Sampling Organisms (Quadrats)

• What should you be able to describe by the end of the video?

  How to measure population size
• What is the purpose of using sampling techniques in this context?

  To investigate the effect of a factor on distribution
• What is the first step in estimating the total population of daisies?

  • Use random sampling
  • Employ a quadrat
  • Count daisies in sampled areas
• What size quadrat is used in the practical?

  0.5 meters by 0.5 meters
• How are the tape measures positioned for sampling?

  At right angles to each other
• What is the length of each tape measure used in the practical?

  20 meters
• What is the process for selecting random sampling points?

  Students draw numbers from a bag
• How many samples should students collect in total?

  Ten samples
• What is the equation to estimate the total population size?

  Total population size = (total area / area sampled) * number counted
• What is the total area of the field in square meters?

  $400 \text{ m}^2$
• What is the area sampled when using the quadrat?

  $2.5 \text{ m}^2$
• How many daisies were counted across the ten quadrats?

  300 daisies
• What is the estimated total population of daisies in the field?

  48,000 daisies
• Why is the population estimate considered an estimate?

  Sampling may not represent the whole area
• What should be done if the quadrat throws do not represent the area?

  Increase the number of quadrat throws
• What is the method to measure the effect of light intensity on daisies?

  1. Use a transect line
  2. Place a tape measure from the tree
  3. Count daisies and record light intensity
  4. Move the quadrat along the transect
  5. Repeat measurements at intervals
• What tool can be used to measure light intensity?

  A light meter or an app
• Why might there be fewer daisies under the tree?

  Lower light intensity affects growth
• What other abiotic factor might affect the number of daisies?

  Water and minerals from the soil
• What should students do to prepare for the required practical?

  • Review questions in the workbook
  • Understand sampling techniques
  • Familiarize with equipment used