Thermodynamics in Biological Systems

Inherited Characteristics and Acclimation

• Permanent inherited characteristics are part of the gene pool, enduring across generations.
• Acclimation refers to physiological adjustments made by individuals to cope with environmental stressors.

Poikilothermic Adaptations

• Poikilothermic organisms can exhibit behavioral adaptations to regulate their internal environment rather than being passive conformers.
• Galapagos Marine Iguanas: Larger males dive in cold water due to their reduced body surface area, enhancing resistance to heat loss.

Homeostasis and Physiological States

• True homeostasis maintains a steady state where internal fluctuations remain largely independent of external conditions.
• Evolution of sophisticated neurological systems, especially involving the hypothalamus, supports the maintenance of homeostasis.

Thermal Properties of Aquatic Environments

• Seawater has a higher specific heat capacity than air, causing rapid heat loss in aquatic organisms.
• To retain internal temperatures above the ambient conditions, aquatic animals develop heat conservation strategies.

Counter-current Exchange Mechanisms

• Found in many large fish, counter-current heat exchange minimizes heat loss by maintaining a temperature gradient within blood vessels.
• A rete mirabile, a network of closely aligned arteries and veins, helps preserve core body temperatures in large fish.

Heat Conservation in Aquatic Vertebrates

• Counter-current heat exchange mechanisms are also present in other aquatic homeotherms, such as dolphins and whales.
• Forms of insulation, including feathers, fur, and blubber, aid in temperature regulation.

Biological Systems and Thermodynamics

• Organic compounds like urea are synthesized from inorganic components, adhering to thermodynamic laws.
• The concept of a vital force was debunked through research linking biological processes to physical laws.

Thermodynamics in Biological Reactions

• Chemical reactions obey the Arrhenius equation, but biological reactions often exceed these predictions.
• Q10 defines how reaction rates vary with temperature, typically yielding values between 2 and 3.

Enzyme Efficiency and Thermal Tolerance

• Enzymes enhance biological system efficiency but are also sensitive to temperature changes, affecting organism thermal tolerance.
• Thermal tolerance varies due to structural and enzymatic differences among species.

Terminology in Thermal Biology

• Eurytherm: Organisms that can tolerate a wide temperature range.
• Stenotherm: Organisms with a narrow temperature tolerance.
• Poikilotherm: Ectothermic organisms with variable body temperature.
• Homeotherm: Endothermic organisms that maintain a constant internal temperature.

Performance in Extreme Environments

• Poikilothermic organisms face significant temperature fluctuations over short time intervals, driving adaptations.
• Adaptation is a genetic process allowing populations to evolve in response to environmental factors, distinct from individual acclimation.

Explore the laws of nature governing biological systems, including thermodynamics and its applications in biological reactions. Learn how the synthesis of urea challenged the concept of vital force and understand the role of temperature in chemical reactions.