paper 2 practicals

• practical on investigating reaction time?

  1. person should be sat with their arm resting on the edge of the table to prevent movement
  2. Hold a ruler vertically between their thumb and forefinger so that the zero end is level with their thumb and finger
  3. let go without any warning to prevent predictability
  4. the number is read on the top of the thumb, the lower its caught down the slower their reaction time
  5. repeat and calculate mean, then repeat 10 minutes after taking a caffienated drink
  6. same: hand, person, height
• practical on investigating plant growth responses?

  effect of light..

  • put 10 cress seeds into three different dishes labelled A B and C each lined with moist filter paper
  • shine a light onto one of the dishes from above, two of the dishes from different directions
  • leave for a week and observe that they grow towards the light due to phototropism
  • control : number and type of seeds, temp , water and light
  • gravitropism by placing seeds on damp cotton wool with roots pointing in different directions in the dark- grow downwards
• practical on using quadrats to study the distribution of small organisms?

  • a quadrat is a square frame enclosing a known area 1m^2
  • place a 1m2 quadrat on the ground at a random point within the first sample area by dividing the area into a grid and use a random number generator to pick coordinates
  • count all the organisms within a quadrat
  • repeat steps 1 and 2 as many times as you can
  • work out the mean TOTAL N of organism / N of quadrats
  • repeat in second sample area and compare means
• a practical on using transects?

  you use transects to help find how common an organisms distribution is across an area

  1. mark out a line in the area you want to study using a tape measure
  2. collect data along the line
  3. you can do this by counting all the organisms youre interested in that touch the line
  4. or you can place quadrats next to each other or at intervals
• practical on investigating the effect of temperature on the rate of decay by the eznyme lipase?

  1. measure 5cm3 lipase and add it to a test tube labelled L
  2. measure 5cm using MC of milk and add to a differert test tube followed by 5 drops of phenolpthalein
  3. then add 7cm3 sodium carbonate into the milk and p test tube , makes milk alkaline so should turn pink
  4. put both tubes in a water bath at 30c and leave until reaches using thermometer, use calibrated dropping pipette add 1cm3 lipase into milk and start stopwatch then stir to decompose
  5. repeat with different temperatures 3x and calc mean/rate