SAMPLING ORGANISMS

• Measuring population size of a common species in a habitat

  1. Use random sampling with quadrats

  2. Place two 20m tape measures at right angles

  3. Select random numbers to determine quadrat placement

  4. Count number of organisms in each quadrat

  5. Estimate total population using formula
• Using sampling techniques to investigate effect of a factor on species distribution


  1. Place transect line from tree outwards

  2. Use quadrats to count organisms at intervals along transect

  3. Measure light intensity at each quadrat

  4. Observe relationship between light intensity and organism count
• Quadrats

  • Come in a range of sizes
  • Used to sample a known area
• Random sampling


  Using random numbers to determine quadrat placement
• Estimating total population size = (Total area / Area sampled) x Number of organisms counted
• Increasing number of quadrats improves accuracy of population estimate
• Factors affecting species distribution include light intensity and soil resources
• Transect line used to observe changes in species distribution with distance from tree
• Light meter or app used to measure light intensity