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Lecture 15: Big Ideas II: Homeostasis (Temperature Regulation (Ectotherms:…
Lecture 15: Big Ideas II: Homeostasis
Homeostasis:
The maintenance of a steady state by means of physiological or behavioral feedback responses
Negative feedback
: Information and commands that oppose the current trend in the system, thus tending to return the system toward a set point.
Positive feedback:
Information and commands that reinforce the current trend in the system, thus causing an acceleration in that trend.
Internal signaling mechanisms to maintain homeostasis include hormones & nerve signals
To remain well-suited to their environment, organisms can use:
Evolutionary Adaptation
Physiological/Behavioral Adjustments
Temperature Regulation
Ectotherms: Rely mainly on External energy sources to regulate body temperature
Metabolism increases linearly with temperature
Ectotherms regulate behavior throughout the day to keep a good temperature for functioning
Endotherms: Rely on metabolic energy and physiological mechanisms to regulate body temperature
Metabolism is lowest at optimal temperature (Thermoneutral Zone)
Heterotherms: Includes members of the above two categories who behave as endotherms sometimes, ectotherms other times (e.g. mammals that hibernate)
Four ways of exchanging heat with the environment: Evaporation, Radiation, Convection, Conduction
Controlling blood flow to skin for temperature regulation occurs in endotherms & ectotherms
Rate of warming greater than rate of cooling
In cold environments, countercurrent exchange mechanisms store heat in the core
The hypothalamus is the thermostat of the body
Plants, fungi, microorganisms can adapt via enzymatic changes, membrane structure, presence of antifreeze compounds