Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.

Part of

You will complete 21 required practical activities if you are studying GCSE combined science: Trilogy. You could be asked questions about the apparatus, methods, safety precautions, results, analysis and evaluation of these experiments.

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.

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.

*These questions have been written by a Bitesize consultant as a suggestion to the type of questions that may appear in an exam paper.*

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

Location | Tree 1 | Tree 2 | Tree 3 | Tree 4 | Tree 5 | Tree 6 | Tree 7 | Tree 8 | Tree 9 |
---|---|---|---|---|---|---|---|---|---|

London | 4 | 6 | 11 | 13 | 4 | 2 | 6 | 2 | 4 |

North Wales | 21 | 13 | 18 | 7 | 16 | 2 | 5 | 19 | 15 |

- 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.

- 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.

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 |

- 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?