South Tuen Mun Government Secondary School

South Tuen Mun Government Secondary School

MOCK EXERCISE

BIOLOGY PAPER 1

Marking Scheme

Section A

1. C 2. D 3. B 4. D 5. B 6. B

7. B 8. D 9. C 10. A 11. B 12. B

13. C 14. A 15. A 16. B 17. A 18. C

19. A 20. C 21. A 22. C 23. B 24. D

25. B 26. C 27. C 28. C 29. B 30. A

31. A 32. C 33. B 34. C 35. B 36. D

Section B

* spelling must be correct

1. (a) (i) 70% (1) (ii) 27% (1)

(b) There is a true nucleus / DNA surrounded by nuclear membrane (1) and membrane-bounded organelles

such as mitochondria, chloroplasts (1) in algae while bacteria do not.

2. (a) mRNA (1) it carries the genetic information from nucleus to the cytoplasm for translation. (1)

(b) It has a lot of rough endoplasmic reticulum (RER) (1) which is used to make protein products for

secretion. (1) It has a lot of mitochondria (1) which carries out respiration to provide energy for making

secretory products. (1)

[Accept : Structure A is very large (1), showing that DNA is actively transcribed to produce protein

products used for secretion. (1)]

3. (a) Living R strain picked up some substance in heat-killed S strain that made R strain become S strain. (1)

(b) (i) Either protein, RNA or DNA are picked up by living R strain to change into S strain. (1)

(ii) Cell extract + distilled water is the control set-up and the other 3 are experimental set-ups. (1) The

control set-ups are used to compare with the experimental set-up to show that the effect of the

experiment is caused either by absence of protein, RNA or DNA. (1)

(iii) DNA is taken to transform R strain into S strain, (1) while RNA and protein cannot be used to

transform R strain into S strain. (1)

(iv) The experiment is done only in bacteria, but not other living things OR enzymatic treatment is not

enough to remove all proteins / RNA; but it removes all DNA (1) [accept other reasonable

answer]

(v) A conclusion is made from the data. (1) Science inquiry is an ongoing process. (1)

4. (a) The diseased allele is recessive (1). (1) Two normal parents (B and C) can give a diseased male

offspring. (1) showing that the female parent [do not accept either parents] is heterozygous (1), the

female parent is normal, thus diseased allele is not expressed – the diseased allele is recessive. (1)

(b) Let D be the dominant normal allele while d be the recessive diseased allele. (1)

Parents : XDY x XDXd (1)

Gametes : XD Y XD Xd

Genotypes of offspring XDXD XDXd XDY XdY (2)

Phenotypes of offspring : 3 normal : 1 diseased male

Probability of a diseased child = ¼ (1)

chance that many of their genes at different loci become homozygous. (1) Accumulation of homozygous

alleles at many gene loci may lead to the expression of recessive characters, some of them may be

genetic diseases. (1)

5. (a) Title (1)

Correct choice of axis (½), label of X axis (½), Y axis (½)

Correct plotting of points and joining of points of both plant A and plant B (1)

Key (½)

(b) temperature (½) and concentration of carbon dioxide (½)

dioxide fixation increases in both plant A and B. (1) At 100 arbitrary units, the rates of net carbon dioxide

fixation of plant A and plant B are equal. (1) At 100 – 500 arbitrary units, when light intensity increases,

the rate of net carbon dioxide of plant A increases while that of plant B remains unchanged. (1) Above 500

arbitrary units, when the light intensity increases, the rates of net carbon dioxide fixation of plant A and

plant B remain unchanged. (1)

[accept : from 40 – 100 arbitrary units of light intensity, the rate of net carbon dioxide fixation of

plant B is higher than that of plant A (1); from 100 – 600 arbitrary units of light intensity, the rate of

net carbon dioxide fixation of plant A is higher than that of plant B (1)]

(d) Plant B lives in shady habitat while plant A lives in sunny habitat. (1)

6. (a) P (½) and Q (½). At point A, the blood pressure of left ventricle is higher than the left atrium, (1) valve P

is pushed closed, (½) blood cannot flow into the left atrium. (½) The blood pressure of left ventricle is

lower than the aorta, (1) valve Q is pushed closed, (½) blood cannot flow from the left ventricle into the

aorta. (½)

(b) (i) The ventricle contracts. (1)

(ii) The pressure change in the right ventricle is lower in magnitude (1) because the muscular wall of the

left ventricle is thicker than that of the right ventricle. (1)

7. (a) A à G à B à C à D à auditory nerve à cerebrum à cerebellum à spinal cord à motor nerve

à leg muscles [½ mark for each arrow, total 5 marks; if a step is missed, carry on normal marking;

if a step is wrong, stop marking the steps afterward]

(b) The external air pressure of the ear decreases and becomes lower than that of the inner ear. (1) The

eardrum is pressed outward and cannot vibrate easily. (1) Thus he cannot hear well.

He / she should open his / her mouth OR swallow saliva (1) so that air can get out of the inner ear to

equalize the air pressures on the two sides of the eardrum. (1)

In A, mucus is secreted to stick the infectious bacteria / foreign particles together. (1)

8. (a) In the hospitals, antibiotics are frequently used to kill specific bacteria (1), thus those bacteria that have a

resistant towards the antibiotics can survive (1), mature and reproduce (1). Their antibiotic resistance

genes are passed to the next generation (1). Thus the proportion of bacteria that has the antibiotic resistant

character greatly increase. (1) [Any 4 points – maximum 4 marks]

(b) (i) Action 1 prevents the indiscriminative use of antibiotics OR allows the doctor to prescribe the specific

antibiotic to kill the specific type of bacteria. (1)

Action 2 prevents the contamination of the staff’s hand and instrument by the infectious bacteria (1)

and thus reduces the chance of spread of the infectious disease inside the hospital. (1)

(ii) Action 2 is not successful to prevent the spread of the disease, thus there must be some other

instrument that is contaminated leading to the spread of the disease among patient. (½) Thus it is

suggested that the disinfecting fluid using to clean the thermometer cannot successful kill the

infectious bacteria / the infectious bacteria become resistant to the originally used disinfecting

fluid. (1)

Action 1 has not been successful because the prescribed antibiotics cannot successfully kill the

infectious bacteria. (½) Action 4 has to be done to find out another antibiotic that can kill the

infectious bacteria successfully. (1)

9. (a) In figure 1, when the two species are cultured separately, both of them grows and reaches a maximum

weight in the tank (1). However, when they are cultured together, species X grows and reaches a

maximum weight while species Y grows slowly and then declines in their weight (1). This shows that

X and Y have very severe interspecific competition and species Y is not capable to survive under

such a strong competition (1).

(b) The vegetable fields provide a very rich nutrient to the ditches, thus reduce the interspecific competition

as resources / nutrients are not limiting (1).

The population of X is controlled by predators in the natural environment. Y faces less competition with

X (1).

The assessment of essay is divided into 2 areas, i.e. content and effective communication.

Content (Maximum 7 marks)

Ideas / concepts and mark allocation suggested in the marking scheme will give markers some guidelines in assessing essays in this section. Nevertheless these ideas / concepts should not be treated as the only acceptable answers.

Effective communication (Maximum 3 marks)

Criteria on effective communication

Marks

/ Clarity of expression and relevance to the question / Logical and systematic presentation
3 / ü Answers are easy to understand. They are fluent showing good command of language.
ü There is no or little irrelevant materials. / ü Answers are well structured showing coherence of thought and organization of ideas.
2 / ü Language used is understandable, but there is some inappropriate use of words.
ü A little irrelevant material is included, but does not mask the overall answer. / ü Answers are organized, but there is some repetition of ideas
1 / ü Markers have to spend some time and effort to understand the answer(s).
ü Irrelevant materials obscure some minor ideas. / ü Answers are a bit disorganized, but paragraphing is evident. Repetitions are noticeable.
0 / ü Language used is incomprehensible.
ü Irrelevant material buries the major ideas required by the question. / ü Ideas are not coherent and systematic. Candidate shows no attempt to organize thoughts

Content [maximum 7 marks] + effective communication [maximum 3 marks]

10. Content

Fertilization as a necessary requirement for sexual reproduction:

l Male and female gametes are formed by meiotic cell division, where the chromosome number is reduced to half of the original number / becomes haploid. (1)

l Thus fertilization is required to restore the chromosome to the original / becomes diploid. (1)

l So the fertilized ovum / zygote can divide by mitotic cell division into a normal diploid individual. (1)

How can fertilization be accomplished?

l Male and female sex organs must be matured to produce gametes at the same time. In man, they have different sexes. Two individuals are required to meet and reproduce. (1)

l The male and female mature after puberty, they are ready for reproduction at nearly the same ages. (1)

l Moreover, in man, the period of ovulation follows the menstrual cycle and the time of mating near the period of ovulation is important. If man and woman carry out sex intercourse at nearly the period of ovulation, fertilization can be successful. (1)

l For successful fertilization, it is necessary that the male gamete meets the female gametes. In man, there is copulation so that the penis can insert into the vagina. (1)

l Semen containing sperms is ejected into vagina, sperms swim towards the ovum for fertilization. (1)

l This insertion is important as it ensures sperms to enter the female reproductive tract, so it increases the chance that sperms can meet the ovum. (1)

l It reduces the wastage of gametes and increases the chance of successful fertilization. Eventually, woman produces one ovum per menstrual cycle (every 28 days). The numbers are less and there is less wastage of energy. (1)

South Tuen Mun Government Secondary School

MOCK EXERCISE

BIOLOGY PAPER 2

Marking Scheme

* spelling must be correct

1. (a) (i) urea and sodium ion (1) [do not accept urea or sodium ion]

(ii) It is because their concentrations in plasma are higher than those in the dialysing fluid (1), they

diffuse through the membrane / peritoneum into dialysing fluid. (1)

(iii) When there is an excess of sodium ion intake, the concentration of sodium ion in the plasma is very

high. When the concentration of sodium ion in the dialysing fluid becomes equal to the that of the

plasma, no more diffusion can take place (1) thus the sodium ion will remain high in the

plasma. (1) OR The dialysing mechanism cannot remove most of the sodium ions by diffusion (1),

thus the sodium ion concentration will remain high in the plasma. (1)

A higher sodium ion concentration in the plasma decreases the water potential of the body fluid. (1)

The body cells has a higher water potential than that of the body fluid, thus they lose water by

osmosis. (1) With less water, the metabolism of the body cells become lower. (1) [Any 2 –

maximum 2 marks] OR A higher sodium ion concentration in the plasma increases the blood

pressure (1) and causes damage to the blood vessels / heart. (1)

(iv) The treatment using kidney machine is more effective. (1) It is because the dialysing fluid in the

kidney machine is moving / is running in the opposite direction as the blood, (1) a higher

concentration gradient can be maintained between the dialysing fluid and the plasma, thus more

urea can be removed by diffusion. (1)

(b) (i) The mouth is closed while the skin is exposed to the external environment. (1) Therefore the skin

loses more heat to the environment by conduction, convection and radiation. (1) OR The mouth is

more richly supplied with blood capillaries than that of the skin surface. (1) Therefore more body heat

is brought to the mouth. (1)

(ii) The temperature remains unchanged at about 37℃. (1) 37℃ is the suitable temperature for the

action of amylase, to break down starch in the food. (1)

(iii) (1) The rate of blood flow to the skin increases (1) so that more body heat is brought to the skin

surface, (1) more heat is lost to the environment by conduction, convection and radiation. (1)

(2) The temperature receptor in the skin is stimulated by the higher external temperature, a nerve

impulse is generated. (1) The nerve impulse is sent to the hypothalamus by nerve, the

hypothalamus thus sends a nerve impulse to the arteriole of the skin. (1) The arteriole dilates to

increase the blood flow to the capillaries on the skin surface. (1)

2. (a) (i) Incineration produces a large amount of carbon particles / particulars. (1)