Practical questions

You will complete ten required practical activities if you are studying GCSE Biology and twenty-one if you are studying GCSE Combined Science. You could be asked questions about the methods, safety precautions you might take, results and conclusions of these experiments.

Sample question 1 - Foundation

Lugworms (Arenicola marina) live in burrows in the sand on beaches. At one end of the burrow is a hole and at the other end is a mound of sand, called the cast, which the lugworm has removed from the burrow. Each burrow is occupied by one lugworm only.

Owen was asked by his teacher to estimate the number of lugworms, on a section of Whiteford Beach on Gower, by counting the number of casts. Owen decided to use 1 m2 quadrats to estimate the number of lugworms present in an area of the beach measuring 80 × 40 m.

These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.

Question

Which of the following methods would be the correct way for Owen to use the quadrats to sample the number of lugworms? [1 mark]

Tick (✓) the correct answer.

MethodTick (✓)
Place the quadrats where there are lots of casts
Place the quadrats randomly within the sample area
Place the quadrats carefully so as not to damage the casts

Place the quadrats randomly within the sample area [1]

Question

Owen counted the number of casts in 10 quadrat samples. The table below shows his results.

Quadrat numberNumber of casts
15
27
31
411
54
66
79
84
913
102
Mean

(i) Calculate the mean number of casts per quadrat. [1 mark]

(ii) Estimate the number of lugworms in the section of the beach using the following equation. [2 marks]

\text{number of lugworms} = \text{mean number of lugworms per quadrat} \times \text{area of section of beach}

(i) Mean = 6.2 [1]

(ii) Estimated number of lugworms = 6.2 × 3200 [1] = 19,840 [1]

HINT- In most calculation questions there is a mark available for writing out the equation used and then another for the answer. The correct answer will get both marks automatically but just in case a calculation error is made it is always good practice to write out the workings.

Question

Suggest why this sampling method would not be suitable for estimating the population of earthworms in an area of grassland. [1 mark]

Any one from:

  • Earthworms move
  • Earthworms may be hidden by the grass
  • It does not take into account earthworms that are under the soil

Sample question 2 - Foundation

Two students visited two locations and measured the number of lichens on nine trees in each location. Their results are below.

LocationTree 1Tree 2Tree 3Tree 4Tree 5Tree 6Tree 7Tree 8Tree 9
London46111342624
North Wales211318716251915
Question

Calculate the mean for each location. Give your answer to one decimal place. [2 marks]

London mean = 5.8

North Wales mean = 12.9

One of the students said "This definitely proves that there are more lichens in North Wales than London."

Question

Suggest why the second student might not have been so sure. [2 marks]

The have only looked at nine trees in one location in North Wales and London. They would need to sample many, many more trees in many different locations to prove anything.

Sample question 3 - Higher

Question

Describe the method used to investigate the effect of changing light intensity on the rate of photosynthesis. [6 marks]

Six from:

  1. Place a small piece of pondweed into a test tube of water.
  2. Place the test tube 10cm from a table lamp.
  3. Wait for three minutes for the pondweed to acclimatise.
  4. Count the number of bubbles of oxygen given off in one minute.
  5. Move the test tube a further 10cm from the table lamp.
  6. Repeat steps 3 and 4.
  7. Repeat for 30, 40, 50 and 60cm.

Sample heading 4 - Higher

In order to investigate how nitrogen is recycled by bacteria in soil, the apparatus shown in the diagram was kept at 25°C for two days.

At the start, the indicator paper in both tubes was yellow. After two days, the indicator paper in tube A was green but the indicator paper in tube B was still yellow.

Investigation showing how nitrogen is recycled by bacteria in soil

A word equation representing the reaction in tube A is:

\underset{\text{(from bacterial cytoplasm)}}{\text{urea + water}} \overset{\text{enzyme}}{\rightarrow} \text{ammonium carbonate}

Question

What can you conclude about the results obtained from tube A? [2 marks]

  • The bacteria produced an enzyme. [1]
  • The enzyme broke down urea into ammonium carbonate, which is an alkali between pH 8-11 [1]
Question

What can you conclude about the results obtained from tube B? [3 marks]

  • Burning the soil killed the bacteria [1]
  • Enzyme denatured, this means the active site is destroyed [1]
  • So contents remained neutral at pH 7 [1]