Practical: Investigating Light & Photosynthesis Flashcards
All 6 cards in this deck
In the core practical, how is the rate of photosynthesis measured using pondweed?
By counting the number of oxygen bubbles released per minute (or measuring the volume of gas collected).
What are the steps to investigate the effect of light intensity on photosynthesis using pondweed?
e.g. lamp placed at 10, 20, 30 cm
- Place pondweed in sodium hydrogencarbonate solution and set the lamp at the first distance, e.g. 10 cm
- Leave to acclimatise, then count oxygen bubbles per minute
- Repeat at each distance, keeping temperature and the same, and calculate means
Which variables must be controlled in the light intensity and photosynthesis core practical?
Temperature, carbon dioxide concentration, and the species/mass of plant used.
Why is a heat shield (glass tank of water) used between the lamp and the plant in this core practical?
To absorb heat from the lamp so temperature stays constant and does not act as a variable.
How do you calculate the rate of photosynthesis from a bubble count?
e.g. 30 bubbles counted in 2 minutes
Divide the number of bubbles by the time: bubbles per minute.
True or false? Counting bubbles is a less reliable measure of photosynthesis than measuring the volume of gas.
True. Bubbles vary in size and are easily miscounted.