Temperature

Temperature

Temperature and Wildlife Homeostasis

Temperature and Wildlife Homeostasis

1. General Effects & Climate Change

• Temperature is a dominant ecological variable affecting:

• Survival

• Reproduction

• Distribution of species

• Influences on environmental aspects:

• Physiology

• Morphology

• Behavior

• Performance of organisms

• Darwinian fitness is related to temperature, which limits what species can thrive in certain areas.

2. Species-Specific Temperature Ranges

• Generalists vs. Specialists:

• Generalists:

  • Have a broad distribution and can survive a wider temperature range.

• Specialists:

  • Have a specific temperature range for optimal performance.

• Interaction:

  • Generalists may struggle when specialists thrive in an optimal temperature range.

3. Terminology Clarifications

• Cold-Blooded vs. Warm-Blooded:

• Anthropocentric terms:

  • Endotherm: Relies on internal heat sources.

  • Ectotherm: Relies on external heat sources.

• Homeothermic vs. Poikilothermic:

• Homeothermic: Body temperature is stable within a narrow range.

• Poikilothermic: Body temperature varies significantly.

• Clarification:

• Poikilothermy emphasizes temperature fluctuation;

• Ectothermy emphasizes external influence on temperature.

4. Ectotherm and Endotherm Characteristics

• Endotherms are generally homeotherms, although some (like hummingbirds) can be poikilotherms.

• Conversely, ectotherms are typically poikilotherms, but some (like certain reptiles and fish) can be homeotherms.

• Environmental differences:

• Aquatic environments typically mirror water temperature.

• Terrestrial environments often do not reflect air temperature.

5. Ectotherm Diversity

• Ectothermic organisms can be classified based on temperature tolerance:

• Eurythermal (Generalist): Can function over a broad temperature range (e.g., goldfish).

• Stenothermal (Specialist): Can function only within a narrow range (e.g., deep-sea fish).

6. Heat Tolerance & Avoidance

• The physiological implications of small temperature changes can be significant since high and low temperatures are relative.

• Heat Tolerance:

• Ruppell’s Fox: Survives in extreme desert conditions (up to 159°F).

• Antarctic Krill: Intolerant to temperatures exceeding 39°F.

• Metabolic Rate:

• Increased temperatures generally lead to increased metabolic rates, especially in ectotherms.

6.1 Heat Tolerance Mechanisms

• Acclimatization: Adjustments in physiology to withstand temperature changes.

• Consequences of Extreme Heat:

1. Enzymatic activity can become impaired; enzymes may denature.

2. Disruption of cell membrane integrity due to elevated temperatures.

3. Various tissues have different thermal limits, particularly critical areas like the CNS and reproductive organs.

6.2 Heat Avoidance Behaviors

• Behavioral adaptations that allow organisms to mitigate excessive heat exposure.

7. Cold Tolerance & Avoidance

• Organisms in extreme cold conditions employ methods for survival:

• Behavior is generally a more energetically economical method than physiological adaptations.

• Factors influencing cold tolerance:

• Age: Younger animals are usually less tolerant.

• Length of exposure can affect tolerance levels.

• Recent history: Acclimatization time matters.

• Evolutionary history: Species adapted to cold environments show more resilience.

7.1 Risks of Extreme Cold

• Risks posed by cold environments:

• Intracellular ice formation can be catastrophic due to high water content (70% in most animals).

• Dramatic drops in chemical reaction rates can impair bodily functions.

7.2 Cold Tolerance Adaptations

• Some adaptations include:

• Lowering the freezing point through solute addition, leading to supercooling.

• Production of antifreeze proteins within cells remains active despite freezing conditions (e.g., polyhydric alcohols and glycoproteins).

How Does Temperature Affect Wildlife Homeostasis

1. General Effects & Climate Change

• Climate change can lead to shifts in wildlife habitat and behavior due to temperature variations.

• Increased temperatures may lead to stress in various species as they strive to maintain homeostasis.

2. Heat Tolerance & Avoidance

• Organisms have developed different strategies to deal with excessive heat, which can include behavioral and physiological adaptations.

• Habitats: Animals may choose specific environments to escape extreme heat, utilizing burrows or shaded areas.

3. Cold Tolerance & Avoidance

• Similarly, animals have mechanisms in place to avoid extreme cold, such as migration or hibernation.

4. Thermoregulation in Endotherms

• Maintaining a constant body temperature is energetically costly.

• Small Animals: Have a narrower Thermal Neutral Zone (TNZ); require more energy to regulate body temperature.

• Large Animals: Tend to have a broader TNZ, allowing better temperature regulation with less energy expenditure.

5. Keeping Warm

Behavioral Adaptations

• Altering Posture:

  • Reduces surface area exposure to minimize heat loss.

  • Protects sensory organs from cold.

• Hibernation:

  • Dropped body temperature and slowed metabolism over several days to months.

• Torpor:

  • Temporary hibernation; body temperature and metabolism lower daily to mitigate harsh weather.

  • Not universal across species.

Physiological Adaptations

• Altering Insulation:

  • Ptiloerection (feathers) and Piloerection (fur) create air layers, preventing heat loss.

  • Muscles at the base of each feather or hair control these changes, which are regulated by the nervous system.

  • Addition of winter coats or fat for insulation.

• Altering Blood Flow:

  • Vasoconstriction: Reduces blood flow to peripheral areas.

  • Countercurrent heat exchange and regional heterothermy allows animals to retain core heat effectively.

• Thermogenic Mechanisms:

  • Increase metabolic heat production through processes like:

  • Shivering: Unsynchronized muscle contractions, seen in adult birds and mammals.

  • Brown Adipose Tissue: Specialized fat in young placental mammals that generates heat when metabolized.

6. Keeping Cool

Behavioral Adaptations

• Habitat Selection: Choosing to stay in burrows or shaded areas during the hottest parts of the day.

• Estivation: Periods of rest to avoid heat stress.

Physiological Adaptations

• Altering Insulation:

  • Shedding thick winter coats for lighter coverings.

  • Ptiloerection for feathered species offers a protective layer with reduced insulation.

• Altering Blood Flow:

  • Peripheral vasodilation: Expanding blood vessels in peripheral areas to release heat.

• Adaptive Hyperthermia:

  • Allows organisms to store heat during hot days and release it when temperatures cool at night.

  • Common in animals with thick fur and complex nasal passages.

• Evaporative Heat Loss:

  • As a last resort, include:

  • Sweating: Water loss helps to cool the body temperature.

  • Panting: Uses less water for cooling but is energy-intensive.

Gular Fluttering: Rapid mouth movement in birds, a low-energy alternative to cooling.