Fig. 1. The oxygen-carbon dioxide cycle
The carbohydrates formed by photosynthesis are complex compounds of carbon, hydrogen, and oxygen, and include sugar, starch, and cellulose – the first two familiar as important nutrients, the last the chief constituent of cell walls in plants (wood is mostly cellulose). Photosynthesis can be represented by the equation
CO2 + H2 O + sunlight → carbohydrates + O2
The energy in sunlight is not taken up directly by the carbon dioxide and water but instead by the substance chlorophyll, which is part of the green coloring matter of leaves; the chlorophyll is not permanently changed but serves to pass on the energy it absorbs to the reacting molecules in a complicated way. About 70 billion tons of carbon dioxide are cycled through plants each year.
The reverse reaction, called respiration, is the process by which living things obtain the energy they require for growth, motion, and so forth. Like photosynthesis, respiration occurs in a series of complex steps, but its overall result is straightforward: Carbohydrates + O2 → CO2 + H2O + energy
Photosynthesis not only maintains the oxygen content of the atmosphere but was apparently responsible for it in the first place. The early atmosphere of the earth, which is thought to have consisted of gases emitted during volcanic action, contained oxygen only in combination with other elements in such compounds as water (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2). Primitive organisms, which probably obtained their own energy by fermentation, eventually began to produce free oxygen by photosynthesis, and in time the oxygen content of the atmosphere increased to the point where more complex organisms could evolve. In addition to the oxygen now present in the atmosphere, photosynthesis is believed to account for the much larger quantity combined with other elements in the oxides, carbonates, and sulfates found in sediments and sedimentary rocks.
Ex. 1. Say if these statements are true or false.
1. Oxygen and hydrogen are important in interaction with living things.
2. Nitrogen is a key ingredient of the amino acids.
3. Plants can utilize carbon through their roots in manufacturing amino acids.
4. The oxygen-carbon dioxide cycle is an essential aspect of all plant and animal life.
5. The reverse reaction of photosynthesis is perspiration.
6. The energy in sunlight is taken up directly by carbon dioxide and water.
7. Plants and animals derive energy by using atmospheric oxygen .
8. The substance chlorophyll is changed and absorbed in the process of photosynthesis.
Ex. 2. Complete the following sentences.
1. Nitrogen is a key ingredient of …
2. Certain bacteria convert atmospheric nitrogen into …
3. All proteins consist of …
4. Animals obtain the carbohydrates and amino acids by …
5. An essential aspect of all plant and animal life is …
6. The carbohydrates are complex compounds of …
7. Chlorophyll is a substance which is part of …
8. Chlorophyll serves to …
9. The reverse reaction of photosynthesis is …
10. The process of photosynthesis is responsible for …
11. The early atmosphere contained oxygen only …
12. Photosynthesis accounts for much quantities of oxygen combined with …
Ex. 3. Write out the key words from the text and sum up the information you have learned using these words.
Text С
Task. Scan the text and state the main problems raised in it.
The Ozone Layer
1. Many scientists prefer to regard the stratosphere and mesosphere as being different parts of the same layer, because apart from temperature their properties are similar. Sounding balloons filled with hydrogen or helium routinely penetrate the stratosphere with instruments of various kinds and send down data by radio to ground stations; some aircraft, too, are capable of exploring the stratosphere. The still higher elevations of the mesosphere require rocket-borne apparatus if direct measurements are to be made, but a number of experimental methods have been devised that enable observatories on the ground to determine some of the physical properties of this part of the atmosphere.
2. The most striking feature of the stratosphere and the lower mesosphere is the presence of ozone, a form of oxygen whose molecules contain three oxygen atoms instead of the usual two. The chemical symbol for ozone is accordingly O3. Ozone is an excellent absorber of ultraviolet radiation; so excellent, in fact, that the relatively small amount of ozone in the upper atmosphere completely filters out the dangerous short-wavelength ultraviolet radiation emitted by the sun. Living things on earth would certainly have evolved very differently without the protection of the ozone layer, since few of today's organisms could survive exposure to solar ultraviolet rays at their full strength.
3. The ozone layer lies between 15 and 55 km. At its maximum density less than 1 molecule in 4 million is О3 - hardly an impressive concentration for so efficient a filter. At sea-level temperature and pressure, all the ozone in the atmosphere would form a layer less than an inch thick. The elevated temperatures of the upper stratosphere and lower mesosphere are due to the heating effect of the solar ultraviolet energy absorbed at the top of the ozone layer.
4. Why is the ozone content of the atmosphere concentrated in a particular region instead of being more or less uniformly distributed? The first step in the formation of an ozone molecule is the breaking up of an O2 molecule into two О atoms by solar ultraviolet light. The second step is the attachment of an О atom to an O2 molecule to form O3. The rate of ozone production thus depends upon both the O2 concentration and the intensity of solar ultraviolet light. At extremely high altitudes there are not enough O2 molecules for an appreciable amount of О3 to be formed. Between 15 and 55 km above the ground, however, the atmosphere is dense enough for the production of О3 but not so dense that the unstable ozone molecules break up into O2 + О too often in collisions with other molecules. At lower altitudes the ultraviolet light has already been absorbed so no ozone can come into being there except as a result of lightning strokes in the lower atmosphere.
Ex. 1. Put the sentences in the logical order.
1. The second step in the formation of an ozone molecule is the attachment of an О atom to an O2 molecule.
2. Ozone is an excellent absorber of ultraviolet radiation.
3. Apart from temperature their properties are similar.
4. The ozone layer lies between 15 and 55 km.
5. The first step in the formation of an ozone molecule is the breaking up of an O2molecule into two О atoms by ultraviolet light.
6. Many scientists regard the stratosphere and mesosphere as being different parts of the same layer.
7. The rate of ozone production depends upon both the O2 concentration and the intensity of solar ultraviolet concentration.
8. The most striking feature of the stratosphere and the lower mesosphere is the presence of ozone
Ex. 2. Check your understanding.
1. Look at the first paragraph and say which of the following statements is correct:
· The stratosphere and mesosphere
a) are exactly the same
b) differ in their temperatures
c) have the same temperature
d) have different properties except for temperature
· Information about the stratosphere is usually gathered
a) only by rockets
b) only by ground stations
c) by balloons
d) only by special aeroplanes
2. Now look at paragraph 2 and say which words have the same meaning as:
· very good
· attracting interest/attention
· comparatively
3. Now look at paragraph 3. Is this statement correct or incorrect?
· The ozone layer in the upper atmosphere is less than an inch thick.
4. Now look at paragraph 4 and say which of the following statements is correct:
· The formation of О3 requires
a) only the presence of O2 molecules
b) only the existence of ultraviolet light
c) neither O2 molecules nor ultraviolet light
d) both O2 molecules and ultraviolet light
· At a height of 15 to 55 km above the earth, О3 molecules
a) do not exist
b) always break up
c) sometimes break up
d) never break up
Ex. 3. Fill in the logical structural chart of the text.
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Ex. 4. Using your own words and the chart write a short description of the ozone layer. Use the information in the text.
Text D
Task. Read the text, study Fig. 1 and say what role the ionized layers high up in the atmosphere play.
The Ionosphere
In the year 1901 Marconi was able to send radio signals across the Atlantic Ocean for the first time. Radio waves, like light waves, tend to travel in straight lines, and the curvature of the earth therefore apparently presents an insuperable obstacle to long-distance radio communication. For this reason Marconi's achievement came as a great surprise. In a short time, however, Oliver Heaviside in England and Arthur Kennelly in the United States suggested that the effect could be caused by a reflecting layer high up in the atmosphere. Such a layer, together with the sea, could channel radio waves from one side of the Atlantic to the other (Fig. 1). Electromagnetic theory was able to predict the mechanism of the reflection: If some of the atoms and molecules in the upper atmosphere are ionized (become electrically charged) by the action of solar ultraviolet light and x-rays, the resulting assembly of charged particles will behave precisely like a mirror to radio waves (though not to the shorter-wavelength light waves).
Experimental confirmation of the presence of ionized layers high up in the atmosphere followed, and today the region properly called the thermosphere is often referred to as the ionosphere. During the day the ionosphere has four distinct layers, D, E, F1 and F2 in order of ascending altitude. At night the D layer disappears, the E layer wekens, and the F1 and F2 layers coalesce into a single weak F layer. The D layer tends to absorb rather than reflect radio waves, which is why radio reception from distant stations is best at night when this layer is absent. Solar outbursts from time to time increase the ionization in the D layer and produce radio blackouts that prevent long-range radio communication.
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Fig. 2. The D, E, f1, and F2 layers in the ionosphere. Several possible paths of radio waves are indicated. The D layer tends to absorb rather than reflect radio waves. At night much of the ionization disappears, leaving only E and F layers in weakened form.
Dialogue
Ex. 1. Read the following dialogue and act as an interpreter. Try to guess where this conversation might take place and who the people talking to each other might be.
1. Кислород – это химический элемент?
2. Да, кислород – это газ. У него нет цвета. Это бесцветный газ. Он не имеет ни вкуса, ни запаха.
1. Воздух – тоже газ, как и кислород. У него есть вес?
2. Воздух тоже имеет вес. И у кислорода, и у воздуха есть вес. Но воздух легче кислорода. Кислород немного тяжелее воздуха.
1. Кислород – это химически активное вещество?
2. Это самое химически активное вещество из всех известных.
1. Водород – тоже газ, как и кислород?
2. Да, подобно кислороду, у него тоже нет ни цвета, ни запаха. Как и кислород, водород тоже химически активен. Тогда как кислород – самый химически активный элемент, водород – самый легкий элемент.
1. Кислород широко распространен в земной коре?
2. Да, кислород – наиболее часто встречающийся элемент. Он составляет почти 50% массы земной коры.
1. Кислород – устойчивый элемент?
2. При обычной температуре и давлении кислород встречается в свободном состоянии в больших количествах и известен как устойчивый элемент.
1. С какими другими элементами соединяется кислород?
2. Кислород очень активный элемент. Например, соединяясь с водородом, он образует воду, а при соединении с углеродом – углекислый газ. Как кислород, так и водород соединяются со многими химическими элементами, образуя важные соединения.
Ex. 2. Dramatize the possible situation using the following key words:
colourless, tasteless, odourless, to have weight, chemically active substance, to be heavier than, the lightest of the elements, to occur, to unite, important compounds, widely spread element, stable element, a free state, under conditions of ordinary temperature and pressure.
Ex. 3. Reproduce this dialogue in the form of a monologue. Use the key words from Ex. 2.
Listening Comprehension
Text “The Atmosphere”
Part A. Pre-listening activities
Task 1. Make sure that you know the following words.
altitude – высота
to pant – задыхаться, часто и тяжело дышать
left hand side – левая сторона
Task 2. Before listening to the lecture answer the following questions.
1. What are the regions of the atmosphere?
2. What happens if you climb high mountains?
Part B. Listening activities
Task 1. As you listen to the tape mark whether these statements are correct or incorrect.
1. The subject of last week's lecture was the properties of the atmosphere.
2. The lecturer expects all the students to have climbed mountains.
3. If you climb a mountain, the air gets colder but not thinner.
4. In the lower atmosphere, the temperature falls at 6,5° C per kilometer of altitude.
5. The temperature falls at 3,6° F per mile.
6. At higher altitudes the temperature continues to drop.
7. Instruments to measure temperature are only carried in aeroplanes.
8. At even higher altitudes, the pressure continues to drop.
9. At even higher altitudes, the temperature continues to drop in the same way as at lower altitudes.
Task 2. Label the diagram in the way the lecturer tells you to.
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Part C. After listening activities
Task 1. Summarize the information the lecturer has given you.
Task 2. Interview one of your groupmates who has ever climbed high mountains.
What are the possible questions?
Revision
Ex. 1. Fill in the text with the appropriate word from the box
| sources, destroys, circulate, acid rain, industrialized, pollutants, harmful, inversion,smog, erupt, occurs. |
Air pollution
In the past, air pollution in (1) _____ countries caused a visible haze called smog. (2) _____ is a mixture of different pollutants (mainly sulphur dioxide gas and particles of soot) and water vapor in still, cold air. It occurs in unusual weather conditions when there is temperature (3) _____ that is, a layer of cold air close to the ground with a layer of warmer air above it. With temperature inversion the air does not (4) _____ so pollutants become trapped close to the ground.
When these (5) _____ combine with fog, they form a visible suspension in the air; this is known as smog. The main (6) _____ of sulphur dioxide and soot are fossil fuels, particularly coal. Oil, natural gas and hard, black coal produce much less sulphur dioxide than soft, brown coal. Sulphur-based smog rarely (7) _____ in developed countries today, but it is a major source of pollution in newly-industrializing countries such as India and China. Sulphur dioxide is, incidentally also emitted from volcanoes when they (8) _____ . Air pollution in the upper atmosphere does not cause smog, but it has other (9) _____ effects. Sulphuric and nitric acids are carried long distances with air currents and become (10) _____ . Acid rain damages crops and forests, destroys aquatic life in lakes and rivers, and ruins buildings.
It (11) _____ buildings by corroding metal and dissolving stone; some important historical monuments are being washed away by acid rain.
Ex. 2. Translate the text into Russian in writing. Give the title to this text.
How can we stop the greenhouse effect from getting worse? The most important way is to reduce the emission of carbon dioxide by industry and motor vehicles. At the 1992 United Nations Conference of Environment and Development in Rio de Janeiro, 150 countries signed the climatic change treaty, in which they agreed to work toward reducing global emission of carbon dioxide by the turn of the century. However, delegates were worried that the changes would be expensive and inconvenient. Delegates from the United States refused to allow specific targets for reducing carbon dioxide emissions, so the treaty is little more than a general statement of principles.
We cannot see, hear, taste or smell the earth's atmosphere, but it provides vital oxygen, protects us from damaging solar radiation and stabilizes the earth's climate. Pollution has already caused a large hole in the ozone layer and increased global warming. Some people do not believe that CFCs are harmful. They are ignoring the4 scientific evidence. Some people argue that the phenomenon of global warming has not yet been proven beyond doubt. Temperatures vary between day and night (diurnal variation), between winter and summer (seasonal variation), and between different geographical regions (regional variation). It is difficult to prove that average temperatures throughout the world are half a degree higher than they were 50 years ago. But it is surely sensible to try to reduce emissions of greenhouse gases today, rather than wait for another 10 or 15 years until the phenomenon of global warming is absolutely certain. Reducing CFC production and greenhouse gas emission will cost money and compromise our comfortable lifestyle. But if we do not take action to protect the earth's atmosphere, it will soon become unable to protect us.
Ex. 3. Translate into English using the vocabulary of the Unit.