Biology Question #2220

Leah W., a 14 year old female from Duluth asks on August 24, 2004,

What is the smallest living thing? What is the largest living thing?

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The answer

Barry Shell answered on August 24, 2004

It depends on how you define living. Mycoplasma genitalium is the smallest known organism capable of independent growth and reproduction. Viruses are smaller, but require a host to "live" and reproduce. Even smaller than a virus is a prion, but this is just a protein bent in a certain way, and not really living. For an exhaustive and detailed answer look at Mike Conrad's answer at the Mad Scientists Network.

For the biggest living thing, again it depends on your definition. The blue whale or the giant redwood are the biggest living things, but there is also this fungus that lives in the roots of trees called armillaria ostoyae. It grows underground and one can be over 5 kilometers in size (3 miles). Find out more at the American Society of Microbiology.

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