Practicals

• What is a reaction time?

  The time taken to respond to changes in the environment
• Describe how you would investigate how practice affect reaction times in humans

  • Work in partners. One partner places the forearm of their non-dominant hand on the table, with their hand hanging off the edge.

  • One partner should hold the ruler between the fingers of the other partner at the 0 mark.

  • The partner holding the ruler drops it without any warning, and the other partner should catch the ruler as quickly as possible.

  • Record the number level after the ruler has been caught - repeat at least 5 times per person.

  • Find reaction times using a conversion table.
• What other factors could you investigate in this experiment?

  The effect of caffeine or exercise on reaction times
• What safety precautions should be taken during this experiment?

  Avoid injury from falling ruler
• How would you use random sampling to estimate the population size of a plant species?

  • Create a grid of the area using tape measures

  • Use a random number generator to generate coordinates

  • Set down quadrat at coordinates and record number of required species within quadrat

  Repeat using many sampling sites

  • Estimate population size: area sampled / total area x number of plants species counted
• Why would you use a random number generator to determine coordinates?

  To avoid bias and obtain representative results
• What is random sampling?

  Sampling technique in which each sample has an equal probability of being chosen
• What is systematic sampling?

  Sampling technique where there is a fixed, periodic interval between consecutive samples
• Describe how you would use continuous sampling to investigate the effect of an abiotic factor in the distribution of a plant species

  • Create hypothesis on the effect of the change in an abiotic factor on the distribution of a plant species

  • Lay tape measure along an area with an ecological gradient

  • Place quadrat at start and count number of plants

  Repeat at 5m intervals along the transect

  • Record the value of the abiotic factor eg. light intensity at each sampling site

  • Produce a graph of plant numbers (y) against the abiotic factor (x)