The relationship between natural selection and the second law of thermodynamics is complex and indirect. While both concepts operate in different domains, they can be understood in the context of the organization and complexity of living systems.
The second law of thermodynamics, often referred to as the law of entropy, states that in a closed system, the total entropy, or disorder, tends to increase over time. It implies that spontaneous processes in a closed system generally lead to a decrease in the system's ability to do work and an increase in randomness or disorder.
On the other hand, natural selection is a fundamental mechanism of evolution that acts on living organisms. It favors certain heritable traits that enhance an organism's ability to survive, reproduce, and pass on its genes to future generations. Over time, these favorable traits become more prevalent in a population, leading to adaptive changes in the species.
While the second law of thermodynamics suggests that disorder tends to increase, living organisms, in contrast, exhibit high levels of complexity and organization. This apparent contradiction can be resolved by considering that living organisms are not closed systems but open systems that exchange matter and energy with their environment.
Living systems are able to maintain and increase their complexity by acquiring energy from the environment, such as through the process of consuming food and utilizing energy from the Sun in the case of photosynthesis. This influx of energy allows organisms to build and maintain complex structures, sustain metabolic processes, and maintain homeostasis.
In this context, natural selection plays a role in shaping the organization and complexity of living systems. Organisms with traits that confer an advantage in their environment have a higher chance of survival and reproduction. Over successive generations, these advantageous traits become more prevalent, leading to the evolution of complex and organized structures, behaviors, and functions.
While the second law of thermodynamics remains valid on a larger scale, natural selection allows living systems to locally reverse the trend toward increasing entropy by utilizing energy and evolving adaptive complexity. Thus, the relationship between natural selection and the second law of thermodynamics can be understood as a tension between the tendency towards disorder in the physical world and the emergence of complexity and organization through biological processes.