Abiotic Environment #5: Stress, Avoidance/Tolerance Strategies

Stress: When environmental conditions are far from optimal - Condition in which environmental change decreases rate of important physiological process - ALWAYS defined relative to organism (ex. Tropical frog cold in -5C but Arctic fox thrives at -5C) - Organism may acclimatize to stress over time, compensating for stress effects - Over several generations, populations may undergo stress adaption and physiological processes may return to pre-stress rate Example: - Endotherms (warm-blooded): Varying mechanisms to avoid extreme low body temps - Ectotherms (cold-blooded): During winter, lose more heat exposed, lose less heat sheltered, and maintain most heat aggregated (warmer near centre) Example: Temperature Stress - Abiotic patterns matter at scales of 100 km (aspen limited to specific geographic range by temperature tolerance range) - Abiotic patterns matter at scales of cm (mussels in intertidal zones must survive temperature fluctuations: direct sunlight during low tide or cold water at high tide) - Sun contact area matters for survival (mussels live on N side rather than S side of rock to avoid sun) - Morphological traits matter (oysters bigger, lighter shell colour; greater SA but reflects more solar energy away) - Physiological traits matter (oysters have higher thermal tolerance than mussels) - Mobility can protect from extreme temperatures (finding cooler environments)

Conduction: Direct transfer of heat (gain/loss) between organism and surface to regulate organism temperature Example: - Animal bedded in snow has subskin temperature higher than snow; heat energy passes through skin and hair coat to snow - Animals gaining heat from warm surfaces - Plants losing heat to cooler soil Note: Organism’s body temperature matters over environmental temperature

Convection: Transfer of heat through movement of fluids (air/water) within environment to regulate organism temperature heat loss/gain Example: - Mammals can lose body heat to cooler air through convection; cool wind replaces warm air around their bodies - Water currents help distribute heat throughout lakes/oceans, affecting temperature and habitat conditions for aquatic organisms - Plants lose heat through convection as air moves (windy conditions) across their leaves, preventing overheating

Avoidance Strategy: Minimizing exposure to stress by altering behavior, physiology, or habitat Example: - Animals might migrate to avoid harsh weather conditions - Plants may adjust leaf orientation to reduce water loss during drought - Nocturnal behavior in animals can help avoid extreme daytime temperatures or predation Example: Temperature - Seek shade or water (solar irradiance) - Aggregation (sticking together with own kind) - Shivering (increases metabolic rate) - Shell texture (convection) - Move substrates/limit surface area (tippy toes) on substrate (conduction) - Mushrooming?

Tolerance Strategy: Enduring stress by developing adaptations that reduce unfavourable effects Example: - Some plants possess thick cuticles or store water to tolerate drought conditions - Animals may have physiological adaptations, like increased thermal tolerance or ability to detoxify harmful substances - Some microorganisms can survive in extreme conditions through specialized enzymes or cellular mechanisms Example: Temperature - Heat Shock Response (physiology): Rapid production of heat shock proteins (HSPs) to maintain protein stability, repair damaged proteins, and protect cells from thermal damage caused by exposure to elevated temperatures

Acclimation: Individual organism adjusts to change in its environment Example: - Changing thermal tolerance to adjust to hotter/colder environmental conditions