Biology 356 Foundations of Ecology

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Biology 356 Announcements 1) Homework
2 will be posted on the web page 2) Homework 1
and 2 due Monday 3) Field-class 1 (today) is
due Monday HOW CAN YOU GET HELP? Office hours
Fri 10-11, Mon 9-10 in the Greenhouse Desert Room
(Also Tues 230-330)
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Ch. 4-6Organisms must maintain

• Heat balance
• Water balance
• Energy balance

This is the domain of physiological ecology.
Physiological ecologists often examine an
organisms performance over a range of
environmental conditions.
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Performance of

• Human
• Plant
• Fish
• Bacterium

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Performance curves
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Causes of performance curves

• Temperature affects both the shape and stiffness
  of enzymes
• Too cold reactions are slow
• Too hot enzymes denature
• Example acetylcholinesterase promotes breakdown
  of neurotransmitter (acetylcholine to acetic acid
  and choline), turning off neurons

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• Two forms of enzyme
• Winter temperatures just above freezing
• Summer temperatures 15 C
• Heat-stressed fish thrash or swim in circles
  why?

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Body temperature regulation

• Poikilotherms no regulation
• Ectotherms external energy sources
• Endotherms metabolic heat energy
• Homeotherms special endotherm case, maintaining
  constant body temperature

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Why is this moth endothermic?
Answer flying releases a lot of metabolic heat
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More importantly, what keeps Manduca from
overheating?
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More importantly, what keeps Manduca from
overheating?
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Body temperature regulation

• Poikilotherms no regulation
• Ectotherms external energy sources
• Endotherms metabolic heat energy
• Homeotherms special endotherm case, maintaining
  constant body temperature

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General equation of heat gains and losses

• Hs Hm Hcd Hcv Hr He
• Hs heat stored in body
• Hm metabolic heat
• Hcd conduction, direct physical contact
• Hcv convection, body to fluid (e.g. wind)
• Hr electromagnetic radiation (e.g. sun)
• He evaporative cooling (latent heat of
  vaporization 580 cal/g water)

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Heat gains and losses
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This plant produces Hm!!!
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Arctic plants increase Hcd and Hr, reduce losses
to Hcv. Desert plants do the opposite.
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Internal temperatures of homeotherms are very
tightly regulated but check out the variation in
Thermal neutral zones!! (Body T 37 C)
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Some homeotherms arent always

• Torpor short-term low metabolic rate and low T
• Hibernation overwinter reduction in metabolic
  rate
• Estivation over-summer reduction in metabolic
  rate

Fat-tailed dwarf lemurs hibernate through the
dry season