Bacteria was one of the first life forms on
Earth. They are single-celled microorganisms
(that means really small living things) that
either live by itself (get its own food, move
around on its own) or as a parasite (is dependent
on another living thing to stay alive).
A virus is a microorganism (even smaller than a
bacteria) that cannot grow or live outside another
living cell. Viruses invade living cells and uses
all the cell’s resources (food, energy). Viruses
also cannot reproduce (they make clones or copies
of themselves). The viruses keep making more and
more copies until the cell that was invaded
bursts. Then the copied viruses go out and try
and find a new cell to invade.
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