investigating abundance and distribution

• Abundance and distribution

  • Abundance refers to how many organisms there are.
  • Distribution refers to where the organisms are.
• sampling

  •  they only measure a subset of the organisms, and use that subset to make predictions about the whole population. 
• 2 sampling methods

  1. Transects - to measure how distribution change
  2. Quadrats - to measure abundance
• quadrat

  Square frames, that have been subdivided into lots of smaller squares.

  • We can use them to sample a habitat and estimate the size of a population.
• using quadrats to estimate dandelion numbers

  Describe how you might use a 1m x 1m quadrat to estimate the number of dandelions in a 100m x 100m field.

  1. Place multiple tape measures along the length and width of the field, forming a large grid.
  2. Use a random number generator to generate 10 pairs of random coordinates.
  3. Place quadrats at those coordinates and count how many dandelions are found in each quadrat.
  4. Calculate the mean number of dandelions per m2.
  5. Estimate the total population size using our mean number of dandelions per m2 and the total area of the field.
• transects

  used to observe and record changes in species distribution across an area.
• Using transects to study the distribution of dandelions in an open field stretching from a lake to a woodland

  1. Tape measure is laid out in a straight line between the lake and woodland
  2. Quadrats are placed at regular intervals along the transect line. 
  3. The abundance of dandelions is measured by counting the number of dandelions in each quadrat along the transect line, from the lake to the woodland.
  4. Steps 1-3 are repeated using new transect lines (these must be parallel to the first). By using multiple transect lines, the data gathered is more representative of the area.