Oxford Cambridge and RSA
A Level Biology A
H420/03 Unified biology
Time allowed: 2 hours 15 minutes
You can use:
a scientific or graphical calculator
a ruler (cm/mm)
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 24 pages.
ADVICE
• Read each question carefully before you start your answer.
Turn over
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, 2
1 Scientists investigated phototropism and geotropism in seedlings to understand how
plants respond to environmental stimuli.
(a) Phototropism is the directional growth response of plants to light.
(i) The diagram below shows experimental observations on phototropism in oat seedlings.
1 2 3
4 5
Using evidence from experiments 2 and 3 in figure , explain why the shoot tip
must be present for phototropism to occur.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [2]
for more papers: tyrionpapers.com
, 3
(ii) Experiment 4 shows that placing a mica barrier on one side of the shoot prevents
bending towards the light on that side only.
State and explain what this suggests about the mechanism of phototropism.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [3]
(b) The figure shows the results of an investigation into auxin distribution in shoots exposed
to unilateral light. The total auxin levels measured in intact shoots, split shoots, and split
shoots with divided auxin collection.
Intact shoot in dark
Shoot in unilateral light
Shoot in unilateral light with
divided collection
for more papers: tyrionpapers.com
A Level Biology A
H420/03 Unified biology
Time allowed: 2 hours 15 minutes
You can use:
a scientific or graphical calculator
a ruler (cm/mm)
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 24 pages.
ADVICE
• Read each question carefully before you start your answer.
Turn over
for more papers: tyrionpapers.com
, 2
1 Scientists investigated phototropism and geotropism in seedlings to understand how
plants respond to environmental stimuli.
(a) Phototropism is the directional growth response of plants to light.
(i) The diagram below shows experimental observations on phototropism in oat seedlings.
1 2 3
4 5
Using evidence from experiments 2 and 3 in figure , explain why the shoot tip
must be present for phototropism to occur.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [2]
for more papers: tyrionpapers.com
, 3
(ii) Experiment 4 shows that placing a mica barrier on one side of the shoot prevents
bending towards the light on that side only.
State and explain what this suggests about the mechanism of phototropism.
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
...................................................................................................................................................
.............................................................................................................................................. [3]
(b) The figure shows the results of an investigation into auxin distribution in shoots exposed
to unilateral light. The total auxin levels measured in intact shoots, split shoots, and split
shoots with divided auxin collection.
Intact shoot in dark
Shoot in unilateral light
Shoot in unilateral light with
divided collection
for more papers: tyrionpapers.com
