Aquatic Photosynthesis of Elodea Leaves Lab
Design
Problem: What is the effect of temperature (warm, cool, room temperature) on the rate of photosynthesis in Elodea leaves measured by the levels of dissolved oxygen in the flask solutions?
Hypothesis: If temperature is related to the rate of photosynthesis (levels of dissolved oxygen) then increasing the temperate will increase the rate of photosynthesis up to an optimal temperature.
Variables:
Independent: temperature of the water bath which the Elodea plant is immersed in
Dependent: the rate of photosynthesis measured by the level of oxygen dissolved in the flask solution
Constants: Relative size of the Elodea leaf, relative surface area of the Elodea leaves, (around 3 cm each), volume of water in all beakers, amounts of light exposure to the plants, and type of light source.
Method:
Materials:
Light Source
Elodea. Keep this warm and illuminated before you use it,
3 small flasks,
10g/L sodium bicarbonate (NaHCO3) solution,
oxygen sensor
Lab Quest data logger.
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Overall this is a fairly poor piece of work. The student has completed the experiment and collected data, but has made a fundamental error of understanding and so drawn the wrong conclusions. This demonstrates how important it is to pay attention to what is actually being plotted on a graph. I would also expect an undergraduate to be able to elaborate on null and alternative hypotheses.In a first year practical this write up might get 2/5, as the demonstrators should have cleared up the misunderstanding.