Sampling Organisms

• 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 method is used to estimate the total population of daisies?

  • Random sampling
  • Use of quadrats
  • Counting daisies in samples
• What is the size of the quadrat used in the practical?

  0.5 meters by 0.5 meters
• How do students select random sampling points in the field?

  By drawing numbers from a bag
• If a student draws the number 8, where do they place the quadrat?

  At the 8 meter point on one tape measure
• How many samples do students take in total?

  Ten samples
• How do you calculate the area sampled using quadrats?

  Area sampled = $0.5 \times 0.5 \times 10$
• What is the total area of the field being sampled?

  400 square meters
• What was the number of daisies counted in the sample?

  300 daisies
• What is the equation to estimate the total population size?

  Total population size = $\frac{total area}{area sampled} \times number of organisms$
• Why is the total population size an estimate?

  Sampling may not represent the whole area
• What should you do if you suspect uneven distribution of daisies?

  Increase the number of quadrat throws
• What is the effect of light intensity on the distribution of daisies?

  • Light intensity affects photosynthesis
  • Daisies may be fewer under trees
  • Measure light intensity with a light meter
• What tool is used to measure light intensity?

  A light meter
• How do you conduct a transect line for measuring daisies?

  Place a tape measure from the tree outward
• What happens to the number of daisies as you move away from the tree?

  It may increase due to higher light intensity
• What other factors might affect the number of daisies besides light intensity?

  Water and minerals absorption by the tree
• What should students be aware of regarding the required practical?

  • Potential questions in the workbook
  • Importance of understanding sampling techniques
  • Need for accurate measurements