Plant structures and functions - One- to four-mark questions

One- to four-mark questions will start with command words such as 'describe' or 'explain'. Some command words are easy to understand such as:

• 'calculate' or 'determine' for maths questions
• 'complete' to fill in a gap in a table or graph
• 'define' to give the meaning of an important word
• 'suggest' where you use your knowledge in an unfamiliar situation
• 'compare' where you describe the similarities and/or differences between things

The command words 'describe' and 'explain' can be confusing. If you are asked to describe a graph, you will be expected to write about its overall shape, whether it is linear or curved, the slope of gradients etc. If you are asked to explain why a pattern or trend is seen in a graph, you will be expected to use your science knowledge, not just say what you see (which is a description), eg the graph shows a steep linear increase for the first three hours because...

'Explain how and why' questions often have the word 'because' in their answer. 'Describe' questions don't.

The number of marks per question part is given in this form '[2 marks]'. It is essential that you give two different answers if a question is worth two marks. Sometimes you can gain a second mark by giving the units in a calculation or stating specific data points, eg during the first two years the number of lions decreased by seven.

You will be expected to write in more depth for three- and four-mark questions. They might ask you about a process such as the carbon cycle or the method you would use in an experiment.

Edexcel questions courtesy of Pearson Education Ltd.

Sample question 1 - Foundation

Question

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

[1] for an explanation that combines identification - understanding and [1] for reasoning/justification - understanding, eg:

• transpiration rate is increased [1]
• because water molecules have more energy/move faster [1]

Sample question 2 - Higher

Question

Define both translocation and transpiration. Include the names of vessels involved in your answer. [2 marks]

Transpiration is the movement of water through xylem vessels from plant roots to their leaves for photosynthesis [1]. Translocation is the movement of sugar (dissolved in water) made in photosynthesis through phloem vessels to all cells of a plant [1].

Sample question 3 - Higher

Question

Describe the conditions that increase the rate of transpiration. [4 marks]

• low humidity [1]
• higher wind [1]
• higher temperature [1]
• more light intensity [1]

Sample question 4 - Higher

Question

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]

[1] for an explanation that combines identification - improvement of the experimental procedure and [1] for justification/reasoning, which must be linked to the improvement, eg:

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

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