What types of bacteria do you know? — КиберПедия 

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What types of bacteria do you know?

2017-08-11 322
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Various types of bacteria that are present in water can cause disease in humans, and water-purification plants are designed to destroy these microorganisms. Bacteria from industrial wastes may also act as pathogens, or agents of disease. Conversely, some types of bacteria act as cleansing agents in water, and water-treatment facilities utilize some such bacteria to break down the organic matter that is present in sewage.

Various types of bacteria contaminate foods and can cause food poisoning in humans. Pasteurization is routinely used to neutralize bacteria that may be present in milk, for example. Other sterilization techniques include high temperature, radiation, ethylene oxide, and other antiseptics and germicides.

What is virulence?

The ability of a bacterium to cause a disease is called virulence. One contributing factor to the degree of virulence is the type of capsule a bacterium has. Some bacteria have a specificity for various parts of the body: meningo-coccal bacteria infect the brain membranes, and tubercule bacteria infect the lungs. Some are slightly more generalized: staphylococcal bacteria can infect the skin, causing boils; the bloodstream, causing blood poisoning; and the bones, causing the condition known as osteomyelitis.

Are all bacteria harmful?

Although human interest in bacteria frequently focuses on their harmful effects, most bacteria are harmless to human beings, and many of them are actually beneficial. Saprophytic bacteria, for example, perform an ecologically indispensable role in the breakdown of dead organisms and organic wastes; with out such agents of decomposition, the cycling of various elements vital to living organisms (including nitrogen, carbon, and phosphorus) would cease in the biosphere.

How are bacteria used?

Bacteria also form highly beneficial associations with animals. For instance, the bacterial inhabitants of the ruminant stomach break down cellulose; this enables cows, sheep, and other ruminants to digest grass. Humans also harbour beneficial bacteria, such as those in the lower intestine that synthesize vitamin K. Bacteria are also used in various industrial processes, especially in the food industry; the production of buttermilk, yogurt, cheeses, pickles, and sauerkraut are all dependent upon bacterial action.

What is the scientific classification of bacteria?

The scientific classification of bacteria is in transition, particularly at the higher taxonomic levels. The bacteria form the only prokaryotic kingdom, that of the Monera. Within this kingdom, at least two groups have been distinguished, the eubacteria and archaebacteria. DNA hybridization studies of ribosomal RNA have proven useful in defining these groups.

 

5. Read the text and find English equivalents to the Russian sentences given below.

Fish

Fish are vertebrates (animals with a backbone) that are completely adapted for life in water. They breathe under water and have a streamlined body for swimming. They have fins to propel, balance, and steer themselves. Fish are found in both freshwater and marine habitats. Sharks and rays belong to an ancient group of fish that existed 200 million years before dinosaurs. They are called cartilaginous fish because they have a skeleton made of cartilage, a kind of gristle. Their big, oily liver helps them float, and they have a skin with toothlike scales.

1. У них есть плавники, при помощи которых они передвигаются, держат равновесие и управляют направлением движения.

2. Их называют хрящевыми рыбами, так как у них скелет состоит из своего рода хрящей.

3. Они дышат под водой и имеют обтекаемое тело для плавания.

4. Их большая жирная печень помогает им держаться на воде, а кожа покрыта зубчатой чешуей.

5. Средой обитания для рыб может как пресная, так и морская вода.

6. Read the text, tell about characteristic features of amphibians and the differences between frogs and toads; find English equivalents to the Russian expressions:

Выпученные глаза;

Припадающий к земле корпус;

Перепончатые лапы;

Бородавчатая кожа.

Amphibians

Amphibians are animals that can live on land but need to return to water to breed.

Amphibians are ectothermic vertebrates (animals with a backbone). The group includes frogs, toads, salamanders, and newts. Frogs and toads are the most common amphibians.

The adults have bulging eyes, a squat body, and no tail. Frogs have a smooth skin and long, powerful back legs with webbed feet for jumping and swimming. They normally live in or near water. Toads have a dry, warty skin and shorter legs with less webbing between the toes. They prefer to live on land, except during breeding.

7. Read the text and match the words in column A with their equivalents in column B.

Arthropods

Arthropods make up the largest group in the animal kingdom. A typical arthropod has a segmented body, a hard outer skeleton called an exoskeleton, and jointed legs; many arthropods have compound eyes. Having an exoskeleton limits the growth of an organism, so arthropods molt (shed their exoskeleton) and grow to fill a larger one. Arthropods normally molt several times during their life.

A B

Arthropods Линять

Segmented Составной

Outer Внешний

Exoskeleton Членистоногие

Jointed Сегментированный

Compound Наружный

To molt Составной

 

6. Read the text and answer the questions:

Reptiles

Reptiles are vertebrates that have successfully adapted to life on land. They have a scaly skin to avoid drying out and have well-developed lungs to breathe in air.

Most reptiles lay eggs that have food and water in the waterproof shell. These characteristics enable them to survive in dry places.

Reptiles are ectothermic, which means their body temperature varies with the surroundings.

There are three main groups of reptiles: snakes and lizards, crocodiles and alligators, and turtles.

1. What is a reptile?

2. What does the term “ectothermic” mean?

3. How many groups of reptiles do you know?

 


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