From: Karen Kalumuck (karenk@exploratorium.edu)
Date: Fri May 09 2003 - 11:45:14 PDT
Message-Id: <v01540b02bae1a4ec4572@[192.168.111.188]> Date: Fri, 9 May 2003 11:45:14 -0700 From: karenk@exploratorium.edu (Karen Kalumuck) Subject: Re: pinhole Biomass Pyramids and decomposers ...
Hi, Sue --
Like all models, the biomass "pyramids" are just that - a model that
attempts to illustrate a not-easily-observed first hand phenomenon or
principle. They have their positive points and a level at which they break
down.
The biomass pyramids are an attempt to show how much biomass it takes to
support each ascending trophic level. It's an energy transfer/efficiency/
waste illustration device. Typically only about 10% of available energy
contained in the biomass is passed along to each subsequent level. When
you get to top predators, it's an amazingly small amount from that
available from the primary producers at the base of the pyramid. I'm not
sure why there would be decomposers at the top of this pyramid, unless this
model was trying to synthesize several ideas into one illustration.
All the food nets/webs/chains out there, as well as this pyramid, are
various ways to conceptualize the interrelatedness of organisms (as I'm
sure you know). Decomposers are critically important - without them we'd
be miles high in dead stuff quite quickly, with all the available nutrients
and energy locked away in the stuff. Personally, I'd prefer a model that's
rather Escher-esque, with all pathways ultimately returning to the
decomposers....or a spiral with decomposers at the center as well as the
edges...
Sorry, can't recommend any websites off the top of my head. Good luck!
---Karen Kalumuck
Karen E. Kalumuck, Ph.D.
Biologist/Educator
Exploratorium Teacher Institute
3601 Lyon St.
San Francisco, CA 94123
415-561-0388
FAX 415-561-0307
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