Random sampling

• What is the aim for the required practical - measuring population size in a habitat

  To measure the species richness on the school field in areas in which the grass is regularly and irregularly cut.
• What is the first step of the measuring population practical?

  • choose a starting point on the school field in an area where the grass is often cut.
• What is step 2 of the measuring population practical?

  • use random numbers to generate a set of coordinates to place your first quadrat
• What is a quadrat?

  a square frame of known area used for sampling the abundance and distribution of slow or non-moving organisms.
• What is step 3 of the measuring population practical?

  • count the number of different plant species within this quadrat (the species richness)
• What is step 4 of the measuring population practical?

  • return to your starting position and repeat steps two and three a further 14 times using different random numbers
• What is step 5 of the measuring population practical?

  repeat steps one to four for a part of the school field which the grass is infrequently cut
• what is step 6 (the final step) of the measuring population practical?


  • compare your results by calculating a mean for each location
• What is the conclusion of the measuring population practical?

  The mean of the number of plant species in the cut school field is lower than on the uncut school field. Therefore, there is greater species richness on the school field in uncut areas.
• What limitations might there be in drawing these conclusions?

  the two students only placed 15 quadrats. completing more would allow them to be more confident in their conclusions.