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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
Cambridge International Level 3 Pre-U Certificate
Principal Subject
* 0 6 1 9 6 8 5 5 6 1 *
9790/02
BIOLOGY
Paper 2 Structured
May/June 2012
1 hour 45 minutes
Candidates answer on the Question Paper.
No additional materials are required.
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name on all the work you hand in.
Write in dark blue or black pen.
You may use a soft pencil for any diagrams, graphs or rough working.
Do not use staples, paper clips, highlighters, glue or correction fluid.
Answer all questions.
Write your answers in the spaces provided on the question paper.
At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.
For Examiner’s Use
1
2
3
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6
Total
This document consists of 17 printed pages and 3 blank pages.
DC (NF/SW) 46688/3
© UCLES 2012
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Answer all the questions.
1
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In the 1950s, chemists thought that the Earth’s atmosphere, before the existence of life, was
highly reducing. In 1953, Stanley Miller, working under the supervision of Harold Urey at
the University of Chicago, published the results of an experiment that showed that organic
molecules could have formed in such an atmosphere.
A diagram of Miller’s apparatus is shown in Fig. 1.1.
electrode
powerful spark
A
gases present in the
Earth’s atmosphere
before the
existence of life
sampling tap, B, to
collect liquid
for analysis
condenser to
cool products
boiling water
liquid containing
products
heat source
Fig. 1.1
(a) (i)
Name three gases, apart from water vapour, that were present in this early
atmosphere and that Miller put into chamber A.
1. ..............................................................................................................................
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(ii)
Name two different types of organic molecule that Miller collected at B.
1. ...............................................................................................................................
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(iii)
State the role of the powerful spark in Miller’s apparatus.
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(iv)
Explain why liquid water had to be present for life to originate on Earth.
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Fig. 1.2 shows a time line for the early history of the Earth.
5.0
origin of the Earth
4.0
time /
billion years
before the
present
age of the oldest rocks on Earth
rocks of this age in Greenland are enriched with carbon-12
iron oxides present in rocks of this age
stromatolites present in rocks of this age
3.0
steranes present in shales of this age in Australia
2.0
evidence of multicellular life in rocks of this age in Gabon in Africa
Fig. 1.2
(b) State the significance of,
(i)
the enrichment with carbon-12 of rocks that are 3.9 billion years old
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(ii)
the presence of stromatolites in rocks that are 3.5 billion years old
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(iii)
presence of steranes in shales that are 2.7 billion years old.
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(c) Life may have originated around hydrothermal vents. Today, communities associated
with these vents are rich in chemoautotrophic bacteria.
Describe briefly the nutrition of chemoautotrophic bacteria.
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2
The Mongolian gerbil, Merionthes unguiculatus, lives in semi-arid desert habitats in the
steppes of northern Asia where much of the vegetation and drinking water has a high salt
content.
A laboratory study was carried out to investigate the effect of supplying gerbils with drinking
water with different concentrations of salt. Gerbils were divided into five groups and given
equal volumes of either water or four different concentrations of sodium chloride solution for
five days. The animals were kept under identical conditions and supplied with the same food.
The urine was collected each day and analysed. The volumes of urine collected on the fifth
day and their concentrations of sodium ions are shown in Fig. 2.1.
4.5
4.0
3.5
volume of
3.0
urine /
2.5
cm3 per 100 g 2.0
body mass
1.5
1.0
0.5
0.0
0.00
0.25
0.50
0.75
concentration of NaCl / mol dm–3
1.00
0.00
0.25
0.50
0.75
concentration of NaCl / mol dm–3
1.00
1200
1000
concentration 800
of Na+ in urine
/ mmol dm–3 600
400
200
0
Fig. 2.1
(a) Describe and explain the results shown in Fig. 2.1.
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(b) Humans cannot survive if given a solution of 0.25 mol dm–3 sodium chloride to drink
over several days.
Explain how the kidneys of gerbils allow them to survive while drinking water with a high
concentration of salt.
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(c) Another investigation found that gerbils given:
•
0.25 mol dm–3 sodium chloride solution for five days had stores of ADH
(antidiuretic hormone) in the posterior pituitary gland;
•
0.50, 0.75 and 1.0 mol dm–3 sodium chloride solutions for five days had
significantly less ADH in their posterior pituitary glands.
Suggest an explanation for these observations.
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(d) M. unguiculatus has both physiological and behavioural adaptations to its desert habitat.
Suggest examples of the physiological and behavioural adaptations that small mammals,
such as M. unguiculatus, have for desert habitats.
Do not include the adaptations of the kidney.
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[Total: 16]
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BLANK PAGE
Question 3 begins on page 10
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3
T cells (T lymphocytes) differentiate inside the thymus gland. During T cell differentiation,
specific cell surface proteins known as CD proteins are produced and inserted into the cell
surface membrane.
Fig. 3.1 shows the stages involved in the synthesis of a CD protein in a T cell.
promoter
DNA
5'
3'
pre-mRNA
‘cap’
added
poly(A) added
to be
degraded
CD protein
via Golgi body
Not to scale
cell surface
membrane of T cell
Fig. 3.1
(a) Explain the function of the promoter region of the DNA.
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(b) Using Fig. 3.1 as a guide, describe the events that occur in the nucleus of the T cell to
produce a functional molecule of mRNA encoding a CD protein.
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Examiner’s
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(c) Explain why the cuts made in pre-mRNA are necessary for the T cell to produce a
functional CD protein.
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(d) Suggest possible functions for the ‘cap’ and the poly-A region attached to the mRNA.
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(e) Each clone of fully differentiated T cells expresses a particular set of CD proteins on the
cell surface membranes.
Explain how monoclonal antibodies are able to identify different CD proteins.
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(f)
Explain why it is necessary to use hybridoma cells, rather than B cells, to produce
monoclonal antibodies.
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Question 4 begins on page 14
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4
(a) ATP is often known as the universal ‘energy currency’.
For
Examiner’s
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Outline how ATP is suitable for acting as an energy currency.
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Most ATP is made in cells by membrane systems that create proton gradients by pumping
protons from one compartment to another.
Fig. 4.1 shows three such membrane systems.
A
B
C
Fig. 4.1
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(b) (i)
Identify the precise location of membranes A, B and C.
A ...............................................................................................................................
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B ...............................................................................................................................
C .......................................................................................................................... [3]
(ii)
Draw arrows onto each of the membrane systems in Fig. 4.1 to show the direction
in which protons are pumped.
[1]
(iii)
Outline how energy is made available for pumping protons across such membranes.
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(iv)
Explain how ATP synthase is involved in the production of ATP.
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5
Certain flowering plant species, such as the violet, Viola odorata, produce some flowers that
open and are cross-pollinated by insect pollinators and others that never open and are selfpollinated.
(a) Suggest the advantages of having flowers that self-pollinate.
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Many species of orchid have flowers that look as if they offer food to their insect pollinators,
but offer no edible reward in the form of nectar. This form of attraction is known as food
deception. An example is Calypso bulbosa as shown in Fig. 5.1.
Other species of orchid practise sexual deception as their flowers look like female bees or
wasps. These flowers release a scent that attracts males which then attempt to mate with
the flowers. While doing this the insects pick up or deposit pollen. Fig. 5.2 shows Ophrys
scolopax which is such a species.
Orchids that practise food deception attract a wide variety of different insect species as
pollinators. Those that mimic a female bee or wasp attract males of a single species.
10 mm
10 mm
Fig. 5.1
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(b) (i)
State an advantage of attracting insects without offering an edible reward.
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(ii)
Explain the advantage of mimicking the appearance of a female of only one species
of insect.
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(iii)
State a disadvantage of the sexual deception strategy of pollination.
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(c) Suggest different ways in which the success of pollination mechanisms might be
assessed experimentally.
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6
The rate of contraction of the mammalian heart is influenced by impulses from neurones that
terminate in the heart. The impulses originate from the cardiac (cardiovascular) centre in the
brain as shown in Fig. 6.1.
Stimulation by neurone X decreases the heart rate; stimulation by neurone Y increases the
heart rate.
J
K
cardiac centre
X
Y
spinal cord
heart
Fig. 6.1
(a) (i)
Name the part of the brain in which the cardiac centre is located.
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(ii)
Name the parts of the brain labelled J and K on Fig. 6.1.
J
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K
...................................................................................................................... [2]
(b) With reference to Fig. 6.1, explain how the cardiac centre controls the heart rate.
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(c) Fig. 6.2 shows endings of neurones X and Y in the heart.
Stimulation of Y leads to an increase in the concentration of the second messenger,
cyclic AMP (cAMP), in the cytoplasm of the heart cell and the stimulation of X leads to a
decrease.
Y
X
P
membrane of
sinoatrial
node cell
adenyl cyclase
Fig. 6.2
Describe the events that follow the arrival of an impulse at P on neurone Y that leads to
an increase in cAMP.
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BLANK PAGE
Copyright Acknowledgement:
Question 5, Figure 5.1, Calypso bulbosa flower, Orchi/Wikimedia Commons.
Question 5, Figure 5.2, Bee pollinating Ophrys orchid, Claude Nuridsary and Marie Perennou/Science photo library.
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every
reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the
publisher will be pleased to make amends at the earliest possible opportunity.
University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of
Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.
© UCLES 2012
9790/02/M/J/12