cpac 16

• Required Practical 16 (a and b)

  Investigate the effect of one abiotic factor on the distribution or morphology of one species
• Practical 16a: Investigate the effect of one abiotic factor on the distribution of one species

  1. Choose an area with a clear gradient of light intensity

  2. Lay a 20m tape measure from the open area to the shaded area

  3. Pick a plant species that clearly changes in number along the line

  4. Lay the quadrat next to the 0m mark of the tape

  5. Measure the light intensity at ground level

  6. Record the abundance of the chosen species

  7. Move the quadrat 2m along the tape and repeat

  8. Continue until you have 10 measurements along the transect

  9. Take 2 more transects and repeat to have repeats
• Considerations for Practical 16a

  • Take the readings close together in time to ensure that light intensity does not vary much
  • Using an interrupted transect is quicker and can be used to measure a greater distance
  • Instead of recording abundance through counting the number of the species, we can also estimate percentage coverage
• Risk assessment for Practical 16a

  • Be careful when handling quadrats and ensure that they are not thrown
  • Cover cuts and wash hands after fieldwork
  • Use sunscreen if working in high UV areas
  • Do not enter water and ensure that you can be seen by others
  • Wear gloves if working with nettles
  • Inform teacher of any allergic reaction from pollen
• Conclusion for Practical 16a
• Practical 16b: Investigate the effect of one abiotic factor on the morphology of one species


  1. Plan a suitable title and do background research

  2. Form a hypothesis and write hypothesis and null hypothesis

  3. Create a step-by-step plan for the investigation

  4. Consider the variables that need to be controlled

  5. Decide which statistical tests to use

  6. Write an equipment list and check with teacher

  7. Carry out a risk assessment

  8. Carry out the investigation and record results in a table
• Analysis of results for Practical 16b

  1. Draw a graph of results

  2. Carry out an appropriate statistical test (t-test or test for correlation)

  3. Write a conclusion explaining the results

  4. Evaluate the investigation - comment on reliability and validity of data, explain any anomalies, give values for the uncertainty of key measurements

  5. Write a reference list for the research sources
• Considerations for Practical 16b

  • Check whether the research sources have any commercial interests that could create bias, whether the authors have published elsewhere, and whether the publication is widely cited
  • Include how you will avoid bias when choosing your samples
  • Understand the difference between risk and hazard
• Example topics for Practical 16b

  • The effect of light intensity on the morphology of plants
  • The effect of height on the shore or wave exposure on the morphology of rocky shore organisms
  • Mineral ion availability and morphology of seedling growth