Is a virus alive?

Dr E. Buxbaum EB15 at le.ac.uk
Wed Feb 19 10:40:29 EST 1997


ajh28 at pantheon.yale.edu (A J Harrington) wrote:

>ok, well, there are some orchids that can't reproduce without fungi, >they must not be alive either.


Orchid seeds contain very little food reserves for the growing plant.
Therefore the seedling is supported by symbiontic fungi until it has
grown leaves to do photosynthesis. Thes fungi then live from in part from
the sugar produced by the orchid. However, the orchid is able to
reproduce without the fungus on suitable substrates, and this is actually
done on a large scale by orchid breeders nowadays.


>And then what's to say that crystals aren't alive?  They reproduce,
>consume energy, all the good stuff that's listed in Intro Biology books.
>For that matter so does fire.  Why aren't they alive?

They do not reproduce. Crystalls grow under suitable conditions on any
seed available, like specks of dust or bumps on the vessel. They do not
require "parents", i.e. other crystals of the same species. They do not
have a metabolism, that is the conversion of one chemical into another
for the purpose of energy gain. Actually their growth liberates, rather
than consumes energy. Additionally, crystals do not show movement in
response to environmental stimulation.

>
>Face it, any definition of life is by nature arbitrary.  We decide >what's alive and what's not and then we try to come up with some rules >that include the things we think are alive and exclude everything else. >There are bound to be exceptions.
>
>A better question is, does it matter??

You can not have biology (literally: Science of life) without defining
what life (and for that matter, science) is. Such a definition has to be
practically usefull, which limits the degree of arbitrariness you are
allowed.




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