Life needs energy to survive. Energy is needed to perform basic life functions like movement, hunting and gathering, protecting from prey and natural elements. It is converted from one form to another. Eventually, the energy within the living organism is expelled from the organism while useful work is performed.
Why and how energy for life?
Work is done when there is change in energy. In other words, energy has to go somewhere, so work gets done.
While humans and other animals do physical activity like walking or running, the energy in their cells is eventually converted to carbon dioxide and heat during metabolism, both of which are expelled from the organism. The environment is in a state to receive these byproducts. In this way, the overall energy difference between the organism and the environment slightly decreases.
We then ingest energy from outside the environment and replenish our energy supply, thus raising the energy available to us. This causes the overall energy difference between the organism and the environment to increase. This assumes that there is an infinite source of energy, but that is not the case. Think of it this way, if at the beginning, Life had 10J of energy and Environment had 100J of energy available, the difference in energy between the two is 90J. If later, Life consumed 20J from Environment, the score is now: Life=30J, Environment=80J. The difference however is now 50J; it has reduced.
The form of energy due to work done is eventually mostly lost as heat (Ref. 1), and we will approach a state where energy will be evenly distributed. In our example, if Life and Environment approach equal energy, there is no way for one to borrow energy from the other. If we extrapolate this to everything in the universe, it will eventually lead to the Heat death of the Universe - a thermodynamic equilibrium - insert < a vague, sinking feeling here >.
The energy difference between the life forms and the environment can decrease over time – food sources can vanish and water bodies can dry up. Remembering that energy is the ability to do work, life forms can no longer survive in that immediate environment and organisms will need to forage for food sources further away.
What is Entropy?
Entropy is the relative distribution of energy in a closed system. The earth can be thought of a closed system where living organisms ingest food from the environment. One can also think of life as an open system which interacts with the environment and continously draw energy from it – also known as negentropy.
Thus energy is redistributed among different living things as they go through the life and death process. In other words, living beings need to be in a state of higher energy with respect to their environment, thus lowering their entropy. And remembering once again, work is done only when there is a energy difference between the initial state of the system and the final state.
In the end
Life is a low entropy system. When death comes about, the organism is no longer able to feed itself and raise it’s energy (or lower it’s entropy) and it’s energy is assimilated or diffused into the environment, thus the overall entropy of the system increases. This is in accordance with the second law of thermodynamics which states that the entropy of the universe is always increasing.
So in life and death, the second law of thermodynamics makes it’s point.
References
- Heat death from Wikipedia
- What is Life? by Erwin Schrodinger
While there were many sources where I read and heard about this topic, I was pleasantly surprised to see this being expounded by none other than Erwin Schrodinger in his book What is Life? - the excerpt of which is below.
