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2024 BIOLOGY AQA A LEVEL EXCHANGE, ENERGY TRANSFERS AND RESPONSE EXAM WITH CORRECT ANSWERS
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2024 BIOLOGY AQA A LEVEL EXCHANGE, ENERGY TRANSFERS AND RESPONSE EXAM WITH CORRECT ANSWERS
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2024 BIOLOGY AQA A LEVELEXCHANGE, ENERGY TRANSFERS
AND RESPONSE EXAM WITH
CORRECT ANSWERS
A scientist investigated the effects of different fertilisers on the growth of
spinach plants. The scientist:
- Set up a large sample of identical pots of soil
- Added different masses of different fertilisers to selected pots
- Did not add fertiliser to the control pots
- Planted the same number of young spinach plants in each pot
- After 20 days, determined the biomass of spinach plants in each pot.
The results the scientist obtained after 20 days are shown in figure 4.
Calculate how many times greater the mean growth rate per day was using
37.5G potassium nitrate than using 37.5G ammonium sulphate.
Assume the mean biomass of the spinach plants at the start of the
investigation was 0.5G per pot. (1 marks) - CORRECT-ANSWERS3.7g/pot - AS
4.9g/pot - PN
3.7-0.5 = 3.2
4.9-0.5 = 4.4
3.2/20 = 0.16. 4.4/20 = 0.22
0.22/0.16 = 1.4x
The scientists concluded that this heat treatment damaged the phloem.
Explain how the results in figure 9 support this conclusion. (2 marks) -
CORRECT-ANSWERS1. The radioactively labelled carbon is converted into
sugar/organic substances during photosynthesis;
2. Mass flow/translocation in the phloem throughout the plant only in plants
that were untreated/B/control
OR
Movement of sugar/organic substances in the phloem throughout the plant
only in plants that were untreated/B/control;
, OR
1. Movement in phloem requires living cells/respiration/active transport/ATP;
2. Heat treatment damages living cells so transport in the phloem
throughout the plant only in plants that were untreated/B/control
OR
Heat treatment stops respiration/active transport/ATP production so
transport in the phloem throughout the plant only in plants that were
untreated/B/control;
The scientists also concluded that this heat treatment did not affect the
xylem.
Explain how the results in table 4 support this conclusion. (2 marks) -
CORRECT-ANSWERS1. (The water content of the leaves was) not different
because (means ± 2) standard deviations overlap;
2. Water is (therefore) still being transported in the xylem (to the leaf)
OR
Movement in xylem is passive so unaffected by heat treatment;
CHECK Figure 3 shows pressure and blood flow during the cardiac cycle in a
dog.
At P on figure 3, the pressure in the left ventricle is increasing. At this time,
the rate of the blood flow has not yet started to increase in the aorta.
Use evidence from figure 3 to explain why. (2 marks) - CORRECT-ANSWERS1.
Blood pressure increases in the left ventricle as blood comes in from the
atrium.
2. Blood pressure in the ventricles has not yet exceeded that of the aorta at
P at 11.5KP so the semi lunar valves are still closed preventing blood to enter
the aorta.
At Q there is a small increase in pressure and in the rate of blood flow in the
aorta.
Explain how this happens and it's importance. (2 marks) - CORRECT-
ANSWERS1. The aorta has high elasticity in it's walls to ensure constant high
pressure essential for blood to be constantly delivered to tissues.
2. The elasticity produces a recoil action and produces the temporary rise in
pressure allowing a slight increase in blood flow too.
A student correctly plotted the right ventricle pressure on the same grid as
the left ventricle pressure in figure 3.
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