Saturday, December 19, 2015

Viruses, Lichens, and Slime Molds

Life is weird.  Biologists have a basic understanding of what life is, but then there are all these exceptions  There are all these things that refuse to fit into categories.  

Like viruses.  Are viruses alive?  Depends on your definition of life.  One source refers to them as being "at the edge of life."  Another gets around the question by defining viruses as “A submicroscopic infectious agent that is unable to grow or reproduce outside a host cell.”  It further points out that a virus “is non-cellular but consisting of a core of DNA or RNA surrounded by a protein coat.”  Viruses kind of mess up the idea that there is a big divide between living things and nonliving things.  And viruses are at least closer to life than prions which still manage to cause disease in spite of not having any genetic material.

And then there’s lichens.  Lichens are not plants.  Above all, they are not mosses, although they sometimes look like them and even occasionally have names like reindeer moss that would make you think they are mosses.  They are not even one particular kind of living thing.  They are a ‘mutualistic symbiosis’, a composite of a fungi and either an alga or a cyanobacterium, and these two organisms are so intertwined that they act like a single organism.  Sometimes the organisms can not live on their own and other times they can but they look very different. One lichenologist described lichens as “...fungi that have discovered agriculture".  Lichens blur the boundary between the different ‘kingdoms’ of life: fungi, plants, and animals.

Finally there are slime molds.   The slime molds also don’t fit in a clear ‘kingdom’ model.  But what makes them really interesting is that they are a single celled creature that occasionally aggregates into a multicellular being and ends up looking something like a slug.  They’re found on every continent and seem to get everywhere.  They can find things in mazes and imitate highway systems.  Scientist love them.  (And I wrote about them in my post on Emergence on 6/10/15.)

Alive?  One thing or a conglomerate?  Uni- or multi-cellular? Life sometime just refuses to fit into easy categories.

Life is weird.  Life is wonderful.

Quote of the Day: “Everybody knows what a caterpillar is, and it doesn't look anything like a butterfly.” - Lynn Margulis

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