In your biology career, you may come across people attempting to use the Second
ID: 1770639 • Letter: I
Question
In your biology career, you may come across people attempting to use the Second Law of Thermodynamics to discredit the idea of evolution. Their argument goes something like this: The theory of evolution says that life evolved from smaller inorganic molecules to larger organic molecules to simple one-celled organisms to more complex multicellular organisms, moving towards more complexity and organization. But the Second Law of Thermodynamics says that entropy always increases, with everything moving towards increasing disorder. Therefore, if the Second Law is correct, then evolution is impossible. How would you respond to this argument? Are they correct that evolution and the Second Law are fundamentally incompatible? If so, which one (evolution or the Second Law) is wrong, and why? If not, what are the flaws in their argument? Explain your reasoning, based on your knowledge of thermodynamics and evolution.Explanation / Answer
II LAW OF THERMODYNAMICS
The entropy of the entire universe always increases
(OR)
The total entropy of an isolated system can never decrease over time
EVOLUTION
It is a process in biological system where successive generations show change in heritable characteristics. These changes (which are random) may be beneficial, neutral, or harmful depending on the environment. If the changes are beneficial, the offspring survives and may pass on that change to the next generation.
With these definitions, one can deduce whether evolution whether the process of evolution violates 2nd law or not. The second law clearly states that the entropy of a closed (isolated) system can never decrease. The emphasis is on the 'closed' system. A closed (isolated) system is a system where there is no input or output of energy or matter.
For the sake of argument, let us consider that the earth is a closed system (it is not!). Even if a system is closed, the second law does not prohibit decrease in entropy locally as long as the total entropy of the system increases. Taking evolution, there are many random mutations (changes) which may increase the entropy of earth. Only few are beneficial and creates order decreasing the entropy. Hence, the total entropy of earth has increased while entropy has decreased locally.
The above argument has considered that earth is an isolated sytem. But earth is not an isolated system. It accepts energy from sun in the form of heat and light which powers the evolution process indirectly. While the entropy is decreasing locally (at earth), the total entropy of solar system and the universe in increase which again follows 2nd law of thermodynamics.
Second law of thermodynamics and evolution are perfectly compatible and both are facts. The incorrect definition of system while extending the second law to evolution causes the incorrect conclusion. Earth is not an isolated system and hence there can be a decrease in entropy.