ТЕКСТЫ ДЛЯ ДОПОЛНИТЕЛЬНОГО ЧТЕНИЯ
Biology
Biology is the Study of living things and their vital processes. The field deals with all of the physicochemical aspects of life.
Because biology is such a board subject, it has been subdivided into separate branches for convenience of study. Despite apparent differences, all these subdivisions are interrelated by the basic principles that underlie all biological manifestations. The current approach to the study of living things is based on the levels of biological organization involved-whether molecules, cells, individuals, or populations – and on the specific subject matter under investigation – e.g., structure and function, types and classification, and growth and development. The study of the individual organism as a whole (organismic biology) dominated biology until the invention of the compound microscope (17th century) and the consequent rise of cell biology.
Because each of the aforementioned levels is still too board to be easily grasped by any one individual, a number of subdivisions have arisen over time. These include morphology, the study of the shape and structure of plants and animals; physiology, the study of the functions of cells, tissues, organs, and organ systems in living things; taxonomy, which attempts to classify living things into groups according to observed natural or hypothetical relationships; embryology, which is concerned with the formation and development of the embryo in plants and animals; genetics, which is the study of inheritance and variation in organisms and the mechanisms by which these processes operate; and ecology, the study of organisms and their interactions with other organisms and their environment.
Each of these subdivisions, in turn, can be further subdivided: morphology, for example, is divided into anatomy, which is the study of structures that can be observed with the naked eye; histology, the study of microscopic structure; and cytology, the study of the particular minutiae of cellular structure. There has also been an overlapping of the field of biology with other scientific disciplines; for instance, the modern principles of chemistry and physics are integrated with those of biology in biochemistry and biophysics, respectively. Molecular biology, which studies the chemical structures and processes of biological phenomena at the molecular level, draws on several disciplines and has become one of the most important biological sciences.
In another approach to classification, a field of biology may be especially concerned with the investigation of the type of living thing – e.g., botany, the study of plants; zoology, the study of animals; ornithology, the study of birds; ichthyology, the study of fishes; herpetology, the study of amphibians and reptiles; entomology, the study of insects; mycology, the study of fungi; microbiology, the study of microorganisms; protozoology, the study of protozoa; and bacteriology, the study of bacteria.
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Zoology
Zoology is branch of biology that studies the members of the animal kingdom and animal life in general. It includes both the inquiry into individual animals and their constituent parts, even to the molecular level, and the inquiry into animal populations, entire faunas, and the relationships of animals to each other, to plants, and to the nonliving environment. Thought this wide range of studies results in some isolation of specialties within zoology, the conceptual integration in the contemporary study of living things that has occurred in recent years emphasizes the structural and functional unity of life rather than its diversity.
Prehistoric man’s survival as a hunter defined his relation to other animals, which were a source of food and danger. As man’s cultural heritage developed, animals were variously incorporated into man’s folklore and philosophical awareness as fellow living creatures. Domestication of animals forced man to take a systematic and measured view of animal life, especially after urbanization necessitated a constant and large supply of animal products.
Study of animal life by the ancient Greeks became more rational, if not yet scientific, in the modern sense, after the cause of disease – until then thought to be demons – was postulated by Hippocrates to result from a lack of harmonious functioning of body parts. The systematic study of animals was encouraged by Aristotle’s extensive descriptions of living things, his work reflecting the Greek concept of order in nature and attributing to nature an idealized rigidity. (See Greece, ancient.) In Roman times Pliny bought together in 37 volumes a treatise, Historia naturalis, that was an encyclopaedic compilation of both myth and fact regarding celestial bodies, geography, animals and plants, metals, and stone. Volumes VII to XI concern zoology; volume VIII, which deals with the land animals, begins with the largest one, the elephant. Although Pliny’s approach was naïve, his scholarly effort had a profound and lasting influence as an authoritative work.
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Zoology continued in the Aristotelian tradition for many centuries in the Mediterranean region and by the Middle Ages, in Europe, it had accumulated considerable folklore, superstition, and moral symbolisms, which were added to otherwise objective information about animals. Gradually, much of this misinformation was sifted out: naturalists became more critical as they compared as they compared directly observed animal life in Europe with that described in ancient texts. The use of the printing press in the 15th century made possible an accurate transmission of information. Moreover, mechanistic views of life processes (i.e., that physical processes depending on cause and effect can apply to animate forms) provided a hopeful method for analyzing animal functions; for example, the mechanics of hydraulic systems were part of William Harvey’s argument for the circulation of the blood – although Harvey remained thoroughly Aristotelian in outlook. In the 18th century, zoology passed through reforms provided by both the system of nomenclature of Carolus Linnaeus and the comprehensive works on natural history by Georges-Louis Leclerc de Buffon; to these were added the contributions to comparative anatomy by Georges Cuvier in the early 19th century.
Physiological functions, such as digestion, excretion, and respiration, were easily observed in many animals, though they were not as critically analyzed as was blood circulation.
Following the introduction of the word cell in the 17th century and microscopic observation of these structures throughout the 18th century, the cell was incisively defined as the common structural unit of living things in 1839 by two Germans: Matthias Schleiden and Theodor Schwann. In the meanwhile, as the science of chemistry developed, it was inevitably extended to an analysis of animate systems. In the middle of the 18th century the French physicist Rene Antoine Ferchault de Reaumer demonstrated that the fermenting action of stomach juices is a chemical process. And in the mid – 19th century the French physician and physiologist Claude Bernard drew upon both the cell theory and knowledge of chemistry to develop the concept of the stability of the internal bodily environment, now called homeostasis.
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The cell concept influenced many biological disciplines that of embryology, in which cells are important in determining the way in which a fertilized egg develops into a new organism. The unfolding of these events – called epigenesis by Harvey – was described by various workers, notably the German-trained comparative embryologist Karl von Baer, who was the first to observe a mammalian egg within an ovary. Another German-trained embryologist, Christian Heinrich Pander, introduced in 1817 the concept of germ, or primordial, tissue layers into embryology.
In the latter part of the 19th century, improved microscopy and better staining techniques using aniline dyes, such as hematoxylin, provided further impetus to the study of internal cellular structure.
By this time Darwin had made necessary a complete revision of man’s view of nature with his theory that biological changes in species occur through the process of natural selection. The theory of evolution – that organisms are continuously evolving into highly adapted forms – required the rejection of the static view that all species are especially created and upset the Linnaean concept of species types. Darwin recognized that the principles of heredity must be known to understand how evolution works; but, even though the concept of hereditary factors had by then been formulated by Mendel, Darwin never heard of his work, which was essentially lost until its rediscovery in 1900.
Genetics has developed in the 20th century and now is essential to many diverse biological disciplines. The discovery of the gene as a controlling hereditary factor for forms of life has been a major accomplishment of modern biology. There has also emerged clearer understanding of the interaction of organisms with their environment. Such ecological studies help not only to show the interdependence of the three great groups of organisms – plants, as producers; animals, as consumers; and fungi and many bacteria, as decomposers – but they also provide information essential to man’s control of the environment and, ultimately, to his survival on Earth. Closely related to this study of ecology are inquiries into animal behaviour, or ethology. Such studies are often cross disciplinary in that ecology, physiology, genetics, development, and evolution are combined as man attempts to understand why an organism behaves as it does. This approach now receives substantial attention because it seems to provide useful insight into man’s biological heritage – that is, the historical origin of man from nonhuman forms.
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The emergence of animal biology has had two particular effects on classical zoology. First, and somewhat paradoxically, there has been a reduced emphasis on zoology as a distinct subject of scientific study; for example, workers think of themselves as geneticists, ecologists, or physiologists who study animal rather than plant material. They often choose a problem congenial to their intellectual tastes, regarding the organism used as important only to the extent that it provides favourable experimental material. Current emphasis is, therefore, slanted toward the solution of general biological problems; contemporary zoology thus is to a great extent the sum total of that work done by biologists pursuing research on animal material.
Second, there is an increasing emphasis on a conceptual approach to the life science. This has results from the concepts that emerged in the late 19th and early 20th centuries: the cell theory; natural selection and evolution; the constancy of the internal environment; the basic similarity of genetic material in all living organisms; and the flow of matter and energy through ecosystems. The lives of microbes, plants, and animals now are approached using theoretical models as guides rather than by following the often-restricted empiricism of earlier times. This is particularly true in molecular studies, in which the integration of biology with chemistry allows the techniques and quantitative emphases of the physical sciences to be used effectively to analyze living systems.
The Cell
The cell is one of the most basic units of life. There are millions of different types of cells. There are cells that are organisms onto themselves, such as microscopic amoeba and bacteria cells. And there are cells that only function when part of a larger organism, such as the cells that make up your body. The cell is the smallest unit of life in our bodies. In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on. All of these cells have unique functions and features. And all have some recognizable similarities. All cells have a «skin», called the plasma membrane, protecting it from the outside environment. The cell membrane regulates the movement of water, nutrients and wastes into and out of the cell. Inside of the cell membrane are the working parts of the cell. At the center of the cell is the cell nucleus. The cell nucleus contains the cell’s DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside of the cell – small structures that help carry out the day-to-day operations of the cell. One important cellular organelle is the ribosome. Ribosomes participate in protein synthesis. The transcription phase of protein synthesis takes places in the cell nucleus. After this step is complete, the mRNA leaves the nucleus and travels to the cell’s ribosomes, where translation occurs. Another important cellular organelle is the mitochondrion. Mitochondria (many mitochondrion) are often referred to as the power plants of the cell because many of the reactions that produce energy take place in mitochondria. Also important in the life of a cell are the lysosomes. Lysosomes are organelles that contain enzymes that aid in the digestion of nutrient molecules and other materials.
There are many different types of cells. One major difference in cells occurs between plant cells and animal cells. While both plant and animal cells contain the structures discussed above, plant cells have some additional specialized structures. Many animals have skeletons to give their body structure and support. Plants do not have a skeleton for support and yet plants don’t just flop over in a big spongy mess. This is because of a unique cellular structure called the cell wall. The cell wall is a rigid structure outside of the cell membrane composed mainly of the polysaccharide cellulose. The cell wall gives the plant cell a defined shape which helps support individual parts of plants. In addition to the cell wall, plant cells contain an organelle called the chloroplast. The chloroplast allow plants to harvest energy from sunlight. Specialized pigments in the chloroplast (including the common green pigment chlorophyll) absorb sunlight and use this energy to complete the chemical reaction:
6 CO2 + 6 H2O + energy (from sunlight) → C6H12O6 + 6 O2
In this way, plant cells manufacture glucose and other carbohydrates that they can store for later use.
Organisms contain many different types of cell that perform many different functions.
Environment and Ecology
Ecology is the science of how living things are related to their environment. Many people all over the world are concerned about the ecology today. The word «ecology» came from the Greek which means «home». This idea of «home» includes the whole planet of ours. We must protect our planet from littering, air pollution, water pollution, destruction of natural resources.
We know that polluted air, land and water are harmful to plants, animals and people.
Many territories, lakes, rivers, seas, oceans and the atmosphere are polluted with all kinds of technological, chemical, nuclear and other wastes. Awful harm is caused to our home by nuclear tests, atom bombs and accidents on the atomic power stations.
How can we keep our earth clean?
Don’t buy drinks in plastic bottles. These bottles can’t be recycled, and plastic won’t even degrade. If you throw this bottle, it will still litter the earth forever. Only buy water and other drinks in aluminium cans or glass bottles. Buy milk and juice in cartoons. Glass, aluminium and cartoon can be recycled.
The energy saved from one recycled aluminium can will operate a television set for three hours. If you throw an aluminium can out of the train window, it will still litter the earth up to 500 years later. If you throw the glass bottle you litter the earth forever.
It takes 500,000 trees just to make the newspapers we read every Sunday.
Save your family newspapers. Find out how to recycle newspapers in your area. Most paper thrown away in the office just has printing on one side. Ask your parents to bring home some of this paper. So you can use the blank side for writing or drawing.
Save water. If there is the leaky toilet or tap in your house, get someone to fix them. If you water the garden in the middle of the day when the sun is hot, most of the water evaporates before it gets to the roots. It is better to water the garden in the coolest part of the day. The best time to water is early in the morning before the sun gets hot.
The electric power stations burn coal to produce the energy that keeps your light on. That burning coal gives off gases, that – acid rains. So, save electric power. Turn off the lights when you leave the room. Turn off the TV or the stereo when you are not watching or listening.
Don’t cut wild flowers. In England since the Second World War 22 wild flower species have disappeared forever, 317 are standing on the brink.
English writer John Galsworthy said: «If you don’t think about the future you will not have it.»
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