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Lecture 2

Biology Lecture 2 Article 2.docx

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University of Toronto St. George
Scott Browning

BIOLOGY LECTURE #2 Homeostatic Processes for Thermoregulation - Key factor in success = ability for many species to adapt to external environmental fluctuations and maintain a consistent internal environment AKA HOMEOSTASIS! - Homeostasis mech = dynamic + regulate many diff parameters in the body (Ex. pH, dissolved O 2 - Internal temp changes may adversely affect physiology (Ex. Enzyme func, muscle act, en metabolism) Type of Thermoregulation: - 2 main responses to fluctuating Ta: POIKILOTHERMY + HOMEOTHERMY - Poikilotherms: can’t to generate heat on their own - Body temp conforms to their environment - “cold-blooded” animals - Ectotherms: their body heat is derived only from their external environment - Feed less and more likely to be able to live in resource poor enviornments - Use behavioral thermoregulations = sustained avg body temp Sidewinder rattlesnakes: ball that’s optimal for imp metabolic activities groups where core temp is - 1) shuffling b/w areas with lower and high temps stable while outside temp of - 2) changing body positions to adjust heat exchange thru conduction 42 which is lethal critical level + radiation - use it periodically: actively thermoreg in day and passively conform in night - Hormone Melatonin: implicated by temp regulation in many ectotherms - Melanistic polymorphism may be related to thermoreg. - Warm up more quickly than lighter colored species with higher thermal reflectance - Heat retention = remain active when cold - Color choice: can also be social/ camouflage - Homeotherms: have specific physiological adaptations for regulating their body temps - Body temp fluctuates less than poikilotherms - Maintain high body temps: 36-42 DEGREES - “warm-blooded” - Endotherms - Higher metabolic rate + mpre active over wider range of temp than poik - Cost= need to divert lots of energy intake to thermoreg - Constrains where they can live unless lots of energy sources - Solution= torpor adaptation - Thyroid hormone has thermogenic effect - Thermostat for vertebrae in hypothalamus of brain… it triggers physiological response to outside temp above and below set points - Disrupting hypothalamic reg of temp = hypothermia - Also use behavioral thermo BUT they don’t depend solely on outside source of heat like poi. - Use behavioral means to keep themselves in
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