From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once

stages adults recruitment pack of wolves

refer to recover boil down exponential increase

explosion reproducing rule out herd of deer

fluctuate interbreeding birthrate relative phenomenon

foresee population replacement level school offish

mitigate death rate flack of birds biotic potential

1. Each species in an ecosystem exists as a___ — that is to say, an

_____ ,______ group.

2. Thus, the problem of ecosystem balance_____ to a problem of

how_____ or_____ are balanced for each species in the ecosys­
tem.

3._____ , which is defined as making it through the early growth

_____ to become part of breeding, reproducing population, is

equally important.

4. All these factors taken together are______ as the_____ of the species.

5. Such a multiplying series is called an____ .

6. In populations it is commonly called a population____ .

7. One may already____ the result of the interplay between biotic

potential and environmental resistance.

8. Of course, some____ also perish, particularly the old and weak.

9. If recruitment is at the____ , just enough to replace these adults,

then the population size will remain constant.

7 - 4938



Unit Seven

Ecosystems: What Keeps Them the Same?




10. From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru It should be noted that balance is a___ .

11. Some balances_____ very little, others_____ widely.

12. Indeed, in nature, neither possibility is____ .

13. Conversely, as population density decreases, environmental resis­tance is generally , allowing the population to________________ .

14. Furthermore, the biotic potential of many species depends on a

minimum population base_____ a_____ , a_____ , a______ , or

a_____ , for example.

III. PREPOSITIONS Fill in the correct preposition for each blank space.

1. The one thing that enables ecosystems to sustain a given composi­tion species long periods time is that all rela­tionships the system are_________ a dynamic balance.

2. An ecosystem's remaining stable____ a long period_____ time

implies that the population____ each species_____ the ecosys­
tem remains more or less constant____ size and geographic dis­
tribution.

3._____ other words, most_____ the young fish and plants perish

_____ the early stages_____ growth.

4. Populations_____ natural ecosystems do not explode because all con­ditions are seldom favorable any extended period time.

5. Sooner or later, any population increase will be curtailed____

one or more factors____ environmental resistance.

6. general, the reproductive rate________ a species remains fair­
ly constant because that rate is part___ the genetic endowment

_____ the species.

7._____ example, loss______ suitable habitat often prevents animals

_____ breeding.

8. What prevents a population____ going______ an explosion or

_____ extinction?

9.______ general, populations remain_____ a certain size range be­
cause most factors______ environmental resistance are density-
dependent.
10. Human impacts,_____ the other hand, readily result_____ ex­
tinction because they are not density-dependent.

11. Furthermore, the biotic potential_____ many species depends

_____ a minimum population base______ a herd______ deer, a

pack_____ wolves, a flock_____ birds, or a school_____ fish,

_____ example.

IV. DEFINITE/INDEFINITE ARTICLES

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

Each species in______ ecosystem exists as______ population - that

is to say,_____ interbreeding, reproducing___ group.____ eco­
system's remaining stable over____ long period of_____ time im­
plies that____ population of each__ species in_ ecosys­
tem remains more or less constant in____ size and geographic

distribution. Any continuing increase or decrease in____ popula­
tion would be observed as______ change in_____ ecosystem. In turn,

_____ population's remaining constant over_____ long______ time

means that_____ reproductive rate is equaled by_____ death rate.

Thus,_____ problem of______ ecosystem balance boils down to_______

problem of how____ birth rate and_____ death rate are balanced

for each_____ species in_____ ecosystem.

V. VALUES DISCUSSION

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

1. When can ecosystem change?

a. As conditions are altered.

b. As conditions are not altered.

с As the relationships in the system are in a dynamic balance, d. other

2. What would be observed as a change in the ecosystem?

a. Any continuing increase in population.

b. A population's remaining constant over a long period of time,
с Any continuing decrease in population.

d. other

3. How is recruitment defined?

a. Maintaining or increasing a population.

7*



Unit Seven

Ecosystems: What Keeps Them the Same?




From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru b. Making it through the early growth stages to become part of

breeding, reproducing population, с Substantial population increase, d. other

4. What does a relatively low reproductive rate result in?

a. a substantial population increase

b. high recruitment

с low recruitment >*U

d. other

5. What are additional factors that influence population growth and
geographic distribution?

a. the ability of animals to mitigate

b. defense mechanisms

с resistance to adverse conditions and disease d. other

6. What does environmental resistance effectively reduce?

a. the early stages of growth

b. adverse conditions
с recruitment

d. other

7. When will the population size remain constant?

a. If recruitment is not sufficient to replace losses in the breeding
population.

b. If recruitment is at the replacement level.

с If the reproductive rate for a species remains constant, d. other

8. What may environmental resistance effect in certain situations?

a. reproduction с mortality (death)

b. certain pollutants d. other

9. When may the system be said to be balanced?

a. Ifbiotic potential remains constant.

b. As long as decreased populations restore their numbers.

с As long as the balance is maintained within a certain range, d. other 10. Why do populations remain within a certain size range?

a. Because population density increases.

b. Because population density decreases.

с Because most factors of environmental resistance are density-dependent, d. other

11. What human impacts are readily resulted in extinction?

a. ecosystem destruction с exploitation

b. pollution d. other

12. What does the biotic potential of many species depend on?

a. flock of birds с a herd of deer

b. a minimum population base d. other

VI. ROLE-PLAY Choose one of the following situations to act out.

1. An audience (which can be the whole class) is asking a lecturer questions about the relationships in ecosystems (for example, about interbreeding, reproducing groups, reproductive and death rate, problems of ecosystem balance).

2. A specialist who knows how birth rate and death rate are balanced for each species in the ecosystem is giving advices to a group of farmers. The farmers (which can be the whole class) will then ask questions.

3. A reporter is interviewing a scientist about additional factors that influence population growth and geographic distribution of ani­mals and seeds.

4. A scientist from Russia is talking with a scientist from the United States about the result of the interplay between biotic potential and environmental resistance.

5. You are speaking about recruitment. From your point of view, pop­ulation increase may be nil if recruitment is low. Your colleague has an opposite opinion.

6. Two environmentalists are talking about certain pollutants that af­fect reproduction.

7. A lecturer is explaining to a group of students (which can be the whole class) specific mechanisms of population balance. The au­dience will ask questions after a short (5 minutes) talk.

8. A Russian politician is speaking to a group of reporters (which can be the whole class) about human impacts on ecosystems. The re­porters will then ask questions.



Unit Seven

Ecosystems: What Keeps Them the Same?




9. From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru A scientist from Russia and a scientist from the United States are comparing human impacts such as ecosystem destruction, habitat alteration, pollution, and exploitation in the two places.

10. A specialist who knows that the problem of ecosystem balance boils down to a problem of how birth rate and death rate are balanced for each species in the ecosystem is arguing with someone who doesn't know this.

VII. FOR DISCUSSION AND COMPOSITION

Choose one of the following to discuss or write about.

1. Are all the relationships in the system in a dynamic balance? Dis­cuss.

2. Describe a change in the ecosystem. What does maintaining or in­creasing a population depend on?

3. Describe additional factors that influence population growth and geographic distribution of animals and seeds. Are all these factors referred to as the biotic potential of the species?

4. What do you know about biotic and abiotic factors? What is re­ferred to as environmental resistance?

5. Is it possible to foresee the result of the interplay between biotic potential and environmental resistance? Discuss.

6. Give examples when environmental resistance may effect repro­duction as well as causing mortality (death) directly.

7. Write about the result of a dynamic balance between biotic poten­tial of a population and environmental resistance.

8. Why do population remain within a certain size range? Discuss.

9. Describe human impacts on ecosystems. Why do they readily re­sult in extinction?

:) VIII. RENDERING IN ENGLISH

Очень важно понять, что нет сил или жестких структур, ко­торые предохраняют экосистемы от изменения. Фактически эко­системы могут изменяться, даже резко, когда изменяются усло­вия. Сохранить данный состав видов в течение долгого времени экосистемам позволяет то, что все взаимодействия (взаимоот­ношения) в них находятся в динамическом равновесии.

Каждый вид в экосистеме существует в виде популяции, т.е. воспроизводящей группы. Свойство системы оставаться стабиль­ной (самовыживание) в течение долгого периода времени озна­чает, что популяция каждого вида в экосистеме остается более или менее постоянной по размеру и географическому распро­странению. Любое продолжительное увеличение или уменьше­ние популяции считается изменением в экосистеме. В свою оче­редь, пребывание популяции постоянной в течение долгого времени означает, что воспроизводство уравновешивается смерт­ностью. Таким образом, проблема равновесия экосистемы сво­дится к проблеме, как сбалансированы рождаемость и смертность каждого вида в экосистеме.

Сохранение или увеличение популяции зависит не только от темпа размножения, важным является также пополнение вида. Например, многие рыбы откладывают тысячи и даже миллионы икринок, а растения — тысячи семян. Тем не менее увеличение популяции может равняться нулю, т.е. пополнение очень низкое. Другими словами, большая часть молодых рыбок и растений по­гибает на ранних стадиях роста. И наоборот, даже относительно низкий темп размножения может привести к значительному уве­личению популяции при высоком пополнении.

Дополнительными факторами, которые влияют на рост и географическое распространение, являются: способность жи­вотных мигрировать, а семян — распространяться в подобную среду обитания в других регионах; способность адаптироваться и завоевывать новую среду обитания кроме той, которая была первоначально занята; защитные механизмы и сопротивление неблагоприятным условиям и болезням. Все эти факторы, вме­сте взятые, называются способностью вида к размножению. Не­смотря на различные стратегии относительно способности к размножению, у них есть одно общее — каждый вид имеет вы­сокую воспроизводительную способность и быстро увеличивает свою популяцию при благоприятных факторах для высокого по­полнения. Действительно, каждое новое поколение будет при­умножаться числом женских особей. Например, кролики, даю­щие потомство 20 штук, из которых 10 — женские особи, могут увеличиваться в каждом поколении в 10 раз: 10, 100, 1000 и т.д.



Unit Seven

UNIT EIGHT



From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru From the list of words and expressions below, choose the correct word or expression for each blank space. Use each word or expression only once - student2.ru Это явление в популяциях обычно называется популяционным взрывом.

Но в естественных экосистемах популяционный взрыв про­исходит редко, так как все условия среды не бывают благоприят­ными долгое время. Один или два абиотических и биотических фактора становятся лимитирующими. Сочетание абиотических и биотических факторов, которые могут ограничивать увеличе­ние популяции, называется устойчивостью среды. Увеличивает­ся ли популяция, остается устойчивой или уменьшается, явля­ется результатом динамического равновесия.

В основном, популяции остаются в пределах определенной величины, так как большинство факторов устойчивости среды зависит от плотности. Это означает, что, когда плотность попу­ляции (число особей на единицу площади) увеличивается, со­противление среды становится более интенсивным и вызывает увеличение смертности, так что рост прекращается или снижа­ется. И наоборот, когда плотность популяции уменьшается, со­противление среды обычно ослабевает, позволяя популяции вос­становиться.

С другой стороны, воздействие человека легко приводит к вымиранию, так как оно не зависит от плотности популяции. Такие воздействия человека, как разрушение экосистемы, нару­шение среды обитания, загрязнение и эксплуатация, происхо­дят при любой плотности популяции.

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