Efficiency of Life?

Q:
Hi,I stumbled upon this wonderful source of amazing answers while I was looking for answer to a question jumped at me this morning when I looked out the bus window at these trees planted by the park sidewalk. I acknowledge that at my age, having gone through tertiary education, the question perhaps is fundamentally baseless.In nutshell, looking the dead leaves fallen by the base of the tree, I marveled at the chemical loops within the life of a tree and wondered at the level of efficiencies inherent in "life-loops" such as life of a tree. Imagine if tree was planted in a self-contained, hermetically sealed glassed dome with just the sufficient amount of soil minerals, CO2/O2 and water (with natural access to sunlight/energy) that the seed might need to grow to it full potential. The seed will grow into tree and in time die a natural death (assume without progeny). If we were to call this loop "life-loop", how can we quantify and evaluate the "efficiency" of this loop? What, in physics terms, would have been "gained" by this life-loop (in absence of any progeny)? Am I looking at it the wrong way?
- Ravi (age 37)
Singapore
A:

It's hard to answer questions about "efficiency" unless there's some defined goal and some scarce resource. We can answer little partial questions, however. For example, that tree will be hit by some sunlight. We can determine how efficiently that tree turns the scarce resource (sunlight) into something else (plant material) by taking the ratio of the free-energy of the incoming light to the increase of chemical free energy as the plant makes sugars, etc. There would be a gain, not permanent, in the free-energy of the chemicals left around even after the plant dies. A familiar striking example of that is all the free-energy left around as fossil fuels, which we are now using up destructively.

Mike W.

(published on 11/03/2017)

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