Comprehension and Discussion
Ex. 1. Complete the following sentences:
The atmosphere is the layer of gas that …
Without air there would be no …
Air in its natural state is a …
Scientists divide atmosphere into …
The troposphere contains …
The upper portion of the atmosphere ranges …
The blue colour of the sky is due to …
The troposphere varies in thickness from …
Very thin air and electrically charged particles reflect …
Ozone absorbs …
Ex. 2. Here are the answers to some questions on the text. What are the questions?
One of the most unique features of Earth is the presence of a stable atmosphere (what).
Yes, air has weight.
The air gradually thins out far above the earth (where).
The atmosphere shapes our weather, climate and vegetation patterns (disjunctive).
The troposphere is the layer near the surface (alternative).
The lower atmosphere contains a considerable quantity of small solid particles (special).
No, it isn’t, all our weather is formed in the troposphere.
The ozone layer protects us from the harmful, burning rays of the sun (special).
Ex. 3. Draw a chart showing the layers of the atmosphere and their composition.
Ex. 4. Characterize different layers of atmosphere and their properties using the chart.
Text B
Task. Read the text and get ready to discuss its main points
Oxygen-Carbon Dioxide Cycle
Nitrogen and oxygen are important biologically, and each has a characteristic cycle of interaction with living things. Nitrogen is a key ingredient of the amino acids of which all proteins consist, and certain bacteria are able to convert atmospheric nitrogen into nitrogen compounds which plants can utilize in manufacturing amino acids.
Plants also combine carbon dioxide from the air with water absorbed through their roots to form carbohydrates in the process of photosynthesis, with oxygen as a by-product. Animals obtain the carbohydrates and amino acids they need by eating plants (or other animals that eat plants). Plants and animals both derive energy by using atmospheric oxygen to convert carbon in their foods to carbon dioxide. Thus the oxygen-carbon dioxide cycle is an essential aspect of all plant and animal life (Fig. 1).
?__________1 ?_____________ 2
Burning of organic matter
and fossil fuels (coal, oil, and
natural gas)
?_________5 ?______________3
Food eaten
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.
Oxygen and hydrogen are important in interaction with living things.
Nitrogen is a key ingredient of the amino acids.
Plants can utilize carbon through their roots in manufacturing amino acids.
The oxygen-carbon dioxide cycle is an essential aspect of all plant and animal life.
The reverse reaction of photosynthesis is perspiration.
The energy in sunlight is taken up directly by carbon dioxide and water.
Plants and animals derive energy by using atmospheric oxygen .
The substance chlorophyll is changed and absorbed in the process of photosynthesis.
Ex. 2. Complete the following sentences.
Nitrogen is a key ingredient of …
Certain bacteria convert atmospheric nitrogen into …
All proteins consist of …
Animals obtain the carbohydrates and amino acids by …
An essential aspect of all plant and animal life is …
The carbohydrates are complex compounds of …
Chlorophyll is a substance which is part of …
Chlorophyll serves to …
The reverse reaction of photosynthesis is …
The process of photosynthesis is responsible for …
The early atmosphere contained oxygen only …
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.