species concepts

[Jerry Bricker]

When I read the first posting regarding the species concept I knew it
would lead to a long and heated debate regarding the topic.  That is not
a criticism but praise of those out there that make the study of such
things their live's work.

My gut feeling came from an observation that I made a while ago.  My job is
as a community college instructor.  I teach first-year biology to majors
(and a number of nonmajors) and I try to instill in my students the
fundamental concepts related to living organisms.  These concepts are
usually framed in the from of a question (What is a cell?") or stated as a
theory ("The cell theory is...").  I've arranged my courses around
presenting several central theories of biology.  I believe that if my
students understand, in depth, those central theories then they will be
prepared for their upper division studies.  I try to point out that this
approach will examine the chemical theory of life (they just love that
section of the course), cell theory, metabolism (as related to the second
law of thermodynamics), particulate theory of inheritance (Mendelian
genetics), molecular genetics, evolutionary theory, etc.  Many students
still get lost in what they see as overwhelming detail ("the trees")
describing a few central themes ("the forest").

I've noticed that if I can't distill the essence of a concept/theory down
into a simple and understandable explanation for my students then it
really is itself poorly understood.  Hence, the example of the species
concept.

I've yet to think of a way of presenting the species concept in simple
terms that my general biology students can use in constructing their own
world view.  My usual statement to them is don't sweat it because even
the "experts" can't come up with a simple, workable hypothesis either.  I
also point out that Richard Feynman defined science as "the belief in the
ignorance of experts."  (That definition still cracks me up!)

It is important that they understand that science is a process and not
black and white statements.  Is it really so bad that we
don't have a single species concept to give to the lay public and to
general biology students?  No, it is a reflection of how this area of
inquiry actually works and that is really the most useful educational
tool we have.  The media and general public would like to think of
science as a collection of facts that explain everything in life.  I'm
sorry but it doesn't work that way and the sooner we all realize it the
better.  After all, isn't the current effort to ban the teaching of
evolution (e.g., efforts in the Tennessee legislature this year) just a
way of making the world fit into our tight little definition of life?  If
we don't recognize that there are processes that are difficult to explain
then we, as adults, won't have to try to explain them (and show how
little we really know about the universe).

I'm now led to ask the most difficult question posed by any general
biology textbook.  One that usually is presented in chapter 1 and that is
treated so poorly that the student walks away confused (many never shake
this feeling during the rest of the semester).  The question simply is
"what is life"?

We know that biology is "the study of life."  Every text
that I've consulted then goes on to explain that to be living "life" must
possess certain traits including metabolism, organization, reproduction,
ability to adapt, and growth.  Always being the smartass, I ask that if
all the items on the list are not met can the entity be alive.  I love to
throw out viruses and viroids.  They lack their own metabolism so are they
alive?  If not, then are they dead?  (Since death is the "permenant
cessation of life" - thanks Mr. Webster - then something cannot be
simultaneously not living but not dead.)  Many biologists seem to take the
"let's ignore those trivial exceptions" viewpoint.  I tend to think this
displays an unwillingness to admit they really don't understand any more
than the freshman biology student.  I would also point out that
although there are currently 5,000 described species of viruses the
estimated number in the wild goes as high as 500,000 species.  No
trivial exeption, that.

Never wanting to admit that I don't understand a concept (is that a sign
of stupidity itself?) I have pondered this question from the first time I
taught a biology course.  I finally came up with a workable (in my
opinion) definition of life.  For all of you that have tolerated this
rambling essay here it is.  "Life: any entity possessing a
complex polynucleotide (DNA or RNA) and capable of directing its
own reproduction."  That is a pretty stripped down definition but it
works for all known life forms.  Are viruses and viroids alive?  Yes,
they fit the definition.  Amoeba, humans, and pigs?  Yes, the also meet
the polynucleotide criteria.  Prions?  No, prions are simply protein so
they are not alive.

It all sounds pretty simple (in my own opinion).  In any case, I would
like Campbell, Raven and Johnson, and all the other textbook authors to
adopt my definition.  I would make things a lot easier on us lowly teachers.

Jerry Bricker
Laramie County Community College
Cheyenne, Wyoming


My opinions, like my misteaks, are all my own.
        -Henry Derr