Why are anaerobic organisms simple and aerobic organisms complex?

[William Tivol]

Joy Abramson (ad954 at torfree.net) wrote:
: Why are anaerobic organisms limited to being simple, small, and 
: unicellular while aerobic organisms may be large complex, and 
: multicellular?

Dear Joy,
	My guess is that anaerobes extract only about 5% of the useful energy
from food compared to aerobes.
				Yours,
				Bill Tivol