RP: Sampling Organisms

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

  How to measure population size of a species
• What sampling techniques should you be able to describe?

  Techniques to investigate a factor's effect on distribution
• What is the first step in estimating the total population of daisies?

  Using random sampling
• What tool is used in random sampling to estimate population size?

  A quadrat
• What should be placed at right angles to each other in the field?

  Two tape measures
• How long should the tape measures be?

  20 meters
• What do the two bags contain for the random sampling?

  Numbers 1 to 20
• How many students typically work in each group for this practical?

  Three
• What does the first student do in the random sampling process?

  Removes a number from a bag
• After a number is removed from the bag, where does the first student move?

  To the meter point on a tape measure
• What does the second student do after the first student has moved?

  Selects a number from their bag
• What does the third student do with the quadrat?

  Places it at the coordinate point
• What should the students record in the quadrat?

  Number of daisies
• How many times do the students repeat the quadrat sampling process?

  Ten times
• What does the equation calculate?

  Total population size
• What does "total area" represent in the equation?

  Area of the entire field
• What does "area sampled" represent in the equation?

  Total area of all quadrats combined
• What does 'the number of organisms of that species counted in the sample' represent in the equation?

  Total number of daisies in all quadrats
• Given a field of 20m x 20m, what is the total area?

  400 square meters
• If a 0.5m x 0.5m quadrat is thrown 10 times, what is the area sampled?

  2.5 square meters
• Using the equation, what is the estimated total population size if total area is 400 square meters, area sampled is 2.5 square meters, and 300 daisies are counted?

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

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

  Increase the number of quadrat throws
• In this required practical, what factor's effect are we measuring on the distribution of a species?

  Light intensity
• What is used to see how the number of daisies changes from the tree outwards?

  A transect line
• Where is the tape measure placed when using a transect line?

  Up the tree
• What measurements are recorded at the start of the transect?

  Number of daisies and light intensity
• What tools can be used to record light intensity?

  A light meter or an app
• How is the quadrat moved down the tape measure?

  One meter at a time
• Why might there be fewer daisies under the tree?

  Lower light intensity
• Why do plants need light?

  To photosynthesize
• What other factor, besides light intensity, might affect the number of daisies near a tree?

  Water and mineral absorption
• Why does a tree affect water and mineral availability?

  It absorbs a lot from the soil