, zoology and botany.
The deepening of knowledge about living nature and the systematization of previously accumulated facts that took place in the 16th-18th centuries culminated in the introduction of binary nomenclature and the creation of a coherent taxonomy of plants (C. Linnaeus) and animals (J. B. Lamarck).
The description of a significant number of species with similar morphological features, as well as paleontological finds, became prerequisites for the development of ideas about the origin of species and the paths of the historical development of the organic world. Thus, the experiments of F. Redi, L. Spallanzani and L. Pasteur in the 17th-19th centuries refuted the hypothesis of spontaneous spontaneous generation put forward by Aristotle and existed in the Middle Ages, and the theory of biochemical evolution by A.I. Oparin and J. Haldane, brilliantly confirmed by S. Miller and G. Urey, made it possible to answer the question of the origin of all living things.
If the process of the emergence of the living from non-living components and its evolution in themselves no longer raise doubts, then the mechanisms, ways and directions of the historical development of the organic world are still not fully elucidated, since none of the two main competing theories of evolution (the synthetic theory of evolution , created on the basis of the theory of Ch. Darwin, and the theory of J. B. Lamarck) still cannot provide exhaustive evidence.
The use of microscopy and other methods of related sciences, due to progress in the field of other natural sciences, as well as the introduction of experimental practice, allowed the German scientists T. Schwann and M. Schleiden to formulate a cell theory back in the 19th century, later supplemented by R. Virchow and K. Baer. It became the most important generalization in biology, which formed the cornerstone of modern ideas about the unity of the organic world.
The discovery of the patterns of transmission of hereditary information by the Czech monk G. Mendel served as an impetus for the further rapid development of biology in the XX-XXI centuries and led not only to the discovery of the universal carrier of heredity - DNA, but also the genetic code, as well as fundamental mechanisms for controlling, reading and variability of hereditary information .
The development of ideas about the environment led to the emergence of such a science as ecology, and the formulation the doctrine of the biosphere as a complex multi-component planetary system of interconnected huge biological complexes, as well as chemical and geological processes occurring on Earth (V. I. Vernadsky), which ultimately allows at least to a small extent to reduce the negative consequences of human economic activity.
Thus, biology has played an important role in the formation of the modern natural-science picture of the world.
Level organization and evolution. The main levels of organization of living nature: cellular, organismic, population-species, biogeocenotic, biospheric. Biological systems. General features of biological systems: cellular structure, features chemical composition, metabolism and energy transformations, homeostasis, irritability, movement, growth and development, reproduction, evolution
Level organization and evolution
Living nature is not a homogeneous formation, similar to a crystal, it is represented by an infinite variety of its constituent objects (about 2 million species of organisms alone have now been described). At the same time, this diversity is not evidence of the chaos that reigns in it, since organisms have a cellular structure, organisms of the same species form populations, all populations living on the same land or water site form communities, and in interaction with bodies of inanimate nature form biogeocenoses. , which in turn make up the biosphere.
Thus, living nature is a system, the components of which can be arranged in a strict order: from the lowest to the highest. This principle of organization makes it possible to single out individual levels and gives a comprehensive view of life as a natural phenomenon. At each level of organization, an elementary unit and an elementary phenomenon are defined. As elementary unit consider a structure or object whose changes constitute a contribution specific to the corresponding level to the process of preserving and developing life, while this change itself is elementary phenomenon.
The formation of such a multi-level structure could not happen instantly - this is the result of billions of years of historical development, during which there was a progressive complication of life forms: from complexes of organic molecules to cells, from cells to organisms, etc. Once having arisen, this structure maintains its existence due to a complex system of regulation and continues to develop, and at each level of organization of living matter, corresponding evolutionary transformations occur.
The main levels of organization of wildlife: cellular, organismal, population-species, biogeocenotic, biospheric
Currently, there are several main levels of organization of living matter: cellular, organismal, population-species, biogeocenotic and biospheric.
Cellular level
Although the manifestations of some properties of living things are already due to the interaction of biological macromolecules (proteins, nucleic acids, polysaccharides, etc.), nevertheless, the unit of the structure, functions and development of living things is a cell that can carry out and match the processes of realization and transmission of hereditary information with metabolism and energy conversion thus ensuring the functioning of higher levels of the organization. The elementary unit of the cellular level of organization is the cell, and the elementary phenomenon is the reaction of cellular metabolism.
Organism level
organism is a complete system capable of independent existence. According to the number of cells that make up organisms, they are divided into unicellular and multicellular. The cellular level of organization in unicellular organisms (common amoeba, green euglena, etc.) coincides with the organismic level. There was a period in the history of the Earth when all organisms were represented only by unicellular forms, but they ensured the functioning of both biogeocenoses and the biosphere as a whole. Most multicellular organisms are represented by a combination of tissues and organs, which in turn also have a cellular structure. Organs and tissues are adapted to perform certain functions. The elementary unit of this level is an individual in its individual development, or ontogenesis, therefore the organismal level is also called ontogenetic. An elementary phenomenon of this level is the changes in the organism in its individual development.
Population-species level
population- this is a collection of individuals of the same species, freely interbreeding with each other and living apart from other similar groups of individuals.
In populations, there is a free exchange of hereditary information and its transmission to descendants. The population is the elementary unit of the population-species level, and the elementary phenomenon in this case are evolutionary transformations, such as mutations and natural selection.
Biogeocenotic level
Biogeocenosis is a historically established community of populations of different species, interconnected with each other and the environment through the metabolism and energy.
Biogeocenoses are elementary systems in which the material-energy cycle is carried out, due to the vital activity of organisms. Biogeocenoses themselves are elementary units of a given level, while elementary phenomena are energy flows and the circulation of substances in them. Biogeocenoses make up the biosphere and determine all the processes occurring in it.
biosphere level
Biosphere- the shell of the Earth inhabited by living organisms and transformed by them.
The biosphere is the most high level organization of life on the planet. This shell covers the lower part of the atmosphere, the hydrosphere and the upper layer of the lithosphere. The biosphere, like all other biological systems, is dynamic and actively transformed by living beings. It itself is an elementary unit of the biospheric level, and as an elementary phenomenon, they consider the processes of circulation of substances and energy that occur with the participation of living organisms.
As mentioned above, each of the levels of organization of living matter contributes to a single evolutionary process: the cell not only reproduces the inherent hereditary information, but also changes it, which leads to the emergence of new combinations of signs and properties of the body, which in turn undergo the action of natural selection at the population-species level, etc.
Biological systems
Biological objects of varying degrees of complexity (cells, organisms, populations and species, biogeocenoses and the biosphere itself) are currently considered as biological systems.
A system is a unity of structural components, the interaction of which generates new properties in comparison with their mechanical combination. Organisms are made up of organs, organs are made up of tissues, and tissues make up cells.
Characteristic features of biological systems are their integrity, the level principle of organization, as mentioned above, and openness. The integrity of biological systems is largely achieved through self-regulation, functioning on the principle of feedback.
To open systems include systems between which and the environment there is an exchange of substances, energy and information, for example, plants in the process of photosynthesis capture sunlight and absorb water and carbon dioxide, releasing oxygen.
General features of biological systems: cellular structure, chemical composition, metabolism and energy conversion, homeostasis, irritability, movement, growth and development, reproduction, evolution
Biological systems differ from bodies of inanimate nature by a set of features and properties, among which the main ones are cellular structure, chemical composition, metabolism and energy conversion, homeostasis, irritability, movement, growth and development, reproduction and evolution.
The elementary structural and functional unit of the living is the cell. Even viruses belonging to non-cellular life forms are incapable of self-replication outside of cells.
There are two types of cell structure: prokaryotic and eukaryotic. Prokaryotic cells do not have a formed nucleus; their genetic information is concentrated in the cytoplasm. Bacteria are primarily classified as prokaryotes. Genetic information in eukaryotic cells is stored in a special structure - the nucleus. Eukaryotes are plants, animals and fungi. If in unicellular organisms all manifestations of the living are inherent in the cell, then in multicellular organisms specialization of cells occurs.
In living organisms, not a single chemical element is found that would not be in inanimate nature, however, their concentrations differ significantly in the first and second cases. Elements such as carbon, hydrogen and oxygen, which are part of organic compounds, predominate in living nature, while inorganic substances are mainly characteristic of inanimate nature. The most important organic compounds are nucleic acids and proteins that provide the functions of self-reproduction and self-maintenance, but none of these substances is the carrier of life, since neither individually nor in a group they are capable of self-reproduction - this requires an integral complex of molecules and structures, which is the cell.
All living systems, including cells and organisms, are open systems. However, unlike inanimate nature, where substances are mainly transferred from one place to another or their state of aggregation changes, living beings are capable of chemical transformation of consumed substances and use of energy. Metabolism and energy conversion are associated with processes such as nutrition, respiration and excretion.
Under nutrition usually understand the entry into the body, digestion and assimilation of substances necessary for replenishing energy reserves and building the body of the body. According to the mode of nutrition, all organisms are divided into autotrophs and heterotrophs.
Autotrophs These are organisms that are capable of synthesizing organic substances from inorganic substances.
Heterotrophs- These are organisms that consume ready-made organic substances for food. Autotrophs are divided into photoautotrophs and chemoautotrophs. Photoautotrophs used for synthesis organic matter energy sunlight. The process of converting light energy into energy chemical bonds organic compounds is called photosynthesis. Photoautotrophs include the vast majority of plants and some bacteria (for example, cyanobacteria). In general, photosynthesis is not a very productive process, as a result of which most plants are forced to lead an attached lifestyle. Chemoautotrophs extract energy for the synthesis of organic compounds from inorganic compounds. This process is called chemosynthesis. Typical chemoautotrophs are some bacteria, including sulfur bacteria and iron bacteria.
The remaining organisms - animals, fungi and the vast majority of bacteria - are heterotrophs.
Respiration is the process of splitting organic substances into simpler ones, in which the energy necessary to maintain the vital activity of organisms is released.
Distinguish aerobic respiration, requiring oxygen, and anaerobic, proceeding without the participation of oxygen. Most organisms are aerobes, although anaerobes are also found among bacteria, fungi, and animals. During oxygen respiration, complex organic substances can be broken down into water and carbon dioxide.
Excretion is usually understood as the excretion from the body of the end products of metabolism and the excess of various substances (water, salts, etc.) that came with food or formed in it. The excretion processes are especially intensive in animals, while plants are extremely economical.
Thanks to the metabolism and energy, the body's relationship with the environment is ensured and homeostasis is maintained.
homeostasis- this is the ability of biological systems to resist changes and maintain the relative constancy of the chemical composition, structure and properties, as well as ensure the constancy of functioning in changing environmental conditions. Adaptation to changing environmental conditions is called adaptation.
Irritability- this is a universal property of living things to respond to external and internal influences, which underlies the adaptation of an organism to environmental conditions and their survival. The reaction of plants to changes in external conditions consists, for example, in turning the leaf blades towards the light, while in most animals it has more complex forms that have a reflex character.
Traffic is an essential property of biological systems. It manifests itself not only in the form of movement of bodies and their parts in space, for example, in response to irritation, but also in the process of growth and development.
New organisms that appear as a result of reproduction do not receive ready-made traits from their parents, but certain genetic programs, the possibility of developing certain traits. This hereditary information is realized during individual development. Individual development It is expressed, as a rule, in quantitative and qualitative changes in the body. Quantitative changes in the body are called growth. They manifest themselves, for example, in the form of an increase in the mass and linear dimensions of the organism, which is based on the reproduction of molecules, cells and other biological structures.
Development of the organism- this is the appearance of qualitative differences in the structure, the complication of functions, etc., which is based on cell differentiation.
The growth of organisms can continue throughout life or end at some particular stage of it. In the first case, one speaks of unlimited, or open growth. It is characteristic of plants and fungi. In the second case, we are dealing with limited, or closed growth inherent in animals and bacteria.
The duration of existence of an individual cell, organism, species and other biological systems is limited in time, mainly due to the influence of environmental factors, therefore, constant reproduction of these systems is required. The reproduction of cells and organisms is based on the process of self-duplication of DNA molecules. The reproduction of organisms ensures the existence of the species, and the reproduction of all species inhabiting the Earth ensures the existence of the biosphere.
heredity called the transfer of characteristics of parental forms in a number of generations.
However, if the signs were preserved during reproduction, adaptation to changing environmental conditions would be impossible. In this regard, a property opposite to heredity appeared - variability.
Variability- this is the possibility of acquiring new features and properties during life, which ensures the evolution and survival of the fittest species.
Evolution- this is irreversible process historical development of the living.
It is based on progressive reproduction, hereditary variability, struggle for existence and natural selection. The action of these factors has led to a huge variety of life forms adapted to different environmental conditions. Progressive evolution has gone through a series of stages: pre-cellular forms, unicellular organisms, increasingly complex multicellular organisms up to man.
Genetics, its tasks. Heredity and variability are properties of organisms. Methods of genetics. Basic genetic concepts and symbolism. Chromosomal theory of heredity. Modern ideas about the gene and genome
Genetics, its tasks
Advances in natural science and cell biology in the 18th-19th centuries allowed a number of scientists to speculate about the existence of certain hereditary factors that determine, for example, the development of hereditary diseases, but these assumptions were not supported by appropriate evidence. Even the theory of intracellular pangenesis formulated by H. de Vries in 1889, which assumed the existence of certain “pangens” in the cell nucleus that determine the hereditary inclinations of the organism, and the release into the protoplasm of only those of them that determine the cell type, could not change the situation, as well as the theory of "germ plasm" by A. Weisman, according to which the traits acquired in the process of ontogenesis are not inherited.
Only the works of the Czech researcher G. Mendel (1822–1884) became the foundation stone modern genetics. However, despite the fact that his works were cited in scientific publications, contemporaries did not pay attention to them. And only the rediscovery of the patterns of independent inheritance by three scientists at once - E. Chermak, K. Correns and H. de Vries - forced the scientific community to turn to the origins of genetics.
Genetics is a science that studies the laws of heredity and variability and methods of managing them.
The tasks of genetics at the present stage are the study of the qualitative and quantitative characteristics of the hereditary material, the analysis of the structure and functioning of the genotype, the decoding of the fine structure of the gene and methods for regulating gene activity, the search for genes that cause the development of human hereditary diseases and methods for their "correction", the creation of a new generation of drugs by type DNA vaccines, genetically and cell-engineered construction of organisms with new properties that could produce necessary for a person medicines and food products, as well as a complete transcript of the human genome.
Heredity and variability - properties of organisms
Heredity- is the ability of organisms to transmit their characteristics and properties in a number of generations.
Variability- the property of organisms to acquire new characteristics during life.
signs- these are any morphological, physiological, biochemical and other features of organisms in which some of them differ from others, for example, eye color. properties They also call any functional features of organisms, which are based on a certain structural feature or a group of elementary features.
Organisms can be divided into quality and quantitative. Qualitative signs have two or three contrasting manifestations, which are called alternative features, for example, blue and brown eyes, while quantitative ones (milk yield of cows, wheat yield) do not have clearly defined differences.
The material carrier of heredity is DNA. There are two types of heredity in eukaryotes: genotypic and cytoplasmic. Carriers of genotypic heredity are localized in the nucleus, and further we will talk about it, and carriers of cytoplasmic heredity are circular DNA molecules located in mitochondria and plastids. Cytoplasmic inheritance is transmitted mainly with the egg, therefore it is also called maternal.
A small number of genes are localized in the mitochondria of human cells, but their change can have a significant impact on the development of the organism, for example, lead to the development of blindness or a gradual decrease in mobility. Plastids play an equally important role in plant life. So, in some parts of the leaf, chlorophyll-free cells may be present, which, on the one hand, leads to a decrease in plant productivity, and on the other hand, such variegated organisms are valued in decorative gardening. Such specimens are reproduced mainly asexually, since ordinary green plants are more often obtained during sexual reproduction.
Genetic methods
1. The hybridological method, or the method of crosses, consists in the selection of parent individuals and the analysis of offspring. At the same time, the genotype of an organism is judged by the phenotypic manifestations of genes in offspring obtained by a certain crossing scheme. This is the oldest informative method of genetics, which was most fully applied for the first time by G. Mendel in combination with statistical method. This method is not applicable in human genetics for ethical reasons.
2. The cytogenetic method is based on the study of the karyotype: the number, shape and size of the body's chromosomes. The study of these features makes it possible to identify various developmental pathologies.
3. The biochemical method makes it possible to determine the content of various substances in the body, in particular their excess or deficiency, as well as the activity of a number of enzymes.
4. Molecular genetic methods are aimed at identifying variations in the structure and deciphering the primary nucleotide sequence of the studied DNA sections. They allow you to identify genes for hereditary diseases even in embryos, establish paternity, etc.
5. The population-statistical method makes it possible to determine the genetic composition of a population, the frequency of certain genes and genotypes, the genetic load, and also to outline the prospects for the development of a population.
6. The method of hybridization of somatic cells in culture allows you to determine the localization of certain genes in chromosomes when cells of various organisms merge, for example, mice and hamsters, mice and humans, etc.
Basic genetic concepts and symbolism
Gene- This is a section of a DNA molecule, or chromosome, that carries information about a certain trait or property of an organism.
Some genes can influence the manifestation of several traits at once. Such a phenomenon is called pleiotropy. For example, the gene that determines the development of the hereditary disease arachnodactyly (spider fingers) also causes the curvature of the lens, the pathology of many internal organs.
Each gene occupies a strictly defined place in the chromosome - locus. Since in the somatic cells of most eukaryotic organisms the chromosomes are paired (homologous), each of the paired chromosomes contains one copy of the gene responsible for a particular trait. Such genes are called allelic.
Allelic genes most often exist in two versions - dominant and recessive. Dominant called an allele that manifests itself regardless of which gene is on the other chromosome, and suppresses the development of a trait encoded by a recessive gene. Dominant alleles are usually indicated by capital letters of the Latin alphabet (A, B, C, etc.), while recessive alleles are indicated by lowercase letters (a, b, c, etc.). recessive alleles can only be expressed if they occupy loci on both paired chromosomes.
An organism that has the same allele on both homologous chromosomes is called homozygous for that gene, or homozygous(AA, aa, AABB, aabb, etc.), and an organism that has different gene variants on both homologous chromosomes - dominant and recessive - is called heterozygous for that gene, or heterozygous(Aa, AaBb, etc.).
A number of genes can have three or more structural variants, for example, blood groups according to the AB0 system are encoded by three alleles - I A, I B, i. Such a phenomenon is called multiple allelism. However, even in this case, each chromosome from a pair carries only one allele, that is, all three gene variants in one organism cannot be represented.
Genome- a set of genes characteristic of a haploid set of chromosomes.
Genotype- a set of genes characteristic of a diploid set of chromosomes.
Phenotype- a set of signs and properties of an organism, which is the result of the interaction of the genotype and the environment.
Since organisms differ from each other in many traits, it is possible to establish the patterns of their inheritance only by analyzing two or more traits in the offspring. Crossing, in which inheritance is considered and an accurate quantitative account of offspring is carried out for one pair of alternative traits, is called monohybrid m, in two pairs - dihybrid, according to more signs - polyhybrid.
According to the phenotype of an individual, it is far from always possible to establish its genotype, since both an organism homozygous for the dominant gene (AA) and heterozygous (Aa) will have a manifestation of the dominant allele in the phenotype. Therefore, to check the genotype of an organism with cross-fertilization, analyzing cross- crossing, in which an organism with a dominant trait is crossed with a homozygous recessive gene. In this case, an organism homozygous for the dominant gene will not produce splitting in the offspring, while in the offspring of heterozygous individuals an equal number of individuals with dominant and recessive traits is observed.
The following conventions are most often used to write crossover schemes:
R (from lat. parent- parents) - parent organisms;
$♀$ (alchemical sign of Venus - a mirror with a handle) - maternal individual;
$♂$ (alchemical sign of Mars - shield and spear) - paternal specimen;
$×$ - cross sign;
F 1, F 2, F 3, etc. - hybrids of the first, second, third and subsequent generations;
F a - offspring from analyzing crosses.
Chromosomal theory of heredity
The founder of genetics G. Mendel, as well as his closest followers, had no idea about the material basis of hereditary inclinations, or genes. However, already in 1902–1903, the German biologist T. Boveri and the American student W. Setton independently suggested that the behavior of chromosomes during cell maturation and fertilization makes it possible to explain the splitting of hereditary factors according to Mendel, i.e., in their opinion, genes must be located on the chromosomes. These assumptions have become the cornerstone of the chromosome theory of heredity.
In 1906, the English geneticists W. Batson and R. Pennet discovered a violation of Mendelian splitting when crossing sweet peas, and their compatriot L. Doncaster, in experiments with the gooseberry moth butterfly, discovered sex-linked inheritance. The results of these experiments clearly contradicted Mendelian ones, but given that by that time it was already known that the number of known features for experimental objects far exceeded the number of chromosomes, and this suggested that each chromosome carries more than one gene, and the genes of one chromosomes are inherited together.
In 1910, the experiments of T. Morgan's group began on a new experimental object - the Drosophila fruit fly. The results of these experiments made it possible by the mid-20s of the 20th century to formulate the main provisions of the chromosome theory of heredity, to determine the order in which genes are arranged in chromosomes and the distance between them, i.e., to compile the first maps of chromosomes.
The main provisions of the chromosome theory of heredity:
- Genes are located on chromosomes. Genes on the same chromosome are inherited together, or linked, and are called clutch group. The number of linkage groups is numerically equal to the haploid set of chromosomes.
- Each gene occupies a strictly defined place in the chromosome - a locus.
- Genes are arranged linearly on chromosomes.
- Disruption of gene linkage occurs only as a result of crossing over.
- The distance between genes on a chromosome is proportional to the percentage of crossing over between them.
- Independent inheritance is characteristic only for genes of non-homologous chromosomes.
Modern ideas about the gene and genome
In the early 1940s, J. Beadle and E. Tatum, analyzing the results of genetic studies conducted on the neurospore fungus, came to the conclusion that each gene controls the synthesis of an enzyme, and formulated the principle of "one gene - one enzyme" .
However, already in 1961, F. Jacob, J. L. Monod and A. Lvov managed to decipher the structure of the Escherichia coli gene and study the regulation of its activity. For this discovery they were awarded in 1965 Nobel Prize in physiology and medicine.
In the course of the study, in addition to structural genes that control the development of certain traits, they were able to identify regulatory ones, the main function of which is the manifestation of traits encoded by other genes.
The structure of the prokaryotic gene. The structural gene of prokaryotes has a complex structure, since it includes regulatory regions and coding sequences. Regulatory regions include promoter, operator, and terminator. promoter called the region of the gene to which the RNA polymerase enzyme is attached, which ensures the synthesis of mRNA during transcription. FROM operator, located between the promoter and the structural sequence, can bind repressor protein, which does not allow RNA polymerase to start reading hereditary information from the coding sequence, and only its removal allows transcription to begin. The structure of the repressor is usually encoded in a regulatory gene located in another part of the chromosome. The reading of information ends at a section of the gene called terminator.
coding sequence structural gene contains information about the sequence of amino acids in the corresponding protein. The coding sequence in prokaryotes is called cistronome, and the set of coding and regulatory regions of the prokaryotic gene - operon. In general, prokaryotes, which include E. coli, have a relatively small number of genes located on a single ring chromosome.
The cytoplasm of prokaryotes may also contain additional small circular or open DNA molecules called plasmids. Plasmids are able to integrate into chromosomes and be transferred from one cell to another. They can carry information about sexual characteristics, pathogenicity, and antibiotic resistance.
The structure of the eukaryotic gene. Unlike prokaryotes, eukaryotic genes do not have an operon structure, since they do not contain an operator, and each structural gene is accompanied only by a promoter and a terminator. In addition, significant regions in eukaryotic genes ( exons) alternate with insignificant ( introns), which are completely transcribed into mRNAs and then excised during their maturation. The biological role of introns is to reduce the likelihood of mutations in significant areas. Eukaryotic gene regulation is much more complex than that described for prokaryotes.
The human genome. In each human cell, there are about 2 m of DNA in 46 chromosomes, densely packed into a double helix, which consists of about 3.2 $ × $ 10 9 nucleotide pairs, which provides about 10 1900000000 possible unique combinations. By the end of the 1980s, the location of about 1,500 human genes was known, but their total number was estimated at about 100,000, since only about 10,000 hereditary diseases in humans, not to mention the number of various proteins contained in cells .
In 1988, the international project "Human Genome" was launched, which by the beginning of the 21st century ended with a complete decoding of the nucleotide sequence. He made it possible to understand that two different people have 99.9% similar nucleotide sequences, and only the remaining 0.1% determine our individuality. In total, approximately 30–40 thousand structural genes were discovered, but then their number was reduced to 25–30 thousand. Among these genes, there are not only unique ones, but also repeated hundreds and thousands of times. However, these genes encode a much larger number of proteins, such as tens of thousands of protective proteins - immunoglobulins.
97% of our genome is genetic "garbage" that exists only because it can reproduce well (the RNA that is transcribed in these regions never leaves the nucleus). For example, among our genes there are not only "human" genes, but also 60% of genes similar to the genes of the fruit fly, and up to 99% of our genes are related to chimpanzees.
In parallel with the decoding of the genome, chromosome mapping also took place, as a result of which it was possible not only to detect, but also to determine the location of some genes responsible for the development of hereditary diseases, as well as drug target genes.
The deciphering of the human genome does not yet have a direct effect, since we have received a kind of instruction for assembling such a complex organism as a person, but have not learned how to make it or at least correct errors in it. Nevertheless, the era of molecular medicine is already on the threshold, all over the world there is a development of so-called gene preparations that can block, remove or even replace pathological genes in living people, and not just in a fertilized egg.
We should not forget that in eukaryotic cells DNA is contained not only in the nucleus, but also in mitochondria and plastids. Unlike the nuclear genome, the organization of mitochondrial and plastid genes has much in common with the organization of the prokaryotic genome. Despite the fact that these organelles carry less than 1% of the cell's hereditary information and do not even encode the complete set of proteins necessary for their own functioning, they can significantly affect some features of the body. Thus, variegation in plants of chlorophytum, ivy, and others is inherited by an insignificant number of descendants, even when two variegated plants are crossed. This is due to the fact that plastids and mitochondria are transmitted mostly with the cytoplasm of the egg, so this heredity is called maternal, or cytoplasmic, in contrast to the genotypic, which is localized in the nucleus.
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Biology [ Complete reference to prepare for the exam] Lerner Georgy Isaakovich
1.1. Biology as a science, its achievements, research methods, connections with other sciences. The role of biology in the life and practical activities of man
Terms and concepts tested in the examination papers for this section: hypothesis, research method, science, scientific fact, object of research, problem, theory, experiment.
Biology The science that studies the properties of living systems. However, it is quite difficult to define what a living system is. That is why scientists have established several criteria by which an organism can be classified as living. Chief among these criteria are metabolism or metabolism, self-reproduction and self-regulation. A separate chapter will be devoted to the discussion of these and other criteria (or) properties of the living.
concept the science is defined as "the sphere of human activity to obtain, systematize objective knowledge about reality." In accordance with this definition, the object of science - biology is life in all its manifestations and forms, as well as on different levels .
Every science, including biology, uses certain methods research. Some of them are universal for all sciences, such as observation, proposing and testing hypotheses, and building theories. Other scientific methods can only be used by a particular science. For example, geneticists have a genealogical method for studying human genealogies, breeders have a hybridization method, histologists have a tissue culture method, etc.
Biology is closely related to other sciences - chemistry, physics, ecology, geography. Biology itself is divided into many special sciences that study various biological objects: plant and animal biology, plant physiology, morphology, genetics, taxonomy, breeding, mycology, helminthology and many other sciences.
Method- this is the path of research that a scientist goes through, solving any scientific problem, problem.
The main methods of science include the following:
Modeling- a method in which a certain image of an object is created, a model with the help of which scientists obtain the necessary information about the object. So, for example, when establishing the structure of the DNA molecule, James Watson and Francis Crick created a model from plastic elements - a DNA double helix that corresponds to the data of X-ray and biochemical studies. This model fully met the requirements for DNA. ( See section Nucleic acids.)
Observation- the method by which the researcher collects information about the object. You can observe visually, for example, the behavior of animals. It is possible to observe with the help of devices the changes occurring in living objects: for example, when taking a cardiogram during the day, when measuring the weight of a calf during a month. You can observe seasonal changes in nature, the molting of animals, etc. The conclusions drawn by the observer are verified either by repeated observations or experimentally.
Experiment (Experience)- a method by which the results of observations, put forward assumptions are checked - hypotheses . Examples of experiments are crossing animals or plants in order to obtain a new variety or breed, testing a new drug, identifying the role of any cell organelle, etc. An experiment is always the acquisition of new knowledge with the help of a given experience.
Problem- a question, a problem that needs to be solved. Problem solving leads to new knowledge. A scientific problem always hides some contradiction between the known and the unknown. Solving the problem requires the scientist to collect facts, analyze them, and systematize them. An example of a problem is, for example, the following: “How does the adaptation of organisms to the environment arise?” or “How can I prepare for serious exams in the shortest possible time?”.
It can be quite difficult to formulate a problem, but whenever there is a difficulty, a contradiction, a problem appears.
Hypothesis- an assumption, a preliminary solution to the problem. Putting forward hypotheses, the researcher is looking for relationships between facts, phenomena, processes. That is why the hypothesis most often takes the form of an assumption: "if ... then." For example, “If plants emit oxygen in the light, then we can detect it with the help of a smoldering torch, because. oxygen must support combustion. The hypothesis is tested experimentally. (See Hypotheses for the Origin of Life on Earth.)
Theory is a generalization of the main ideas in any scientific field of knowledge. For example, the theory of evolution summarizes all the reliable scientific data obtained by researchers over many decades. Over time, theories are supplemented by new data, develop. Some theories may be refuted by new facts. True scientific theories are confirmed by practice. So, for example, the genetic theory of G. Mendel and the chromosome theory of T. Morgan were confirmed by many experimental studies in different countries peace. The modern evolutionary theory, although it has found many scientifically proven confirmations, still meets opponents, because. not all of its provisions can be confirmed by facts at the present stage of development of science.
Private scientific methods in biology are:
genealogical method - used in the compilation of pedigrees of people, identifying the nature of inheritance of certain traits.
historical method - establishing relationships between facts, processes, phenomena that have occurred over a historically long time (several billion years). The evolutionary doctrine has developed largely due to this method.
paleontological method - a method that allows you to find out the relationship between ancient organisms, the remains of which are in the earth's crust, in different geological layers.
centrifugation – separation of mixtures into component parts under the action of centrifugal force. It is used in the separation of cell organelles, light and heavy fractions (components) of organic substances, etc.
Cytological or cytogenetic , - study of the structure of the cell, its structures using various microscopes.
Biochemical - the study of chemical processes occurring in the body.
Each particular biological science (botany, zoology, anatomy and physiology, cytology, embryology, genetics, breeding, ecology, and others) uses its own more particular research methods.
Every science has its own an object and your subject of study. In biology, the object of study is LIFE. The carriers of life are living bodies. Everything related to their existence is studied by biology. The subject of science is always somewhat narrower, more limited than the object. So, for example, one of the scientists is interested in metabolism organisms. Then the object of study will be life, and the subject of study will be metabolism. On the other hand, metabolism can also be an object of study, but then the subject of study will be one of its characteristics, for example, the metabolism of proteins, or fats, or carbohydrates. This is important to understand, because questions about what is the object of study of a particular science are found in exam questions. In addition, it is important for those who will be engaged in science in the future.
EXAMPLES OF TASKS
Part A
A1. Biology as a science studies
1) general signs of the structure of plants and animals
2) the relationship of animate and inanimate nature
3) processes occurring in living systems
4) the origin of life on Earth
A2. I.P. Pavlov in his works on digestion used the research method:
1) historical 3) experimental
2) descriptive 4) biochemical
A3. Ch. Darwin's assumption that each modern species or group of species had common ancestors is:
1) theory 3) fact
2) hypothesis 4) proof
A4. Embryology studies
1) the development of the organism from the zygote to birth
2) the structure and functions of the egg
3) postpartum human development
4) development of the organism from birth to death
A5. The number and shape of chromosomes in a cell is determined by research
1) biochemical 3) centrifugation
2) cytological 4) comparative
A6. Selection as a science solves problems
1) creation of new varieties of plants and animal breeds
2) conservation of the biosphere
3) creation of agrocenoses
4) creating new fertilizers
A7. Patterns of inheritance of traits in humans are established by the method
1) experimental 3) genealogical
2) hybridological 4) observations
A8. The specialty of a scientist who studies the fine structures of chromosomes is called:
1) breeder 3) morphologist
2) cytogeneticist 4) embryologist
A9. Systematics is the science that deals with
1) the study of the external structure of organisms
2) the study of body functions
3) identifying relationships between organisms
4) classification of organisms
Part B
IN 1. Indicate three functions that modern cell theory performs
1) Experimentally confirms scientific data on the structure of organisms
2) Predicts the emergence of new facts, phenomena
3) Describes the cellular structure of different organisms
4) Systematizes, analyzes and explains new facts about the cellular structure of organisms
5) Puts forward hypotheses about the cellular structure of all organisms
6) Creates new methods of cell research
Part FROM
C1. The French scientist Louis Pasteur became famous as the "savior of mankind", thanks to the creation of vaccines against infectious diseases, including such as rabies, anthrax, etc. Suggest hypotheses that he could put forward. Which of the research methods did he prove his case?
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