Centre Candidate
Surname
Number Number
Other Names 2
GCE AS – NEW
B400U20-1 S17-B400U20-1
BIOLOGY – AS component 2
Biodiversity and Physiology of Body Systems
TUESDAY, 6 JUNE 2017 – AFTERNOON
1 hour 30 minutes
For Examiner’s use only
Maximum Mark
Question
Mark Awarded
1. 11
B 40 0U201
2. 16
01
3. 14
4. 14
5. 11
6. 9
Total 75
ADDITIONAL MATERIALS
In addition to this examination paper, you will need a calculator and a ruler.
INSTRUCTIONS TO CANDIDATES
Use black ink or black ball-point pen. Do not use gel pen. Do not use correction fluid.
Write your name, centre number and candidate number in the spaces at the top of this page.
Answer all questions.
Write your answers in the spaces provided in this booklet. If you run out of space, use the continuation
pages at the back of the booklet, taking care to number the question(s) correctly.
INFORMATION FOR CANDIDATES
The number of marks is given in brackets at the end of each question or part-question.
The assessment of the quality of extended response (QER) will take place in question 6.
The quality of written communication will affect the awarding of marks.
JUN17B400U20101 © WJEC CBAC Ltd. VP*(S17-B400U20-1)
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Answer all questions.
1. The diagram below shows a trace used by doctors to investigate the health of a patient’s heart.
Electrodes are placed on the patient’s skin and detect tiny electrical changes on the skin caused
by the electrical output of the heart. The output is amplified and recorded on a moving graph
paper trace using a standard grid so that it is possible for doctors to analyse the output. The
horizontal axis on the graph paper represents time.
(a) (i) What name is given to this type of trace? [1]
................................................................................................................
(ii) Calculate the heart rate of this person in beats per minute given that each small
square on the trace represents 0.04 seconds. Show your working. [2]
Heart rate = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . b.p.m.
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(b) The diagram below shows the trace for one cardiac cycle. only
P T
Q
S
(i) In the table below, use letters from the diagram to indicate which sections of the
trace correspond to the events of the cardiac cycle. [2]
Cardiac cycle events Section of trace
Ventricular diastole
Atrial systole
B 40 0U201
Ventricular systole
03
(ii) These events in the cardiac cycle are coordinated by specialised tissues in the
heart muscle. Describe the role of the following tissues in the cycle.
I. Sino-atrial node [2]
II. Atrio-ventricular node [2]
III. Bundle of His and Purkyne (Purkinje) fibres [2]
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2. A student used the apparatus shown in the diagram below to carry out an investigation into the
rate of water uptake by a freshly cut leafy shoot.
With the shoot in place in the apparatus, the level of water in the pipette was recorded every
10 minutes for a total of 40 minutes.
The apparatus was then reset and a transparent polythene bag placed over the leafy shoot. The
recordings were then repeated.
graduated pipette
syringe shoot
rubber bung
B 40 0U201
05
water
(a) (i) Name the apparatus used to measure the rate of water uptake. [1]
................................................................................................................
(ii) Why is it important that no air bubbles enter the apparatus? [1]
(iii) State two precautions the student should take when setting up the experiment to
ensure that no air bubbles enter the apparatus. [2]
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(b) (i) Explain why the temperature and light intensity were controlled during this
investigation. [3]
temperature
light intensity
Readings were taken and the total volume of water taken up by the leafy shoot was
calculated, as shown in the table below.
Total volume of water taken up by the leafy
shoot / cm3
Time not enclosed in enclosed in
/ minutes polythene bag polythene bag
0 0 0
10 2.4 2.2
20 4.1 2.9
30 5.6 2.9
40 6.6 2.9
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(ii) Plot the results shown in the table opposite on the graph paper below. [4]
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(iii) Describe and explain the results shown. [5]
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3. A microscope was calibrated at x100 magnification using an eyepiece graticule and stage
micrometer, as shown in the image below.
The eyepiece graticule scale shown in the diagram is divided into 100 units. The section labelled
0 – 1 on the image is equal to 10 eyepiece units.
stage micrometer
scale
10 20 30 40
0 1 2 3 4 5 6 7 8 9 10
B 40 0U201
09
eyepiece
graticule
scale
(a) Use this image to calculate the size of 1 eyepiece unit at this magnification. [2]
1 stage micrometer division = 10 µm
1 eyepiece unit = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . µm
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(b) A student used the microscope to examine a T.S. slide of duodenum of a mammal and
drew a low power plan.
Low Power Plan of TS Duodenum. (x10 eyepiece lens, x10 objective)
Y X
X1
Y1
(i) Use clear label lines and the letters A-D to identify the following structures on the
low power plan above. [4]
A Serosa
B Mucosa
C Circular muscle
D Longitudinal muscle
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(ii) Using the eyepiece graticule, the height of the villus and the thickness of the gut
wall were measured at the points indicated. The student recorded the following
measurements.
X – X1 =
20 epu
1
Y–Y =
25 epu
epu = eye piece unit
Use the answer from (a) to calculate the height of the villus marked X – X1. [1]
Height of X – X1 = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . µm
(iii) Using the measurement lines shown on the diagram, state if the student’s low
power plan is in proportion to the actual specimen. Explain how you reached your
conclusion. [3]
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(c) The protease enzyme trypsin is an endopeptidase secreted by the acinar cells of the
pancreas. The enzyme is secreted in an inactive form called trypsinogen. Another enzyme
called enterokinase converts the inactive trypsinogen to the active form, trypsin, in the
duodenum.
(i) Explain why the enzyme is secreted in an inactive form. [1]
(ii) The optimum pH of trypsin is in the range 7.8 – 8.7. Explain how this pH is maintained
in the duodenum. [3]
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4. Myoglobin is a type of protein that works in a similar way to haemoglobin. It is found inside
muscle cells.
The table below shows both the myoglobin concentration and oxygen carrying capacity of
skeletal muscle from a variety of terrestrial and marine mammals.
Myoglobin O2 carrying
Habitat Organism concentration capacity
/g kg –1 muscle /cm kg –1 muscle
3
Human 6.0 8.0
Terrestrial Dog 6.7 9.0
Rat 3.0 4.0
Harbour porpoise 41.0 56.0
Marine Harbour seal 52.1 69.8
Weddell seal 44.6 59.8
(a) A Harbour seal is a marine mammal which lives and hunts for food (mostly fish) in the
sea. It is very well suited to its environment and spends long periods of time under water
when hunting.
(i) A Harbour seal has a muscle mass of 60% of its total body mass. Calculate the
muscle mass of a 70 kg Harbour seal and use this to calculate the total oxygen
carrying capacity of its myoglobin. [2]
Total oxygen carrying capacity = ........................................................ cm3
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(ii) A 70 kg human would have an oxygen carrying capacity of approximately 300 cm3 only
oxygen bound to myoglobin in their skeletal muscle. Using the data in the table,
explain the difference in the oxygen carrying capacity of the muscle of these
mammals and suggest how this would be an advantage to the seal. [2]
All mammals have an organ, known as the spleen, which acts as a reservoir for
blood. When the seal swims under water, the spleen contracts forcing more blood
into the general circulation as shown in the diagram below.
At rest When swimming under water
to general to general
circulation circulation
posterior posterior
vena cava diaphragm vena cava
blood
reservoir
spleen portal liver
vein
(b) Suggest how this adaptation helps the seal stay under water for prolonged periods when
hunting its prey. [4]
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(c) The diagram below shows three dissociation curves.
100
myoglobin
80
oxygen
saturation 60
/% llama haemoglobin
40
adult human haemoglobin
20
0
0 2 4 6 8 10 12
partial pressure of oxygen / kPa
(i) Explain the significance of the position and shape of the myoglobin curve. [4]
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(ii) Explain the position of the dissociation curve of the llama haemoglobin relative to
that of adult human haemoglobin. [2]
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5. Phytoplankton is the term used to describe the microscopic photosynthetic organisms that live
in bodies of water, mainly near the surface. They are the main food source of many shellfish and
crustaceans. However, some phytoplankton species can produce toxins that accumulate in the
tissues and organs of shellfish. If the shellfish are eaten by humans, this can cause a form of
food poisoning.
Members of European Union states are required to monitor both the presence and distribution
of marine phytoplankton which can produce toxins in areas where shellfish are harvested.
One possible method for estimating the biodiversity of phytoplankton is to use a net to capture the
organisms present in a known volume of water. This is then followed by microscopic examination
of the organisms to identify them and estimate population numbers.
A diagram of one net used is shown below.
buoys to keep the net floating upon towing
towing rope
PVC cylinder
frame
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(a) When using this method to catch phytoplankton, the mesh size (size of the holes in the
net) for the net has to be chosen carefully. Photomicrographs of three of the most harmful
phytoplankton are shown below.
Alexandrium Dinophysis Pseudo-nitzschia
50 µm 50 µm 50 µm
Suggest what mesh size would be used to obtain the most accurate count of these
phytoplankton. Explain your answer. [2]
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(b) The table below shows the results of monitoring two different sites along a 2 km stretch of
coastline for potentially harmful phytoplankton. All samples were taken on the same day
using the same sampling method.
Number of cells at each site / cells dm –3
phytoplankton
SITE 1 SITE 2
Pseudo-nitzschia 780 49 000
Alexandrium 530 0
Dinophysis 650 400
Prorocentrum lima 0 0
Prorocentrum cordatum 420 1 480
Lingulodinium polyedrum 0 0
Protoceratium reticulatum 0 20
(i) Use the data to state which site has the greatest biodiversity. Explain your answer.
[3]
(ii) Name a statistical test which could be used to compare the biodiversity of the two
sites. [1]
(iii) The two sites sampled showed significant variation in the distribution of
phytoplankton. Suggest improvements to the sampling method in order to further
investigate biodiversity along the stretch of coastline. [3]
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(iv) The data collected from phytoplankton monitoring are used to provide early warnings
to the shellfish industry to try to minimise the risk of food poisoning. Phytoplankton
levels are monitored at different frequencies throughout the year as shown below:
Time of year Sampling frequency
March to September Weekly
October to November Fortnightly
December to February Monthly
The Chart below shows the average water temperature at the sampling site.
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Average 12
water
temperature / °C
10
0
y
ry
ch
ril
ay
ne
ly
st
er
r
be
be
be
ar
Ju
Ap
gu
ua
ob
ar
Ju
nu
em
em
em
Au
br
ct
Ja
O
Fe
pt
ov
ec
Se
Month
Explain why monitoring takes place more frequently between March and September.
[2]
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6. Tubifex worms have a similar structure to earthworms. They are one of the few multi-cellular
organisms that can survive in heavily polluted water which has low oxygen levels. Some of their
adaptations to these conditions are described below.
• Diameter of approximately 3 mm, length up to 45 mm.
• Outer body surface is folded.
• Head and front part of body buried in mud – when highly active, less of the body is buried.
• Part of the body exposed to the water moves vigorously.
• Red in colour due to presence of haemoglobin.
Explain how these adaptations enable Tubifex worms to survive in water with very low oxygen
levels. [9 QER]
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Question Additional page, if required. Examiner
number Write the question number(s) in the left-hand margin. only
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