Comprehensive Reviewer on Temperature and Thermoregulation

Biology 12: Comprehensive Reviewer on Temperature & Thermoregulation WHAT IS TEMPERATURE? Temperature is a physical quantity that expresses how hot or cold an object is. It reflects the average kinetic energy of molecules in the body. It is crucial in biology because enzymes and physiological processes are temperature-dependent. It is measured in degrees Celsius or Fahrenheit. BODY TEMPERATURE & HOMEOSTASIS Homeostasis refers to the body's ability to maintain stable internal conditions, including temperature. Normal human temperature is approximately 36.5-37.5°C. Enzymes function best within this narrow range. HYPOTHALAMUS: THE THERMOREGULATORY CENTER The hypothalamus regulates temperature by integrating input from thermoreceptors and initiating corrective responses. Peripheral thermoreceptors detect external temperature; central thermoreceptors detect core temperature. THERMOREGULATION PATHWAY WHEN HOT 1. Thermoreceptors detect rise in temperature. 2. Hypothalamus is activated. 3. Effector responses: vasodilation, sweating, reduced muscle activity. THERMOREGULATION PATHWAY WHEN COLD 1. Thermoreceptors detect drop in temperature. 2. Hypothalamus activates heat-retention mechanisms. 3. Responses: vasoconstriction, shivering, piloerection (erector pili muscles), behavioral changes. HEAT EXCHANGE MECHANISMS Conduction: heat via direct contact. Convection: heat via fluid/air movement. Radiation: infrared transfer without contact. Evaporation: liquid to gas transition absorbs heat. COOLING AND WARMING MECHANISMS Cooling: Sweating, vasodilation, reduced muscle activity. Biology 12: Comprehensive Reviewer on Temperature & Thermoregulation Warming: Shivering, vasoconstriction, piloerection, metabolic increase. THERMOREGULATION STRATEGIES Poikilotherms: Body temp varies with environment. Homeotherms: Constant internal temp. Heterotherms: Can switch strategies. Ectotherms: Rely on external sources. Endotherms: Generate internal heat via metabolism. AQUATIC VS TERRESTRIAL ECTOTHERMS Aquatic: Temp = water temp; some use counter-current exchange. Terrestrial: Behavioral and structural adaptations like basking, color change, waxy cuticle. ADAPTATIONS Structural: Fur, body size, fat. Behavioral: Migration, basking, burrowing. Physiological: Sweating, torpor, shivering. SHELFORD'S LAW OF TOLERANCE Species survive within a range of conditions (minimum, optimum, maximum). Influenced by age, health, life stage, and environment. ACCLIMATIZATION VS ADAPTATION Acclimatization: Short-term, reversible changes. Adaptation: Long-term, genetic changes over generations. TORPOR & HIBERNATION Torpor: Short-term metabolic drop. Hibernation: Extended torpor for seasonal survival. CLIMATE CHANGE IMPACTS Biology 12: Comprehensive Reviewer on Temperature & Thermoregulation Includes coral bleaching, migration disruptions, and species shifting ranges to maintain suitable environmental conditions.