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.
In this Ecology section there are two required practical activities:
- Required Practical Activity 9 - Measure the population size of a common species in a habitat. Use sampling techniques to investigate the effect of a factor on the distribution of this species.
- Required Practical Activity 10 - Investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change.
There will be a number of different types of practical based questions. Some will be on the set required practicals, some will cover the working scientifically terms and some will be on other science practicals which you might have done in class. Use all the information given in the question particularly any diagrams to help you understand what the question is about.
These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.
Sample question 1 - Foundation
Question
Two students are investigating the effect of temperature on the rate of decay of fresh milk by measuring pH change.
What safety precautions should they take? [2 marks]
They should wear safety googles and tie their hair back if it is long. They should work standing up and wash their hands after the experiment is finished. Decayed milk presents a biohazard due to increased numbers of bacteria present, so there should be no eating or drinking allowed in the room. Temperatures should be chosen for this investigation that reduce risk, and water baths, preferably electrically controlled, should be used in preference to naked flames.
Sample question 2 - Foundation
Question
Describe the method you would use to determine if there are more species of plant on the school field rather than in woodland. [6 marks]
Marks will be awarded when referencing these points:
- choose a starting point on the school field and use random numbers to generate a set of coordinates to place your first quadrat
- count the number of different plant species within this quadrat (the species richness)
- return to your starting position and repeat steps two and three a further 14 times using different random numbers.
- repeat steps one to four for a woodland
- compare your results by calculating a mean for each location
- explain that the number of quadrats used should be representative of the size of the area being studied
It is important when answering six-mark questions that you plan your answer and use good English to explain your points in a logical manner. Marks are awarded for your level of response as well as the number of points you make.
Sample question 3 - Higher
Two students visited two locations and counted the number of lichens on nine trees in each place.
They cut out 20 cm squares of acetate sheet to use as quadrats, which they attached to the bark of the tree trunk using adhesive tape. They then counted how many separate lichens they could see in each of their quadrats. Their results are below.
| Sample 1 | Sample 2 | Sample 3 | Sample 4 | Sample 5 | Sample 6 | Sample 7 | Sample 8 | Sample 9 | |
| London | 4 | 6 | 11 | 13 | 4 | 2 | 6 | 2 | 4 |
| North Wales | 21 | 13 | 18 | 7 | 16 | 2 | 5 | 19 | 15 |
| London | |
|---|---|
| Sample 1 | 4 |
| Sample 2 | 6 |
| Sample 3 | 11 |
| Sample 4 | 13 |
| Sample 5 | 4 |
| Sample 6 | 2 |
| Sample 7 | 6 |
| Sample 8 | 2 |
| Sample 9 | 4 |
| North Wales | |
|---|---|
| Sample 1 | 21 |
| Sample 2 | 13 |
| Sample 3 | 18 |
| Sample 4 | 7 |
| Sample 5 | 16 |
| Sample 6 | 2 |
| Sample 7 | 5 |
| Sample 8 | 19 |
| Sample 9 | 15 |
Question
Calculate the mean number of lichens per tree for each location. Give your answer to one decimal place. [2 marks]
London 5.8 and North Wales 12.9
Question
One of the students said “This definitely proves that there are more lichens growing on trees in North Wales than London.”
Suggest why the second student might not have been so sure. [2 marks]
They have only looked at nine trees in one location in North Wales and London. They would need to sample many more trees in many different locations to definitely prove anything.
Question
Suggest two things they should have considered when deciding how to sample the lichens. [2 marks]
Marks will be given from any of the following comments:
- species of tree chosen - they should choose the same species in each location
- position of quadrat - it should be a similar height above the ground in each case
- direction of quadrat - the same compass direction should be chosen as lichen growth is influenced by the prevailing wind and the direction of the Sun.
- size of quadrat - was the quadrat the correct size to provide a representative sample?
Sample question 4 - Higher
Question
Describe the method you would use to investigate the effect of containers made of different materials on the rate of decay of fresh milk by measuring pH change. [6 marks]
- Place 20 cm of fresh milk into each of three different containers made of materials, such as glass, polythene and porcelain.
- Heat the containers of milk to the same temperature (for example 20°C) and maintain at this temperature for the duration of the experiment.
- Use universal indicator paper or solution to determine the pH of the milk in the three containers.
- Cover each beaker in clingfilm and incubate.
- Use universal indicator paper or solution to determine the pH of the milk in the three containers after 24, 48 and 72 hours.
