Paper 2

What is the practical for investigating the effect of light intensity of the rate of photosynthesis?

1. Place pond weed at different distances from light bulb

2. Add sodium carbonate to provide carbon dioxide

3. Count the number of bubbles produced in a set time

4. Calculate the rate of photosynthesis

What are the variables in the practical for investigating the effect of light intensity of the rate of photosynthesis?

• Independent variable: distance of plant from the light bulb

• Dependent variable: the number of bubbles produced

• Control variable: temperature (LED bulb + less heat), carbon dioxide availability, species of plant, size of plant

What is the practical for investigating the rate of respiration in living organisms?

• The apparatus consists of two tubes, one containing the living organisms and the other with glass beads to act as a control.

• Both tubes contain an alkali such as sodium hydroxide to absorb any carbon dioxide given off during respiration. This ensures that any volume changes measured in the experiment are due to oxygen uptake only.

• Once the apparatus has been set up, the movement of the coloured liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration.

• The reduction of volume in the tube increases pressure causing the coloured liquid to move.

• The distance moved by the liquid in a given time is measured will provide the volume of oxygen taken in by the insect per minute.

• Volume is given by volume of a cylinder. The unit of rate of respiration is cm³/min.

To investigate temperature the experiment is repeated at different temperatures, eg 10, 15, 20, 25, 30°C.

What is the practical for investigating the relationship between organisms and their environment? (to measure distribution)

1. Lay a tape measure in the area to be sampled

2. Place quadrats at equal intervals e.g. every 2 meters, on the same side of the transect line

3. Count how many of the species are in each quadrat

4. Repeat using 3 transect lines parallel to the original transect

5. Calculate the mean number of species at each location

What is the practical for investigating the relationship between organisms and their environment? (to measure abundance)

1. Place 1m² quadrat randomly (prevents bias)

   How? Make a grid by laying 2 tape measures at a right angle and use a computer to generate random coordinates

2. Count number of daisies inside the quadrat

3. Repeat 10 times

4. Calculate the estimated population size

   Add both equations