Syllabus Edition

First teaching 2023

First exams 2025

|

Control & Coordination in Plants (CIE A Level Biology)

Exam Questions

1 hour9 questions
1a
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1 mark

State why the Venus flytrap (Dionaea muscipula) is a carnivorous plant.

1b
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3 marks

State the events that lead to a Venus flytrap closing to entrap its prey.

1c
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2 marks
(i)

State the name of the group of proteins that allow cell elongation under the effects of auxins like IAA (indole 3-acetic acid).

[1]

(ii)

State their mode of action.

[1]

1d
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2 marks

Following the effect you described in part (c) (ii), explain the events that cause the cell to elongate.

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2a
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2 marks

State the two processes that are controlled by gibberellins in plants.

2b
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2 marks

Farmers wishing to preserve stocks of harvested barley seeds have to keep them dry and cool to avoid early germination.

Explain this in the context of gibberellins and their mode of action.

2c
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4 marks

Table 1 gives some events associated with the germination of barley.

Table 1

Event Description
A  starch is hydrolysed to maltose and glucose
B  seeds are dormant (very dry and metabolically inactive)
C  aleurone layer is stimulated to express amylase genes
D  seeds begin to absorb water
E  the embryo can respire and release energy for growth
F  seeds produce gibberellins

Place the events into chronological order, 1st to 6th, in the sequence below.

One event has been completed for you. 

1st   2nd   3rd   4th   5th   6th
  → D →   →   →   →  
2d
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2 marks

Give the name and function of the large, central part of a barley grain that occupies most of the grain's volume.

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3a
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2 marks

State the name of the gene that governs the height of certain plants and the names of its two alleles.

3b
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3 marks
The recessive allele of the gene mentioned in part (a) contains a mutation that gives rise to a loss of function.

Describe this mutation and its effect.

3c
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2 marks

Gibberellin causes stem elongation in plants.

Fig. 1 shows the effect of gibberellin on pea plants.m5E1m8Jz_igya-gibberellins-hf1

Fig. 1

The effect of gibberellin is to increase the distance between the groups of leaves on the stem; this distance is called the internodal length.

Explain why gibberellin is referred to as a plant hormone.

3d
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3 marks

Fig. 2 shows the results of a study in which a researcher used a range of volumes of gibberellin and measured the rate of increase of intermodal length in pea plants over a 25-day period.QS1iDKRw_cie-ial-15-2-q3d-e---sq

Fig. 2

Calculate how many times more effective it was to double the volume of gibberellin used from 2 to 4 arbitrary units. 

State your answer to the nearest whole number. 

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1a3 marks

Fig.1 shows the effect of increasing IAA concentration on the growth of plant roots and shoots.

15-2-fig-3-1
Fig. 1

Describe the effect of increasing IAA concentration on the growth of plant shoots shown in Fig.1.

1b5 marks

Explain the effect of IAA on shoot growth at a concentration of 1 part per million in Fig.1.

1c2 marks

Describe how the effect of IAA on plant roots differs from its effect on plant shoots as shown in Fig.1

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2a3 marks

Fig. 1 shows a drawing of a barley seed.

15-2-fig-4-1
Fig. 1

Identify structures A-C in Fig.1.

2b
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2 marks

Fig. 2 shows the effect of increasing gibberellin concentration on the percentage of barley seeds that germinate. The smaller bars show standard deviations.

15-2-fig-4-2
Fig. 2

Calculate the percentage increase in the seeds germinated at a gibberellin concentration of 100 parts per million in comparison to the seeds germinated at 50 parts per million.

2c2 marks

A student viewed Fig. 2 and concluded that adding gibberellin increases barley seed germination.

Using only information from Fig. 2, evaluate the student's conclusion.

2d5 marks

Explain the results shown in Fig. 2.

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3a
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4 marks

Fig. 1 shows part of a cell in a growing region of a plant.

fig1-1-qp-mayjune-2019-9700-41

Fig. 1

(i)

State the type of protein represented by A.

[1]

(ii)

Proteins B, C and D are transport proteins.

Identify proteins B, C and D.

[3]

3b
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3 marks

Describe the effects on the cell wall of many hydrogen ions moving into the cell wall.

3c
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2 marks

Explain the consequences of an influx of potassium ions into the cell.

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1a
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4 marks

Fig. 1 shows an image of a Venus flytrap plant.


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Image courtesy of Noel Elhardt. Licensed under Creative Commons Attribution-Share Alike 2.5 Generic license. Reused and distributed under conditions found at https://creativecommons.org/licenses/by-sa/2.5/deed.en 

Fig. 1

(i)
Identify two features visible in Fig. 1 that enables the Venus flytrap to gain nitrogen compounds.

[2]

(ii)
Explain one other feature that is not visible in Fig. 1 that aids the plant in the same process.
[2]
1b
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4 marks

Some researchers measured the release of calcium ions into groups of cells in the leaves of a Venus flytrap when the leaves were stimulated by movement. Some of their results are shown in Fig. 2.

15-2-fig-1-2
Fig. 2

(i)

State what happens at threshold A in Fig. 2

[1]

(ii)

Explain what causes the event stated in part i).

[3]

1c
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3 marks

Fig. 2 shows that when threshold B is reached there is a change in gene expression in the plant.

(i)

Suggest which genes are expressed at threshold B.

[1]

(ii)

Suggest the benefit to the plant of not changing gene expression until a second threshold is reached.

[2]

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2a
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2 marks

Electrical activity occurs in living organisms as the result of the movement of charged particles, or ions, across cell membranes. The reversal of electrical charge across a cell membrane is known as depolarisation.

Outline how the cell surface membrane of an animal neurone is depolarised.

2b
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4 marks

Plant cells can also be depolarised. The cells of the sensitive Mimosa plant, Mimosa pudica, can become depolarised in response to a touch stimulus. Fig. 2.1 shows the first two stages of depolarisation in M. pudica.

15-2-fig-2-1Fig. 1

(i)

Suggest how the cells of M. pudica become depolarised in the next stage of the process shown in Fig. 1.

[2]

(ii)

Suggest how the cells of M. pudica might become repolarised to return to a resting state.

[2]

2c
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2 marks

Touch stimulation of the leaves of M. pudica leads to the sequence of events shown in Fig. 1 and results in the physiological response shown in Fig. 2.

15-2-fig-2-2Fig. 2

The response shown in Fig. 2 comes about due to a reduction in cell volume of certain stem and leaf cells.

Suggest how the process described in part b) could lead to a reduction in leaf volume.

2d
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2 marks

Suggest the advantage to M. pudica of the response shown in Fig. 2.

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3a
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2 marks

Plant roots are particularly sensitive to the effects of auxin (IAA). Fig. 1 shows the results of an investigation that was done to determine the effect of increasing auxin concentration on the growth of young roots.

q2a_9-3_growth_in_plants_medium_ib_hl_biology_sq

Fig. 1

Calculate the difference in the root growth per hour between the roots that were not exposed to auxins and those exposed to an auxin concentration of 1.0 µM.

Show your working.

3b
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3 marks

A pot plant was accidentally knocked over.

Based on the information in Fig. 1, suggest and explain how the growth of the root could be affected by this.

3c
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1 mark

An investigation was carried out to determine the effect of increasing auxin (IAA) concentration on the growth of plant shoots. Fig. 2 shows the results of this investigation. The investigation was then repeated with shoots that were treated with a respiratory inhibitor.

picture2

Fig. 2

Use the axes in Fig. 2 to sketch a graph of the plant growth that would be observed in the shoots treated with the respiratory inhibitor.

3d
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3 marks

Suggest a reason for your answer at part (c).

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