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Lecture 2

BIO120H1 Lecture Notes - Lecture 2: Volumetric Heat Capacity, Sun Bear, Evaporation


Department
Biology
Course Code
BIO120H1
Professor
Jon Abbatt
Lecture
2

Page:
of 2
Lecture 2 & 3:Physical challenges of the environment
Geographic Ranges
Animals Geographic ranges usually correspond to biomes (limit to climates or
vegetation), but sometimes it is also affected by other factors:
Special habitats
Pronghorns have a broad temperature tolerance range but a narrow
habitat range
Other organisms ( enemies, friends)
Elf owls, gila woodpekers depends on cactus.
Transcendent biomes
Tigers can live in any habitat either hot or cold.
History
Thermal Ecology:
Ways to gain or loss heat:
Radiation: emission of electromagnetic energy by a warm surface.
Conduction: transfer of the kinetic energy of heat between substances in contact
with one another.
Convection: transfer of heat by the movement of liquids and gases
Evaporation: efficient cooling from wet surface.
Redistribution: circulatory system redistributes heat among body parts.
Body size and thermal inertia:
Larger organisms tend to lose heat across their surfaces less rapidly than smaller
individuals this is because the surface-to-volume ratio is smaller(V SA ). It is
easier for them to maintain a constant internal environment in the face of
varying external conditions.
Bergmanns Rule: Homeotherms tend to be larger at a higher altitude.
Polar bear lives in the Artic are bigger than Sun bear that live
in the tropics.
Allens Rule: appendages reduced in cold temperature.
Pika has spherical ear and round body; lives in tundra. Gliding
snake has flat body; lives in tropics
Aquatic animal uses body fats to keep themselves warm.
Countercurrent Circulation:
Blood flowing from the body toward the outside environment continuously
meetings blood returning to the body; arteries and veins should be appressed in
appendages to conserve heat. Ex: Birds leg
Trade-offs
Def: a consequence of devoting limited time, energy, or materials to one
structure, function, or behavior at the expense of another.
Being long and makes weasels subject to thermal stress but allow
them to be better predatorsthe fitness gains of being a good hunter
balance out the fitness costs of an expansive metabolism.
Extreme Physical Challenges-Kangaroo Rats:
K-rats lives in Sonoran desserts, they can survive without taking any water,
because:
Bipedal less heat gain from the ground.
Efficient kidney that can produce concentrated urine.
Metabolic water water produced by its own fats and seeds.
Nocturnalspend hot days underground
Sleep with their foodseeds can recapture water vapor from
exhalation.
Overwhelming stress:
Food supply is usually the cause of hibernation and migration.
Chipmunk hibernates
Pika make hays
Migration vs. Residents
Birds migrate because of the food supply. Therefore birds that doesn’t migrate means that
they have a stable food supply.