Sunday, October 10, 2010

Virus Evolution


It's a topic one doesn't hear much on.  How did viruses evolve?  How did they come into existence and when?  My interest piqued below's a little net trolling I've done on the topic.



Virus Facts
Overview: Viruses aren't technically alive (life=metabolism, maintain homeostasis, possess a capacity to grow, respond to stimuli, reproduce and, through natural selection, adapt to their environment in successive generation).  They depend on invading other cells to reproduce.  They're essentially intricate molecular structures filled with genetic information to hijack other cells.



Scale:  they're one hundredth the size of a cell (on average).

Mimivirus - the largest virus


Relevance/Common Ailments Caused by Viruses: influenza, herpes, HIV/AIDS, chicken pox, warts, hepatitis, rabies, polio, and most everything else nasty.

H1N1



Evolution of Viruses:   To cut to the chase, we don't know.  Why we don't know is almost as interesting as knowing, though.  They're too delicate to fossilize (although I guess the earliest virus evidence found was a plant abnormality from 200 mya).  Analyzing their genome doesn't help much either.  It's a tangled mess for a couple reasons.  One reason is the means by which they sometimes replicate their genome, the reverse transcriptase, is quite error prone.  Furthermore, they often sneak their genome into the genome of their host so the host cell will treat it like its own and build more proteins that build viruses.  It's probably not too hard to see how that can get kinda sloppy - lots of cross over.  That's part of the reason why we call them 'swine flu' and 'bird flu'; they literally contain bird and swine DNA.



There a couple of theories about how they might have evolved (and this might have happened several ways on multiple occasions).

  • They could have come from escaped genetic info that evolved to hijack other cells.
  • They could be trimmed down cellular parasites.
  • They might have coevolved early on in life's history and been an important part of the genetic exchange that catalyzed the genesis of life.



Prevalence: there are fifteen times as many viruses in the oceans as there are bacteria and archaea.  Woah.  They infect every branch of the tree of life and hence suggesting a very early origin (as does their diversity).


Relevance in Evolutionary History: viruses are an important source of horizontal gene transfer - viruses taking DNA from one organism and putting it in another.  It's been speculated that this may actually be a big part of evolutionary change.

Medicinal Treatment:  they're kind of like zombies - you can't kill what's undead (or more aptly, unliving).  So, we vaccinate/immunize to preemptively teach our body to recognize them and digest them when caught.  The tough thing about HIV/AIDS and other viruses is that the evolve so quickly and are so tricky about showing up on our immune systems radar.







Virus Infects A Cell from New Life Ministries on Vimeo.


Works Sighted [sic]:

http://en.wikipedia.org/wiki/Virus
http://www.wired.com/wiredscience/2009/02/capsidimage/
http://www.scientificamerican.com/article.cfm?id=experts-where-did-viruses-come-fr
http://www.nsf.gov/news/special_reports/fibr/step.jsp
http://www.mcb.uct.ac.za/tutorial/virorig.html
http://www.microbiologybytes.com/blog/category/biology/page/48/
http://www.biology-online.org/articles/origin-evolution-viruses-escapeddna-rna/origin-evolution-viruses.html
http://rybicki.wordpress.com/2008/03/19/from-what-did-viruses-evolve-or-how-did-they-initially-arise/

6 comments:

  1. love this stuff! pathophiz jiznas!!

    ReplyDelete
  2. Great topic. So what is the most popular topic on your site?
    Thanks, George
    Retired in Escondido, CA USA

    ReplyDelete
  3. Hey George! Thanks for commenting! The biggest source of traffic on my blog are my images. Images.google.com is my number 1 referring website and here are the top hits in order of frequency, starting with the most hit:

    http://thesymbiont.blogspot.com/2010/12/inflatable-animals.html
    http://thesymbiont.blogspot.com/2010/10/why-are-women-pretty-or-why-do-men-like.html
    http://thesymbiont.blogspot.com/2010/11/species-cliques.html
    http://thesymbiont.blogspot.com/2010/09/are-humans-still-evolving.html

    Top search terms:

    bonobo
    1,696
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    bullseye
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    virus
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    dimetrodon
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    sea star
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    human evolution
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    human organs
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    land crab
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    bonobos
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  4. I love this site. and the video's compiled.
    great job, on a great topic.

    p.s. also a homonym lesson on: (sight vs. cite vs. site).

    ReplyDelete
  5. I appreciate the comment! Yes, isn't that little word 'sic' fun?

    ReplyDelete
  6. These videos are the fabrication of an overactive mind. They are animated because they are all theoretical. A "virus" hijacking a cell so he says, as if it has some kind of intelligence even though it is not an organism as defined by biological science on this planet, just a strand of rna and some protein crap and then telling us that it is taking over a completely formed and intelligent T cell which by the way is supposed gobble up junk in the body. So what is he telling us?? If you really believe that a virus is hijacking a cell, show me the real live video that demonstrates this theory and then prove to me that it is the so called "virus" that is hijacking the T cell and not the T cell gobbling up the virus. Your lunar modular looking virus is really stretching the imagination. Sorry, I just don't buy bad science.

    ReplyDelete

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