biology
A science that studies the species, structure, function, behavior, development, origin and evolution of organisms at all levels and the relationship between organisms and their surrounding environment. Also known as life science. After 1930s and 1940s, biology combined with physics, chemistry and mathematics, and gradually stepped into the ranks of precision science. People have realized that life is a form of material movement. The basic unit of life is the cell, which is a material system composed of biological macromolecules such as protein, nucleic acid, sugar and lipid. Life phenomenon is the expression of the comprehensive operation of matter, energy and information in this complex system. Living things have many characteristics that non-living things don't have. For example, organisms can use substances absorbed from the environment at normal temperature and pressure to synthesize a variety of organic compounds, including complex biological macromolecules, which are far more efficient than the best machines; Biology can store and transmit information, and has the ability of self-regulation and self-replication; Organisms are also undergoing individual development and species evolution in an irreversible way; Without the interference of powerful external factors, all kinds of creatures on the earth can restrict each other and maintain ecological balance. It is of great theoretical and practical significance to reveal various operating mechanisms in the process of life.
A brief history As early as 5000 BC, human beings have gradually accumulated preliminary knowledge about animals and plants for their own survival. In Aristotle in ancient Greece and Erya's works in Qin and Han Dynasties in China, hundreds of kinds of animals and plants were recorded and described preliminarily. Huangdi Neijing at the end of the Warring States Period in China described the appearance and internal organs of the human body in detail and intuitively. Galen in ancient Greece (129 ~ 199) completed the Anatomy Outline (16) and other works *** 130, which became a classic followed by western academic circles for more than 1000 years. During the Middle Ages, western biology hardly developed, but Arab medicine developed rapidly. China's medical and medicinal plants Materia Medica and agronomy have developed rapidly.
With the Renaissance, biology has made remarkable progress. The Belgian anatomist A. Vesaliua's Human Body Structure corrected many mistakes of Galen. W Harvey, a British doctor and physiologist, expounded the closed-circuit mode of blood circulation in the article "Study on Animal Heart-Blood Movement", except for the capillary part. Harvey is recognized as the founder of experimental biology because his structure is based on the experimental results of animals, including biology. Compendium of Materia Medica written by Li Shizhen in Ming Dynasty recorded about 1500 kinds of drugs and more than 2,000 prescriptions. The descriptions and illustrations of herbs are very detailed, and they are divided into three levels: families, classes and species. Therefore, this book not only occupies an important position in the international pharmacopoeia, but also is a high-level botanical classic.
17 and 18 centuries, European field trips rose and a large number of animal and plant specimens were accumulated. Linnaeus, a Swedish botanist, completed the Linnaeus classification system based on genera and species in the 1930s and 1950s, and established the binomial method of species. His achievements had a great influence on biology and he was recognized as the founder of taxonomy. Due to the invention of the microscope, the British physicist R Hooke (1635 ~ 1703) observed that there was an empty room on a piece of cork in 1665, which was called a cell. A.van Leeuwenhoek, a Dutch microscopist, made a lot of microscopic observations, discovered bacteria in the 65438+70s, and revealed the existence of microorganisms for the first time.
/kloc-In the middle of 0/9th century, with the opening of China, a higher level of western biology was gradually introduced into China. By the middle of the 20th century, after transplantation, western biology had developed in China. Since then, China's modern biology has been brought into the mainstream of the world's biological development. Among them, some regional disciplines have certain regional characteristics.
Biology has been fully developed in the19th century. Physiology, bacteriology and embryology have all become independent disciplines. Cell theory and Darwin's theory of evolution are great achievements that affect the theoretical basis of biology. 1838, German botanist M.J. Schleiden proposed that cells are the basic units of plants. 1839, German zoologist T. Schwann further proposed that "all animals and plants are made up of cells". In the 1940s and 1950s, German zoologist R. remarque (18 15 ~ 1865) and German pathologist R. C. Fairshaw (1821~1965) Cytology, which focuses on cell structure, has gradually developed into an independent discipline, which directly affects the development of histology and embryology. The idea of biological evolution was put forward by French naturalist G.-L.de Buffon as early as 1776. 1809, the French biologist J.-B.de Lamarck expounded the evolution of organisms in "Animal Philosophy", and thought that the mechanism of species variation was "use into waste and retreat" and "acquired inheritance". However, this book is speculative and lacks evidence. British biologist C.R. Darwin put forward the theory of biological evolution with natural selection as the core according to a large number of facts in the Origin of Species. The publication of the Origin of Species gave a great shock to the society, and gradually gained universal recognition after the struggle with religion, which was called the Darwin Revolution in the history of science. But Darwin still left traces of how species mutate. German zoologist A. weismann put forward germplasm theory and germplasm selection theory successively from 1894 to 1896, which is neo-Darwinism. At the turn of the century, social Darwinism prevailed for a period of time, which extended the theory of evolution to the social struggle of human reality and adapted to the needs of the bourgeoisie.
In the 20th century, genetics, biochemistry and microbiology flourished, and the epoch-making elucidation of the double helix structure of 1953 DNA gave a stronger impetus to the development of molecular biology, which had a great impact on biology, medicine and agriculture.
Although J.G. Mendel, an Austrian Catholic monk, published an experimental report on his hybridization with peas as early as 1866, and found the separation phenomenon and the law of free combination of genetic factors, he was buried by Dutch botanist H. de Frees (1848 ~1935) for 35 years until/kloc. From then on, the law he discovered was called Mendel's law, and Mendel was also called the founder of genetics. In the 20th century, the combination of genetic research and cytology achieved brilliant results. The team represented by American geneticist T.H. Morgan has conducted a lot of experimental studies on Drosophila from191to 1930. The results show that genetic genes are located on chromosomes, gene linkage exchange, and different genes have relatively fixed positions. , developed Mendel's law and established chromosome (or cell) genetics. With the vigorous development of genetics, the Soviet Union appeared a political criticism denying the genetics of Mendel, weismann and Morgan from 1930s to 1960s, and established тдддддддддддддддддддддд10
In the first half of the 20th century, biochemistry developed by leaps and bounds: the chemical composition and partial structure of biomacromolecules such as protein, nucleic acid, sugar and lipid were analyzed; The protein nature of biocatalyst enzyme was proved. The structure and function of various hormones and vitamins have been well studied. On this basis, the basic metabolic pathway, photosynthesis, respiration and the key role of adenosine triphosphate (ATP) in energy conversion are expounded. These are mainly the contributions of biochemists from Germany, Britain and the United States.
With the study of infectious diseases, bacteriology has been greatly developed. /kloc-at the end of 0/9, Russian and German microbiologists discovered pathogenic microbial viruses smaller than bacteria. In the second decade of the 20th century, phages smaller than viruses and living in bacteria were discovered. The two smallest known microorganisms have simple structures and the ability of self-replication only in living cells, which play an important role as materials for geneticists to study self-replication.
With the development of genetics in the late 1920' s, the question of exploring the chemical entity of genetic gene was put forward. It is neither a geneticist nor a biochemist who solved this problem, but an American bacteriologist, O.T. Avery. 1944, he used experiments to prove that the transforming factor between different kinds of pneumococci was DNA, and DNA gradually entered the genetic stage. 1953, American biologist J. D. Watson and British physicist F.H.C C. Crick, who are familiar with the crystal structure of protein, cooperated in Cambridge University, England to clarify the double helix structure of DNA, which opened the door to molecular genetics. As a result, great research results emerge one after another: the double helix is divided into two single chains, which complement each other to form two double helices; The central principle guiding protein biosynthesis was put forward and the genetic code was decoded. Clarify the operon mechanism of gene regulation in prokaryotic cells; Recombinant DNA technology and the establishment of genetic engineering (1970s) and so on. At the end of 1980s, a cross-century international cooperation project-Human Genome Project-was drawn up and put into practice, which laid the foundation for solving the problems of human heredity and evolution. The elucidation of the double helix structure of DNA promoted the research on the relationship between the structure and function of biological macromolecules, and molecular biology was born, which had a far-reaching impact on all branches of biology, medicine and agriculture. Therefore, the elucidation of DNA double helix structure is recognized as the greatest achievement of biology and even natural science in the 20th century, and has triggered a biological revolution.
The breakthrough in the mystery of genes has inspired the scientific community to March into another biological fortress that needs further exploration-nerves and brains. From the discovery of nerve cells in 65438 to the establishment of neuron theory in 1980s, British physiologist C.S. Sherrington has done a lot of research on the structure and conduction of nerve cells. 192 1 ~ 1932 Austrian pharmacologist O. levy (1873 ~1961) and British physiologist H. H. Dale (1877). A lot of progress has been made in brain waves, the functions of the two hemispheres of the brain and the mechanism of comprehensive processing of the brain, which preliminarily shows that the brain activity composed of109 ~1kloc-0/1neurons is hierarchical and regular.
The great achievements of biological science in the 20th century also influenced the development of evolution. From the late 1930s to the mid-1940s, with the efforts of a group of biologists such as dobrzanski, a Russian-American geneticist, the theory of evolution combined with genetics and developed into a comprehensive theory of evolution, which totally denied acquired inheritance, emphasized gradualism, recognized evolution as a group phenomenon, and reaffirmed the overwhelming importance of natural selection in evolution. From 65438 to 0968, influenced by molecular biology, the neutral theory of molecular evolution appeared. 1972, according to the discovery of neopaleontology, the discontinuous equilibrium theory was put forward.
At the beginning of the 20th century, ecology still stayed in the study of the relationship between animals and plants, the environment and biological communities. 1926, V.I. Vernaschi of the Soviet Union clearly put forward the concept of biosphere. 1935 After British ecologist A.G. Tansley (187 1 ~ 1955) put forward the concept of ecosystem, the research of ecology gradually turned to the direction of studying material circulation and energy conversion by mathematical methods. The biosphere is the global ecosystem. Due to the rapid population growth and serious industrial pollution on the earth, environmental problems threaten the survival of mankind. Since 1960' s, global cooperative research on man and biosphere has been made several times. A comprehensive discipline based on ecology-environmental science was born.
Research object There are about 2-4.5 million kinds of living things on the earth. It is estimated that at least150,000 species are extinct. Every species has a variety of morphological structures and lifestyles. Among them, some are composed of prokaryotic cells and some are composed of eukaryotic cells; Some are single-celled organisms or groups, some are multicellular organisms; Some are photosynthetic autotrophic, some are absorbing heterotrophic or saprophytic heterotrophic, and some are swallowing heterotrophic; Some are producers of organic matter, some are consumers and some are decomposers. 1969, R.H. Whitaker of the United States put forward a five-boundary system of biological classification. He classified bacteria, cyanobacteria and other prokaryotes as monera, single-celled eukaryotes as protozoa and multicellular eukaryotes as plants, fungi and animals. China and Chen proposed a six-bound system in 1979. This system consists of three general boundaries: acellular, prokaryotic and eukaryotic. The total cell boundary is only virus 1. Prokaryotes are divided into bacteria and cyanobacteria. Eukaryotes include plants, fungi and animals. (See Classification)
Cell-free life-form viruses and phages have no cell morphology and complete enzyme system, and cannot produce adenosine triphosphate (ATP). Therefore, only after the virus enters the host cell can it use all equipment to reproduce. In recent years, a virus-like substance, which is simpler than a virus, has been discovered, with only small RNA molecules. In addition, a prion with only protein and no nucleic acid was found, which can infect mammals with chronic diseases. These incomplete life forms have narrowed the distance between inanimate and living.
Prokaryote prokaryotic cells are characterized by no membrane organelles such as mitochondria and plastids, no protein such as histones in chromosomes, and no nuclear membrane. Prokaryotes include bacteria and cyanobacteria.
Bacteria multiply rapidly, and the number is huge, almost all over the earth. They are important decomposers in the ecosystem and play an important role in the natural nitrogen cycle and carbon cycle. Some bacteria can oxidize inorganic substances and get energy from them to make food; Some bacteria contain bacterial chlorophyll which can be used for photosynthesis. The reproduction of bacteria is asexual. In some species, there is a primitive process of exchanging genetic material between two bacteria-bacteria junctions. Cyanobacteria, also known as cyanobacteria, are photoautotrophic prokaryotes.
The earliest life took place in a reducing atmosphere without free oxygen (see The Origin of Life). Photosynthesis of cyanobacteria makes the earth's atmosphere change from anoxia to aerobic, which creates conditions for the emergence of aerobic organisms. Cyanobacteria is still one of the producers in the modern earth ecosystem.
The original green algae found in recent years, which contain chlorophyll a, chlorophyll b and carotenoids, are similar to green algae and chloroplasts of higher plants, and have attracted the attention of biologists.
Eukaryotic cells have various organelles, such as mitochondria and Golgi apparatus, surrounded by double membrane nuclei, and long-chain DNA molecules combine with histones and other protein to form chromosomes. The proliferation of eukaryotic cells is mitosis and meiosis. As a result of mitosis, the replicated chromosomes are equally distributed to daughter cells.
Protozoa are the most primitive eukaryotes. Its primitiveness is not only manifested in the structural level of a single cell or its population, but also in various nutritional ways such as autotrophic, heterotrophic and mixed nutrition. These indicate that they have not clearly differentiated into animals, plants or fungi. According to these characteristics, Whitaker listed protozoa as one of his five systems. However, the division of this world is still controversial.
Plants are photosynthetic autotrophic eukaryotes. Its cells generally contain vacuoles and cell walls with cellulose as the main component. There are chloroplasts for photosynthesis in cells. Chloroplasts of green algae and higher plants use water as electron donor to release oxygen in photosynthesis. The plant kingdom is developing in the direction of adapting to photosynthesis. In higher plants, plants are divided into photosynthetic organs (leaves), supporting organs (stems) and fixed absorbing organs (roots). Most plants reproduce sexually, forming a life history in which gametophyte and sporophyte alternate generations. Plants are the most important producers in the ecosystem and the main source of oxygen on the earth.
Fungi are eukaryotes whose main nutrition is absorption. The cell wall of fungi contains chitin and cellulose, and there are no plastids and photosynthetic pigments in the cells. Fungi are widely distributed, with strong reproductive ability and diverse ways. The main reproductive unit is all kinds of spores produced by asexual or sexual reproduction. Fungi are also important decomposers in the ecosystem. Myxomycetes are a special kind of fungi. Its life history is partly fungi and partly animals, and its structure, behavior and feeding mode are similar to those of amoeba. Myxomycetes are considered to be between fungi and animals.
Animals are eukaryotes and feed on swallowing. Single-celled animals form food vacuoles after swallowing food, and food is digested in cells. Multicellular animals gradually evolved into extracellular digestion in the evolution process, and digested small molecular nutrients were absorbed by the digestive tract and transported to cells in various parts of the body through the circulatory system. In line with this, multicellular animals gradually formed complex excretory system, gas exchange system, as well as complex sensory organs, nervous system, endocrine system and motor system. In the ecosystem, animals are consumers of organic food. In the early days of life development, there were only cyanobacteria and bacteria on the earth, and the ecosystem was a double-ring system composed of producers and decomposers. With the appearance and development of eukaryotes, especially animals, the double-ring ecosystem has developed into a three-ring system composed of producers, decomposers and consumers. Today's colorful biological world has emerged.
Organisms with biological characteristics not only have diversity, but also have some characteristics and attributes that * * * has.
Biochemical identity The structure and function of biomacromolecules that make up an organism are consistent in all kinds of organisms. For example, the protein of various organisms is composed of 20 kinds of amino acids, and the nucleic acids of various organisms are long chains composed of nucleotides containing one of four bases, and their functions in various organisms are the same. The basic metabolic pathways in different organisms are the same, and even the enzymes needed in different steps are basically the same. Different organisms transfer energy in the form of ATP during metabolism.
Multi-level structure model All living things are composed of the same basic unit-cells. Structurally, the cell is a multi-molecular dynamic system composed of protein, nucleic acid, lipid and sugar. From the point of view of information theory, cells are the transmission system of genetic information and metabolic information; From a chemical point of view, cells are complex macromolecules synthesized from small molecules.
Besides cells, living things have other structural units. There are organelles, molecules and atoms under the cell, and there are organizations, organs, organ systems, individuals, populations, communities, ecosystems, biosphere and other units above the cell. Various structural units are arranged into a series of structural levels according to complexity and step-by-step combination. Every level of life activities depends on the interaction between its components and a specific ordered structure. Therefore, at a higher level, there may be properties and laws that are not available at a lower level.
The metabolic pathway and spatial structure of ordered and dissipative organisms are orderly. The endless metabolism of life system will inevitably increase the entropy value in the system. Biological order is produced and maintained by the energy dissipation process of metabolism.
The living environment of steady-state organisms is changeable, but they can maintain their own stability through self-regulation. For example, people's body temperature is kept at around 37℃, the acidity of blood is kept at around pH7.4, and the chemical composition and metabolic rate of human body tend to be stable. The stability of biological internal environment, that is, steady state, is guaranteed through a series of regulatory mechanisms. At present, the application of the concept of steady state has gone far beyond the scope of individual internal environment, and biological communities and ecosystems are also in a relatively stable state, without the influence of fierce external factors.
The continuation of life, except that the most primitive life was produced from inanimate matter under the environmental conditions of the earth at that time, can only be achieved by reproduction from parent to offspring. So heredity is the basic attribute of life. It is found that DNA is the carrier of genetic information, and the continuity of life is first manifested in the continuity of DNA.
The individual development of an organism is a stable process according to a certain growth pattern. Embryo development and organogenesis are based on endoderm, mesoderm and ectoderm, and are completed through the interaction of all parts. Now biology has proved that individual development is controlled by genetic information, and the basic development mode is determined by genes.
Evolution Theory1859 The publication of C.R. Darwin's Origin of Species established the theory of biological evolution based on natural selection. Evolution is a universal biological phenomenon. Evolution leads to the differentiation of species. The biological world is a unified natural pedigree, and all kinds of creatures, in the final analysis, all come from the most primitive life types. Biology not only has a complex depth level (from biosphere to biomacromolecules), but also has a history of individual development and a long history of species evolution.
Relationships in the ecosystem In nature, all kinds of creatures exist in the form of populations. In the ecosystem, different populations have different functions and functions. The relationship between organisms and their environment determines the characteristics of ecosystems. The external form, internal structure and function, living habits and behaviors of any living thing are always adapted to its position and role in the ecosystem. This adaptation is the result of long-term evolution.
According to the above characteristics, it is not difficult to see that although there is amazing diversity in the biological world, all creatures have the same material basis and follow the law of * * *.
Research methods mainly include observation and description, comparison and experiment.
Observation and description is the most basic method in biology and the most important method in early biological research. With the frequent activities of explorers, the record of species has increased dozens of times. This requires the identification and classification of species, and the methods of careful observation and description have made great progress. Morphology, anatomy and taxonomy were established. In order to distinguish different species clearly, it is necessary to use uniform and standardized terms to name species. This heavy terminology work was mainly done by C. von Linnaeus.
Comparative method studies biology by comparative method, aiming at finding the structural model or prototype of biology from the similarity between species. The results of comparative research reveal the structural unity of the biological world, which will inevitably touch the origin of different types of organisms. In the early days, it was mostly static and * * * comparison. After the establishment of C.R. Darwin's theory of evolution, dynamic and historical comparisons were added. In the 20th century, comparative method has penetrated into protein, nucleic acids and other organisms of different genera and species.