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Session 8. Material Cycles in Ecosystems
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A coniferous forest ecosystem |
Learning Goals
During this session, you will have an opportunity to
build understandings to help you:
- Distinguish between producers, consumers, and decomposers
with regard to material cycling in an ecosystem
- Describe examples of material cycling through an ecosystem
- Contrast
energy flow with material cycling
Video Overview
Our final session looks at life at one of the highest levels of organization:
the ecosystem. Shifting from Session 7’s focus on energy, Session
8 explores matter and its connection to life.
View this video==> 
Video Outline
We know that the living world is composed of matter, but there are
some puzzles. New life is constantly appearing. On a planet where
supplies of matter are finite, where does life get its matter?
Death is an inevitable part of life. Where does the matter that composes
dead things go? Our hosts, Dr. Linda Grisham and Dr. Douglas Zook,
remind us of the chemical nature of living matter by re-introducing
the SPONCH CaFe – a mnemonic representing life’s most
common elements. Dr. Adrien Finzi, an ecologist, acts as our guide
in a forest ecosystem where he points out where these elements
are found.
MaryAnn Bernstein’s third-grade students in Burlington,
Massachusetts consider questions about matter during an experiment
involving “worm
tanks”. Dr. Tina Grotzer, representing the Understandings
of Consequence Project, talks about research on children’s ideas
about decomposition, and the importance of looking at cause and
effect in building accurate scientific understandings. The fourth-
and fifth-grade
children in our Science Studio act as our own subjects of research
on children’s ideas as they answer some tough questions about
matter and life.
Our own exploration of matter and life starts,
once again, with food chains. How do producers obtain the matter
they need? The
process by which producers “fix” is described, and Dr.
Nicky Sheats describes the role of bacteria in fixing nitrogen.
As we consider
the consumers, one consequence of taking in matter for building
bodies is considered: the production of wastes.
We next visit a sewage
treatment plant, where Charles Tyler takes
a closer look at the decomposers and decomposition. Next, Dr. Finzi
introduces us to material cycles as he guides us through the cycling
of carbon – the element that defines life. And we hear from
Dr. Sheats, who walks us through the nitrogen cycle. Our study
of material cycling closes with a consideration of balance in ecosystems.
Of course, Dr. Paul Williams returns, this time with parting looks
at Bottle Biology and encouragement to bring ideas from this
Web site-based activity to K-6 classrooms.
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