Lecture 38: Biological Feedbacks

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Lecture 38 Biological Feedbacks
By the end of this lecture you should be able
to Define positive feedback, negative feedback,
and homeostasis. Discuss trends of obesity and
diabetes Discuss abnormality in physiological
feedbacks leading to diabetes Concepts and
terms blood glucose level, insulin,
glucagon Discuss how the living and non-living
components of the earth are related according to
the Gaia hypothesis. Concepts and terms
Daisyworld, albedo
Provide some evidence supporting the Gaia
hypothesis Concepts and terms  dimethyl sulfate
(DMS), cloud condensation nuclei, temperature
regulation Reference http//www.diabetes.org/ho
me.jsp Kirchner, J.W. 1991. The Gaia hypothesis
Are they testable? Are they useful? In Schneider,
S. (ed.) Scientists on Gaia. Cambridge, MA MIT
Press.
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IB 452 Ecosystem Ecology Professor Hu
(fshu_at_life.uiuc.edu) Next Offer Fall 2007 Mostly
former IB150 students
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For Dr. Hus portion of IB150 Dr. Dixon
will have his own
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Feedback
Homeostasis
http//pespmc1.vub.ac.be/FEEDBACK.html
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Center for Disease Control and Prevention a
record 61 of Americans are now
overweight. Dr. S. Harris, U. Western
Ontario we are all getting fat, and obesity
and overweight rates are about 50 in the
general population."
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www.bio.davidson.edu/ people/midorcas/animalph...
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http//diabetesorg.healthology.com/
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http//www.biology-online.org/4/3_blood_sugar.htm
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Superorganism
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"The Gaia hypothesis says that the temperature,
oxidation state, acidity, and certain aspects of
the rocks and waters are kept constant, and that
this homeostasis is maintained by active feedback
processes operated automatically and
unconsciously by the biota." - James Lovelock,
The Ages of Gaia
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The GAIA Hypothesis
James Lovelock
Lynn Margulis
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Gaia The Greek Goddess of the Earth
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VENUS
EARTH
MARS
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DAISYWORLD
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Emiliana huxleyi a coccolithophorid. Satellite
picture of a 50 km-wide bloom of
coccolithophorid extending some 200 kms along the
coast of Scotland (Margulis)
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• DMS Dimethyl sulfate
• Oxidized to sulfate in atmopshere
• Sulfate particles cloud condensation nuclei
• More clouds -- higher albedo

High insolation -- more DMS -- more cloud
cover -- lower insolation
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Ice-core sulfate levels higher during glacial
periods than interglacial periods
variations in biogenic cloud condensation nuclei
amplify temperature excursion biological
processes may make the world colder when its
colder and warmer when its warmer
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Can the strong Gaia hypothesis be tested?? Can
the superorganism reproduce? Is it science,
metaphor, or myth?