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:

Lbio9502

(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 decrease

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)

ANSWER

1. (a) (Total : 8+1 marks)

(i) it contains enzyme/protease that (1 mark)

digests the proteins in egg stains to small molecules(1 mark)

which can dissolve in water/can be removed by water(1 mark)

communication skill (C) (1 mark)

(ii) –to allow time for the action of enzyme(1 mark)

(iii) Soak clothes in warm water

because the enzyme action is faster at a higher temperature (1+1 marks)

OR

Use more washing powder

Because the enzyme action is faster at a higher enzyme concentration(1+1 marks)

Any one set

(iv) because the enzyme would be denatured above 60 ℃(1 mark)

(v) because protein in skin and wool will be digested by the enzyme(1 mark)

1. (b) (Total : 11+1 marks)

(i) blood group A is dominant (1 mark)

Reasons:

Both individuals 3 and 4 have blood group A, therefore each of them must possess at

least one allele for blood group A (1 mark)

One of their children (individual 1) has blood group O, that means at least one of the

parents must also posses one allele for blood group O(1 mark)

At least one of the parents is heterozygous(1 mark)

In a heterozygous condition, only the dominant allele will be expressed. (1 mark)

OR

Both individuals 3 and 4 have blood group A/are of the same phenotype and

(1 mark)

Produce offspring who are of two phenotypes(1 mark)

Indicating that both parents are heterozygous

Only the dominant allele expresses itself/recessive allele is masked in heterozygous

state(1 mark)

Any ONE set

communication skill (C) (1 mark)

(ii) Defined symbols e.g. :A=allele for blood group A

a= allele for blood group O (1 mark)

(No mark for defining symbols if not using capital letter, for dominant allele and

small letter for recessive allele)

(1) individual 7 :Aa(1 mark)

(2) individual 13 :AA,Aa(1+1 marks)

(iii) (1) 5 and 6 (1 or 0)

(2) 4, 5, 6and 7(1 or 0)

1. (c) (Total: 11 marks)

(i) (1) diameter=5.3(5.0 to 5.5) X 0.03 mm (1 mark)

=0.159 mm (0.150mm to 0.165 mm)

(no unit, no mark) (1 mark)

(2) because cell A contains food store(1 mark)

(ii) (1) ovary(1 mark)

(2) testis(1 mark)

(iii)(1) fertilization

2. (a) (Total :12 marks)

(i) Ventilation rate=1000 X 36 cm3 per minute (1 mark)

=36 000 cm3 per minute (no unit, no mark) (1 mark)

(ii) To supply more oxygen to the skeletal muscles (1+1 marks)

for faster respiration/for more energy supply (1 mark)

to remove carbon dioxide more rapidly(1 mark)

(iii) Dust particles are trapped by the hair in the nose and (1 mark)

mucus along the lining of the air passage/nasal cavity/trachea(1+1 marks)

(iv) large ,clear, accurate diagram (D) (1 or 0 )

labels and title (any four) (L) (0.5 X 4 each)

2. (b) (Total :10 +1 marks)

(i) The fluid in the boils contains the cowpox virus/pathogen/germ (1 mark)

which cannot be killed by the body on its first exposure to the pathogen(1 mark)

The virus multiplies/damages body cells(1 mark)

So James became ill

After a few days, sufficient antibodies/phagocytes (white blood cells) are produced

To kill the pathogen, so James got well again(1 mark)

communication skill (C) (1 mark)

(ii) The previous exposure to the cowpox antigen was ‘memorized’ by certain white

blood cells(1 mark)

the pathogens/antigens of smallpox and cowpox are similar

it can stimulate the production of a lot of antibodies/phagocytes in a short time

and kill the smallpox virus.(1+1 marks)

(iii) No

Because his immunity is specific to the antigen/pathogen (1 mark)

OR because antibodies are specific in action(1 mark)

2. (c) (Total :8+1 marks)

(i) (1) cell type 1-D (1 mark)

(2) cell type 2-C(1 mark)

(ii) (1) Mitosis/cell division(1 mark)

(2) to increase the cell number(1 mark)

for growth/repair of the root(1 mark)

(iii) It has an outgrowth/root hair(1 mark)

to provide a large surface area(1 mark)

for the absorption of water/minerals from the soil(1 mark)

communication skill (C) (1 mark)

3. (a) (Title :9 marks)

(i) Bacteria break down the food (1 mark)

releasing acid (1 mark)

(ii) The acid dissolves the enamel/dentine of the tooth (1 mark)

(iii) –avoid eating snacks between meals )

to reduce the chance of acid formation )

- rinse the mouth/brush the teeth after eating )

to remove food debris/acid/plaque ) any ONE (1+1 marks)

- use alkaline toothpaste )

to neutralize the acid ) 3. (b) (Total : 10 marks)

(i) (1) 5-3-4 (1 or 0)

(2) 1-2-4 (1 or 0)

(ii)

Reflex actions Voluntary actions

Cerebrum is not involved Cerebrum is involved

Stereotyped response is produced Different responses are produced

A receptor is involved A receptor may not be involved/may be

initiated spontaneously

Inborn Not inborn

Usually faster Usually slower

(any two 1+1 MARKS)

(iii) A receives/integrates sensory impulses (1 mark)

to make an appropriate decision for action(1 mark)

OR

A sends nerve impulses to the skeletal muscles(1 mark)

To bring about the movement(1 mark)

(any ONE set)

B coordinates the action of the skeletal muscles/receives

Impulses from semi-circular canals etc. (1 mark)

To maintain balance of the body(1 mark)

C increases/controls the t\rate of heart beat/the rate and depth of breathing (1

mark)

To supply more oxygen to the skeletal muscles(1 mark)

3. (c) (Total :11+2 marks)

(i) Sea water contains a higher concentration of salts/Water potential of sea water is

lower than that of the root cells (1 mark)

as a result, water will be drawn out of the cells by osmosis (1 mark)

and the plants will become dehydrated/wilted (1 mark)

Communication Skill (C) (1 mark)

(ii) Crops absorb minerals from soil/minerals are leached away by irrigation (1 mark)

when the crop is harvested, minerals are removed from the field (1 mark)

As minerals are essential for crop growth(1 mark)

Fertilizers are added to replenish the lost minerals(1 mark)

Communication Skill (C) (1 mark)

(iii) Conservation of rain forests helps

- to maintain a diversity of species(1 mark)

- to conserve the natural habitat(1 mark)

- to maintain a constant level of carbon dioxide/oxygen in the atmosphere(1 mark)

- to prevent soil erosion(1 mark)

(accept other reasonable answers and give credit for elaboration)

4 . (a) (Total : 10 +1 mark)

(i) (1) B, C(E optional) (all or no mark) (1 or 0)

(2) E (1 mark)

(ii) (1) Water moves from cell to cell (1 mark)

by osmosis (1 mark)

(2) Carbon dioxide in air diffuses(1 mark)

through stomatal pores(1 mark)

into the air spaces to cell type B(1 mark)

(iii) Water is split into hydrogen and oxygen (1 mark)

hydrogen combines with carbon dioxide(1 mark)

to form carbohydrate inside cell type B(1 mark)

Communication Skill (C) (1 mark)

4. (b) ( Total :10 +1 marks)

(i) (1) A- * blood capillary (1 mark)

B- * sweat gland(1 mark)

(2) More blood will reach A(1 mark)

As A is close to the surface provides a larger surface area(1 mark)

It will lead to faster heat loss by radiation/conduction/convection(1 mark)

B will produce more sweat to the skin surface(1 mark)

To increase heat loss sweat by the evaporation of water(1 mark)

Which absorbs body heat(1 mark)

Communication Skill (C) (1 mark)

(ii) This damage may lead to excessive loss of water from the body(1 mark)

and bacterial infection(1 mark)

4. (c) ( Total :10 marks)

(i) (1) site B (1 mark)

(2) Pig farm discharges animal waste(1 mark)

Which contains a lot of bacteria/which promotes the growth of bacteria(1 mark)

(ii) A large number of bacteria/decomposers at site B consumes a lot of oxygen (1

mark)

Thus the dissolved oxygen constant is lower at site B than site A(1 mark)

(iii) Ammonia is converted to nitrate(1 mark)

(iv) Algal population increases(1 mark)

Due to an increasing level of nitrate(1 mark)

Which is a nutrient for the growth of algae(1 mark)

(v) To treat the waste before discharging it )

To reuse the waste as fertilizer )

To set up laws to control the discharge of waste ) any ONE 1 mark

(accept other reasonable answers)

(iv) large and clear diagram (D) (1 or 0)

labels and title (any five) (L) (5 X 0.5)

sign of early decay (S) (0.5 mark)