Textos Para Alumnos de Maestria (2)

7/31/2019 Textos Para Alumnos de Maestria (2)

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Fac. de Cs. Ftales.

Ctedra de Ingls

Read the following text and complete the exercises

1.Match the following subtitles to the corresponding paragraphs

a) Ozone is broken down by CFCs.b) Most ozone is high in the atmosphere.c) We can save the ozone layer.d) The ozone layer.

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High up in the Earths atmosphere, between about 12 and 50 km above the ground, is

a layer of the gas ozone. An ozone molecule contains three oxygen atoms, so its formula

is O3.

The ozone in this layer is constantly being formed, broken down and reformed. It is

formed when ultraviolet light (short wavelength light) hits an oxygen molecule. The two

oxygen atoms break apart, forming separate and very reactive individual oxygen atoms.

Each of these can then combine with an oxygen molecule to form an ozone molecule.

This reaction happens at these high levels in the atmosphere because this is where

the most ultraviolet light is present. The ultraviolet light comes from the Sun. Most of it

is absorbed by the ozone layer, so there is much less of it in the lower layers of theatmosphere.

What breaks the ozone down? This happens quite naturally. For example, one of the

three oxygen atoms in an ozone molecule may separate from the others, and then

combine with another ozone molecule to form oxygen:

O3 O2 + O

O3 + O 2O2

Until quite recently, the rates at which ozone formed and broke down in the high

levels of the atmosphere were about equal. The amount of ozone stayed about the same,But since the 1970s, the amount of ozone has been decreasing. Why has this been

happening? And why does it matter?

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Chlorofluorocarbons, or CFCs, are very stable, unreactive, non-poisonous

chemicals. They have had a variety of uses. They have been used as coolants in fridges,

and in air conditioning. They have been used in aerosol propellants, and for filling the

spaces in foam used to make packaging or furniture. It was a long time before anyone

realised the harm that these seemingly harmless chemicals were doing.


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When CFCs escape from fridge cooling systems, from foam packaging or from

aerosols, they go into the atmosphere. Because they are very unreactive, they stay there

for a very long time. They gradually find their way up to the level of the ozone layer.

Here, at last, the large amounts of ultraviolet light begin to break their molecules

apart. Chlorine is released from the CFC molecules. The chlorine reacts with the ozonemolecules, speeding up the rate at which they break down. The CFCs speed up the

breakdown of the ozone molecules, but have no effect on the rate at which they reform.

Therefore, CFCs reduce the amount of ozone in the atmosphere.

Why does this matter? The ozone layer is very important to all living things on

Earth, because it absorbs a lot of the ultraviolet rays hitting the atmosphere. Ultraviolet

light is very damaging. One effect it can have is to damage DNA in cells, causing

mutations.

This can lead to skin cancer. If ozone layer is lost, then we will have no natural

protection from this harmful ultraviolet radiation. High levels of ultraviolet radiation

would also damage crops.

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Now that people understand what is happening to the ozone layer, we can begin to do

something to save it. We must stop using CFCs.

Unfortunately, this will not be an immediate and complete solution to the problem.

Firstly, many countries, especially developing countries, want to go on using CFCs.

Although alternative chemicals have been developed, they are more expensive. Also, it

is now realised that these alternative chemicals, although they may not do any damage

to the ozone layer, may contribute to the greenhouse effect! We need to try to developeven better alternatives to CFCs.

Secondly, you may remember that CFCs are very stable substances. The CFCs

already in the atmosphere will stay there for a long time. Even if everyone stopped

producing and using CFCs immediately, it would take about 100 years for the amount

of ozone to get backto anything like normal.

2. Answer the following questions

1. What is ozone?2. Why is most ozone found in a layer high in the Earths atmosphere, rather than

close to the ground?3. What are CFCs, and what are they used for?4. Describe the harmful effects which might occur if the ozone layer is destroyed?5. How can we save the ozone layer?

3. Write 5 questions about the text and answer them

4. Write a summary in English using no more than 150 words


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U.Na.M. Name:

Fac. de Ciencias Forestales Date:Ctedra de Ingls

Read the following text and complete the exercises.

I Match the following titles and subtitles to each paragraph

Environmental implications

Developing a resource

Will resources run out?

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Resources can be divided into three types according to their renewability and the

human factor. Once a mineral such as soil has been discovered its development depends

on several factors including:

(i) Technology available, (ii) availability of skilled labour, (iii) favourable world prices,

(iv) government policy, (v) cost of the land on which developments will be made, (vi)

infrastructure, (vii) opinions of local landowners, (viii) opinions of environmentalists.

These factors tend to be variable in both space and time. Environmental pressure

groups, for example, have more influence in Britain than they do in much of the Third

World. This can cause delays in the exploitation of resources and may influence their

economic viability.

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Environmentally, the impact of resource development can vary greatly. It can include

the knock on impacts of additional transport requirements, storage depots, miners

houses, etc. However, the impact needs to be seen in a long term perspective. Many

spoil tips have been reclaimed and gravel pits turned into recreational resources.

Environmental impact often involves direct disturbance associated with the mining

operation and also waste disposal. In some cases it is possible to find a ready market for

the spoil. This is the case with iron ore smelting, where the slag is now a sought-after

material for road foundations. In other cases there is no market for the spoil even though

quantities can be prodigious.

In some cases the environmental impact can reach virtually uncontrollable

proportions. Such cases are mainly found in the developing countries, Jamaica, for

example, faces serious environmental problems resulting from the red mud waste, a by-

product of bauxite processing, and Thailand and Malaysia have a large problem in

dealing with the waste from tin mining. However, some of the most serious

environmental problems have resulted from oil spills due to blown well heads.


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Very few resources are inexhaustible. This century has seen a dramatic growth in theworld family and with it an explosive demand for resources. It is easy to understand

why so many people are worried about the availability of resources in the future.

Developing countries are only just industrialising so their demands per capita are much

lower than those in the developed world. The future industrialisation of these countries

is certain to cause ever greater pressure on resources.

There are two possible scenarios for the future.

(i) Population will continue to grow fast. The exhaustion of minerals or severe

intolerable pollution will occur (as witnessed by cities like Mexico City, the greenhouse

effect, the destruction of the ozone layer, etc.). This could lead to the eventual collapseof society and life as we know it will no longer be possible.

(ii) Population will eventually level off. New resources will continue to be discovered

and improved technology will enable previously untapped resources to become

reserves. Industry will become more efficient so that smaller quantities of raw materials

will be required. There will be less wastage, what waste there is will be reused and

pollution will progressively be controlled (as witnessed by recent legislation in many

countries, the change to solar energy etc.

At present it seems unlikely that we will run out of resources, at least in the

foreseeable future. Although some minerals are in short supply, new discoveries keep

putting back the forecast dates for when alternatives will have to be found. Perhaps of

more immediate concern, therefore, is the environmental impact of exploiting resources,

particularly in terms of global pollution.

II Answer the following questions

1. Where do environmental groups have more influence?

2. Are all resources inexhaustible?

3. Which are the two possible scenarios for the future?

4. Which of them do you think is more probable to happen?

III Write five questions and answer them

IV Write a summary in English about the text. Use 150 to 200 words.


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U.Na.M.

Fac. de Ciencias Forestales Ctedra de Ingls


I Match the following titles to the corresponding paragraph

a) Biomassb) The importance of energyc) The environmental impact of fuelwood used) Fuelwood

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Energy is important to every country and region, but its significance varies. For the

USA and the other developed countries that are the major fossil fuel consumers and are

mostly energy deficient, a secure, unrestricted supply is essential to maintain standards

of living. By contrast the Middle Eastern countries, many of whom are energy exporting

countries, rely on high prices to provide external revenues and thus the money to

develop their countries. A fall in the price of oil (as has happened during the 1980s) ,

rather than a reduction in supply, has the most serious consequences for them.

In many developing countries, commercial energy is used by only a minority of thepopulation. Here it is the continued supply of forms of traditional subsistence energy,

such as wood and dung, which is the main priority. The increased consumption of

commercial energy simply makes the balance of payments position worse for these

countries and they see the continued internal provision of energy as the best way

forward.

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Wood, dung and agricultural residues collectively form biomass. This accounts for

about 14 per cent of the total global energy use. In some countries, for example Nepal,

Ethiopia and Tanzania, over 90 per cent of their total energy comes from biomass and,

of this, wood is by far the most important.

Biomass is produced from living matter and is renewable provided there is a balance

between growth and consumption. However, many countries are facing severe shortages

as demand exceeds supply.

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In 1983 the United Nations Food and Agriculture Organisation (FAO) estimated that

1.3 billion people were facing a deficit and would only be able to meet their needs by

depleting existing reserves. It predicted that by the year 2000 more than 3 billion people

will be forced to consume wood faster than it is being grown at present rates of use and


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replanting. Women and children in rural parts of the Third World have to spend

increasing amounts of time fetching wood.

In the past this task might have taken an hour a day -in sub-Saharan Africa it is

estimated that women now spend up to 24 hours a week collecting fuel wood as they

have to go further and further to find suitable supplies.

Many city dwellers in the third World also depend on wood for cooking and this may

cost them up to a third of their income. Often it is a choice between fuelwood , food or

clothes.

Wood is not just used as a domestic fuel. Many small industries, such as bakeries,

breweries, and tobacco curing, burn wood. The Philippines government is pursuing a

programme of establishing small, wood burning electricity generating plants.

Supplying fuelwood is a major industry in most developing world countries. Many

people earn their living by making and selling charcoal, or felling trees and selling the

wood.

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The wood for the city dwellers comes from the forests nearest to the cities. Over the

years, forests have been pushed further and further back, leaving a barren ring

surrounding the cities. On a world scale, wood collecting has contributed greatly to

deforestation and ultimately desertification and soil erosion.

Many countries are implementing programmes aimed at reducing deforestation and at

the same time increasing stocks.

As people seek to find an economic niche, many have turned to charcoal productionbecause it yields a reliable income. Shortages of wood mean that people who once used

their trees for harvesting fruits and nuts or for gum are tempted to cut them down and

make a quick profit by selling the wood.

The long term economic benefits of proper forestry, or of agroforestry techniques,

will only be seen by those countries with sufficient economic security. Improvements to

the fuelwood supply of developing countries can only be expected to occur with

improvements in the economic status of the countries. In the meantime, the best that can

be expected is for isolated schemes to be set up with the help of aid agencies. Here it is

hoped that the economic success of such schemes will persuade others to set up their

own schemes later.

In Africa there are many pilot schemes concerned with agroforestry, growing

leucaena, neem trees or acacias in rows across the landscape. They provide fuelwood

and fodder, and prevent erosion.

Alongside attempts to increase stocks, many governments and outside agencies are

encouraging the use of newly developed wood burning stoves. These are up to 50

percent more efficient: there is considerable resistance, however, from people who are

used to cooking on open fires.

It must also be noted that, although protection of forest through the banning, of

felling might be a good thing for the future, it does have serious short terms effects on

those who depend on wood for fuel and also for earning a living.


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II Answer the following questions

1. What is the significance of energy for the USA and other developed countries?2. Where is commercial energy only used by a minority of the population?3. How is biomass produced?4.

Where does the wood for the city dwellers come from?5. What are many countries implementing?

III Write two questions and answer them

IV Write a summary in English about the text . Use about 150 words.

U.Na.M. Name:

Fac. de Cs. Ftales. Date:

Ctedra de Ingls

PRACTICAL WORK


1 Match the different titles to the correct paragraphsi) Pesticides use can be reducedii) Pesticidesiii) Pesticides help to increase crop yields.iv) Pesticides can harm the environment

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A pesticide is a substance which kills organisms which damage crops. Insects which

eat crops can be killed with insecticides. Fungi which grow on cops are controlled with

fungicides. Weeds which compete with crop plants for water, light and minerals can becontrolled with herbicides. Pesticides may also be used to control organisms which

transmit disease, such as mosquitoes.

In a natural ecosystem, a wide variety of plant species will probably grow in a

particular habitat. A wide variety of animals will live in that habitat too, feeding on

different plants and on each other. A natural ecosystem often has large species diversity.

Factors such as predation on food supply will prevent the population of any one species

from growing too large.

On a farm, only a few plant species are allowed to grow in many of the fields. One

field might contain nothing but wheat, for example. This is called a monoculture.

Insects or fungi which can feed on the wheat have an almost inexhaustible food supply.The usual limits on their population growth do not apply. The populations of the insects


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or fungi may grow very rapidly, until they are so big that they cause extensive damage

to the crop.

If nothing is done about this, then crop yields can be very badly reduced. It has been

estimated that, in developing countries, at least one third of potential crops are

destroyed by pests. If they did not use pesticides, then this would be even worse. InBritain, most farmers use pesticides.

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By definition, a pesticide is a harmful substance. In the 1950s and 1960s, some of

the pesticides used did a lot of damage to the environment. One of these was DDT.

DDT was used to kill insects. People did not realize that DDT is a persistent

insecticide, which means that it does not break down, but remains in the bodies of theinsects or in the soil. When a bird or other organism ate the insects, they ate the DDT

too. The DDT stayed in their bodies, each time they ate an insect, more DDT

accumulated in their tissues. If a bird of prey ate the insect-eating bird, it too began to

accumulate DDT. Birds and other animals near the end of food chains built up very

large concentrations of DDT in their bodies.

Unfortunately, as well as being persistent, DDT is also nonspecific. This means that

it is not only harms the insects it is meant to kill, but is also harmful to other living

things. It is very harmful to birds, for example. In Britain, it affected the breeding

success of peregrine falcons, by making their egg shells very weak, so that they very

rarely hatched. The peregrine falcon population dropped very rapidly.

Once it was realized that DDT was doing so much harm, its use in Britain was

stopped. Now DDT is not used in Britain or the rest of Europe. However, it is still used

in many developing countries, such as much of Africa. This is because, without it,

insects would be such a problem that more people would starve or die of diseases like

malaria. It is also argued that DDT breaks down in the higher temperatures of these

countries.

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Since the scare about DDT, new kinds of pesticide have been introduced which are

less persistent. However, even these have caused problems to other living organisms.For example, a group of insecticides called organophosphates, which are used to kill

pests living on sheep, appear to have caused illness in farmers who use them frequently.

A constant search goes on for pesticides which are only harmful to the organisms we

want to kill.

No-one really wants to use pesticides unnecessarily. They are expensive to buy, take

time to apply, and all farmers are aware of the damage they can do. Research is always

going on to try to find ways of reducing the amount of pesticides which we use.


1. What is a pesticide?2. Why do we use pesticides?


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3. Explain how pesticides can damage the environment.3. Write 2 questions about the text and answer them

4. Write a summary about the text . Do not use more than 150 words.

U.Na.M.

Fac. de Cs. Ftales.

Ctedra de Ingls


1 Match the different titles to the correct paragraphs

(i) Nitrate use must be carefully controlled(ii) Water pollution(iii) Aquatic organisms need clean water

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Many organisms live in water. They are called aquatic organisms. Aquatic habitats

include fresh water, such as streams, rivers, ponds and lakes; and also marine

environmentsthe sea and the oceans.

Most organisms which live in water respire aerobically, and so need oxygen. They

obtain their oxygen from oxygen gas which has dissolved in the water. Anything which

reduces the amount of oxygen available in the water can make it impossible for fish or

other aquatic organisms to live there.

In the UK, there are two main sources of pollution which can reduce oxygen levels

in fresh water. They are fertilizers and untreated sewage.

Farmers and horticulturists use fertilizers to increase the yield of their crops. The

fertilizers usually contain nitrates and phosphates. Nitrates are very soluble in water. If

nitrate fertilizer is put onto soil, it may be washed out in solution when it rains. This iscalled leaching. The leached nitrates may run into streams and rivers.


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Algae and green plants in the river grow faster when they are supplied with these

extra nitrates. They may grow so much that they completely cover the water. They

block out the light for plants growing beneath them, which die. Even the plants on the

top of the water eventually die. When they do, their remains are a good source of food

for bacteria. The bacteria breed rapidly. The large population of bacteria respires using

up oxygen from the water. Soon, there is very little oxygen left for other living things.Those which need a lot of oxygen, such as fish, have to move to other areas, or die.

This whole process is called eutrophication. It can happen whenever food for

plants or bacteria is added to water. As well as fertilizers, other pollutants from farms,

such as slurry from buildings where cattle or pigs are kept, or from pits where grass is

rotten down to make silage, can cause eutrophication. Untreated sewage can also cause

autrophication. Sewage provides a good food source for many kinds of bacteria. Once

again, their population grows, depleting the oxygen levels.

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Eutrophication is not the only problem caused by the leaching of nitrate fertilizers.

Some of the nitrates are carried deep into the soil, where they find their way into water

in rocks deep underground, called aquifers. Water in aquifers may be extracted to use

as drinking water. There is some concern that, if people drink water containing a lot of

nitrate, they may become ill.

Could we stop using nitrate fertilizers? It is not really sensible at the moment to

suggest that we could. People expect to have plentiful supplies of relatively cheap food.

Although fertilizers are expensive, by using them farmers get so much higher yields that

they make more profit. If they did not use fertilizers at all, their yields would be muchlower and they would have to sell their crops for a higher price, in order to make any

profit at all.

Some farmers are doing just this. They do not use inorganic fertilizer, such as

ammonium nitrate, at all. Instead , they use organic fertilizers, such as manure. Organic

fertilizers are better than inorganic ones in that they do not contain many nitrates which

can easily be leached out of the soil. Instead, they release their nutrients gradually, over

a long period of time, giving crops time to absorb them efficiently. Nevertheless,

manures can cause pollution, if a lot is put onto a field at once, at a time of year when

there is a lot of rain or when crops are not growing and cannot absorb the nutrients from

them.

The yields obtained when using organic fertilizers are not usually as great as when

using inorganic ones, so the crops are usually sold for a higher price. Many people are

now prepared to pay extra money for food from crops grown in this way, but many

cannot afford to.

If nitrate fertilizers are used, there is much which can be done to limit the harm

they do. Care must be taken not to use too much., but only to apply an amount which

the plants can take straight away. Fertilizers should not be applied to empty fields, but

only when plants are growing. They should not be applied just before rain is forecast.

They should not be sprayed near to streams and rivers. In some parts of England, whichhave been designated as nitrate sensitive areas, very strict controls have been laid


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down restricting farmers in their use of nitrate fertilizers, and also in the use of organic

fertilizers such as manure.


1. What is eutrophication?

2. What do fertilizers usually contain?

3. What are some farmers using nowadays?

4. In what way are organic fertilizers better than inorganic ones?

5. When can manures cause pollution?

3.Write a summary in English . Use about 150 to 200 words.

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Textos Para Alumnos de Maestria (2)