Abiotic Environment #5: Stress, Avoidance/Tolerance Strategies

Question 1

Stress

Answer 1

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)

Question 2

Conduction

Answer 2

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

Question 3

Convection

Answer 3

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

Question 4

Avoidance Strategy

Answer 4

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?

Question 5

Tolerance Strategy

Answer 5

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

Question 6

Acclimation

Answer 6

Acclimation: Individual organism adjusts to change in its environment

Example:
- Changing thermal tolerance to adjust to hotter/colder environmental conditions