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Lecture 3

Lecture 3 & 4

6 Pages
171 Views

Department
Biology
Course Code
BIO120H1
Professor
Ingrid L.Stefanovic

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Lecture 3 & 4 22:11
Core Ideas in Physiological Ecology
Ranges of tolerance ultimately limit distribution
Reactions occur best at optimum temperature and osmotic conditions
Two types of range: range tolerance and geographical ranges
Animal ranges often correspond to biomes, i.e., limited by climate and/or vegetation
Organismal Digression: some animal ranges can transcend biomes (e.g., the tiger
can live in the cold or desert)
Thermal Ecology: aspects of heat exchange with environment
Radiation: heat transfer by electromagnetic radiation
Conduction: direct contact with substrate (e.g., feet lose heat to ground)
Convection: heat transfer mediated by moving fluid (usually air or water)
Evaporation: efficient cooling from wet surfaces
Circulatory system distributes heat among body parts
The larger the surface area, the slower the equilibration. This is advantageous for
animals. If you are large, you can maintain your body heat easier.
Size matters:
Bergmanns Rule: homeotherms tend to be larger at higher latitudes. (Colder
environments)
What about elephants, rhinoceroses? Elephant dont violate Bergmanns rule
because of the wooly mammoths that have gone extinct but used to live in northern
latitudes.
Shape Matters:
Allens Rule: appendages reduced in cold climates
Sphere has least SA:V
E.g., rabbits in the arctic and in the desert
Insulation Matters:
www.notesolution.com
More important than size or shape in heat regulation
Hair and feathers provide adjustable insulation
Convective cooling enhanced by vascularization: rabbits use their arteries to cool
blood
Arteries and veins should be appressed in appendages to conserve heat; separated
in appendages designed to shed heat
Countercurrent flow maintains gradient
Convection enhanced by evaporation (e.g., humans sweating, dogs panting)
Weasels are made for a warm environment, but in reality, they live in colder
climates. They are the wrong size and shape for this region.
Example of a tradeoff:
Being long and thin makes weasels subject to thermal stresses
…but allows them to be better predators
Because they are long and thin, we infer that the fitness gains of being a good
hunter offset the fitness costs of an expensive metabolism
Kangaroo rat tactics for conserving water in hot, dry environments:
Anatomy:
Erect posture, bipedal; less heat gain from ground
Physiology:
Super-efficient kidneys
Metabolic water sufficient
Behaviour:
Nocturnal; spend hot days underground
Cache seeds underground; recapture water vapour from exhalation
When environments get really stressful, evasion:
Enter dormant stage (seeds, cysts, eggs, pupae)
Nest (protected microhabitat), store food
Hibernate as adult, store fat
Migrate to milder climate
(Hibernation and migration usually driven more by food supply than Abiotic stress)
Plant Ecophysiology: tradeoffs and constraints abound
www.notesolution.com

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Description
Lecture 3 & 4 22:11 Core Ideas in Physiological Ecology Ranges of tolerance ultimately limit distribution Reactions occur best at optimum temperature and osmotic conditions Two types of range: range tolerance and geographical ranges Animal ranges often correspond to biomes, i.e., limited by climate andor vegetation Organismal Digression: some animal ranges can transcend biomes (e.g., the tiger can live in the cold or desert) Thermal Ecology: aspects of heat exchange with environment Radiation: heat transfer by electromagnetic radiation Conduction: direct contact with substrate (e.g., feet lose heat to ground) Convection: heat transfer mediated by moving fluid (usually air or water) Evaporation: efficient cooling from wet surfaces Circulatory system distributes heat among body parts The larger the surface area, the slower the equilibration. This is advantageous for animals. If you are large, you can maintain your body heat easier. Size matters: Bergmanns Rule: homeotherms tend to be larger at higher latitudes. (Colder environments) What about elephants, rhinoceroses? Elephant dont violate Bergmanns rule because of the wooly mammoths that have gone extinct but used to live in northern latitudes. Shape Matters: Allens Rule: appendages reduced in cold climates Sphere has least SA:V E.g., rabbits in the arctic and in the desert Insulation Matters: www.notesolution.com
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