Biology Exam 3 Study Guide

Biology Exam 3 Study Guide - Desert Adaptations: Dealing...

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Desert Adaptations: Dealing with Heat Stress: Bio 182/D. Papaj/Mar. 11, 2008 Key questions for today What is adaptation? A trait that evolved under natural selection and serves some beneficial function. What challenges are faced by organisms in desert environments? High temperatures, low humidity, and resource shortage. Key problems with heat stress: Heat causes protein and DNA to unfold, a process called denaturation. How do animals cope with heat stress? Tolerating Heat: Heat Shock Protein is protein produced in response to elevated temperature or other stress, occurs in all living organisms, acts as molecular chaperone to prevent other proteins from aggregating. Keeping cool: staying cool involves heat transfer; processes: conduction, convection, radiation, evaporation. Terms to know Thermal energy: Heat transfer: transfer of thermal energy from hot body to cold body. Thermal energy = internal kinetic energy of molecules. Conduction: transfer of heat between bodies. Ex. Cold hands warmed by wrapping them around warm mug. Javelina stay in shady during midday, rodents come out at night. Long legged spiders reduce cond. from hot air near soil surface. Heat gain is higher when surface area: volume is greater; heat gain greater for smaller animals. Squirrel returns to burrow where it lays body flat on cool ground; cond. Of heat from body to ground. Meerkats find cool ground and stretch out; flat posture increases surface area in contact with ground. Convection: acceleration of conduction by motion. Ex. The chill of a breeze against your face. Caterpillars feed on pipevine swallowtail close to ground-HOT-crawl up grass stems at midday. Wind velocity at ground = 0, wind velocity on stem > 0, wind cools by convection. Selective brain cooling: Thomson’s Gazelle escape behavior can generate copious heat, brain must work effectively, important to keep brain cool. Veins carry blood from nose to heart, pool of venous blood in nose. Arteries carry blood from heart to brain. Venous blood cooled in nose, while breathing. Arterial blood flows past cooler venous blood. Arterial bllod cooled just before it gets to brain. Cooling involves motion = convection. Radiation: Electromagnetic emission resulting in transfer of heat. Ex. Sun’s rays warming your skin; a rock radiating warmth. Reducing amount of surface area exposed. Sulfur butterfly folds wings upright and points head towards sun when hot, thereby reducing amount of surface area exposed to solar radiation. Jack rabbit: ears large + flat = high sa. Blood close to surface and releases heat as infrared radiation. To cool off, increase blood flow to ears. Big ears: cottontail rabbit, fennec fox, kit fox, mule deer. Evaporation:
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This note was uploaded on 04/10/2008 for the course BIO 101 taught by Professor Hunter during the Spring '08 term at University of Arizona- Tucson.

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Biology Exam 3 Study Guide - Desert Adaptations: Dealing...

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