2018-DSE
BIO (Mock)
PAPER 1B
B Candidate
Form Six Mock Examination 2017-2018 number
DSE BIOLOGY PAPER 1
Question No. Marks
SECTION B: Question-Answer Book B
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This paper must be answered in English 2 /2
INSTRUCTIONS FOR SECTION B 3 / 10
(1) Write your name, class and class number in the space
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provided on this page.
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(2) Refer to the general instructions on the cover of the 6 /5
Question Book for Section A.
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(3) Answer ALL questions.
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(4) Write your answers in the spaces provided in this
Question-Answer Book. Do not write in the margins. 9 /7
Answers written in the margins will not be marked.
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(5) Supplementary answer sheets will be provided on
request. Write your name, class, class number and 11 /11
question number on each sheet, and fasten them with
string INSIDE this Question-Answer Book. Total: / 84
(6) Present your answers in paragraphs whenever
appropriate.
(7) The diagrams in this section are NOT necessarily
drawn to scale.
SECTION B
Answer ALL questions. Put your answers in the spaces provided.
1. For each of the structures in a plant cell listed in Column I, select from Column II one phrase that
correctly describes it. Put the letter in the space provided. (3 marks)
Column I Column II
Cell membrane A. Helps in the synthesis and transport of lipids
Vacuole B. Helps in the synthesis and transport of proteins
Smooth endoplasmic C. Control the movement of substances into or out of a cell
reticulum
D. Provide a site for chemical reactions to take place
E. Support the cell
2. The table below shows how a bird called the bluethroat (Luscinia svecica) is classified by
biologists.
Taxonomic group Name
Domain Eukaryota
Kingdom Animalia
Phylum Chordata
Class Aves
Passeriformes
Family Muscicapidae
Genus
Species
Complete the table by filling in the blanks with the correct terms. (2 marks)
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3, An investigation was carried out to study whether antioxidants in blackcurrant leaf extract (BCL)
and blackcurrant fruit extract (BCF) can protect the pig’s red blood cells from haemolysis.
Pig’s red blood cells, upon removing from plasma, were divided into three groups. The
experimental groups were suspended in an isotonic solution containing the respective plant
extracts while the control group was suspended in an isotonic solution instead. All groups of cells
were kept at 37°C for 1 hour. After that, the three groups of cells were removed from their
solutions by centrifugation and were placed in salt solution from 0.5% to 0.9% separately. The
percentage of cells destroyed by bursting (haemolysis) was recorded and the results were shown in
the graph below.
Percentage of haemolysis of cells modified with BCL and
BCF extract at salt solution of different concentration
Red blood cells destroyed by haemolysis (%)
control
BCF
BCL
Salt concentration (%)
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(a) Explain, in terms of water potential, why some red blood cells burst when placed in 0.7% salt
solution. (3 marks)
(b) Suggest why some red blood cells did not burst in 0.7 % salt solution. (1 mark)
(c) Based on the information shown in the graph, can the blackcurrant leaf extract (BCL) and the
blackcurrant fruit extract (BCF) protect the red blood cells from haemolysis? Give an evidence
to support your answer. (3 marks)
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(d) The investigator suggested that the antioxidant in the blackcurrant plant (leaf/fruit) bind to the
membrane superficially to modify the membrane without inducing haemolysis.
(i) Based on your knowledge about the membrane structure, to which region of the cell
membrane will the antioxidants bind to if the investigator is correct? (1 mark)
(ii) Justify the investigator’s suggestion by giving one evidence from the graph. (2 marks)
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4. Scientists measured the rate of translocation in the phloem of trees by using carbon dioxide
labelled with radioactive 14C. They put a large, clear plastic bag over the leaves and branches of
each tree and added 14CO2 as the diagram shown below. The main trunk of the trees was not in
the plastic bag. At regular intervals after adding the 14CO2 to the bag, the scientists measured the
amount of 14CO2 released from lenticels from the main trunk of the tree using sensor.
Sealed plastic bag
which contains
14CO
2
radiation sensor is used to
measure 14CO2 released
from the lenticel
(a) Describe the pathway through which the 14CO2 in the plastic bag entered mesophyll cells.
(2 marks)
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(b) Briefly describe the cellular processes in which the 14CO2 in mesophyll cells can be utilized and
detected by the sensor. (5 marks)
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5. In the Arctic, snowy owls are predators of lemmings. The lemmings eat Arctic plants.
(a) Draw the food chain for this Arctic ecosystem. (1 mark)
(b) Suggest a method how researchers can identify the food sources of snowy owls. (1 mark)
(c) The graph below shows changes in the populations of snowy owls and lemmings over a six-year
period.
Describe and explain the periodic fluctuation of population sizes of snowy owls and lemmings in
the graph. (4 marks)
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(d) A student said, “A simple food web in the ecosystem is less stable in environmental fluctuation
than a complex food web.” Using the food chain in (a) as an example, justify why the student’s
claim is correct. (2 marks)
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6. The cold receptor protein is encoded by a gene called T. If gene T is mutated, it is possible for the
cold receptor to become less sensitive to coldness. Some of the variations in the triplet codes on
the coding strand in an important region of gene T are shown below. A mRNA codon table is
given for assistance.
Original sequence: -CTT-CTA-TGG-CAC-TAC- Amino acids mRNA codons
Leucine CUA, CUU, CUC
Tryptophan UGG
Variant 1: -CTT-CTA-TGG-CAT-TAC- Histidine CAU, CAC
Tyrosine UAU, UAC
Variant 2: -CTT-CTT-TGA-CAC-TAC- Threonine ACA, ACU
Stop codon UGA, UAA
Variant 3: -CTT-CTT-ATG-ACA-CTA- Methionine AUG
(a) Identify the variant(s) with substitution mutation. (1 mark)
(b) With respect to processes in protein synthesis, explain why variant 2 should cause the most
drastic change in the function of the cold receptor. (4 marks)
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7. In 1920s, Otto Meyerhof did an experiment: If an isolated frog leg is stimulated electrically, the leg
muscles can contract several times but soon became fatigue. During and after the stimulation,
lactic acid level in the leg muscle cells increases.
(a) Explain why the cells in the isolated leg muscle soon became deoxygenated before the
experiment. (1 mark)
(b) Describe how stimulation of leg muscles leads to lactic acid production. (3 marks)
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(c) From the experiment, Otto Meyerhof believed lactic acid accumulation leads to muscle fatigue
and can be used to explain why people feel prolonged muscle fatigue after exercises. However in
1970s, George Brook found out that when different carbohydrates (i.e. lactic acid, glucose,
glycogen and starch) are injected into a living rat, lactic acid is the fastest carbohydrate that can
be broken down completely in the presence of oxygen.
(i) Describe how lactic acid is broken down completely in the liver. (2 marks)
(ii) The finding from George Brook eventually helps to disprove Meyerhof’s hypothesis that
lactic acid accumulation is the main reason for muscle fatigue. What nature of science
can be demonstrated by George Brook’s disproval on Meyerhof’s hypothesis? Elaborate
your answer. (2 marks)
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8. An experiment was performed to investigate the cold sensitivity of animals. Each time two metal
plates are provided to an animal, one in 30°C (control plate) while another in variable temperature
(test plate). The time animal spent on each metal plate is then measured. Below show the
experimental setup (left) and a graph showing the results for mouse and squirrel (right).
(a) With reference to the graph, compare the cold sensitivity between mouse and squirrel. (2 marks)
(b) Hibernation is a behavior in which animals lower their metabolic rate when food availability is
low (i.e. during winter). During hibernation, animals do not wake up. One of the crucial
requirements for successful hibernation is that animals should not be over sensitive to certain
external stimulus.
(i) State which animal, mouse or squirrel, should have a higher chance to hibernate
successfully? (1 mark)
____________________________________________________________________________
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(ii) Explain how the hibernation behavior enables animals to survive in stressful condition like
winter. (3 marks)
(c) Both squirrels and their ancestors can be found in polar region where temperature was moderate
and food supply was good 20 000 years ago. According to the theory of natural selection and the
above information, propose how squirrel might gain the ability to survive in polar region even in
present days. (4 marks)
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9. The diagram shows the light- dependent reactions of photosynthesis.
(a) Name and label the part of chloroplast in which light dependent stage is carried out in the
electromicrograph below. (1 mark)
(b) What is the significance of substrate B and product C to the whole photosynthetic process?
(2 marks)
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(c) In an investigation, single- celled algae were kept in bright light and were supplied with carbon
dioxide containing radioactive carbon atom. After 300 seconds, the carbon dioxide supply was
turned off. The graph shows how the concentrations of carbon dioxide, glycerate 3- phosphate
(GP) and ribulose bisphosphate (RuBP) were changed.
(i) What is the biological significance of higher concentration of GP than RuBP in photosynthesis?
(2 marks)
(ii) Explain the increase of RuBP level between 300 – 380 seconds. (2 marks)
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10. A scientist investigated the role of light, sucrose and fungi in seed germination rate of D. fuchsii,
an orchid commonly found in UK.
The scientist hypothesized as follows:
(1) The germination rate increases with the presence of light.
(2) The germination rate increases with the presence of fungi.
(3) The germination rate increases with the presence of sucrose.
120 seeds were collected and sterilized. The seeds were separated into 6 groups and set into
germination in separate agar plates under different treatment. Water was supplied in each set up.
The table below shows the conditions in each set up and the average change in length of the
plumule after 20 days of germination. Given the initial lengths of the plumules were the same.
Treatment A B C D E F
Presence of sucrose x √ x x √ x
Presence of fungi √ x x √ x x
Presence of light x x x √ √ √
Average change of the
length of plumule after 20 10 7.8 6.2 4 2.5 1
days (cm)
(a) (i) State the importance of water in seed germination. (1mark)
(ii) Explain why the scientist sterilized the surface of the seeds and the agar plates before the
investigation. (2 marks)
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(b) (i) Suggest whether hypothesis 1 is supported with the data given in the table and explain your
claim. (3 marks)
(ii) Which factor, the presence of sucrose or fungi, has a more profound effect on the germination
rate of D. fuchsii? Elaborate your choice with evidence provided by the table. (2 marks)
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(iii) A student suggested to use the change of dry mass for measuring the seed germination rate
instead. He dried the plumule in an oven at 103 °C for 3 days.
Suggest what he should have done during the drying process to be sure that all water had been
removed from the plant samples. (1 mark)
(c) The scientist investigated further on the ecological relationship of fungi and D. fuchsii by
isolating the fungal hyphae from D. fuchsii and grew under different conditions. The fungal
hyphae length was measured after 8 days as an indicator of fungal growth and the results as
shown below:
Treatment G H I J
Presence of D. √ √ x x
fuchsia seed
Presence of light x √ x √
The increase in
length of fungal 45 30 38 15
hyphae (mm)
(i) Based on the table above, suggest the possible ecological relationship between the fungi and D.
fuchsii. (1 mark)
__________________________________________________________________________
(ii) Fungi usually grow in shady environment. Propose a mechanism on the effect of light on the
change in length of fungal hyphae attached on D. fuchsia and hence the germination rate of
D. fuchsia. (3 marks)
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For the following question, students are required to present the answer in essay form. Criteria for marking
will include relevant content, logical presentation and clarity of expression.
11. 'Long-term health problems can be brought about if a person takes in a diet that is high in fat, sugar
and sodium (salt) but low in dietary fibers.' Give an account of the biological basis for this statement.
(11 marks)
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END OF PAPER
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