plant structures and their functions sample exam questions and answers

Question 1

What structure transports water through the stem of the plant?

Answer 1

Xylem

Question 2

Explain the effect of increasing air temperature on the rate of transpiration in a plant. [2 marks]

Answer 2

An explanation that combines identification - understanding (1 mark) and reasoning/justification - understanding (1 mark):

• transpiration rate is increased (1 mark)
• because water molecules have more energy/move faster (1 mark)

Question 3

The student wanted to find out where the hormone that caused the response to directional light was found.

The student had two growing plant shoots and placed them both in a window with light coming from one direction.

Describe a method the student could use to show that the hormone was found in the tip of the plant shoot. [2 marks]

Answer 3

An answer that combines the following points to provide a logical description of the method:

• remove the tip from one of the plant shoots and leave the other (1 mark)
• measure the changes in growth and direction of movement (1 mark)

Question 4

A class was asked to measure the volume of oxygen produced by a water plant called Cabomba in one minute.

One student decided to count the number of bubbles.

Explain the student could improve the method in order to measure the volume of oxygen released more accurately. [2 marks]

Answer 4

An explanation that combines identification - improvement of the experimental procedure (1 mark) and justification/reasoning which must be linked to the improvement (1 mark):

• collect the oxygen produced in a graduated gas syringe (1 mark)
• to reduce the errors generated when counting bubbles which maybe of different sizes (1 mark)

Will accept alternative gas collection method with measuring cylinder and beehive shelf and will accept leave the apparatus for a longer amount of time.

Question 5

The student noticed that the temperature of water near the light increased.

Give one improvement they could make to reduce the effect of this increase in temperature. [1 mark]

Answer 5

Any one improvement from:

• use a lower energy/LED bulb (1 mark)
• use a heat shield (1 mark)
• place the test tube in a beaker of water (1 mark)

Question 6

Explain what would happen to the levels of gas produced if the light intensity decreased to 0.0001 arbitrary units. [2 marks]

Answer 6

An explanation that combines identification via a judgement (1 mark) to reach a conclusion via justification/reasoning (1 mark):

• the volume of gas produced would decrease to below four bubbles (1 mark)
• because light is needed for photosynthesis (1 mark)

Question 7

A gardener grew 20 carrot plants in his garden.

Ten plants were grown under a clear plastic cover.

Ten plants were grown without a clear plastic cover.

Explain why it is important that the clear plastic cover is transparent. [2 marks]

Answer 7

An explanation linking the following points:

• plants need light (1 mark)
• for photosynthesis (1 mark)

Question 8

Carbon dioxide moves into the leaves through the parts labelled X by the process of …………………………….[1 mark]

Answer 8

Diffusion

Question 9

Explain how changes to the guard cells on the warm day help the plant to survive. [2 marks]

Answer 9

Guard cells change shape/(guard cells) close stomata/guard cells close (1 mark)

Accept ‘stop water loss/keep water in’ to reduce water loss /rate of transpiration reduced (1 mark)

Ignore ‘get more water’