HONG KONG EXAMINATIONS AUTHORITY

HONG KONG CERTIFICATE OF EDUCATION EXAMINATION 1995

BIOLOGY PAPER I

1.Attempt THREE questions only

2.Each question consists of three parts.

3.All questions carrry equal marks .

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

5.The diagrams in this paper are NOT necessarity draw to scale.

1. (a) Ordinary washing powder does not remove egg stains from clothes easily.

These stains, however, can be removed by biological washing powder.

Below is some information given on a packet of biological washing powder:

Ingredients:

Protease 0.2%

Detergent 15%

Directions:

Soak clothes in a solution of the washing powder for several hours before washing.

Use warm water for best results.

Do not use water at temperature above 60℃

Cautions:

Do not use with silk and wool.

Rinse your hands well after contact with this product.

(i) Explain why the biological washing powder can remove stains from clothes

more easily. (3 marks)

(ii) Why is it necessary to soak the clothes in a solution of this washing powder

for several hours before washing? (1 mark)

(iii) Suggest a way to shorten the soaking time. Explain your answer. (2 marks)

(iv) Why is it not advisable to use this washing powder with water at

temperature above 60℃? (1 mark)

(v) Suggest why this washing powder should not be used with silk and wool.

(1 mark)

1. (b) The pedigree below shows the inheritance of blood groups in a family:

(i) Based on the given information, which blood group, A or O, is the dominant

character?

Explain your answer without using a genetic diagram. (5 marks)

(ii) State the possible genotype(s) of

(1) individual 7

(2) individual 13

Define the symbols you use. (4 marks)

(iii) Among the children of individuals 1 and 2, list those who can donate blood

to

(1) individual 1 (1 mark)

(2) individual 2 (1 mark)

1. (c) The photograph below shows two types of human cells. A and B:

(i) (1) Using the scale given, calculate the diameter of cell A. (2 marks)

(2) Account for the large size of cell A. (1 mark)

(ii) Name the organ that produces

(1) cell A

(2) cell B (2 marks)

(iii) (1) State the biological process that might take place when cell B

meets cell A. (1 mark)

(2) What is the significance of this process? (2 marks)

(iv) Cell B is found in a fluid called semen. Describe how semen is transferred

from a man to a woman. (3 marks)

2. (a) The table below shows the breathing rate and the volume of air inhaled per

breach of a healthy woman at rest during exercise:

At rest During exercise

Breathing rate (times per minute) 18 36

Volume of air inhaled per breath (cm3) 500 1000

Ventilation rate (cm3 per minute) 9000 ?

(i) Calculate the ventilation rate of the woman during exercise. (2 marks)

(ii) Explain the significance of the increase in ventilation rate during exercise.

(4 marks)

(iii) The air inhaled by the woman contains lots of dust particles but very few of

them reach her lungs. Explain why ? (3 marks)

(iv) Draw and label a set-up to estimate the volume of air exhaust in a breath.

(3 marks)

2. (b) About 200 years ago, many people died of an infectious disease called

smallpox. If a patient suffers from smallpox, a lot of small boils will appear

on the skin. A British doctor, Edward Jenner, noticed that milkmaids often

caught a similar but mild disease called cowpox. However, they never

seemed to catch smallpox.

The following diagrams show two consecutive experiments performed by

Jenner:

(i) With reference to the first experiment, explain why James caught cowpox

and in a few days he well again. (4 marks)

(ii) With reference to the second experiment, explain why James did not catch

smallpox. (4 marks)

(iii) At the end of the second experiment, would James become immune to other

infectious disease? Why ? (2 marks)

2. (c) The diagrams below show the longitudinal section of a young root and two

types of cells taken from it:

(i) Using letters in the diagram, state the region where the following can be

found:

(1) cell type 1

(2) cell type 2 (2 marks)

(ii) (1) Name the process occurring in cell type 1 as shown in the diagram.

(1 mark)

(2) What is the significance of this process in the root? (2 marks)

(iii) Explain how cell type 2 is structurally adapted to its function. (3 marks)

3. (a) Plaque on tooth surface is mainly composed of bacteria. The graph below

shows the changes in pH of the plaque of a child in a certain period. The

critical pH is the below which tooth decay may occur.

(i) Explain why the pH of the plaque drops after the intake of food. (2 marks)

(ii) Explain why a low pH in the plaque may cause tooth decay. (1 mark)

(iii) Based on the information provided, suggest one way of reducing the chance

of tooth decay. Explain your answer. (2 marks)

(iv) Draw a labelled diagram of a vertical section of a tooth at the early stage of

decay. (4 marks)

3. (b) The diagram below shows the arrangement of some neurones in man:

(i) Using numbers in the diagram, indicate the pathway of nerve impulses that

bring about

(1) the withdrawal reflex of the arm (1 mark)

(2) the voluntary action of the arm (1 mark)

(ii) State two differences between reflex actions and voluntary actions.

(2 marks)

(iii) For parts A, B and C of the brain, state and explain one role that each plays

when a riding a bicycle. (6 marks)

3. (c) 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. (a) The photomicrograph below shows the transverse section of a leaf:

(i) Using letters in the photomicrograph, state the cell type(s) which

(1) contains chlorophyll

(2) regulates water loss. (2 marks)

(ii) Describe how cell type B obtains

(1) water from cell type G (2 marks)

(2) carbon dioxide from the atmosphere (3 marks)

(iii) Describe what happens to water and carbon dioxide in cell type B during

photosynthesis. (3 marks)

4. (b) Below is a simplified diagram of a section of the human skin:

(i) (1) Name structures A and B (2 marks)

(2) Explain how they help to speed up heat loss from the body when the

body temperature rises. (6 marks)

(ii) In a fire, a large area of C of a person was burnt. Give tow reasons why

damage may endanger his life. (2 marks)

4. (c) The diagram below shows a river and the location of a pig farm:

(i) (1) Which site has the highest bacterial population? (1 mark)

(2) Explain why this site has such a high population of bacteria. (2 marks)

(ii) Explain the difference in the concentration of dissolved oxygen at site A and

site B. (2 marks)

(iii) What change has occurred in ammonia which causes its concentration to

increase from site B to site D? (1 mark)

(iv) Based on your answer in (iii), suggest a possible change in the size of the

algal population from site B to site D. Explain your answer. (3 marks)

(v) If the pig farm is to remain at the present location, suggest a way to reduce

the water pollution caused by its presence. (1 mark)

End of Paper