chapter 07 question

New Biology – a modern approach 1Chapter 7: Effects of humans on the environment

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Structured Questions

Core Section

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* Read the passage below and answer the questions that follow:

Algae are the producers in the world’s oceans. When produced in vast quantities, they

can provide food for primary consumers. Red tide, which appears reddish in colour, is

actually a large group of algae. It is the result of an algal bloom. In fish farms, the presence

of red tide seriously affects the growth of fish at night.

(i) Describe how algae provide energy for primary consumers. (3 marks)

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(ii) Give an example of a primary consumer in an ocean. (1 mark)

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(iii) State, with reasons, the effect of red tide on the growth of fish at night. (3 marks)

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(iv) Algal blooms may occur in freshwater near an agricultural land. Explain. (2 marks)

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(i) Algae undergo photosynthesis to form glucose. (2 marks)

They change solar energy to chemical energy which is then stored in the glucose molecule.(1 mark)

(ii) fish/ zooplankton (1 mark)

(iii) The fish die. (1 mark)

At night, no photosynthesis takes place in algal cells but respiration still proceeds. (1 mark)

There is a net uptake of oxygen by the algae and as a result the fish cannot get enough oxygen. (1

mark)

(iv) Nitrates in fertilizers leached from an agricultural land increase the nitrate level in the freshwater. (1

mark)

Algae multiply rapidly after absorption of the nitrates. (1 mark)

_________

(9 marks)##

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Eric obtained the following data of four poor-developing countries from his teacher. Life span tells how many

years a human can live in his lifetime.

CountryAverage life span for people born in 1985 /

years

Average life span for people born in 2005 /

years

A 43 48

B 58 40

C 54 50

D 48 48

(i) State the country that shows an increase in life span of its people. (1 mark)

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(ii) Human life span is increasing worldwide. Suggest TWO reasons. (2 marks)

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(iii) AIDS is a disease that shortens the life span of a human.

(1) State the country which shows the most serious problem of AIDS since 1985. Explain your answer.

(2 marks)

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(2) It is difficult to classify HIV which causes AIDS. Explain why and give the group name for HIV. (2

marks)

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(iv) In poor countries, the risk of diarrhoea is high. Suggest TWO ways to reduce the risk of having

diarrhoea. (2 marks)

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(i) A (1 mark)

(ii) Nowadays, humans know the importance of a balanced diet to their health. (1 mark)

Medical care is improved. (1 mark)

(iii) (1) B, (1 mark)

because of a larger number of deaths due to AIDS at a younger stage. (1 mark)



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(2) It does not show all characteristics of living organisms. (1 mark)

HIV belongs to the group of viruses. (1 mark)

(iv) To establish a sanitary environment to keep the drinking water clean. (1 mark)

To educate the people in such countries about personal hygiene. (1 mark)

_________

(9 marks)##

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* STS Connections

Read the passage below and answer the questions that follow:

Chlorofluorocarbons (CFCs) are gases used in industry. After discharge into the

atmosphere, these gases break down the ozone layer. They can remain active in the

atmosphere for many years. As a result, human has a higher risk of developing skin cancer.

An international agreement has been signed by some countries to stop the damage done to

the ozone layer.

(i) State TWO uses of CFCs in industry. (2 marks)

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(ii) State the significance of the ozone layer to human health. (2 marks)

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(iii) Scientists discovered that there was a large ‘hole’ in the ozone layer over Antarctica.

(1) Suggest a cause of the ‘hole’. (1 mark)

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(2) More cases of skin cancer have been found in countries in the Southern Hemisphere than

elsewhere. Explain. (2 marks)

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(3) Suggest TWO ways to prevent enlargement of the ‘hole’. (2 marks)

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(i) As coolants in refrigerators and (1 mark)

making plastic foam. (1 mark)

(ii) The ozone layer can absorb much of the harmful light from the sun, (1 mark)

especially UV light. (1 mark)

(iii) (1) CFCs break down the ozone layer and leave a hole. (1 mark)

(2) UV can pass through the ‘hole’ and reach the Earth’s surface. (1 mark)

UV is a harmful light which is known to increase the incidence of skin cancer in humans.

(1 mark)

(3) To cut down the levels of industrial emission of CFCs. (1 mark)

To find alternative compounds to replace CFCs. (1 mark)

_________

(9 marks)##

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* Pollution is a problem due to urban development. In Hong Kong, the emission of pollutant gases worsens the

air quality. The table below shows the source and amount of some pollutant gases produced by human

activities:

P ollutant gas Human activities that produce the

pollutant gas

Amount produced per year

(millions of tons )

Carbon monoxide Vehicle exhaust 300

Sulphur dioxide Burning fuels in industry 150

Nitrogen dioxide Vehicle exhaust, burning fuels 50

Hydrocarbon Vehicle exhaust, industry 80

(i) State the gas for which human is the greatest source of pollution. (1 mark)

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(ii) Describe the effect of carbon monoxide on human circulation. (3 marks)

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(iii) State TWO gases which cause acid rain. (2 marks)

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(iv) The Hong Kong Government encourages taxi drivers to use liquefied petroleum gas (LPG) instead of

diesel. Describe how this idea can improve the air quality. (3 marks)

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(i) carbon monoxide (1 mark)

(ii) Carbon monoxide combines with haemoglobin. (1 mark)

The combination is irreversible. (1 mark)

This reduces the number of haemoglobin molecules available for carrying oxygen. (1 mark)

(iii) sulphur dioxide and (1 mark)

nitrogen dioxide (1 mark)

(iv) LPG is a cleaner fuel. (1 mark)

Burning LPG releases only carbon dioxide and water to the air. (1 mark)

Thus less pollutant gases would be formed. (1 mark)

_________

(9 marks)##

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Complete the following paragraph with suitable words selected from the list below:

oxygen erosion global warming carbon dioxide lucky

forestation usual habitats deforestation laws

cooling effect uprooting leaching

(i)_________________ is the cutting down of large numbers of trees. If this activity happens in an

extensive way, the (ii)_________________ concentration in the atmosphere will be increased and this may

cause (iii)_________________. Many (iv)_________________ for wild animals to live are destroyed, leading

to extinction of certain species. Removal of trees exposes the topsoil so that (v)_________________ may

occur in heavy rain. The soil will then become infertile and it will be very difficult for trees to grow. So,

(vi)_________________ are set up to fight against the tree destruction. (3 marks)



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(i) Deforestation (1/2 mark)

(ii) carbon dioxide (1/2 mark)

(iii) global warming (1/2 mark)

(iv) habitats (1/2 mark)

(v) erosion (1/2 mark)

(vi) laws (1/2 mark)

__________

(3 marks)##

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* The diagram below shows the effects of an algal bloom on fishes at daytime and at night:

(i) Explain the formation of an algal bloom. (2 marks)

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(ii) When red tide occurs, fishes are not affected at daytime while many of them die at night. Explain

briefly why this happens. (4 marks)

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(iii) The food web below begins with algae:

Some species of algae produce toxic substances which can be transferred through the food web.

Explain why the risk of poisoning is much higher when humans eat carnivorous fishes rather than

herbivorous fishes. (3 marks)

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(iv) Name an example of toxins commonly found in marine fish. (1 mark)

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(v) What is the relationship between humans, marine mammals and birds in the food web above?

(1 mark)

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(i) If there is a sudden increase in nutrients such as nitrates in water, (1 mark)

the microscopic algae, containing a reddish pigment, will grow very fast and accumulate into dense,

visible patches near the surface of water. Such phenomenon is called an algal bloom. (1 mark)

(ii) At daytime, in the presence of light, the algae in red tide carry out photosynthesis. (1 mark)

There is a net absorption of carbon dioxide and a net release of oxygen since the rate of photosynthesis

exceeds that of respiration. (1 mark)

At night, the algae carry out respiration only and use up most of the oxygen in water. (1 mark)

The fishes under the water may die of suffocation. (1 mark)


Algae

Herbivorous fishes

Carnivorous fishes

HumansMarine mammals Birds


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(iii) The toxic substances produced by algae are accumulated throughout the food web. (1 mark)

They can neither be excreted nor digested. (1 mark)

As carnivorous fishes feed on large number of herbivorous fishes, the amount of toxic substances is

much higher in the bodies of carnivorous fishes. The toxins will in turn be transferred to humans. (1

mark)

(iv) ciguatera toxins (or any reasonable answers) (1 mark)

(v) competition (1 mark)

___________

(11 marks)##

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STS Connections

Read the article below and answer the following questions:

“Members of the public are reminded not to bring endangered species into Hong Kong without a

licence on their return from visits to other places”, a spokesman for the Agriculture, Fisheries and

Conservation Department (AFCD) said.

“There has been an increase in the number of cases concerning travellers bringing back items

made from endangered species without a licence. A total of 93 seizures (扣押 ) were made at the

customs checkpoints in the first six months of 2001 and the figure has reached 145 for the same

period in 2002,” the spokesman said.

Statistics showed that items commonly seized from travellers at customs checkpoints included

orchid, cactus, American Ginseng root, crocodile meat and crocodile leather products.

(i) According to the article above, suggest ONE cause of species extinction. (1 mark)

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(ii) Suggest TWO other causes of species extinction. (2 marks)

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(iii) Name ONE organism that

(1) is in danger of becoming extinct. (1 mark)

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(2) has become extinct. (1 mark)

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(i) illegal hunting of animals (1 mark)

(ii) The destruction of habitats due to human population growth and technological advances. (1 mark)

environmental pollution. (or any reasonable answers) (1 mark)

(iii) (1) koala (or any reasonable answers) (1 mark)

(2) dodo (or any reasonable answers) (1 mark)

__________

(5 marks)##

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The graph below shows the changes in oxygen content of river water as the river flows through a large city.

Figures for the years 1955 and 1970 are recorded on the graph:

(i) Account for the drop in oxygen content as the river flowed into the city. (4 marks)

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(ii) The increase in oxygen content which occurred during the fifteen years between 1955 and 1970 was

the result of attempts to reduce pollution in this river. Suggest and describe ONE practical way in

which the improvement might have been brought about. (3 marks)

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(iii) The water from this river is used as drinking water after suitable treatment including settlement and

filtration to remove solids. What further treatment is necessary before the water is safe for human

consumption? (1 mark)

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(i) Due to domestic sewage dumped into the river by the citizens, (1 mark)

the number of saprophytic bacteria / decomposers increased tremendously. (1 mark)

The great consumption of oxygen by bacteria for respiration caused the drop in oxygen content in the

river. (2 marks)

(ii) A sewage treatment plant might have been set up. (1 mark)

Solid particles in sewage could be filtered, (1 mark)

and organic substances in sewage could be decomposed before being drained into the river.

(1 mark)

(iii) chlorination (1 mark)

__________

(8 marks)##



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* Sewage rich in organic pollutants was discharged into an unpolluted river. Samples of water were taken at

various distances downstream along the river and were analysed. The results are shown in the graphs below:

(i) Suggest a reason to explain why the bacterial level increased rapidly at the point of sewage discharge.

(1 mark)

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(ii) Suggest the reason why the dissolved oxygen dropped gradually at the point of sewage discharge and

then rose downstream. (4 marks)

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(iii) Explain the changes in the concentrations of ammonia and nitrate and how these might be interrelated.

(4 marks)

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(i) The sewage contained a large number of bacteria. (1 mark)

(ii) At the point of sewage discharge, more bacteria consumed oxygen for respiration. (1 mark)

Fewer algae produced oxygen by photosynthesis. (1 mark)

Later in the downstream, the bacterial population decreased and less oxygen was consumed.

(1 mark)

More algae were present to produce oxygen from photosynthesis. (1 mark)

(iii) Some of the ammonia was introduced in the sewage. (1 mark)

Some might be formed as a result of the decomposition action of bacteria. (1 mark)

Ammonia could be changed to nitrate by nitrification / nitrifying bacteria, causing the nitrates to

increase gradually. (1 mark)

Both ammonia and nitrate decreased slowly downstream due to the dilution effect caused by the joining

of other streams with the river. (1 mark)

__________

(9 marks)##

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* The table below shows the number of days in Hong Kong in each year on which the visibility was low.

Visibility is generally considered poor when it is below 8 km.

Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

**Frequency of visibility

below 8 km (%)4.4 4.9 5.5 5.7 5.5 8.8 10.1 8.2 8.9 6.3

(**Note: The relative humidity must be less than or equal to 75%)



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(i) Using the data above, plot a graph to show the trend of visibility impairment from year 1991 to year

2000. (4 marks)

(ii) With reference to the graph, describe the trend of visibility impairment in these ten years. (3 marks)

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(iii) Explain why the data should not include the days with invisibility below 8 km but with the relative

humidity above 75%? (2 marks)

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(iv) Suggest reasons for the pattern of frequency of visibility below 8 km during the period 1995 to 1997.

(3 marks)

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(v) What are the effects on people who live for a long period of time in an environment with a large

amount of substances in the air that cause low visibility? (2 marks)

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(vi) Suggest and explain ONE possible way in which you as a citizen can do in daily life to help reduce air

pollution. (2 marks)

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(i)

Correct plotting of points (2 marks)

Correct choice of axes and title (1 mark)

Correct labelling of axes with units (1 mark)

(ii) The problem of visibility impairment became worse, in a steady rate from the year 1991 to year 1995.

(1 mark)

During the period 1995 - 1997, the frequency of visibility impairment rose sharply in each year. (1

mark)

From 1997 to 2001, the frequency continued to drop. (1 mark)

(Bonus: but it did not return to the level observed before year 1995) (1 mark)*

(iii) When the relative humidity is higher than 75%, it may mean that not only the air pollutants, but also



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the rain or fog, may affect the visibility. (1 mark)

Recording the day with humidity less than at or below 75% ensures that the decrease in visibility is

mainly due to air pollutants but not to other factors. (1 mark)

(iv) The general decrease in visibility might be due to increase in particulate emissions by incomplete

combustion from vehicles or incinerators. (1 mark)

The increased amount of nitrogen oxides or other pollutants from vehicles exhaust might increase the

amount of photochemical smog formed annually. (1 mark)

Photochemical smog was dark in colour and decreased the visibility. (1 mark)

(v) Photochemical smog irritates the eyes and respiratory tract. (1 mark)

Soot particles may damage our lungs and cause respiratory diseases such as asthma. (1 mark)

(vi) Switch off electrical appliances when they are not in use in order to save electricity. (1 mark)

This can help reduce pollutants such as nitrogen oxides and particulates

emitted from power plants. (or any reasonable answers) (1 mark)

__________

(16 marks)##

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* STS Connections

The pie charts below show the percentages of municipal solid waste recovered in 2000 and

2002, respectively:

Chart showing proportion of major recyclable materials

recovered from municipal solid waste in 2000

Chart showing proportion of major recyclable materials recovered

from municipal solid waste in 200 2



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(i) Which TWO categories of waste showed an increase in percentage? (2 marks)

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(ii) Name THREE kinds of solid waste that are collected by recycling bins set up by the Food and

Environmental Hygiene Department. State the colours of these bins. (3 marks)

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(iii) Suggest with examples, TWO other ways to reduce pollution with reference to 3Rs concept.

(4 marks)

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(iv) The category of ‘other’ includes wastes derived from high technology products. This kind of wastes

was first collected and recycled in the year 2002. Suggest ONE example of this kind of wastes. (1

mark)

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(v) Group the solid wastes below into three different categories: (51/2 marks)

rechargeable batteries banana peel aluminium cans

paper wrapping sheets glass bottles plastic bottles

(Each item can be used more than once.)

Biodegradable waste Non-biodegradable waste Recyclable waste



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(i) Ferrous metal and others. (2 marks)

(ii) plastic bottles – brown (1 mark)

aluminum cans – yellow (1 mark)

waste paper – blue (1 mark)

(iii) - Reduce

~ Bring your own bag for shopping, and use fewer plastic bags.

- Reuse

~ Use hoardings and formworks again.

(or any reasonable answers) (4 marks)

(iv) electrical & electronic equipment (1 mark)

(v)

Biodegradable wastes Non-biodegradable wastes Recyclable wastes

banana peel

paper wrapping sheets

rechargeable batteries

aluminium cans

glass bottles

plastic bottles

rechargeable batteries

aluminium cans

paper wrapping sheets

glass bottles

plastic bottles

(1/2 mark each) (51/2 marks)

_________

(151/2 marks)##

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* Apparatuses X and Y are installed in the car exhaust system and in the power station, respectively, in order to

reduce the amount of pollutants emitted into the air.

(i) Name apparatuses X and Y. (2 marks)

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(ii) What are the TWO major compounds that can be removed by apparatus X? (2 marks)

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(iii) Which gas is reduced by apparatus Y in the power station? State ONE adverse effect of this gas. (2

marks)

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(iv) Taxis that use diesel oil are gradually replaced by LPG taxies. Explain why LPG is considered to be a

cleaner fuel than diesel. Compare the compounds present in the car exhausts. (4 marks)

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(v) Apart from installing apparatus Y, suggest another method to limit the amount of gas mentioned in (iii)

emitted from the factories or power plants. (1 mark)

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(vi) Large amounts of soot particles are also produced for the old coal-burning power plants. Suggest ONE

apparatus that can be installed so as to reduce the emission of particulates. (1 mark)

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(i) X: catalytic converter (1 mark)

Y: scrubber (1 mark)

(ii) unburnt hydrocarbons, carbon monoxide, nitrogen dioxide (any two) (2 marks)

(iii) sulphur dioxide (1 mark)

It causes acid rain which damages buildings and statues / irritates eyes /

attacks the respiratory systems (any one) (1 mark)

(iv) Incomplete combustion of diesel (1 mark)

will produce air pollutants such as sulphur dioxide, nitrogen dioxide and carbon monoxide.

(1 mark)

The burning of LPG produces only carbon dioxide and water (1 mark)

since it is a complete combustion. These compounds will not cause air pollution. (1 mark)

(v) using fuels of lower sulphur content. (or any reasonable answers) (1 mark)

(vi) electrostatic precipitator (1 mark)

__________

(12 marks)##

|!|EQB00700013|!|

* The diagram below shows the construction plan of a sewage treatment plant for treating domestic sewage:



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(i) Give the names of the physical or biochemical processes that take place inside the following

compartments: (3 marks)

(1) primary settlement tank

(2) aeration tank

(3) anaerobic digester

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(ii) State the fate of the following substances after production in the sewage treatment plant. (3 marks)

(1) sludge

(2) methane gas

(3) large stones and grit

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(iii) What are the TWO conditions needed for the process in the anaerobic digester tank to occur efficiently?

(2 marks)

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(iv) If a large amount of chlorine bleach or disinfectants are poured into the household toilet and then enter

the treatment plant, how will the quality of the treatment be affected? Explain briefly. (4 marks)

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(i) (1) sedimentation (1 mark)

(2) decomposition (1 mark)

(3) anaerobic respiration / fermentation (1 mark)

(ii) (1) used in farms as fertilizer (1 mark)

(2) used as a clean fuel to generate electricity (1 mark)

(3) no specific use / transport to landfill (1 mark)

(iii) a relatively high temperature (1 mark)

lack of oxygen (1 mark)

(iv) The large amount of chlorine or disinfectants will kill the bacteria or microorganisms present in

different treatment tanks. (1 mark)

The process of decomposition of the organic wastes by the bacteria will be hampered. (1 mark)

The organic matter in the sewage thus cannot be broken down into inorganic compounds and will be

directly discharged into the sea, which may cause algal bloom. (1 mark)

Disinfectants remained in the effluent may poison or kill the marine organisms in the sea. (1 mark)

___________

(12 marks)##



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Extension Section

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* The diagram below shows a map of a city:

(i) Where would you go fishing? Point X or Y? Give THREE reasons to explain your answer.

(4 marks)

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(ii) The trees in the woodland die or grow with yellow leaves and weak stems. Explain with TWO reasons.

(3 marks)

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(iii) Without the sewage treatment plant, the sewage from the residential area will be drained into the river

directly. What will happen to the oxygen level of the river? Explain. (4 marks)

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(iv) The farmers make use of DDT as an insecticide. How does it affect the fish-eating birds? Explain your

answer. (6 marks)

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(i) Point X. (1 mark)

It is because the river at point Y will be heavily polluted by discharge from the power station, farms

and the residential area. (1 mark)

There will be less fish. (1 mark)

The fish may be poisonous. (1 mark)

(ii) Smoke from the power station contains soot and acidic gas. (1 mark)

Soot will cover the leaves and thus the rate of photosynthesis will decrease. (1 mark)

Acidic gas may dissolve in water. The acidic water may kill the plants. (1 mark)

(iii) There will be organic pollutants in the sewage. (1 mark)

Bacteria depending on the organic pollutants will grow rapidly. (1 mark)

Bacteria will use up oxygen in the water by respiration, (1 mark)

so the oxygen level will drop. (1 mark)

(iv) DDT is not biodegradable (1 mark)

and cannot be excreted. (1 mark)

DDT is washed into the river by rain, and it is concentrated in the cells of the water plants.

(1 mark)

When a fish eats the water plants, DDT is passed to the fish body. (1 mark)

Similarly, when the birds eat the fish, DDT is passed to the bodies of the birds. (1 mark)

DDT is accumulated along the food chain. The level of DDT is high enough to kill the birds.

(1 mark)

__________

(17 marks)##


chapter 07 question

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