Download File - A. Hammond Biology

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A. Popperwell
1. The following diagram shows a
simplified plan of the mammalian
circulatory system.
(a) Using information in the diagram
explain what is meant by the
statement ‘mammals have a double
circulation’.
Double circulation is where the blood
……………………………………………
passes twice through the heart. 
……………………………………………
……………………………………………
…………………………………………(4)
(b) State four advantages of a having double circulation.
There is a more efficient delivery of oxygen to the tissues. 
1.………………………………………………………………………………………
Higher blood pressure can be maintained. 
2………………………………………………………………………………………
The mammal can be more active. 
3………………………………………………………………………………………
4……………………………………………………………………………………(4)
(Total 8 marks)
Examiner’s Comments
1. (a) Not only is this an incomplete answer as it should read: “A double circulation is where the
blood passes twice through the heart per complete circulation” but the student has not, as
instructed in the question, used the diagram to explain what a double circulation is.
A good answer would read: “blood is pumped by the heart to the capillaries in the lungs, via the
pulmonary artery, to become oxygenated - this is the pulmonary circulation. It is then returned to
the heart, via the pulmonary vein, from where it is pumped again all the way around the body via
the aorta - this is the systemic circulation.”
1. (b) The student has provided three correct responses but clearly did not know a fourth. If you
are in this position don’t waste a lot of time thinking about another answer, but move on to
another question. Mark the unanswered part with an asterisk, and return to the question when you
check through your answers. The asterisk will help you find the unanswered part more quickly.
Other acceptable answers are: there is less resistance to blood flow and it is easier to return
blood to the heart.
2. The following diagram shows a section through a mammalian heart.
Semi lunar valve 
A……………………..
Papillary muscle 
B……………………..
Chordae tendinae
C……………………..
Tricuspid valve
D……………..…..
(a) Name the parts labelled A, B, C and D writing your answers on the dotted lines
provided.
(4)
(b) Complete the following table by writing the function of each of the structures listed.
Structure
Function
A
These valves prevent the backflow of blood.

B
Stops the valves turning inside out.

(2)
(c) The diagram shows the heart in a specific stage of the cardiac cycle.
Name this stage and give two reasons to support your answer.
Diastole 
Stage name…………………………………………………………………………
 and the tricuspid valve is open.
The semi lunar valves are closed
Explanation…………………………………………………………………………
………………………………………………………………………………………
…………………………………………………………………………………. (3)
(Total 9 marks)
Examiner’s Comments
2. (a) The student knows the names of some of the structures in the heart but has not
used them in the correct places. Labelling diagrams and naming structures are fairly
common types of questions.
Don’t skip over diagrams when you are revising because you think it is more important
to concentrate on the text.
Diagrams should form an integral part of your understanding. You need to be able
to label all the key diagrams you have encountered during the course.
The student has got labels B and C the wrong way round and has incorrectly identified
the valve on the left side of the heart as the tricuspid valve, when this is on the right and
the bicuspid valve is on the left.
A tip to help you remember this:
tricuspid = right
Examiner’s Comments
2. (b) The student knows that valves prevent the backflow of blood. This would have been an
acceptable answer at GCSE but at ‘A’ level you need to be more specific and explain where the
valves are preventing backflow to. An acceptable answer would be: These valves prevent the
backflow of blood into the ventricles when the heart has contracted and pumped blood to the
lungs and body.
2. (c) The student has correctly identified the stage in the heart cycle and it is clear that they
know why this is so. However, you need to remember that both sides of the heart work
simultaneously and that if the tricuspid valves are open then the bicuspid valves must also be
open. The student has only made reference to the valves on one side of the heart.
3. The following diagram illustrates graphically the changes in pressure in the right
and left ventricles and in the aorta of the human heart, during the cardiac cycle.
Time zero signifies the start of atrial systole.
contraction 
(a) What is meant by the term ‘systole’? ……………………………………(1)
(b) Using the diagram, compare and explain the changes in pressure in the right
ventricle with those in the left ventricle.
 - systole takes less
Both ventricles contract and relax in phase with one another
…………………………………………………………………………………
than 0.5 seconds to complete. The change in pressure is greater, by about 12 kPa,
…………………………………………………………………………………
 than the right ventricle. This is because the left ventricle
in the left ventricle
…………………………………………………………………………………
contracts more forcefully than the right ventricleas it pumps blood all around the
…………………………………………………………………………………
body, whereas the right ventricle only pumps blood as far as the lungs.
………………………………………………………………………………(4)
(c) Using the diagram compare and explain the changes in pressure in
the left ventricle with those in the aorta.
There is a steep increase in both although the pressure in the aorta
…………………………………………………………………………………
This is because the
increases
a
little
later
than
that
in
the
left
ventricle.
…………………………………………………………………………………
left ventricle contracts first forcing blood into the aorta which
…………………………………………………………………………………

consequently
sees
an
increase
in
pressure
slightly
later.
The pressure
…………………………………………………………………………………
changes in the left ventricle are from 0 to 15kPa while that in the aorta is
…………………………………………………………………………………
from 11 to 15 kPa so there is a much greater pressure change in the left
………………………………………………………………………………(4)
ventricle. 
This is because the left ventricle relaxes after it has contracted
whereas pressure in the aorta is maintained fairly high all the time
This is because the heart is the major pumping
because of elastic recoil.
organ in the body and this creates the pressure which is passed onto the
aorta. Having contracted there is a steeper decrease in pressure in the left
ventricle than the aorta.
(d) On the graph, show by means of labelled arrows, where the aortic semilunar
valve opens and closes.
(2)
closes 
opens
(Total 11 marks)
Examiner’s Comments
3. (a) A correct answer.
3. (b) The student has successfully compared the changes in pressure in the right
and left ventricles. They have also used the diagram to do the comparison as they
have quoted figures from the graph.
However, the student has only provided an explanation for the relatively large
difference in the pressure changes inside the two ventricles and not for the fact
that they beat in phase. Therefore the student will lose 1 of the 4 marks available.
The missing explanation: “This is because the wave of contraction for both
ventricles is originates at the same time from the same region (AVN) and moves
through the ventricular muscle at a constant speed and in a symmetrical manner.”
Examiner’s Comments
3. (c) This is an excellent answer but the student has wasted a considerable
amount of time writing far too much.
If 4 marks are available for a compare and explain question then 1 mark will be
awarded for the first correct point of comparison and the second mark will be for
the correct explanation of the compared point.
This is then repeated for the second point of comparison and accompanying
explanation.
Examiner’s Comments
3. (d) A correct answer. You may also be expected to know when the bicuspid
valve opens and closes - so make sure that you would be able to label these events
on the diagram.
Similarly, if a diagram of the right hand side of the heart had been provided,
knowledge of the tricuspid valve and pulmonary semilunar valve positions would
be examined .
4. Give an account of the structure and functioning of cardiac muscle.
The
heart is made of a special tissue called cardiac muscle. The heart is
…………………………………………………………………………………
divided
into four chambers, two upper atria and two lower ventricles. The
…………………………………………………………………………………
heart
beats on average 72 times per minute. Cardiac muscle is special in
…………………………………………………………………………………
that
it is not subject to fatigue.The heartbeat is initiated by a special patch
…………………………………………………………………………………

of
tissue called the AV node or pacemaker.
People can have an artificial
…………………………………………………………………………………
pacemaker
…………………………………………………………………………………
fitted if the need arises. Heart muscle contains many
mitochondria
to supply the energy to keep it pumping. Cardiac muscle is
…………………………………………………………………………………
described
as myogenicbecause it can contract automatically. The rate of
…………………………………………………………………………………
The heart has a
the
heartbeat is accelerated by the hormone adrenaline.
…………………………………………………………………………………
very
good blood supply from the coronary arteries and veins which deliver
…………………………………………………………………………………
oxygenated
blood to the heart and remove deoxygenated blood from it.
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
……………………………………………………….…………(Total 10 marks)
Examiner’s Comments
4. The student has only scored half of
the marks available. They have made
one fundamental error in saying that
the pacemaker is called the
atrio-ventricular node when it is the
sino atrial node. It is also not advisable
to use an abbreviated form of a term
without first having first referred to the
structure’s full name.
If you are going to use a term several times then write it in full the first time you use it followed by the
abbreviation and from then onwards you can use the abbreviated form, e.g. sino atrial node (SAN). The
student has also not kept to the title which refers to cardiac muscle only and not to the gross structure of
the heart. A model answer would read:
“Cardiac muscle consists of many branching multinucleate cells. There are large numbers of
mitochondria to provide the cardiac muscle with the energy needed for contraction. Cardiac muscle cells
are joined by structures known as intercalated discs, which transmit the force of contraction and allow the
rapid spread of electrical excitation throughout the muscle. It is composed of the proteins actin and
myosin and has cross-striations similar to those of skeletal muscle.
Cardiac muscle is said to be myogenic. This means that, unlike striated muscle, cardiac muscle is selfexciting. Cardiac muscle cells beat continuously contracting on their own.
The heartbeat can be changed by nervous or hormonal influences. Cardiac muscle never tires. The
heartbeat is initiated in a special patch of cells in the right atrium called the sino atrial node. Cardiac
muscle has a very dense capillary network which receives blood by means of the left and right coronary
arteries.”
5. The following diagram illustrates structures in the heart concerned with the
coordination of contraction.
(a) Name structures X, Y and Z.
SAN

X…………………………………
X
Y
AVN

Y…………………………………
Septum 
Z…………………………………(3)
Z
(b) Explain how the structures illustrated on the
diagram coordinate the contraction of the heart.
The SAN send out impulses which spread across the atria causing them
……………………………………………………………………………
to contract.The impulses then reach the AVN at the junction between
……………………………………………………………………………
 the passage of the
the
atria
and
the
ventricles.
This
node
delays
……………………………………………………………………………
impulses. From here the impulses pass down to the base of the
……………………………………………………………………………
ventricles via the Bundle of His which contains Purkinje fibres.
…………………………………………………………………………(3)

The ventricles contract from the base upwards.
5. (c) The rhythmic contraction of cardiac
muscle during the cardiac cycle can be
captured and displayed as an (ECG)
electrocardiogram. The trace shown is
that of a healthy person’s ECG.
(i) Explain what the following letters
represent in the cardiac cycle.
The P wave is caused by electrical excitation of the atria. The wave
P…………………………………………………………………………….
spreads across the atria from the SA node. It represents atrial systole. 
………………………………………………………………………………
The QRS wave or complex is the result of excitation of the
QRS complex………………………………………………………………
ventricles and represents ventricular systole. 
……………………………………………………………………………..
The T wave is the result of recovery of the atria. 
T…………………………………………………………………………..
(3)
(ii) From the ECG trace, calculate the heart rate in beats per minute. Show
your working.

From the tract the time taken from one T wave to the next T wave is 0.7 seconds.
…………………………………………………………………………………
60 / 0.7 = 85.7. 
……………………………………………………………………………….(3)
(Total 12 marks)
5. The following diagram illustrates structures in the heart concerned with the
coordination of contraction.
(a) Name structures X, Y and Z.
SAN

X…………………………………
Examiner’s Comments
X
Y
AVN

Y…………………………………
Septum 
Z…………………………………(3)
Z
(b) Explain how the structures illustrated on the
diagram coordinate the contraction of the heart.
The SAN send out impulses which spread across the atria causing them
……………………………………………………………………………
to contract.The impulses then reach the AVN at the junction between
……………………………………………………………………………

the atria and the ventricles. This node delays the passage of the
……………………………………………………………………………
impulses. From here the impulses pass down to the base of the
……………………………………………………………………………
ventricles via the Bundle of His which contains Purkinje fibres.
…………………………………………………………………………(3)

The ventricles contract from the base upwards.
5. (a) This student knows what these structures are but do not abbreviate the
names of important structures. Z is not the septum but is the special nervous
tissue known as Purkinje fibres or the Bundle of His.
5. (b) It would be particularly mean to penalise this student for the same
error twice, namely abbreviating the names of structures. This is a clear
answer scoring all 3 marks available.
Examiner’s Comments
5. (c) (i) The T wave is the result of recovery of the ventricles not the atria as
stated by this student. Recovery of the atria would not be not detected as the
small voltage changes involved are masked by the QRS wave.
5. (c) (ii) The student has correctly taken the measurement T to T as 0.7 from
the ECG trace and manipulated the figures correctly. However, they have
carelessly omitted the units ‘beats per minute’ so lose 1 of the 3 marks
available.
6. The following structural drawings show sections of three types of blood
vessel found in mammals. They are not drawn to scale.
Capillary 
X……………………
Artery 
Y……………………
Vein
Z……………………

(a) Name the three blood vessels X, Y and Z on the dotted lines above.
(2)
(b) Give two functional differences between arteries and veins.
Arteries carry blood away from the heart. 
…………………………………………………………………………………
Arteries carry oxygenated blood. 
………………………………………………………………………………
(2)
(c) State two ways in which structure X is adapted to carry out its function.
There are pores to allow molecules to pass
The
walls are very thin.
…………………………………………………………………………………
through
the walls.
………………………………………………………………………………
(2)
(Total 6 marks)
Examiner’s Comments
6. (a) Notice that you have to
name three structures to gain
2 marks. This is because this
is thought to be a relatively
easy question and is marked
as follows - all correct 2
marks, one mistake 1 mark
more than one mistake no marks awarded.
So even though the student correctly identified X as a capillary they do not gain any
marks because X and Y have been incorrectly identified. In fact, Y is a vein and Z is an
artery.
6. (b) Unfortunately, neither of these correct statements can be awarded a mark because
they are unfinished statements. The student has assumed that the person marking the
script knows that veins do the opposite of arteries. You must not assume things like this
but must always make sure that your answer contains sufficient detail so as not to leave
the reader in any doubt whatsoever. The student should have written “arteries carry blood
away from the heart, while veins return blood to the heart.”
6. (c) The student has provided two correct statements and gains both marks available
but there was no need to provide an explanation for the pores as the question merely
instructed you to ‘state’.
7. The following table displays features about mammalian blood cells.
If the statement is correct, place a tick ( ) in the appropriate space and if it is
incorrect , place a cross () in the appropriate space.
Statement
Lymphocyte
Erythrocyte
Neutrophil
Contains haemoglobin




Destroys bacteria by
phagocytosis




Possess a nucleus




Produces antibodies




Can carry oxygen around the
body




(Total 5 marks)
Examiner’s Comments
7. The student has not left any spaces but it is worth noticing that in order to score
each mark you have to get all the responses in one line correct.
This means that if you make one mistake in each line you will not be awarded any
marks.
Both lymphocytes and neutrophils possess a nucleus and only neutrophils can
destroy bacteria by phagocytosis.
8. The following diagram of a capillary bed illustrates important pressures in
tissue fluid and lymph formation.
Capillary bed
Arterial end
Blood pressure = 4.5 kPa
Solute potential = 3.4 kPa
Venous end
Blood pressure = 1.8 kPa
Solute potential = 3.4 kPa
Tissue fluid & Lymph
Hydrostatic pressure = 1.1 kPa
Solute potential = 1.2 kPa
(a) (i) Making reference to the diagram in your answer, explain fully how fluid leaves
the capillary at the arterial end of the capillary bed.
The blood pressure at the arterial end is greater than at the venous end (4.5kPa to
………………………………………………………………………………………
1.8kPa) so fluid is forced out at the
arterial end. This is possible because there
………………………………………………………………………………………
are pores in the capillary walls.
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
(3)
(a) (ii) Making reference to the diagram in your answer, explain fully how fluid
is returned to the capillary at the venous end of the capillary.
Capillary bed
Arterial end
Blood pressure = 4.5 kPa
Solute potential = 3.4 kPa
Venous end
Blood pressure = 1.8 kPa
Solute potential = 3.4 kPa
Tissue fluid & Lymph
Hydrostatic pressure = 1.1 kPa
Solute potential = 1.2 kPa
Obviously
the situation at the venous end is the direct opposite of that at the
………………………………………………………………………………………
arterial
end. Now the blood pressure has fallen considerably to 1.8kPa so is not
………………………………………………………………………………………
great
enough to force fluid out of the capillary. However, the solute pressure inside
………………………………………………………………………………………
the
capillary is more negative than that outside (-3.4kPa to -1.2kPa) so fluid is
………………………………………………………………………………………
drawn
back in. 
………………………………………………………………………………………
(3)
(b) State two ways in which capillaries are adapted to enable the formation of
tissue fluid.
The endothelial lining is very thin being only onecell thick.
1……………………………………………………………………………………....
The cells themselves are very thin. 
2…………………………………………………………………………………...(2)
(c) Why is the solute potential of the blood more negative than the solute potential
of the tissue fluid?
Although
there are pores in the capillary walls these are too small to allow red
……………………………………………………………………………………….
blood
cells and large molecules such as proteins to pass through
as tissue fluid is
……………………………………………………………………………………….
formed.
These remain in the capillary creating a more negative solute
…………………………………………………………………………………….(2)
 potential.
(d) In elderly people the absorption of tissue fluid back into the capillaries is
not always as efficient as it should be. Sometimes this results in swelling
(oedema). Suggest two factors that could contribute to oedema.
 pressure would force more fluid out of the capillary at the
Raised
blood
………………………………………………………………………………………
arterial
end. If the capillary walls became more leaky with age then more
………………………………………………………………………………………
fluid
would be able to pass through the walls and therefore lead to swelling.
…………………………………………………………………………………….(2)
(Total 12 marks)
Examiner’s Comments
8. (a) (i) The student has started the answer along the right lines and has made reference to the
diagram to extract figures. However, the answer is not a detailed enough explanation. It is not
just the difference in blood pressure between the arterial end and the venous end that is
important but the relative pressure differences between inside the capillary and outside in the
tissue fluid bathing the cells. This means that more detailed calculations need to be performed
in order to explain fully how fluid leaves the capillary at the arterial end.
The net pressure forcing blood out of the capillary at the arterial end is 4.5 -1.1 = 3.4kPa
The net solute potential drawing fluid back into the capillary is 3.4 -1.2 = 2.2kPa
3.4kPa is greater than 2.2kPa so this means that more fluid is forced out of the capillary (at the
arterial end) than is drawn back in.
Examiner’s Comments
8. (a) (ii) This is a more detailed answer providing more explanation as to how the fluid is
returned to the capillary, but again the calculations fall short of being detailed enough as it is
the relative differences that are important. Never start a sentence with ‘obviously’.
Nothing is obvious in the absence of an explanation. What does ‘opposite’ mean in this
situation? Make sure that you do not write ambiguous responses. The student has correctly
stated that the solute pressure inside the capillary is more negative than that outside (-3.4kPa
to -1.2kPa) so fluid moves back in. However, the student has not gone on to do the final allimportant subtraction (2.2kPa). Always take calculations to the full and logical end point.
The net pressure forcing blood out of the capillary at the venous end is 1.8 - 1.1 = 0.7kPa.
The net solute potential drawing fluid back into the capillary is 3.4 - 1.2 = 2.2 kPa.
2.2kPa is greater than 0.7kPa so this means that more fluid moves back into the capillary (at
the venous end) than leaves.
Examiner’s Comments
8. (b) A good answer. Other valid points would be that there are pores in the capillary
walls and the walls are selectively permeable.
8. (c) A very good answer. Tissue fluid and blood have both been referred to.
8. (d) These are two good answers but the question only required you to ‘suggest’
and not explain so don’t waste time writing too much. You will not gain any extra
credit by doing so.
9. The following graph shows the oxygen dissociation curves for myoglobin, fetal
haemoglobin and normal haemoglobin.
(a) Identify each curve by writing the
number 1, 2 or 3 on the dotted lines.
2

Myoglobin…………………………
1

Fetal haemoglobin…………………
3
Normal haemoglobin ………………(3)

(b) Explain the importance of the position of the fetal haemoglobin curve.
The fetus has to get its oxygen from the mother’s blood so its
……………………………………………………………………………………
haemoglobin needs to have a greater affinity for oxygen than the normal
……………………………………………………………………………………
haemoglobin.Curves displaced to the left of the normal haemoglobin
……………………………………………………………………………………
mean that the respiratory pigment picks up oxygen more easily but gives it
…………………………………………………………………………………(3)
up more sparingly.The fact that fetal haemoglobin has a greater affinity
for oxygen than maternal haemoglobin ensures that the fetus gets an
adequate supply of oxygen. 
(c) Explain the importance of the position of the myoglobin curve.
Myoglobin acts as an oxygen store in mammals. 
…………………………………………………………………………………(2)
(Total 8 marks)
Examiner’s Comments
9. (a) The student has correctly identified the normal haemoglobin and knows that both the
other types are displaced to the left of this. However, remember that myoglobin is displaced
further to the left than fetal haemoglobin. It is an energy store.
9. (b) Factually this is an excellent answer. However, it does overspill the allocated space.
Remember that as well as demonstrating a sound knowledge of biological concepts you must
be able to communicate your ideas in a succinct manner. Practice summarising passages to
help you become more adept at this skill.
9. (c) The fact that the student did not know that the oxygen dissociation curve for myoglobin
is further to the left than that of the fetal haemoglobin makes this question more difficult for
them to answer. However, they have made a valid point and score 1 of the 2 marks available.
They need to appreciate that oxygen is only released when the partial pressure of oxygen in the
muscles is very low, for instance during strenuous exercise.
10. The following graph shows the haemoglobin oxygen dissociation curves for
Arenicola and a human. Arenicola, (lugworm) lives in the waterlogged sand or
muddy sand of shorelines and estuaries.
(a) Explain why the Arenicola haemoglobin oxygen dissociation curve is displaced to
the left of the human curve.
There would not be very much oxygen available in a muddy waterlogged
…………………………………………………………………………………………
burrow so if Arenicola is to obtain oxygen at all its haemoglobin must
…………………………………………………………………………………………
have a very high affinity for it. This
 is why the oxygen dissociation
…………………………………………………………………………………………
curve is displaced to the left of the human curve.
………………………………………………………………………………………(3)

(b) The following graph shows the oxygen dissociation curves for haemoglobin
under different conditions. Curve X shows normal conditions.
(i) State two factors which could
be responsible for the shift of
the curve from X to Y.

Exerciseand temperature.
…………………………………
……………………………….(2)
(ii) Explain the importance to the body tissues of the curve shifting from X to Y.
During respiration the concentration of carbon dioxide increases and the
…………………………………………………………………………………
 The body tissues need
oxygen levels decrease as a result of respiration.
…………………………………………………………………………………
to be delivered to them so the curve shifts to the right and the
more oxygen
…………………………………………………………………………………
oxygen is released from the haemoglobin morerapidly.
………………………………………………………………………….…..(3)
(Total 8 marks)
Examiner’s Comments
10. (a) A good answer. All available space has be used to show relevant knowledge and
understanding. The explanation was made as both Arenicola and the human dissociation
curves were considered and related.
Examiner’s Comments
10. (b) (i) The student is thinking along the right lines but has not been specific enough in
the answer to score either of the 2 marks available. It is true the person may have been
exercising. But the student needed to state the exact factors that would cause the curve to
shift to the right. Exercise would lead to an increase in the carbon dioxide concentration and
a decrease in the pH of the blood. It is never a good idea to use the word temperature. It is
too vague. In this case increasing the temperature would cause the curve to shift to the
right.
10. (b) (ii) This is a good answer. All available space has be used to show relevant
knowledge and understanding. The explanation was made as both dissociation curves were
considered and related.
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