Fill in the correct preposition for each blank space. 1. Herein is the first basic principle _ ecosystem sustainability:

1. Herein is the first basic principle____ ecosystem sustainability:

____ sustainability, ecosystems dispose_______ wastes and replen­
ish nutrients_____ recycling all elements.

2. This principle is_____ harmony______ the Law_____ Conser­
vation ____ Matter.

•>• Wfe can see this even more clearly______ focusing______ the path­
ways ____ three key elements: carbon, phosphorus, and nitrogen.

⁴- It is convenient to start the carbon cycle_____ the "reservoir"

------ carbon dioxide molecules present_____ the air and dis­
solved ____ water.

Unit Five

Ecosystems: How They Work

 

5. Through food chains, the carbon atoms then move___ and be­
come part_____ the tissues_____ all the other organisms____

the ecosystem.

6. However, it is unlikely that a particular carbon atom will be passed

_____ many organisms_____ any one cycle because____ each

step there is a considerable chance that the consumer will break
_____ the organic molecule_____ cell respiration.

7. As this occurs, the carbon atoms are released back_________ the envi­ronment molecules carbon dioxide, thus complet­ing one cycle, but_____ course ready to start another.

8. Phosphate dissolves____ water but does not enter air.

9. The phosphate may then be reabsorbed____ plants to start an­other cycle.

10. No matter_____ carbon dioxide is released, it will mix________ and

maintain the concentration_____ carbon dioxide_____ the air.

11. A very serious case____ humans interfering______ the phospho­rus cycle is seen the cutting tropical rainforests.

12. This type of ecosystem is supported___ a virtually 100 percent

efficient recycling____ nutrients.

13. Meanwhile, phosphorus is replaced____ croplands_____ min­
ing phosphate rock______ a process that will ultimately result___

depletion.

14. Fixed organic nitrogen is passed____ the legumes_____ other

organisms_____ the ecosystem_____ food chains.

IV. DEFINITE/INDEFINITE ARTICLES

Use a/an or the where needed. If no article is needed, write an A" in the blank space.

However, it is unlikely that____ particular_____ carbon atom

will be passed through many____ organisms on any one_____ cy­
cle because at each step there is______ considerable chance that__ .

consumer will break down_ organic molecule in________ cell res­
piration. As this occurs,______ carbon atoms are released back to .

environment in____ molecules of______ carbon dioxide, thus com­
pleting one cycle, but of course ready to start____ another. Like­
wise, burning_____ organic material returns_____ carbon atoms

locked up in_____ material to______ air in______ carbon dioxide

molecules. No two successive cycles of________ particular carbon atom

are likely to be_____ same. Nor are______ two cycles likely to be

_within______ same ecosystem because in_____ atmosphere_____

wind will carry them around____ globe.

V. VALUES DISCUSSION

Answer the following questions. Then discuss your answers with your classmates.

1. What are the organic material and oxygen produced by?

a. heterotrophs b. green plants с detritus feeders d. other

2. What do consumers and other heterotrophs require?

a. green plants b. the food с oxygen d. other

3. What is the first basic principle of ecosystem sustainability?

a. Ecosystems dispose of wastes.

b. Ecosystems replenish nutrients by recycling all elements.

с Atoms are neither created nor destroyed, nor converted one

into another, d. other 4.1s this principle in harmony with the Law of Conservation of Mat­ter? a. no b. yes с I don't know. d. other

5. Where may carbon dioxide molecule be found?

a. present in soil с dissolved in water

b. present in the air d. other

6. How do carbon atoms from carbon dioxide become the carbon atoms
of all the organic molecules?

a. through all the organisms in the ecosystem

b. through further metabolism
с through photosynthesis

d. other

7. When are the carbon atoms released back to the environment in
molecules of carbon dioxide?

a. When the consumer will break down the organic molecule in
cell respiration.

b. When completing one cycle.

с When burning organic material, d. other

62 Unit Five

8. Where does phosphorus exist as inorganic phosphate ion?

a. in water с in various rock

b. in soil d. other

9. How do plants absorb phosphate?

a. from the soil с from water solution

b. from air d. other

10. What is an important difference between the carbon cycle and the
phosphorus cycle?

a. When carbon dioxide is released, it will mix into the air. !

b. When carbon dioxide is released, it will maintain the concen­
tration of carbon dioxide in the air. . 'I

с The phosphorus cycle does not have a gas phase, d. other

11. How does phosphate make its way into waterways?

a. directly by way of runoff from agricultural croplands

b. by mining phosphate rock

с indirectly by way of discharge of sewage effluents d. other

12. Why is the nitrogen cycle more complex than the carbon and phos­
phorus cycles? s

a. It has a mineral phase.

b. It has a gas phase. -
с It has both a gas phase and a mineral phase.

d. other

13. Where is the main "reservoir" of nitrogen?

a. in the soil b. in water с in the air d. other

14. How can plants utilize nitrogen gas?

a. as ammonium ion с as nitrate ion

b. directly from the air d. other .

15. What process is called biological nitrogen fixation?

a. symbiosis of the legume and the bacteria *

b. symbiosis of nodules on roots of legumes and the bacteria
с conversion of nitrogen gas to the ammonium form

d. other

16. What is atmospheric nitrogen fixation?

a. Animals break down proteins and other organic compounds.

b. Nitrogen is excreted, generally in the ammonium ion form.

gcosystems: How They Work 63

c. Nitrogen gas is converted to the ammonium form by discharg­
es of lightning.

d. other

17. What do all natural ecosystems depend on?

a. legumes with their symbiotic bacteria

b. nitrogen-fixing organisms
с a huge diversity of plants
d. other

18. What plants are the first to recolonize a burned-over area?

a. desert shrubs с legumes

b. clovers d. other

19. How do you feel about the nitrogen cycle in aquatic ecosystems?

a. It differs from terrestrial systems.

b. It is similar to terrestrial ecosystems.

с It is the same as in terrestrial ecosystems, d. other

20. How have humans been able to bypass the necessity for legumes
when nonlegume crops are being grown?

a. They produce ammonium and nitrate compounds.

b. They alternate legumes with nonlegume crops,
с They fix nitrogen in chemical factories.

d. other '••■■

VI. ROLE-PLAY

Choose one of the following situations to act out.

1. Two post-graduates are talking about nutrient cycling, particularly about the various inputs and outputs of producers, consumers, de­tritus feeders and decomposers.

2. A scientist is explaining to an audience (which can be the whole class) the first basic principle of ecosystem sustainability and its harmony with the Law of Conservation of Matter. The audience can then ask questions.

3. Two young scientists are changing their views and opinions about the carbon cycle.

4- As a reporter at a conference, you are speaking about the phospho­rus cycle and an important difference between it and the carbon

64 Unit Five Ecosystems: How They Work______________ 65

cycle. The participants (which can be the whole class) will then ask questions.

5. You are reporter and are interviewing a famous scientist about the nitrogen cycle. You are especially interested in different nitrogen fixations (biological, atmospheric). You are asking him many ques­tions and he is answering them.

6. Two adult students are preparing for their examination on the ni­trogen cycle. They are discussing nitrogen-fixing organisms and how all natural ecosystems depend on them.

7. Two middle-income farmers are discussing the high cost of indus­trially fixed nitrogen.

8. Two farmers are discussing problems of enriching the soil by nitro­gen. They are discussing two ways of doing this: applying fertilizers and alternating legumes with nonlegume crops.

9. A teacher is explaining to a group of adult students (which can be the whole class) the phosphorus cycle, and an important differ­ence between the carbon cycle and the phosphorus cycle. The stu­dents can then ask questions.

10. Two environmentalists are changing their views and opinions about very serious case of humans interfering with the phosphorus cycle that is seen in the cutting of tropical rainforests.

VII. FOR DISCUSSION AND COMPOSITION Choose one of the following to discuss or write about.

1. What do we know about nutrient cycling today?

2. Explain the first basic principle of ecosystem sustainability.

3. Describe the carbon cycle starting with the "reservoir" of carbon dioxide molecules present in the air and dissolved in water.

4. Describe the phosphorus cycle. What is usually referred to as or­ganic phosphate?

5. Compare the carbon cycle and the phosphorus cycle. What is an important difference between them?

6. Discuss a very serious case of humans interfering with the phos­phorus cycle that is seen in the cutting of tropical rainforests.

7. Describe the nitrogen cycle. Why is it more complex than the car­bon cycle and the phosphorus cycle?

g. Compare biological nitrogen fixation and atmospheric nitrogen fix­ation.

9. Compare the nitrogen cycle in terrestrial and aquatic ecosystems. What are the most significant nitrogen fixers in both ecosystems?

10. Describe industrial nitrogen fixing. Why do many farmers readopt the natural process of enriching the soil by crop rotation?

11. Where does phosphate from agricultural croplands make its way? Why does this addition result in overfertilization?

12. What are major constituents of fertilizer? Why do many farmers have to readopt the natural process of enriching the soil by crop rotation?

VIII. RENDERING IN ENGLISH

Первый основной принцип выживания экосистемы гласит: для своего выживания экосистемы удаляют отходы и пополня­ют питательные вещества путем рециклирования всех элемен­тов. Этот принцип согласуется с законом сохранения веществ. Поскольку атомы не создаются, не разрушаются и не превраща­ются друг в друга, они могут использоваться непрерывно. Имен­но это и делают природные экосистемы — они рециклируют одни и те же атомы снова и снова. Особенно ясно это видно на круго­вороте трех ключевых элементов: углерода, фосфора и азота.

Круговорот углерода. Этот круговорот удобно начать с моле­кул углекислого газа (С0₂), находящихся в воздухе и растворен­ных в воде. В результате фотосинтеза и дальнейшего метаболиз­ма атомы углерода (С) из С0₂ становятся атомами С всех органических молекул, образующих тело растения. Через пище­вые цепи атомы С входят внутрь и становятся частью тканей всех остальных организмов в экосистеме. Конечно, маловероятно, что какой-то определенный атом С пройдет через многие организ­мы за один цикл, так как на каждом этапе существует большая вероятность того, что потребитель разрушит органическую мо­лекулу при клеточном дыхании. Когда это происходит, атомы С опять освобождаются в окружающую среду в виде молекул С0₂, завершая таким образом один цикл, и готовы начать новый. По­добным образом, сжигание органического материала возвраща-

^S — 4938

Unit Five

ет атомы С, связанные в этом материале, в воздух в виде молекул СО_г Двух одинаковых, следующих один за другим круговоротов атома С, по-видимому, не существует. Не существует также и двух одинаковых циклов атома С в пределах одной экосистемы, так как ветер в атмосфере разносит атомы по всему миру.

Круговорот фосфора.Фосфор находится в различных горных и почвенных минералах в виде ионов неорганического фосфата. Поскольку горы постепенно разрушаются, фосфат и другие пи­тательные вещества освобождаются в виде ионов. Фосфат рас­творяется в воде, но не поступает в воздух. Растения поглощают фосфат из почв или водного раствора, и когда он связывается растением в органическое соединение, его часто называют орга­ническим фосфатом. Через пищевые цепи органический фос­фат переносится от производителей к остальным организмам экосистемы. Как и в случае с углеродом, на каждом этапе суще­ствует большая вероятность, что органический фосфат будет раз­рушен при клеточном дыхании, освобождая неорганический фосфат в виде мочевины или других отходов. Затем фосфат мо­жет вновь поглощаться растением, чтобы начать новый цикл.

Существует важное различие между круговоротом углерода (С) и фосфора (Р). Не имеет значения, где освобождается угле­кислый газ (С0₂), он смешается и сохранит концентрацию С0₂ в воздухе. А минеральные питательные вещества, не имеющие газовой фазы, рециклируют только тогда, когда отходы, в кото­рых они содержатся, осаждаются в почве, из которой эти пита­тельные вещества первоначально пришли. Это основное, что происходит в естественной экосистеме. Однако люди склонны нарушать этот круговорот. Губительное вмешательство человека в круговорот Р видно на примере вырубки влажных тропических лесов. Этот тип экосистемы фактически на 100% поддерживает­ся эффективным рециклированием питательных веществ. Дру­гими словами, в почве их мало или нет вообще. Когда лес выру­бают и сжигают, питательные вещества, которые связаны в деревьях, вымываются и земля становится непродуктивной. Фос­фат с сельскохозяйственных земель уносится в основном в сброс­ные каналы либо непосредственно с поверхностным стоком, либо косвенно, путем сброса сточных вод. Поскольку из воды

Ecosystems: How They Work 67

_по существу нет возврата фосфата, такое его поступление при­водит к переудобренности водоемов. Тем временем на сельско­хозяйственных землях фосфат замещается фосфатом горных пород, что приводит к истощению земель.

Круговорот азота.Этот круговорот более сложный, так как имеет и газообразную и минеральную фазы. Основной запас азо­та находится в воздухе, который на 78% состоит из азотного газа. Растения не могут использовать азотный газ прямо из воздуха, азот должен быть в минеральной форме, например, в виде ио­нов аммония или нитрата. Ряд бактерий, а также некоторые сине-зеленые водоросли, которые фактически также являются бакте­риями, могут превращать азотный газ в аммонийную форму. Этот процесс называется «биологическая фиксация азота». Среди азот-фиксирующих организмов наиболее важное значение име­ет бактерия «ризобиум», которая живет в клубеньках на корнях бобовых растений. Это пример симбиоза: бобовые обеспечива­ют бактерию местом для проживания и пищей (сахаром), а в об­мен получают источник азота. Связанный органический азот пе­реносится от бобовых к другим организмам экосистемы через пищевые цепи.

Таким образом, все естественные экосистемы зависят от азот-фиксирующих организмов, наиболее важными среди которых являются бобовые с их бактериями. Семейство бобовых вклю­чает огромное разнообразие растений, начиная от клевера (обыч­ного для пастбищ) через кустарники пустыни к многочислен­ным деревьям. Все крупные экосистемы суши, от тропических влажных лесов до пустыни и тундры,'имеют свои характерные виды бобовых. Бобовые обычно являются первыми растениями, которые захватывают выжженную территорию.

Круговорот азота в водных экосистемах такой же, как и в эко­системах суши, но наиболее важными фиксаторами азота в них являются сине-зеленые водоросли.

Только человек способен пренебрегать необходимостью иметь бобовые при выращивании таких небобовых культур, как кукуруза, пшеница и другие зерновые. Мы фиксируем азот на химических заводах (промышленная фиксация азота). Искусст­венно созданные аммонийные и нитратные соединения явля-

5*

68 Unit Five

ются главными составляющими азотного удобрения. Однако высокая стоимость промышленной фиксации азота и другие почвенные факторы заставляют фермеров возвращаться к есте­ственному процессу обогащения почвы азотом путем чередова­ния бобовых и небобовых культур, т.е. с помощью севооборотов.

UNIT SIX

TEXT

Ecosystems: How They Work

1. The environmental problems we face and the questionable long-term viability of our current human system are caused by our failure to adhere to basic ecological principles of sustainability. These principles may show us the direction we need to take. Let's look at our human system from the point of view of each of the principles of ecosystem sustainability.

2. First Principle of Sustainability:For sustainability ecosystems dis­pose of wastes and replenish nutrients by recycling all elements. In con­trast to this principle, we have based our human system in large part on one-directional flow of elements. We mine elements in one location and dispose of them in another. For example, phosphate withdrawn from soils by agricultural crops comes to us with our food supplies, but then effluents of our wastes containing the phosphate are discharged into var­ious waterways (rivers, lakes, bays and estuaries) rather than back into the soil. To make up for the removal of phosphate from soil, phosphate rock is mined at various locations and added to soil as a constituent of fertilizer. Thus, there is basically a one-way flow of phosphate from mine to waterways. The same can be said for such metals as aluminum, mer­cury, lead, and cadmium, which are the "nutrients" of our industry. We have created a flow of these elements from natural deposits through our systems to dumps and landfills.

3. This one-way flow leads to two problems: depletion of the resource at one end and pollution at the other. Pollution has proved to be, by far, the more severe problem. Countless waterways around the world and even sections of the ocean are suffering severe ecological disturbances from being oversupplied with nutrients such as phosphate. This problem is known as ^eutrophication. Likewise, many rivers and other bodies of water are con­taminated with toxic elements from various discharges. For example, thousands of kilometers of tributaries of the Amazon are badly contami-

7б

Unit Six

Ecosystems: How They Work

 

nated with mercury, a waste product of gold mining. Putting such waste materials into dumps is problematic on two counts. Finding space for dumps and landfills is reaching crisis proportions in many regions. Then, even when such toxic materials are put into dumps, they tend to leak out causing pollution of both ground and surface water.

4. Aggravating the problem is the fact that we produce and use thou­sands of products, such as plastics, that are synthetic organic compounds that are nonbiodegradable. That is, detritus feeders and decomposers are unable to attack and break them down. Thus, enormous amounts of non­biodegradable products compound the problem of finding dump sites. Also, many such synthetic products are toxic and cause pollution in the same way lead and other elements do. The rapid development of recycling pro­grams in the last few years is an encouraging sign that we are beginning to recognize and implement the first principle of sustainability.

5. Second Principle of Sustainability:For sustainability ecosystems use sunlight as their source of energy. In contrast to this principle, our fantastic technological and material progress of the past 200 years has been in large part a story of developing machinery, engines, and heating plants that run on fossil fuels — coal, natural gas, and crude oil. Just consider that virtually all cars, trucks, aircraft, and other vehicles run on fuels refined from crude oil; 70 percent of the electricity in our country comes from coal-fired power plants, and most homes, buildings, and hot water are heated with natural gas. Even food production, which is basically derived from solar energy (photosynthesis of crop plants), is heavily supported by fossil fuels used in farm machinery, production of fertilizer and pesticides, transportation, processing and canning, refrig­eration, and finally cooking. In all, more than 10 calories of fossil fuels are consumed for eveiy calorie of food that is served in the United States.

6. From meager beginnings in the late 1800s, oil consumption now tops 50 million barrels per day worldwide. The byproducts of burning fossil fuels enter the atmosphere and are directly responsible for our most severe air pollution problems — urban smog, acid rain, and most recently, the potential of global warming. Also, we are facing increas­ingly severe crises because of depletion of present oil reserves and en­vironmental destruction in the effort to find more. Nuclear power is being promoted as an alternative, but this source also seems dubious because of the hazards of its radioactive waste products.

 

7. Thus, the danger in continuing to ignore the ecosystem princi­ple regarding solar energy seems clear. In addition to being nonpollut-ing and nondepletable, solar energy is also extremely abundant. Green plants, including agricultural crops utilize a very small fraction of the solar energy that hits the earth. Most of the rest is converted directly to heat as it is absorbed by water or land. In turn, this heated water and land heats the air and causes the evaporation of water. Thus, solar en­ergy is the major driving force behind ocean currents, wind, and rain - i.e., weather. There is ample opportunity to harness some of this energy and put it to work. According to the Laws of Thermodynamics, the final heat at the end of the line is the same whether the energy is harnessed to perform useful work along the way or not. Therefore, even using solar energy on a vast scale would not change the overall dynam­ics of the biosphere.

8. Third Principle of Sustainability:For sustainability the size of con­sumer populations is maintained such that overgrazing does not occur. In contrast to this principle, the human population has increased more than five-fold in the past 200 years. It has nearly tripled in just the last 60 years and is continuing to increase at a rate of over 90 million people per year. It can be argued that this ever-accelerating growth rate is irrelevant because humans are supported by a technological agricultural system, not a natural ecosystem. On the other hand, signs of overgrazing are becoming all too evident. First, there is literal overgrazing. Over the world millions of acres of productive grasslands have been badly degraded or even turned into desert because of overgrazing cattle.

9. Then, there are any number of examples of overgrazing in figu­rative sense. Consider the destruction of tropical and other forests; depletion of groundwater supplies; farming practices that are leading to deterioration of soil and hence of productivity; poor people in a number of less developed countries picking hillsides bare in their guest for firewood, which is their only fuel; depletion of fishing areas, and so °n. Perhaps the most serious form of figurative overgrazing, however, Го-ау be the ever-expanding human development and exploitation that displace and degrade natural ecosystems and consequently cause the extinction of countless species. The effects that this extinction may have will be discussed further. The principle of maintaining a stable (nongrowing) population is a principle that cannot be ignored.

Unit Six

 

USEFUL WORDS AND EXPRESSIONS
paragraph 1	paragraph 4	paragraph 7
long-term viability	nonbiodegradable	evaporation
adhere		driving force
point of view	paragraph 5	ocean currents
	engines	weather
paragraph2	heating plants	harness
dispose	fossil fuels	useful work
phosphate withdrawn	crude oil	vast scale
food supplies	trucks
removal	aircraft	paragraph 8
one-way flow	vehicles	overgrazing
dumps	fertilizer	at a rate of
landfills	pesticides	ever-accelerating growth
	processing	rate
paragraph 3	canning	productive grasslands
severe problem	refrigeration	desert
disturbances
tributaries	paragraph 6	paragraph 9
waste product	urban smog	groundwater supplies
gold mining	acid rain	farming practices
leak out	severe crises	deterioration of soil
ground water	environmental destruction	loss of productivity
surface water	dubious	less developed countries
	hazards EXERCISES	ever-expanding

I. READING COMPREHENSION

What is the main idea of the article?

a. We face the environmental problems and cannot solve them.

b. We fail to adhere to basic ecological principles of sustainability.
с The principles of sustainability may show us the direction we

need take.

First Principle of Sustainability says:

a. We mine elements in one location and dispose of them in an­other.

 

Ecosystems: How They Work

b. Ecosystems dispose of wastes.

с Ecosystems replenish nutrients by recycling all elements.

3. Phosphate withdrawn from soils by agricultural crops comes to us
with

a. effluents of our wastes

b. our food supplies
с various waterways

4. There is basically a one-way flow of phosphate from

a. various locations to soils

b. various waterways to soils
с mine to waterways

5. We have created a flow of aluminum, mercury, lead, and cadmium

a. from mine to our industry

b. from natural deposits to landfills
с through our systems to dumps

6. The one-way flow leads to two problems

a. ecological disturbances

b. depletion of the resources at one end
с pollution at the other end

7. Countless waterways around the world are suffering severe ecolog­
ical disturbances from

a. being oversupplied with nutrients

b. being oversupplied with phosphate
с being oversupplied with nitrogen

8. Many rivers and other bodies of water are contaminated with

a. a waste product of gold mining

b. toxic elements from various discharges
с toxic materials

9. When toxic materials are put into dumps, they tend to leak out
causing pollution of

a. surface water

b. soil

с both ground and surface water Ю. Second Principle of Sustainability is:

a. Ecosystems run on fuels refined from crude oil.

b. Ecosystems use sunlight as their source of energy.

с Ecosystems use energy from coal-fired power plants.

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Unit Six

Ecosystems: How They Work

 

11. In contrast to this principle, we have developed machinery, engines,
and heating plants that run on

a. fossil fuels b. natural gas с crude oil

12. Most homes, buildings, and hot water are heated with

a. electricity b. fossil fuels с natural gas

13. Fossil fuels are used in

a. farm machinery, transportation, and refrigeration

b. production of fertilizer and pesticides
с processing and canning, cooking

14. The byproducts of burning fossil fuels enter the atmosphere and
are directly responsible for

a. urban smog and acid rain

b. the potential of global warming

с most severe air pollution problems

15. Third Principle of Sustainability is connected with

a. changing the overall dynamics of the biosphere

b. using solar energy on a vast scale

с maintaining the size of consumer population without overgrazing

16. In contrast to this principle, the human population

a. is continuing to increase at a rate of 90 mln people per year

b. has increased more than five-fold in the past 200 years
с has nearly trippled in just the last 60 years

17. Humans are supported by

a. a technological agricultural system

b. a natural ecosystem
с both of them

18. The most serious form of figurative overgrazing maybe

a. displacing and degrading natural ecosystems

b. the ever-expanding human development and exploitation
с the extinction of countless species

II. VOCABULARY