Investigating photosynthesis and respiration using a carbon dioxide probe

This resource tackles the learning objective “We can observe the change in carbon dioxide uptake with different environmental conditions”. This is activity 7 in the ‘Photosynthesis: A Survival Guide” scheme.

For schools with a carbon dioxide probe and a datalogger, this resource outlines a lesson plan making use of it to look at the different amounts of carbon dioxide detected as students enter the room, when a Bunsen burner is lit and when placed beside a plant in the dark or the light.

For those without access to this equipment, the accompanying student sheet and Powerpoint gives an example graph that can be used for discussion and analysis.

The activity can also be used to tackle a common misconception regarding respiration. Many pupils believe that plants do not respire or at the very least, they only respire at night. It is important that they understand that respiration is a process fundamental to life and all living things respire all the time. In bright light the net effect of this is that plants take in carbon dioxide and release oxygen. This does not mean that respiration is not taking place but the net effect is that the effects of photosynthesis are masking the effects of respiration.

It should be stressed that the increase in the human population and the burning of fossil fuels as well as deforestation means that we are now putting carbon dioxide back into the air faster than plants can take it in again. This is leading to a build up of carbon dioxide which contributes to global warming.

This resource is designed for 11-14 pupils but could be extended for use with older students as appropriate.