Practise Control and coordination. 15 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Required practical:Plant responses (method, variables and exam tips)
Quick recall
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In which direction do plant roots grow in response to gravity?
Downwards (in the direction of gravity)
A student investigated the effect of light on the growth of newly germinated cress seedlings. This is the method used. 1. Place 20 cress seeds on damp cotton wool in each of three dishes, A, B and C. 2. Leave the seeds in a warm place until they germinate. 3. Put dish A in a box with a slit, so that light enters from one side only. 4. Put dish B in a box in complete darkness. 5. Put dish C under a lamp so that light comes from directly above. 6. After 5 days, measure the length of each seedling and record observations. Give two control variables in this investigation.
E.g. temperature; volume of water added to the cotton wool; type of seed; number of seeds
Give the name of the response in which a plant root grows downwards, in the direction of gravity.
Gravitropism (geotropism)
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Plants produce hormones to coordinate and control their growth.
(a) What is the growth response of a plant to light called? Tick (✓) one box.[1]
Gravitropism
Hydrotropism
Photosynthesis
Phototropism
(b) Which plant hormone causes a shoot to bend towards light? Tick (✓) one box.[1]
Auxin
Ethene
Gibberellin
Insulin
(c) In which direction do plant roots grow in response to gravity?[1]
(d) Which plant hormones are important in starting seed germination? Tick (✓) one box.[1]
Auxins
Ethene
Gibberellins
Oestrogen
(e) Name the plant hormone that controls the ripening of fruits.[1]
Show the answer and mark scheme
(a)Answer: Phototropism
(b)Answer: Auxin
(c)Answer: Downwards (in the direction of gravity)
downwards / towards (the pull of) gravity
(d)Answer: Gibberellins
(e)Answer: Ethene
ethene
Question 2Medium7 marks
A student investigated the effect of light on the growth of newly germinated cress seedlings. This is the method used. 1. Place 20 cress seeds on damp cotton wool in each of three dishes, A, B and C. 2. Leave the seeds in a warm place until they germinate. 3. Put dish A in a box with a slit, so that light enters from one side only. 4. Put dish B in a box in complete darkness. 5. Put dish C under a lamp so that light comes from directly above. 6. After 5 days, measure the length of each seedling and record observations.
(a) Give two control variables in this investigation.[2]
(b) The seedlings in dish A were curved. Suggest how the student could measure the length of a curved seedling accurately.[1]
(c) The lengths of five seedlings from dish A were: 26 mm 29 mm 31 mm 27 mm 32 mm Calculate the mean length.[2]
(d) The student also made a labelled scientific drawing of the seedlings in dish A. Describe what the drawing would show.[1]
(e) Suggest why the student used 20 seeds in each dish rather than 1 seed.[1]
Show the answer and mark scheme
(a)Answer: E.g. temperature; volume of water added to the cotton wool; type of seed; number of seeds
temperature
volume of water / how damp the cotton wool is
type / species of seed
number of seeds per dish
time before measuring
light intensity (in dishes A and C)
(b)Answer: Lay a piece of string or thread along the seedling, then measure the string with a ruler
place string / thread along the seedling and then measure the string (with a ruler)
(c)Answer: 29 mm
(26 + 29 + 31 + 27 + 32) ÷ 5 / 145 ÷ 5
29 (mm)
(d)Answer: The shoots bending / growing towards the side where the light entered
shoots bending / growing towards the light (source) / the slit
(e)Answer: Some seeds may not germinate, and a mean of many seedlings is more representative
some seeds may not germinate / to calculate a (more representative) mean / to identify anomalies
Question 3Hard7 marks
Roots and shoots respond to gravity.
(a) Plan an investigation to find out how gravity affects the direction of growth of the roots and shoots of newly germinated seedlings. Your plan should include how you would record your results.[6]
(b) Explain why the seedlings should be kept on damp cotton wool throughout the investigation.[1]
Show the answer and mark scheme
(a)Answer: Level 3 answers give a logically ordered, workable method with control of variables, repeats, and both measurements and drawings
germinate seeds (e.g. broad bean) on damp cotton wool / filter paper
choose seedlings with roots of similar length
pin seedlings in a Petri dish / on damp cotton wool with roots pointing in different directions, e.g. up, horizontal, down
stand the dishes on their edges
keep the seedlings in the dark so light does not affect growth
keep the temperature and moisture the same for all seedlings
leave for several days, observing at regular intervals
measure the length / angle of curvature of roots and shoots (use string for curved roots)
make labelled scientific drawings of the direction of growth
use several seedlings for each position and calculate means
Marked with levels of response: the full level descriptors are in the app.
(b)Answer: Seedlings need water to grow, and drying out would affect growth
seedlings need water to grow / so they do not dry out (and die)