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Name: Michelle
Status: Student
Age: 15
Location: N/A
Country: N/A
Date: N/A 


Question:
What is the scientific name of the smallest organism??



Replies:
Dear Michelle,

Your question hits one of the fundamental questions of life: what is an organism? What do you define as necessary for life, what are the requirments to be an organism? Let's define an organism as a living thing that is able to live independent of other organisms, that has a metabolism, and that reproduces with offspring identical to the parent. I guess the smallest organisms would be bacteria. Bacteria differ in size but the lower limit of the length of the bacterial body would roughly be 1 micrometer (a thousand's of a milimeter). However, when you include organisms that live as parasites on, or in, others, then viruses are included, and these are much smaller than bacteria. It would be acceptable to include parasites, because parasitic life forms are also found with bigger organisms (bacteria, worms, etc).

There is no fundamental reason to exclude parasites as living organisms. Therefore, viruses can be included as organisms, thus, they are the smallest living organisms. They have a metabolism, they have DNA or RNA for reproduction (although they use the machinery of their involuntary host cells to do so), their offspring is identical to the parents. Does that satisfy your interpretation of a living organism?

Viruses are built of RNA (or DNA) wrapped in proteins. They have different shapes and sizes.

Your question exemplifies how scientific answers depend on precise definitions. You can train yourself to be specific in the question you want to ask. Then you design a hypothesis that can be tested.

This is not to say that science is narrow-minded. Once you have set your definitions and designed your hypothesis, you try to find the flaws. In the example above, I started with a definition (which included that organisms must live independently) and I tested if all organisms were included in that definition. Then I decided that parasites were incorrectly excluded, and I had to alter my definition. A scientist always tries to find the one observation that does not fit the hypothesis, and then examines if the observation is true, and thus if the hypothesis is not correct and in need of refinement.

You can question basically every hypothesis. When you do that, you enter the field of phylosophy. How do you define life, what is your definition of an organism? Can you come up with a hypothesis to test if your definition is correct? These are great things to think about, and excellent training for every scientist and scientist-to-be.

Have fun!
Trudy



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