quadrats and transects prac

• The distribution of an organism is where an organism is found. This is effected by environmental factors - e.g. a shaded spot compared to a sunny one.
• The two ways to study the distribution of an organism:

  • measure how common an organism is in 2 sample areas using quadrats
  • study how distribution changes across an area using a transect line
• Quadrat


  A square frame enclosing a known area, e.g. 1 m²
• Using quadrats to study the distribution of small organisms


  1. Place a 1m quadrat on the ground at a random point within the first sample area

  2. Count all the organisms within the quadrat

  3. Repeat steps 1 and 2 as many times as you can

  4. Work out the mean number of organisms per quadrat within the first sample area

  5. Repeat steps 1 to 4 in the second sample area

  6. Compare the two means
• Mean number of organisms per quadrat

  Total number of organisms / Number of quadrats
• Estimating the population size of an organism in one area

  1. Work out the mean number of organisms per m²

  2. Multiply the mean by the total area (in m²) of the habitat
• Percentage cover


  Estimating the percentage area of the quadrat covered by a particular type of organism
• Transects can be used in any ecosystem, not just fields
• Using transects to study the distribution of organisms

  1. Lay a line in the area you want to study

  2. Collect data along the line by counting organisms or using quadrats placed at intervals