Exam (elaborations)
AQA Biology Alevel - Exchange of substance MARK SCEME
- Module
- Exchange of substance
- Institution
- AQA
Mass transport in animals
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M1.(a) 53−- (beats per minute).1
(b) 13..;
If answer is incorrect, 1 mark for the principle of difference
(11) divided by initial heart rate (81).
or for 1 mark
Ignore + or - signs
2
(c) 1. Allows comparison;
2. (Initial / resting) heart rates different (between males and females).
2
(d) 1. Cardiac output = stroke volume × heart rate
1. Accept CO = SV × HR
2. (So) stroke volume increases / increased size or volume of ventricles.
2. Neutral: more blood leaves heart
2. If the term stroke volume is not used, it must be defined
2 max
[7]
M2.(a) 1. (Carry) oxygen / glucose;
Accept: oxygenated blood
Ignore references to removing waste products
Ignore references to arteries ‘pumping’ blood
2. (To) heart muscle / tissue / cells / myocytes.
Must be supply to heart or cardiac
2
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, (b) (i) A;
Accept: A on its own even if outside box
Reject if two (or more) letters given
1
(ii) H;
Accept: H on its own even if outside box
Reject if two (or more) letters given
1
(c) (Aorta)
1. (is) close / directly linked to the heart / ventricle / pressure is higher / is
very high;
2. (Aorta has) elastic tissue;
Accept elasticity
Ignore reference to muscle
3. (Aorta has) stretch / recoil.
Q Reject: contracts / relaxes / pumps
Accept: for mp 2 and mp 3, converse for small arteries if
qualified by little / less
3
[7]
M3.(a) 1. Many / more capillaries (than arterioles);
2. (Cross-sectional) area of capillaries (much) greater (than of arterioles).
Note: maximum of 1 mark for this question
1 max
(b) 1. Short pathway / short distance between blood and outside of capillary;
Reference to blood and cells required
2. Large surface area (of blood) in contact with walls of capillaries;
Idea is per unit volume of blood but candidates need not say
this
3. Fast exchange / fast diffusion / fast osmosis.
Must relate to increased speed
2 max
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PhysicsAndMathsTutor.com
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