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1. 1991/I/2c

The diagram below shows a sealed glass bottle in which small green plants are growing in moist soil and

humus. When placed in an environment with suitable temperature and light, the plants can live for a year.

(i) For the plants to survive, there must be a supply of

(1) carbon dioxide and oxygen,

(2) water, and

(3) inorganic nutrients.

Explain how these supplies are maintained inside the sealed glass bottle. (6 marks)

(ii) Suggest ONE biotic component which is absent from this particular ‘ecosystem’. (1 mark)

(iii) Explain why the addition of humus to the soil is particularly important in this case. (2 marks)

2. 1992/I/1a

The following food chains are identified in a given habitat :

A. green plants � grasshoppers � spiders � lizards � snakes

B. green plants � grasshoppers � small birds � snakes

C. green plants �mosquitoes � lizards � snakes

D. green plants � bees � small birds � snakes

Based on the food chains shown above, answer the following questions :

(i) Construct a food web showing all the feeding relationships among the organisms concerned.

(3 marks)

(ii) For the same biomass of green plants, through which food chain (A, B, C or D) would the least

amount of energy be made available to snakes ? Explain your answer. (4 marks)

(iii) Of the four invertebrates, which animal is the most important in helping the perpetuation of the

green plants ? Explain your answer. (2 marks)

(iv) Two of the vertebrates are classified into the same group.

(1) Name the group.

(2) State one external feature which is characteristic of this group. (2 marks)

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3. 1995/I/3c

Explain the following :

(i) Sea water should not be used for watering plants. (3 marks)

(ii) Fertilizers are added to agricultural fields to ensure constant crop production year after year.

(4 marks)

(iii) It is important to conserve tropical rain forests. (4 marks)

4. 1996/I/2bi

Explain the following :

Leguminous plants can still grow well in soil deficient in nitrates. (4 marks)

5. 1996/I/4b

The diagram below shows some organisms in a food web in the South Pole region :

(i) Referring to the food web, state the relationship(s) between

(1) the blue whale and the seal, (1 mark)

(2) the squid and the sea bird. (1 mark)

(ii) In the South Pole region, the period of daylight becomes much shorter in winter.

Explain how this affects the algal population. (2 marks)

(iii) Although there is no farming activity in South Pole, a pesticide, DDT, is found accumulated in

penguins. Explain why this occurs. (5 marks)

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6. 1997/I/3c

The diagram below shows part of a food web in a gei wai at Mai Po.

(i) Describe how the energy from the sun becomes available to the gei wai shrimp in this food web.

(4 marks)

(ii) Explain what will happen to the yield of the mouthbrooder after all the shrimps have been harvested

from the gai wai. (2 marks)

(iii) Two of the animals in the food web are classified into the same vertebrate group.

(1) Name the group. (1 mark)

(2) State one external feature used for classifying the two animals into this group. (1 mark)

(iv) Give one reason why the Mai Po reserve area is ecologically valuable. (1 mark)

7. 1999/I/3a

Exhaust gas from power stations is rich in carbon dioxide. Some scientists attempted to make use of the

exhaust gas for growing microscopic green algae. The diagram below shows a set-up used to compare the

effect of air and exhaust gas on the growth of algae :

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In the first treatment, air was passed into the glass tank. Two samples of the algal culture, each of 1 litre,

were withdrawn at an interval of 24 hours. The dry mass of the algae in each sample was determined. In the

second treatment, the same procedure was repeated but exhaust gas was used instead of air. The results are

shown in the table below :

Dry mass of algae (g)

Treatment Gas used at hour 0 at hour 24

I Air 3.60 3.64

II Exhaust gas 3.70 3.88

(i) What is meant by the dry mass of the algae ? (1 mark)

(ii) Explain the difference in dry mass of the two algal samples in treatment I. (4 marks)

(iii) (1) Based on the results of treatments I and II, what is the effect of aerating the algal culture with

the exhaust gas ? (1 mark)

(2) Suggest a reason to explain why there is such an effect. (2 marks)

(iv) Explain how the global air temperature may be affected if the practice of using exhaust gas from

power stations to culture algae is adopted all over the world. (3 marks)

8. 2002/I/3b

In an ecosystem, there are various types of bats. One type of bats, A, is shown in photograph 1 below. When

a sample of its faeces was examined, pieces of legs and wings of a certain group of animals were found as

shown in photograph 2.

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(i) (1) To which group of vertebrates do bats belong ? (1 mark)

(2) Referring to photograph 1, state one external feature of bat A through which it is classified into

the group you stated in (1). (1 mark)

(ii) With reference to photograph 2, suggest the group of animals that bat A feeds on. (1 mark)

(iii) The faeces of another type of bats, B, are found to contain some seeds. Suggest an explanation for

the presence of intact seeds in the faeces of bat B. (2 marks)

(iv) A third type of bats, C, feeds on the blood of large animals. Assuming that bats B and C have the

same amount of daily food intake, compare the daily amount of faeces they produce. Explain your

answer. (2 marks)

(v) Having different types of bats is advantageous to the survival of bats in an ecosystem. Suggest an

explanation for this using the information about bats A, B and C given above. (2 marks)

9. 2003/I/1civ

The diagram below shows a simplified food web in Tai Mo Shan Country Park :

(1) With reference to the given food web, draw a food chain that consists of five trophic levels. (1 mark)

(2) Construct a pyramid of numbers for this food chain. (2 marks)

(3) Explain the shape of this pyramid of numbers. (4 marks)

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10. 2007/I/9a

The photograph below shows an ecosphere:

The ecosphere is a self-sustaining ecosystem sealed in a glass container. It contains bacteria, microscopic

algae, shrimps and branches of dead coral in filtered seawater.

(i) Why is it essential to put the algae into the ecosphere to make it self-containing? (4 marks)

(ii) How can the activity of the bacteria contribute to the growth of algae? (2 marks)

(iii) This ecosphere can only support two trophic levels. Suggest a possible explanation for this.

(2 marks)

11. 2008/I/8a

In order to increase the yield of crops, farmers may add inorganic fertilizers and fungicides to the field.

Fungicides can kill fungi which may infect crop plants. The table below shows the effect of applying these

chemicals to a wheat field.

Yield of wheat (arbitrary unit) Mass of inorganic

fertilizers added (kg) With the addition of fungicides Without the addition of fungicides

0

80

160

240

320

33

54

64

68

70

33

52

60

61

58

(i) Plot a graph to show the yield of wheat when different amounts of inorganic fertilizers are added in

the presence and in the absence of fungicides. (3 marks)

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(ii) With reference to the graph plotted, describe the effect of fungicides and inorganic fertilizers on the

yield of wheat. (3 marks)

(iii) Explain an ecological impact of the excessive use of inorganic fertilizers on the aquatic community

nearby. (3 marks)

HKCEE BIOLOGY | 2.2 Ecosystem | P.7