Our definition of the word "living" doesn't really
account for viruses. They tend to blur the lines.
Viruses don't contain within themselves all of
the information they need to replicate, unlike
living cells, which do. For this reason, we do not
consider viruses to be organisms in the sense that
you and I are.
However, viruses can reproduce with help, and
their ability to reproduce and the information
that distinguishes one virus from another behaves
in a very life-like way. Viruses can evolve by
natural selection, for example; this is why
disease-causing viruses eventually become
resistant to the drugs we use to fight them.
In reality, nature does not make such neat and
tidy distinctions between living and nonliving
that we like to identify, and viruses are an
example of something that makes our human-made
distinctions somewhat blurry. There are other
examples that I can think of, too: the cells in a
tree that make up its wood are not living cells,
but the tree itself certainly is alive, and
without the wood it would die, because it couldn't
get water up from the ground into the leaves where
it gets used. So is wood living or is it dead? I
could ask the same question about the crystals of
mineral that make up your bones and teeth, and so
Click Here to return to the search form.