lq - 06 man and the environment

Certificate Biology New Mastering Basic Concepts Chapter 6Question Bank V2.0 Structured Questions

Ch 6 Man and the environment

[061001]

The following diagram explains the greenhouse effect:

a Name one major air pollutant that traps heat and warms the atmosphere.

(1 mark)

b What will be the effect on the overall air temperature? (1 mark)

c Suggest one possible effect of this temperature change on the environment.

(2 marks)

d Other than industries and motor vehicles, suggest and explain another

human activity which causes an increase in this air pollutant. (2 marks)

e Industrial processes and motor vehicles produce air pollutants which may

cause deaths of trees and marine organisms and also cause damage to man-

made materials. What are these pollutants and how do they cause these

environmental problems? (4 marks)

Oxford University Press 2005 / 18


-- ans --

a Carbon dioxide 1m

b Overall increase in air temperature 1m

c Ice in the polar regions may melt. 1m

The water level of the oceans will rise and the coastal area may sink below the sea

level. 1m

d Deforestation causes the balance of carbon dioxide unable to maintain. 1m

Carbon dioxide produced from respiration of all organisms is more than that

absorbed by plants for photosynthesis. Therefore, the level of carbon dioxide in the

atmosphere rises. 1m

e Sulphur dioxide and nitrogen dioxide 1m

When these gases are dissolved in rain, acid rain results. 1m

Trees and marine organisms are killed because the rain makes soil and water

acidic. 1m

Acid rain is corrosive and erodes metals, stones and other building materials. 1m

-- ans end --



[061002]

A river flows through an area of agricultural land where fertilizers are used

frequently.

a Describe and explain how the use of fertilizers may affect the animals and

plants living in the river. (4 marks)

b Why do farmers use so much fertilizers? What are the alternatives to

fertilizers? (3 marks)

c Besides fertilizers, what chemicals are commonly used by farmers? What

are the bad effects of them on humans and other animals? (3 marks)

-- ans --

a Fertilizers in soil contain phosphates and nitrates which are washed by rain to the

river. 1m

Growth of algae is increased. 1m

Algae use up the dissolved oxygen in river at night. 1m

Aquatic organisms die of suffocation. 1m

b Farmers practice monoculture. Continuous culture of the same crop uses up

certain nutrients in the soil. 1m

Nutrients have to be added to sustain yield. 1m

Mixed cultivation / growing leguminous plants periodically (any 1) 1m

c Pesticides are used to kill pests. 1m

Pesticides are toxic. 1m

Pesticides may accumulate along the food chains. If we consume contaminated

food, our health is at risk. 1m

-- ans end --



[061003]

The diagram below shows a river polluted by the sewage

discharged from both the town and the farm.

a Account for the sharp increase in bacterial population in the polluted water.

(1 mark)

b Explain how the sharp increase in bacterial population causes a decrease in

the fish population downstream. (3 marks)

c Explain why the discharged sewage may lead to algal blooms. Give four

effects of algal blooms on the aquatic life in the river. (5 marks)

d Suggest one way to the government to help solve the problems. (1 mark)

-- ans --

a Sewage discharged from the town and farm contains a lot of nutrients which can

be used by bacteria for growth. 1m

b A lot of oxygen in the river is used up by the bacteria for growth and decomposition

of organic matters. 1m

The fish die of suffocation. 1m

The bacteria also release toxins which poison the fish. 1m

c The discharged sewage contains a lot of nutrients for the growth of algae. 1m

The large population of algae prevents sunlight from passing through the water.

This reduces the photosynthetic rate of aquatic plants. 1m


downstream

town

farm

sewage

fish

upstream

sewage


The large population of algae prevents diffusion of oxygen into the water. The fish

die of suffocation. 1m

The algae block the gills of the fish. The fish die of suffocation. 1m

When the algae die, they are decomposed by the bacteria, which use up oxygen in

the river. The fish die of suffocation. 1m

d Setting up of a sewage treatment plant to make the sewage less harmful before it

is discharged. 1m

-- ans end --



[061004]

The diagram below shows the various components of a sewage treatment plant.

a What is the function of the settling tank? (1 mark)

b Why is air bubbled into the aeration pond? (4 marks)

c What is the function of the digester? Give the names and uses of two

substances produced in the digester. (4 marks)

d Even though the sewage has passed through several stages in the treatment

process, the effluent may still cause algal blooms because of its high content

of a certain substance. What is it? (1 mark)

-- ans --

a To let the solid part of the sewage / sludge settle down to the bottom. 1m

b To stir up the sewage. 1m

To make the bacteria and fungi active 1m

in decomposing organic substances in the sewage 1m

into harmless inorganic compounds. 1m

c Anaerobic bacteria carry out fermentation of the sludge in the digester. 1m

Methane gas 0.5m



As fuel to power the sewage treatment plant. 1m

Sludge 0.5m

As plant fertilizers in farming. 1m

d Mineral 1m

-- ans end --



[061005]

Foam rubber is widely used in packaging and making disposable lunch boxes.

However, it causes a great environmental problem because it is non-

biodegradable.

a Suggest how the industry owners, restaurant owners and the government

reduce the problem caused by foam rubber wastes. (You may consider the

4R principle -- Reduce, Reuse, Replace and Recycle.) (6 marks)

b Suggest two ways of conserving the environment as a consumer and

explain. (4 marks)

-- ans --

a Industry owners:

avoid non-essential packaging

use biodegradable materials for packaging

use recycled foam rubber

Restaurant owners:

use disposable products made of biodegradable materials

allow and encourage customers to bring their own containers

Government:

educate the public in the problems caused by foam rubber wastes

encourage the industrial sectors to use biodegradable materials by providing

subsidies

(any 6) 1m x 6

b BYOB (Bring your own bag) -- cut down plastic wastes



Do not buy commodities with too much packaging -- cut down solid wastes

Buy electric appliances with high energy efficiency -- reduce pollution caused by

power plants indirectly

Buy recycled products -- cut down solid wastes, save resources

Each correct answer with explanation 2m x 2

-- ans end --



[061101]

The graph below shows the concentrations of dissolved oxygen and phosphate,

as well as the densities of organisms A and B in a river. The negative value of

distance means the upstream and positive value means the downstream from a

farm. The concentrations or densities are not in scale.

a i Organism A is a micro-organism. Give one example of it. (1 mark)

ii Give one example of organism B. (1 mark)

b Explain why the phosphate concentration in the river increased suddenly

near the farm. (2 marks)

c Explain why the dissolved oxygen concentration decreased significantly

with the increase in phosphate concentration. (2 marks)

d Give two reasons for the drop in the density of organism B. (2 marks)

-- ans --

a i Microscopic algae 1m

ii Fish, crab or other free-living freshwater animals 1m



b Farmers used excessive fertilizers that contained phosphate. 1m

Rain washed the fertilizers to the river. 1m

c Algae grew rapidly with rich phosphate supply. 1m

Respiration and decomposition of the algae consumed a lot of dissolved oxygen.

1m

d Depletion of oxygen / suffocation. 1m

Killed by the toxins released from the algae. 1m

-- ans end --



[061102]

Answer the questions below with reference to the following news about red tide.

Fish farmers on alert over spread of red tide

The fears of fish farmers grew after two more new blooms of red tide

were discovered off Hong Kong Island. Red tide is an algal bloom

that turns the colour of seawater to pink or reddish brown. Despite

the government's Red Tide Interdepartmental Working Group has

confirmed the species of the algae is non-toxic, fish farmers are

worried that their fish would be killed. The algae outbreak has also

raised the concerns about the pollution level in Victoria Harbour.

a Give three ways of how the algae may kill the fish in fish farms even they

are non-toxic. (3 marks)

b Suggest two measures to the fish farmers to avoid their fish being killed

by the red tide. (2 marks)

c How may the occurrence of red tide be related to the pollution level in the

harbour? (2 marks)

-- ans --

a The algae may use up the dissolved oxygen in the water during the night, hence

the fish die of suffocation.

The algae may block the gills of fish, hence the fish die of suffocation.

The algae may reduce sunlight penetration into the water and therefore the

photosynthetic rate of aquatic organisms is lowered. This decreases the amount

of dissolved oxygen in the water and hence the fish die of suffocation.

The algae may prevent oxygen from dissolving into the water, hence the fish die

of suffocation.



When the algae die, the dissolved oxygen in the water may be depleted during

the decomposition of the algae by bacteria, hence the fish die of suffocation.

(any 3) 1m x 3

b Pumping oxygen into the water at night to increase the dissolved oxygen

content.

Stop feeding the fish to reduce the oxygen requirement of the fish as well as the

ecosystem.

Enclose the fish cages with plastic sheets to separate the fish from the red tide.

(any 2) 1m x 2

c The red tide may be caused by the availability of nutrients such as nitrogen,

potassium and phosphorus. 1m

These nutrients are commonly found in domestic sewage. 1m

-- ans end --



[061103]

Plant refuse is left in an uncovered container undisturbed. The change in

temperature of the refuse is recorded in the graph below.

a Explain the change in temperature during the first two days. (3 marks)

b Suggest one possible use of the plant refuse after two weeks. (1 mark)

c Suggest two methods to speed up the above process. Explain your answer.

(4 marks)

-- ans --

a Bacteria and fungi decompose the plant refuse, 1m

releasing heat energy. 1m

The temperature therefore rises. 1m

b Used as fertilizers. 1m

c Turn the refuse everyday with a plough or punch holes into it with a fork

so that the decomposers can get enough oxygen to carry out decomposition.

Add some water to the dry refuse

to favour the the growth of decomposers.



Cover the refuse with a layer of soil to keep the refuse warm

because decomposers work best at higher temperature.

(any 2 methods and correct explanations) 2m x 2

-- ans end --



[061104]

The graph below shows the amount of greenhouse gases emitted in Hong Kong

from 1990 to 2002.

[Source of information: Environmental Protection Department]

a Give two examples of greenhouse gases. (2 marks)

b How do greenhouse gases lead to greenhouse effect? (3 marks)

c Suggest one reason to account for the decrease in the emission of

greenhouse gases from a peak in the early 1900s throughout the mid- and

late-1990s. (1 mark)

d Give one example of what the government did to reduce the emission of

greenhouse gases. (1 mark)

-- ans --

a Carbon dioxide, nitrous dioxide, methane, sulphur hexafluoride, chloro-fluoro

carbons / CFCs



(any 2) 1m x 2

b Greenhouse gases act as a shield around the Earth 1m

to trap the heat reflected from the ground. 1m

This raises the atmospheric temperature. 1m

c Part of the electricity has been supplied from the Guangdong Daya Bay Nuclear

Power Station since its operation. Therefore, less coal has been used in

electricity generation in Hong Kong.

Migration of local factories to the mainland.

(any 1) 1m

d The introduction of liquefied petroleum gas (LPG) taxis. 1m

-- ans end --


lq - 06 man and the environment

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