Paper 1 > Biology 2000 Paper 1

2000-CE BIO

HONG KONG EXAMINATIONS AUTHORITY

PAPER 1

HONG KONG CERTIFICATE OF EDUCATION EXAMINATION 2000

BIOLOGY PAPER 1 8.30 am – 10.00 am (1½ hours) This paper must be answered in English

1.

Attempt THREE questions only.

2.

Each question consists of three parts.

3.

All questions carry equal marks.

4.

In each question, 2 additional marks will be awarded for effective communication.

5.

The diagrams in this paper are NOT necessarily drawn to scale.

香 港 考 試 局 　 　 保 留 版 權 Hong Kong Examinations Authority All Rights Reserved 2000 2000-CE-BIO 1–1

1. (a)

The diagram below outlines a clinical test used to examine whether a human foetus has any abnormality in its chromosomes :

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(i)

The cells of A and the cells of the foetus have the same genetic composition. How would you explain this ? (2 marks)

(ii)

(1)

With reference to the chromosomes in the diagram, state the sex of the foetus. (1 mark)

(2)

Describe how the sex of this foetus is determined at the time of fertilization. (3 marks)

(iii) What abnormality is found in the chromosomes of the foetus ? (1 mark) (iv) As the uterine wall may be stimulated to contract when removing cells from A, what would be the risk associated with this test ? (1 mark) (v)

State two differences between the blood entering the foetus and that leaving the foetus. (2 marks)

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1. (b)

The diagram below shows part of a section of a leaf :

(i)

Name tissues A and B.

(2 marks)

(ii)

Regions 1 and 2 have the same area. Work out the ratio of the density of chloroplasts in region 1 to that in region 2. (2 marks)

(iii) With reference to your answer to (ii), what would be the significance of this pattern of chloroplast distribution in the leaf ? Explain your answer. (4 marks) (iv) It is suggested that cell type C is responsible for the transport of water from the stem to the leaf. Design an investigation to test this idea using a leafy shoot. (4 marks)

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1. (c)

The diagram below shows the structure of an air sac of the human lung. The tidal air refers to the air that can be breathed in and out of the body in each breath. The residual air refers to the air that cannot be exchanged with the atmosphere during breathing.

(i)

Describe how oxygen in the tidal air reaches the blood.

(3 marks)

(ii)

(1)

If a person breathes deeply, how will the volume of tidal air inhaled be affected ? (1 mark)

(2)

Based on your answer to (1), explain the effect of deep breathing on the rate of oxygen uptake in the blood. (2 marks)

(iii) Explain one effect of smoking on the process described in (i). (2 marks)

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2. (a)

In order to lose weight, an 18-year-old girl, Jane, had a diet as shown in the table below : Vitamin Vitamin CarboCalcium Iron Energy Protein Fat D C hydrate (mg) (mg) (kJ) (g) (g) (μ μg) (mg) (g) 900

8

1

44

80

2.3

0

0

Jam

300

0

0

20

5

0.4

3

0

Coffee

400

3

2

20

90

0

0

0

Ham sandwich

1050

16

13

15

12

2.5

0

0

Coffee

400

3

2

20

90

0

0

0

Fish

540

20

5

0

300

2.7

0

8.0

Rice

3000

12

2

174

8

1.0

0

0

Lettuce

30

1

0

1

23

1.0

15

0

Total intake per day

63

25

294

608

9.9

18

8.0

Average daily requirement

58

*

*

600

15

30

2.5

Dinner

Lunch

Breakfast

Bread

* Amount variable (i)

If the average daily energy requirement for Jane is about 9200 kJ, explain why this diet will be effective in helping her to lose weight. (3 marks)

(ii)

Protein in the diet can be absorbed into the body as amino acids. Explain how amino acids can provide energy for Jane’s daily activity. (3 marks)

(iii) If Jane continues this diet for several months, what disease will she probably develop as a result of mineral deficiency ? (1 mark) (iv) Describe a food test to show that fat is present in ham.

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(3 marks)

2. (b)

An investigation was carried out to study the effect of light on the pupil of the eye. A person sat in a room in which the light intensity could be varied. The size of the pupil of the person was measured at different light intensities. The graph below shows the results of the investigation :

(i)

Referring to the graph, describe the effect of light intensity on the size of the pupil. (2 marks)

(ii)

Explain the significance of the change in pupil size in response to an increase in light intensity. (2 marks)

(iii) The pupil response to light intensity is a reflex action coordinated by the brain. By means of a flowchart, show the nervous pathway involved. (Hint : This nervous pathway is similar to that of a spinal reflex arc.) (3 marks) (iv) People have different eye colours, such as brown, blue or green, but their pupils always appear to be black. Explain why the pupil always appears to be black. (2 marks)

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2. (c)

The diagram below shows a section of a pea flower :

(i)

Under natural conditions, pea flowers are self-pollinated, i.e. the stigma receives pollen grains from the same flower. Suggest one advantage and one disadvantage of this method of pollination. (2 marks)

(ii)

In a genetic experiment, a scientist wanted to ensure that the stigma of a pea flower only received the pollen grains of another pea flower. Suggest how the scientist could achieve this by making use of a plastic bag and a brush. (3 marks)

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(iii) The colour of the pea pod (fruit) is controlled by a pair of alleles. The scientist first crossed a pea plant homozygous for green pods with another pea plant homozygous for yellow pods to produce the first filial generation (F1). She then allowed the F1 plants to self-pollinate to produce the second filial generation (F2). The results of the crosses are summarized in the table below :

All F1 plants produced green pods

Result of the first cross Result of the second cross

(1)

428 F2 plants produced green pods 152 F2 plants produced yellow pods

What can you conclude from the result of the first cross ? (1 mark)

(2)

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Use a genetic diagram to show how the pod colours of the F2 plants were inherited from the F1 plants. (5 marks)

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3. (a)

The photomicrograph below shows some muscle cells of the human small intestine and their associated blood vessels :

(i)

(ii)

(1)

What type of blood vessel is A ?

(1 mark)

(2)

Based on the photomicrograph, state one feature of A to support your answer to (1). (1 mark)

The muscle cells in the photomicrograph are surrounded by a fluid. Explain how this fluid is formed from the blood in blood vessel A. (2 marks)

(iii) Draw a labelled diagram to show what you would see in the cross section made along line BC. (3 marks) (iv) By means of a flowchart, show the route by which a red blood cell from the small intestine reaches the lung. Indicate the major blood vessels and organs involved. (3 marks)

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3. (b)

Diabetes mellitus is a disease found in humans and other mammals. The main symptom of this disease is the presence of glucose in the urine. In the early twentieth century, the cause of diabetes mellitus was still unknown. In order to study this disease, a scientist performed the following experiments on dogs :

Experiment

Experimental subject

Treatment

Result

1

Healthy dogs

Removing the pancreas

Symptoms of diabetes appeared

Diabetic dogs Injecting extracts of from experiment 1 pancreas

2

(a) Injecting extracts of pancreas which had been treated with protease

Symptoms of diabetes disappeared Symptoms of diabetes remained

Diabetic dogs from experiment 1 (b) Injecting extracts of pancreas which Symptoms of had been treated diabetes disappeared with lipase

3

(i)

Comparing the results of experiments 1 and 2, what conclusion can be drawn ? (2 marks)

(ii)

What is the aim of performing experiment 3 ?

(2 marks)

(iii) Based on the results of experiments 2 and 3 (a), explain whether the diabetic dogs would show symptoms of the disease if they were treated with the extracts of pancreas by feeding instead of by injection. (3 marks) (iv) Based on your biological knowledge, explain why the urine of a diabetic person usually contains glucose. (5 marks)

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3. (c)

To study the effect of sucrose solution on plant cells, a student used the lower epidermis of a Rhoeo discolor leaf, the cells of which contain a red pigment. He mounted a piece of the lower epidermis in a sucrose solution. He then observed the epidermis under the microscope immediately and after 10 minutes. The photomicrographs below show the conditions of the same epidermal cells under the low power of the microscope :

(i)

Describe and explain the change in the appearance of cell A 10 minutes after mounting. (4 marks)

(ii)

Suggest a reason why cell B did not show the same change as cell A. (1 mark)

(iii) The student wanted to examine cell A under the high power of the microscope. (1)

State one action that he might need to take before turning to the high power objective. (1 mark)

(2)

State two actions that he might need to take after turning to the high power objective. (2 marks)

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4. (a)

In the production of beer, the raw material used is barley grains, which contain a large amount of starch. When barley grains germinate, amylase is produced. The grains are then crushed and mixed with warm water. After several hours, yeast is added to the mixture for fermentation. (i)

What is the action of amylase on the starch in the barley grains ? (1 mark)

(ii)

After the crushed grains are mixed with warm water, why is it necessary to wait for several hours before adding the yeast ? (1 mark)

An investigation was carried out to study the effect of temperature on the activity of barley amylase. For each temperature, the same amount of crushed grains and water were used. The amylase activity was estimated by the rate of disappearance of starch using the iodine test. The results obtained are shown in the graph below :

Amylase activity (arbitrary unit)

10 9 8 7 6 5 4 3 2 1 0 0

10

20

30

40

50

60

70

80

90

Temperature (°C) (iii) What conclusions can be drawn from the graph about the effect of temperature on amylase activity ? (3 marks) (iv) If you want to store the mixture of crushed grains and water with minimal reaction so that it can be used several days later, what temperature would you choose ? Why ? (3 marks) (v)

Suggest another method to estimate the amylase activity for this investigation. (2 marks)

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4. (b)

To monitor the quality of seawater in Hong Kong, water samples were taken for analysis from four different sites A, B, C and D as shown in the map below :

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The quantities of suspended solids and bacteria in each water sample are as follows :

(i)

(ii)

Site

Suspended solids (mg L−1)

Bacteria (number per 100 mL)

A

8.3

105

B

6.0

1986

C

5.5

23 140

D

2.5

15

(1)

Explain how the concentration of suspended solids may affect the population of producers in seawater. (3 marks)

(2)

Hence, predict which site has the largest population of producers. (1 mark)

In Hong Kong, domestic sewage is the main source of organic pollutants in seawater. (1)

Explain how the bacterial population in seawater may be affected by the amount of organic pollutants present. (3 marks)

(2)

Deduce which site would contain the greatest amount of organic pollutants. (1 mark)

(3)

Suggest one reason for the presence of a large amount of organic pollutants at this site. (1 mark)

(iii) Certain regions of Hong Kong waters have been designated as marine parks. What is the significance of this for conservation ? (1 mark)

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4. (c)

The table below shows the rates of water loss in different ways from a person’s body under two conditions :

Rate of water loss (mL h–1)

Condition

Sweat

Urine

Exhaled air

At rest

4

58

15

During heavy exercise

208

21

27

(i)

Compare the rate of sweat production of the person under the two conditions. Explain why there was such a difference. (3 marks)

(ii)

Account for the decrease in the rate of urine production of the person during heavy exercise. (3 marks)

(iii) (1)

Explain how exhalation may lead to water loss from the body. (2 marks)

(2)

Why did the rate of water loss through exhalation increase during heavy exercise ? (2 marks)

END OF PAPER

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