Wize High School Grade 11 Biology Textbook > Animal Physiology
Thermoregulation
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Thermoregulation
Overview of Homeostasis
- Homeostatic Systems: maintain an equilibrium (balance)
- Negative Feedback (-): a change triggers the system to counteract this change
- Positive Feedback (+): a change triggers the system to amplify this change
- Thermoregulation: body temperature regulation
- Osmoregulation: solute and water regulation
Types of heat exchange
- Conduction: direct transfer of heat between molecules in direct contact
- Convection: mass movement of warm air or fluid to or from a body/object
- Radiation: emission of electromagnetic waves
- Evaporation: loss of heat energy from the surface of a liquid losing molecules as gas
Ectotherms
- Ectothermic: Do not use metabolism to regulate body temperature
- Most reptiles
- Behavioral thermoregulation: Move between sun and shade to maintain optimal temp
- Requires far less energy to support ectotherm (10%)
Endotherms
- Endothermic: Do use metabolism to regulate body temperature
- Hypothalmus: sensors in brain that regulate internal temperature
- Thermostat of the body
- Countercurrent exchange: the transfer of heat between fluids (blood) moving in opposite directions
- helps reduce heat-loss to cold environment Example: Cold blood heading to the heart is heated by warm blood leaving the heart
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Example: Endotherms vs. Ectotherms
Endotherms and ectotherms regulate their internal body temperature very differently.
Identify between the two images of animals, iguana on the left and bear on the right, which is the endotherm and which the ectotherm. Then, describe how each animal regulates its internal body temperature.
(CC BY-SA 4.0)Iguana = ectotherm
Bear = endotherm
Ectotherms regulate their body temperature through behaviours like moving into or out of direct sunlight. This requires less energy.
Endotherms regulate their body temperature automatically through their hypothalamus (part of the brain) that senses changes in body temp and causes physiological changes to maintain it.
Practice: Feedback Systems
You are exercising and your body heats up. Your body begins to sweat to enable evaporative cooling. Sweating causes your internal body temperature to cool.
What type of feedback system is this situation describing?
Mark Yourself Question
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Practice: Lizard Thermoregulation
Describe how a lizard may use behavioural thermoregulation on a hot day.
Practice: Types of Heat Transfer
Match the examples of different heat transfer scenarios to the correct type of heat transfer.
A.
Maintaining internal body temperature through sweating
B.
Using the microwave
C.
Warming up someone's cold hand by holding their hands
D.
Hot air in a room rising
Convection
Conduction
Radiation
Evaporation