Editorial and Opinion:

The Biological Evolution
of Energy Systems

One of the thermodynamic laws of the universe is that closed systems run down. Scientists call this increasing entropy, which can be thought of as a tendency of energy to dissipate, or of matter to become disordered (chaotic). A good example of energy dissipation is a cup of hot coffee, which does not stay hot for very long. The heat is gradually dissipated into the environment until the coffee and cup are at the same temperature as the surrounding environment. The concentration of heat in the coffee represents a state of increased order (decreased entropy) which dissipates into the environment (as entropy increases).

A good example of matter disorganization is diffusion of smells. The scent of a skunk does not stay localized to the skunk. It spreads throughout the environment until everything in the vicinity smells bad. If you were in a closed system (trapped with a skunk in a room with no ventilation), after a while, it wouldn’t matter where in the room you were. The scent chemicals would become so thoroughly scattered (a state of maximum entropy) that it would smell equally terrible everywhere.

Entropy in Living Systems

Living systems can do this because they are open systems. They gather raw materials from the environment, build self-replicating structures and excrete waste products. Although life is anti-entropic, it does not violate the laws of thermodynamics. While entropy is decreased within the organism, entropy is increased to a greater degree outside of the organism. The net entropy effect is positive, in full agreement with thermodynamic principles.

The localized state of increased order (decreased entropy) within living organisms requires energy to maintain. By selectively absorbing materials with high energy potential and excreting materials with low energy potential, energy can be gathered from the environment to maintain the structure and order of the living system.

Energy Molecules

Early in evolution, life forms developed the means to use chemicals to trap the energy needed to support life. Just as batteries can store electrical energy, metal ions of iron, copper and manganese, and redox-active organic molecules, could be used to store energy. Eventually, chlorophylls (cyclic-heme mineral chelates) were developed that allowed the direct absorption of light energy to power biological reactions. The development of photosynthesis was a powerful advance that literally changed the world.

The Plant Eco-tastrophe

Billions of years ago, the Earth was quite different from what it is today. The primitive atmosphere contained almost no free oxygen, and it was rich in carbon- and hydrogen-containing compounds like water, methane and ammonia. The first photosynthetic organisms (the ancestors of blue-green algae) were so successful that they seriously depleted the atmosphere of both hydrogen and carbon (the two most basic building blocks of life). Ammonia (NH3) was stripped of hydrogen to produce nitrogen (N2), water was stripped of hydrogen to produce oxygen (O2), and methane (CH4) was stripped of hydrogen to produce carbon dioxide (CO2). Through biological photosynthesis, the primitive “reducing” atmosphere (hydrogen-rich, electron-rich) was gradually converted into our present “oxidizing” atmosphere (hydrogen-poor, electron-depleted). Although this transformation took many millions of years, it was an ecological catastrophe. Most of the organisms alive at the time were not able to adapt and became extinct. Those that survived were relegated to minor anaerobic niches like bogs and mid-ocean hydrothermal vents.

As reduced-carbon chemicals (methane, ethane, “natural” gas) became scarce, plants had to develop better carbon-scavenging abilities. Eventually they were nearly depleted and carbon dioxide became the only appreciable carbon source. Plants became quite efficient at absorbing it. The modern atmosphere contains only about a third of a percent CO2. Much of the carbon that is not buried in rock or dissolved in the ocean has been incorporated into living structures.

Adaptation to Crisis

As the atmosphere became increasingly oxidized, living systems adapted. They developed antioxidants and ways of directly harnessing the oxidizing power of the atmosphere to drive metabolic reactions. Organisms developed ways of recycling antioxidants to better keep oxidizing free radicals under control.

One of these emerging life forms developed a way to use atmospheric oxygen for the direct production of chemical energy. This process is now called respiration (derived from “breathing” oxygen from the air). Technically, it’s referred to as oxidative phosphorylation, which means oxygen-driven attachment of phosphate to produce ATP (adenosine triphosphate). Oxidative phosphorylation was as great an advance as photosynthesis. It allowed the subsequent development of all animal life forms, including man.

The increased quantity and efficiency of energy production allowed animals to be more active, to run faster, jump higher and heal faster than their predecessors. They even had enough energy to “waste” on maintaining an elevated body temperature, and warm blooded animals began to dominate the earth.

The relative wealth of energy could also be devoted to increased neural processing of information. Central nervous systems became more complex and brains got bigger. Ever increasing neural complexity has led to consciousness, an emergent property of mind that has extended the anti-entropic nature of life into a new realm.

Scientific Myths to Live By

Through our understanding of the underlying mechanisms of life, we are now able to more finely tune our minds to the business of living and surviving as anti-entropic beings in an entropic universe.