quadrats

• • the distribution of an organism is where an organism is found
  • the distribution of an organism is affected by environmental factors
  • distribution can be studied by measuring how common an organism is in two sample areas and compare them
  • this is done by using quadrats
• • the mean is calculated by:
  • total number of organisms/number of quadrats
• to work out the population size of an organism in one area:

  • work out the mean number of organisms per quadrat
  • multiply the mean by the total area of the habitat
• • systematic sampling can be used if there is a trend or pattern across the habitat
• • percentage cover can be calculated to count all individual organisms in a quadrat

  1. count the number of squares covered by organism A and make this a percentage
  2. repeat step 1 for organism B
• method:

  1. measure length and width of field with tape measure and calculate area of field
  2. divide field into grid
  3. use random number generator to select 10 random coordinates to avoid bias
  4. place 1m x 1m quadrat at each coordinate
  5. calculate mean number of plants per quadrat
  6. multiply area of quadrat by mean number of plants
  7. multiply answer from step 6 by area of field