One origin? (viral evolution)
kinman at HOTMAIL.COM
Thu Jul 19 16:09:10 CDT 2001
Viruses are almost certainly related to other forms of life. No doubt
in my mind, given their biochemistries. But whether to regard them as
"living" is an old philosophical problem that I won't get into.
Some think that all viruses are escaped genes (or pieces of genes), and
although most probably are, some viruses may be relicts of prebacterial
evolution. Either way, it is a polyphyletic group and should not be given
it's own Kingdom (as is sometimes done).
Still they need to be classified, so I classify viruses in a clearly
coded polyphyletic lower taxon at Class level (yes, a couple of those are
still necessary--- Class Deuteromycetea is another one). You can explicitly
call them "Form Classes" if that makes one more comfortable.
My classification of Kingdom Monera (prokaryotes), and viruses are
obviously prokaryotic, begins with Phylum Parabacteria to include all
viruses and "progenotes" (theoretical ancestral life forms)---in other words
all the nucleic acid entities that were interacting in the "primordial soup"
(some inside cells and others not). Viruses may have been among the arsenal
that even the earliest bacteria used against one another in the biochemical
warfare that is a part of life, as well as a means of genetic exchange.
Class Viralea is a polyphyletic (but useful) taxon for all viruses
whether they are one of the relicts of the primordial soup, RNA World, or
one the more complicated viruses that popped out of some higher organism's
genome much later.
My view is that viruses have been popping in and out of genomes (and
evolving along the way) since the very beginning of life, and that is why we
have such a large variety of different types. The interrelationships of the
various families and orders or viruses and viroids is still very, very
poorly understood. However, I do believe they should be a part of
classifications of life. But not as a separate Kingdom. As a polyphyletic
group, I decided to give them only Class status (although I wouldn't object
too strenuously to raising them to phylum status if virologists decided that
multiple Classes of viruses would be more useful).
P.S. I just read Tom's post, so will elaborate a little more. TMV (Tobacco
Mosaic Virus) probably has relatives which infect green algae, which in turn
probably have relatives which infect prokaryotes. Most viruses probably
have a long and rich history of popping in and out of genomes and evolving
along the way. I personally think that all viruses have such histories, and
especially think it very unlikely that a virus would arise completely "de
novo" out of any eukaryotic genome.
>From: Richard Pyle <deepreef at BISHOPMUSEUM.ORG>
>Reply-To: Richard Pyle <deepreef at BISHOPMUSEUM.ORG>
>To: TAXACOM at USOBI.ORG
>Subject: One origin?
>Date: Thu, 19 Jul 2001 09:28:04 -1000
>Since I am in "Taxacom-posting" mode at the moment anyway, I'll take this
>opportunity to ask about something that I've never had a good handle on.
>Ron Gatrelle wrote:
> > The idea that all life on earth
> > came from one seed is just an assumption.
>Sticking within the evolutionary paradigm, I ask these questions:
>Are Viruses considered to be "life"?
>Is "Vira" considered as a legitimate Kingdom, alongside the other
>...and most directly to my query:
>Is there a general feeling that Viruses share a common origin with other
>forms of life, or might their origin be independent?
>Thanks, and Aloha,
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp
More information about the Taxacom