ТОП 10:

The Theory of Natural Selection



In the 1800s, Charles Darwin, a British naturalist, developed the theory of natural selection in his book “On the Origin of Species by Means of Natural Selection”. Darwin had the opportunity to travel around the world as the naturalist on a British survey ship. Wherever Dar­win visited, he saw a large number of different kinds of plants and animals and noted how well they were adapted to their particular situations.

He determined that there were several factors that could interact together to allow for natural selection:

1. Individuals within a species showed variation; some of the variations were very useful and others were not. For example, individual animals that are part of the same species show different colour variations. Some colours make the animal more conspicuous while others are less conspicuous.

2. Organisms within a species typically produce many more offspring than can survive. This means that here is not enough suitable habitat for all of the offspring to grow to maturity. A pair of rabbits may have three to four litters of offspring each sum­mer with several young in each litter.

3. Because of the excess number of individuals, there is a struggle for survival. Individuals within the population must compete with each other for food, space, mates, or other requirements that are in limited supply.

Great horned owls and other large owls typically produce two young at a time, but if food is in short supply, the larger of the two young will get the majority of the food.

4. Because of variation among individuals, some would have a greater chance of surviving and reproducing than others. The competition for resources often results in the less fit individuals dying; therefore, they do not get a chance to reproduce themselves. Even if they do not die, they may mature more slowly and not be able to repro­duce as many times as the more fit members of the species.

5. As time passes and each generation is subjected to the same kind of process, there will be an increase in the percentage of individuals showing the favorable variations and a decrease in those having unfavorable variations. The species will become better adapted to its environment.

 

Задание 1. Закончите предложения:

1. Charles Darwin developed the theory of ….

2. Individuals within a species showed ….

3. Organisms within a species typically produce ….

4. Individuals within the population must compete with each other for ….

5. The competition for resources often results in ….

 

Задание 2. Прочитайте примеры естественного отбора из текста.

Modern Veterinary Care

The zoo veterinarian attends to the needs of every animal in the zoo habitat, from the tiniest shrew to the largest elephant, monitoring diet, dental health, and even reproduction. Zoo veterinarians perform blood tests, vaccinations, routine examinations, and even surgery. They manage endangered species to encourage successful mating and reproduction. For pandas, which are solitary in the wild, this might involve isolating individuals during the non-breeding season, and then bringing a pair together to mate when the time is right.

Veterinarians employed in regulatory medicine are responsible for controlling or eliminating certain diseases and protecting the public from animal diseases that can affect people. As food inspectors, they identify diseased livestock and unsafe meat and poultry. Regulatory medicine veterinarians also prevent foreign diseases from entering the country by enforcing quarantines and inspecting animals. They supervise interstate shipments of animals, test for the presence of diseases, and manage campaigns to prevent and eradicate diseases that threaten animal and human health such as tuberculosis, undulant fever, and rabies. Some public health veterinarians evaluate the safety of food processing plants, restaurants, and water supplies. Those in environmental health programs study and evaluate how various pesticides, industrial pollutants, and other contaminants affect human and animal populations. Other public health veterinarians are epidemiologists (specialists who study the cause and incidence of diseases). Public health veterinarians employed in government and private laboratories provide important diagnostic and testing services. They might, for example, inspect beef to insure that it does not contain E. coli bacteria or chicken to insure that it is free of Salmonella bacteria.

 

Задание 1. Соедините две части предложения:

1. The zoo veterinarian … 2. Food inspectors … 3. Regulatory medicine veterinarians … 4. Epidemiologists … 5. Some public health veterinarians… 1. identify unsafe meat and poultry. 2. study the cause and incidence of diseases. 3. perform blood tests, vaccinations, routine examinations. 4. evaluate the safety of food processing plants. 5. manage campaigns to prevent and eradicate diseases that threaten animal and human health.

 

Задание 2. Ответьте на вопрос:

What are the duties of public health veterinarians?

 

 

History of Microbiology

Microbiology began with the development of the microscope in the

17th and 18th centuries. By 1680 the Dutch scientist Anthony van Leeuwenhoek had produced a simple hand-held device that allowed scientists to view a variety of microbes – which Leeuwenhoek called “animalcules” – in stagnant water and in scrapings from teeth.

In the late 1700s Edward Jenner conducted the first vaccinations, using cowpox virus to protect people against smallpox. Later an altered form of the rabies virus was used to protect against the dreadful disease rabies. Vaccines remain the major means of protection against most viral infections.

Modern microbiology had its origins in the work of the French scientist Louis Pasteur – considered the father of microbiology – who developed methods of culturing and identifying microbes. During the second half of the 19th century, he and his contemporary Robert Koch provided final proof of the germ theory of disease. Pasteur was the first to propose that microbes cause chemical changes as they grow. Koch derived a central principle of modern microbiology, known as Koch’s Postulate that determines whether a particular germ causes a given disease.

Pasteur and his contemporaries developed pure culture methods for the growth of microbes. Another great advance in pure culture methods came in the late 19th century, when microbiologists discovered that each kind of microbe preferred a certain medium for optimal growth. In 1929 Alexander Fleming observed that molds can produce a substance that prevents the growth of bacteria. His discovery, an antibiotic is called penicillin, was later isolated and produced commercially to protect people against the harmful effects of certain microorganisms. Today several kinds of penicillin are synthesized from various species of the mold Penicillium and used for different therapeutic purposes. In the 1940s microbiology expanded into the fields of molecular biology and genetics. Viruses were found to be simple microbes that could be studied quantitatively, and they themselves were used to study the nature of deoxyribonucleic acid, or DNA Scientists found that DNA could be removed from living cells and spliced together in any combination. They were able to alter the genetic code dictating the entire structure and function of cells, tissues, and organs.

 

Задание 1. Соотнесите имя ученого с его вкладом в науку:

1. Anthony van Leeuwenhoek 2. Edward Jenner 3. Louis Pasteur 4. Robert Koch 5. Alexander Fleming 1. provided final proof of the germ theory of disease. 2. produced a simple hand-held device that allowed scientists to view a variety of microbes. 3. conducted the first vaccinations. 4. observed that molds can produce a substance that prevents the growth of bacteria. 5. developed methods of culturing and identifying microbes.

Задание 2. Перескажите текст на родном языке.

Animal Kingdom

All living things are divided into five kingdoms. Bacteria belong to the kingdom Monera, while the plantlike algae and animal-like protozoa are members of the Protista. The fungal kingdom includes molds, yeast, and mushrooms, and the kingdom Plantae includes all multicellular plants. The largest kingdom, however, is the Animalia. Its members range from very simple invertebrates, such as sponges, to highly complex mammals, such as whales, monkeys, and humans. Animals display some key differences that distinguish them from other living things. For example, what is the difference between a horse and grass? A horse moves around in the pasture eating grass. It trots toward you when you offer it a lump of sugar and shows pleasure when you stroke its head. The grass, however, is rooted to one place. It does not respond behaviorally to people or to the horse in any way

Most animals move freely from place to place and can sense their surroundings; that is, they can taste, smell, hear, see, and touch. Certain simple animals, such as the corals and barnacles, spend most of their lives fastened to one spot, but they are able to swim freely when they are young. Even these rooted animals have parts that move in order to capture food. Plants, however, cannot shift around at their own will. They react to heat, light, chemicals, and touch, but their responses are involuntary and automatic, quite different from those of animals.

All living things are made up of cells of protoplasm. They may consist of a single cell, as does an amoeba, or billions of cells, as do trees and horses. The cell wall of a plant is composed of a woody material called cellulose. No true animal contains cellulose. Animal cells are bounded by a membrane composed chiefly of fat and protein.

 

Задание 1. Закончите предложения:

1. Plants react to heat, light, chemicals, and touch, but their responses are…

2. The largest kingdom Animalia ranges from…

3. All living things are made up of…

4. Certain simple animals spend their lives…

 

Задание 2. Используя материал текста, ответьте на вопросы:

1. How many kingdoms are all living things divided into?

2. What is the largest kingdom?

3. How do animals sense their surroundings?

4. Do plants react to their surroundings?

5. All living things are made up of cells of protoplasm, aren’t they?

Control of Animal Diseases

Animal diseases are of great concern to humans for several reasons. Diseases can reduce the productivity of animals used to produce food, such as hens and dairy cows. Animals raised as food, such as pigs and beef cattle, that become ill may affect the economic well-being of many industries. Some animal diseases can be transmitted to humans, and control of these types of diseases, known as zoonoses, is vital to public health. In the wild, animal populations reduced by disease can upset the ecological balance of an area. And, in the case of pets, prevention and treatment of animal diseases help pets live long and healthy lives, enhancing the companionship shared by a pet and its human owner. Animal diseases are characterized as infectious and noninfectious. Infectious diseases are caused by an agent, such as bacteria or a virus that penetrates the body’s natural defense mechanisms, while noninfectious diseases are caused by factors such as diet, environment, injury, and heredity. Sometimes the cause of a disease is unknown. An animal may also experience one disease or a combination of diseases at any one time. To identify a disease, a veterinarian (a doctor who treats animals) first determines the animal’s signalment – its species, breed, age, and sex. This information helps to identify a disease because some diseases are more prevalent in certain species, or a disease may preferentially affect one sex or age group. The veterinarian then gathers a complete history of the animal and its problem. This history includes the symptoms the animal is displaying and when they first appeared, as well as whether the animal has been exposed to something new in its surroundings or to other animals. The veterinarian gives the animal a thorough physical examination, which may include measuring its body temperature, listening to its heart, checking its pulse, and feeling its abdomen and lymph nodes. The veterinarian then creates a list of possible diseases that may be making the animal sick. The list may be narrowed by running diagnostic tests such as X-rays, electrocardiograms, blood analyses, and bacterial or fungal cultures. Once the disease is identified, the doctor develops a treatment plan for the animal.

 

Задание 1. Ответьте на вопросы по тексту:

1. Why are animal diseases of great concern to humans?

2. Can animal diseases upset the ecological balance of an area?

3. What are two types of animal diseases?

4. What information helps to identify a disease?

5. When does the doctor develop a treatment plan for the animal?

 

Задание 2. Опишите действия ветеринарного врача по постановке диагноза болезни животного.

Environment

Everything that affects an organism during its lifetime is collectively known as its environment. Environment is a very broad concept. For example, an animal like a raccoon is likely to interact with mil­lions of other organisms (bacteria, food organisms, parasites, mates, predators), drink a large number of liters of water, breathe huge quantities of air, and respond to daily changes in temperature and humidity during its life­time. This list only begins to describe the various components that make up the environment of the organism. Because of this complexity, it is useful to subdivide the concept of environment into abiotic (nonliving) and bi­otic (living) factors.

Abiotic factors include the flow of energy necessary to maintain any organism, the physical factors that affect an organism and the supply of molecules required for an organism’s life functions.

The ultimate source of energy for almost all organisms is the sun. Animals obtain their energy by eating plants or other animals that eat plants. Ultimately, the amount of living material that can exist in an area is determined by the plants and the amount of energy they can trap.

Other physical factors include such things as climate, age, temperature and daily variations; the type (rain, snow, hail), amount, and seasonal distribution of precipita­tion; type of soil present and even the three-dimensional shape of the space the organism inhabits.

All forms of life require atoms such as carbon, nitrogen, and phosphorus, and molecules such as water to con­struct and maintain themselves. Organisms constantly obtain these materials from their environment by eating food or carrying on photosynthesis, use them for a period of time as part of their body structure, and return them to their surroundings through respiration, excretion, or death and decay.

The biotic factors influencing an organism include all forms of life in its environment. Plants that carry on pho­tosynthesis; animals that eat other organisms; bacteria and fungi that cause decay; and bacteria, viruses, and other parasitic organisms that cause disease are all part of an organism’s biotic environment. The kinds of or­ganisms and the number of each kind are also important in characterizing the environment.

Задание 1. Найдите в тексте английские эквиваленты:

окружающая среда, хищники, поток энергии, получать энергию, распределение осадков, формы жизни, структура тела, дыхание, выделение, бактерии и грибы, вызывать болезнь, виды организмов.

Задание 2. Прочитайте предложения, которые описывают составные части окружающей среды организмов.

Modern Veterinary Care

More than 45,000 veterinarians currently practice medicine in the United States, primarily in private hospitals and clinics. Of these, about 60 percent treat small animals such as cats and dogs exclusively; about 10 percent treat large animals such as cattle and other livestock; and some 5 percent specialize in horses. The remainder treats both large and small animals. About 9,000 veterinarians in the United States work in corporations or public institutions, such as pharmaceutical companies, colleges or universities, or in local, state, or federal government agencies such as the United States Army Veterinary Corps. Typical small-animal veterinarians are family advisors as well as animal health care providers. They may help clients select an appropriate species or breed of pet and then guide them in the proper nutrition, grooming, training, and general husbandry of their new pet. A large portion of this practice involves preventive care, such as vaccinating, screening, and treating animals for internal and external parasites, as well as performing operations that prevent pets from bearing unwanted offspring. Small-animal veterinarians also treat their patients’ illnesses and injuries, address the owners’ concerns, and provide references to specialists when necessary. Another important responsibility of veterinarians is to provide humane euthanasia (the act of ending a patient’s life).

Large-animal veterinarians work primarily with livestock. They perform vaccinations, parasite control, and neutering, but there are several important differences. Large-animal veterinarians often treat groups of animals rather than individuals. They insure that infectious diseases do not spread from farm to farm. Most patients of large-animal veterinarians are viewed from the stand point of their economic potential.

They may perform artificial insemination on a herd of cows, treat a horse with colic (severe abdominal pain), or assist a sow in delivering its piglets. Large-animal medicine and surgery is often practiced in stables, barns, and open fields rather than in animal hospitals. Veterinarians must, therefore, carry medicine and instruments with them wherever they go to face almost any challenge.

 

 

Задание 1. Согласитесь или не согласитесь со следующими утверждениями:

1. Typical small-animal veterinarians are family advisors.

2. A large portion of veterinarians’ practice involves preventive care.

3. Small-animal veterinarians treat groups of animals.

4. Large-animal veterinarians work primarily with pets.

5. Large-animal medicine and surgery is never practiced in stables, barns and open fields.

 

Задание 2. Найдите в тексте английские эквиваленты следующим словам и словосочетаниям:

выбрать породу, правильное питание, вакцинация, лечение, внешние паразиты, потомство, правила, искусственное осеменение, инфекционная болезнь.

 

History of zoology

Humans have always been interested in the animals around them. They have benefited from learning about animals that are a source of food and clothing and other species that are harmful.

Animals were first classified in the 4th century BС by the Greek philosopher Aristotle, whose system was based on the similarity of organisms in shape and structure rather than on their phylogenetic lineage. Aristotle classified birds and bats together because they both had wings and could fly. The formal study of many fields of zoology began in the 15th and 16th centuries AD. In the 1500s the Italian artist Leonardo da Vinci and the Greek physician Andreas Veselius demonstrated that the internal anatomy of humans and other vertebrates was similar. The dissection of animals during the next two centuries led to numerous discoveries in anatomy and physiology. In the 1600s the invention of the microscope and the first observation of a single-celled animal, by Dutch microbiologist, Anthony van Leeuwenhoek, evoked new interest and excitement to the field of zoology.

Zoological discoveries at the microscopic level continued. During this period Francis Bacon and other scientists worked out general concepts of scientific observation and experimentation that are still in use.

In the 1750s an important advance was made by Swedish naturalist Carolus Linnaeus in the fields of taxonomy and systematics. Using some of the ideas of classification developed by John Ray during the late 1600s, Linnaeus devised a scheme for classifying plants and animals on the basis of their presumed phylogenetic relationships. Using the binomial names for genera and species to indicate the similarities between species, his system is still used.

The most dramatic development in zoology and all of biology was the 1859 publication of “On the Origin of Species by Means of Natural Selection” by Charles Darwin. Darwin's presentation of the concept of natural selection and evolution provided a universal explanation for the variations, similarities, and differences observed among all organisms. His thesis became the foundation on which modern zoology is based.

Задание 1. Подтвердите или опровергните следующие утверждения предложениями из прочитанного текста:

1. Animals were first classified in the 15th century AD by Leonardo da Vinci.

2. Aristotle demonstrated that the internal anatomy of humans and other vertebrates was similar.

3. The invention of the microscope by Dutch microbiologist Anthony van Leeuwenhoek led to numerous discoveries in anatomy and physiology.

4. Swedish naturalist Carolus Linnaeus classified plants and animals using the binominal names for genera and species to indicate the similarities between species.

5. Charles Darwin’s thesis “On the Origin of Species by Means of Natural Selection” became the foundation on which modern zoology is based.

 

Задание 2. Перескажите текст, используя следующие вопросы:

1. Why have humans always been interested in the animals around them?

2. What was the first classification of animals based on?

3. When did zoological discoveries at the microscopic level become possible?

4. What contribution did Carolus Linnaeus make to the development of systematics?

5. What foundation is modern zoology based on?

Mammals

Despite their size differences, the great blue whale and the pygmy shrew have something in common: they are both members of a warm-blooded, air-breathing class of vertebrate (backboned) animals known as Mammalia, or mammals. In many ways mammals are the most highly developed of all creatures.

The term mammal explains one important way in which creatures in this class are set apart from other animals. It comes from the Latin mamma, which means “breast”. Every female mammal has special glands, mammae that secrete milk. The females of all but the most primitive mamalian species are viviparous. This means they bear their young alive. The уоung are then fed with milk until they have grown enough to get food for themselves.

Hair is a typical mammalian feature. In many whales, however, it exists only in the fetal stages of development. Another basic trait of mammals is their highly developed brains – the most complex known. Particularly well developed is their cerebrum, the part of the brain that controls memory and learning. The mammalian brain enables the young to learn from the experience of their elders. Since the young mammal is dependent on its mother for nourishment, a period of learning is possible. This in turn has brought about a degree of behavioral adaptability unknown in any other group of organisms. Whales, seals, and dogs are among the most intelligent mammals, but monkeys, apes, and humans are the most intelligent of all.

 

Задание 1. Прочитайте и переведите предложения, в которых описаны характерные особенности млекопитающих.

Задание 2. Задайте вопросы к следующим предложениям, начав их с вопросительного слова в скобках:

1. Mammals are the most highly developed of all creatures. (What animals)

2. The term mammal comes from the Latin “mamma”, which means “breast”. (Where)

3. Since the young mammal is dependent on its mother for nourishment, a period of learning is possible. (Why)

 

 

The Importance of Bacteria

Much of our experience with bacteria involves disease. Although some bacteria do cause disease, many kinds of bacteria live on or in the human body and prevent disease. Bacteria play important roles in the environment and in industry. In most cases the bacteria that cause disease are not part of the bacteria that normally inhabit the body. They are picked up from sick people, sick animals, contaminated food or water, or other external sources. Bacterial disease also can occur after surgery, an accident, or some other event that weakens the immune system.

When the immune system is not functioning properly, bacteria that usually are harmless can overwhelm the body and cause disease. These organisms are called opportunistic because they cause disease only when an opportunity is presented. For example, cuts or injuries to the skin and protective layers of the body enable normally friendly bacteria to enter the bloodstream or other sterile parts of the body and cause infection. Surgery may enable bacteria from one part of the body to reach another, where they cause infection. A weakened immune system may be unable to prevent the rapid multiplication of bacteria and other microorganisms.

Opportunistic infections became more important in the late 20th century because of diseases such as acquired immunodeficiency syndrome (AIDS), a viral disease that ravages the immune system. Some dramatic infectious diseases result from exposure to bacteria that are not part of our normal bacterial community. Cholera, one of the world's deadliest diseases today, is caused by the bacterium Vibrio cholerae. Cholera is spread in water and food contaminated with the bacteria, and by people who have the disease. After entering the body, the cholera bacteria grow in the intestines, often along the surface of the intestinal wall, where they secrete a toxin (poison). This toxin causes massive loss of fluid from the gut, and an infected person can die of dehydration (fluid loss) unless the lost fluids, and the salts they contain, are replaced.

Задание 1. Ответьте на вопросы:

1. Do all bacteria cause disease?

2. Where do bacteria play important roles?

3. In what cases can bacterial disease occur?

4. Can bacteria that are usually harmless cause disease?

5. Why do opportunistic infections become more important in the late 20th century?

 

Задание 2. Из списка болезней выберите те, о которых идет речь в тексте:

tuberculosis, cholera, pneumonia, acquired immunodeficiency syndrome, anthrax.

Задание 3. Опишите течение холеры, используя текст и следующие глаголы:to be caused, to be spread, to grow, to secrete, to cause, to die.

 

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