h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Thanks for that great entry!

Just a minor correction I think needs to be made: in the first sentence, it is said that "respiration - the process by which humans breathe - also occurs at night".

Respiration, however, occurs in plant cells all the time. However, due to photosynthesis at daytime, more oxygen is produced by photosynthesis than used by respiration - there is a net gain of oxygen. At night, photosynthesis does not take place so there is a net loss of oxygen.

Also, respiration (in a biological context) is not the process by which humans breathe. In all living cells of humans and plants, respiration constantly takes place. It is performed by the mitochondria (described in A519851) and releases energy that is stored in glucose.

I would suggest that the sentence be changed to "Plants take in carbon dioxide and 'excrete' oxygen while photosynthesis occurs." with a footnote saying, for instance, "Plant cells also continuously respire. This process uses up oxygen and releases carbon dioxide. During the daytime, this is not noticed as respiration uses less oxygen than photosynthesis releases. At night time, however, photosynthesis does not occur so there is a small net loss of oxygen."

Thanks!
RhoMuNuQ

Thanks RhoMuNuQ,

Done!

Anna

Thanks

I suddenly remembered posting this!

RhoMuNuQ