Biology Experiments - help!

Can anybody describe rough procedures for any of the following experiments?

1) Measuring the effects of temp/CO2/02 conc. on the rate of photosynthesis (i was told you could measure gas or use a photosynthometer????!!!)

2) Control of growth of plants (i.e. effects of auxins)

3) Breeding experiments (I have no idea! - guess this means investigating inheritance and working out genotypic ratios???!)

This is for the W2 edexcel exam 2moz and I have no notes on any of these. We are required to plan an experiment, and one of them could be these. If possible, a plan of the main points you need to keep in mind when planning would be ace!

Reply 1

812

For the first one you can measure the gas evolved using a syringe, which gives a general indication of the rate of photsynthesis. You put a plant or whatever in some watr in a test tube and put a bung over the top with a tube going out of it, so it is sealed apart from through the tube. The other end of the tube should be attached to a graduated syringe (i.e. with measurements), and as the gas is given out by the plant it will fill the syringe, so you can see the exact amount produced.
I'm not sure how you would vary the temperature, unless you use a heater. You vary the carbon dioxide by adding different concentrations of sodium hydrogencarbonate, which provides CO2, into the test tube before you seal it (e.g. 0.1, 0.2, 0.3%).

That's pretty rough, sorry I can't go into more detail but I'm in kind of a rush because of this crappy exam as well. If you have the Nelson Thorne book "Genetics, Evolution and Biodiversity", it's in there.