An interesting recent development is a growing awareness of bacteria. It’s now realized that the total biomass of bacteria on earth far outweighs all animals, plants, and other complex living beings put together. A recent claim is that “there are 10 times as many bacterial cells in a typical human body as there are human cells.” If we don’t count blood and bone (about 20% of your mass) estimate the fraction of your mass that is bacterial and not “you”. (A set of approximate biological scales is shown below.) Be sure to clearly state your assumptions and how you came to the numbers you estimated, since grading on this problem will be mostly based on your reasoning, not on your answer.

Joe Redish 8/31/12