Welcome to my new, episodic series on great moments in biology. Let me be clear, these are not Great Moments in the sense of Biology, but personal great moments in my own experience. As such, they are necessarily biased, and anecdotal. Think of this series as a story of personal growth, visible only in retrospect, with the ripeness of time. These are filtered reflections, emerging now partly due to a surfeit of time, pandemic and sabbatical release.
Don’t expect any great revelations here yourself if you’re a scientist or teacher. Most of you already know this stuff at some level, many better than I. My goal is to reflect on my own paths to understanding, and how those came about, to the best of my recollection.
One of my favorite useless conceptions — I’ve had so many! — is a bumper sticker that reads, “Fighting Entropy, 24–7.” LOL, right? Entropy, more formally described as the second law of thermodynamics, is not an immediately intuitive idea for most people, at least as typically explained in a science class. The basic summation is that the entropy of an isolated system always increases. But wait! You can’t use a word in its own definition. Another way of thinking about entropy is the degree of “disorder” in a system, fundamentally conceived at the molecular level, but with concrete results we can grasp at the macro scale of human space and time.
A sugar molecule, like glucose, is highly ordered, in a relative sense. Once that molecule is digested or broken down into smaller components like water, carbon dioxide, and other simpler carbon-containing molecules, it has become more disordered, even though all of the original matter was conserved. The magic of cellular respiration is a living cell’s ability to harness energy released by that breakdown to do work, son! Work like growing, metabolizing other chemicals, building up and breaking down, extending its own existence, and reproducing.
But entropy refers to any system, and all systems may be considered closed if we take in the biggest picture, starting with the universe as we think we know it. The overall entropy of stars, galaxies, and the universe itself appears to be increasing, as everything expands toward its ultimate (perhaps?) fate of heat death. Our star, fondly known as Sol, will expend its nuclear fuel and burn out in a few billion years (better see to those stock investments now!), along with our beloved planet Gaia, and everything else.
That’s one story.
On a more immediate level, the opossum you see rummaging around your garbage can at night is a highly ordered system. That same ‘possum, flattened into a mono-layer on your drive to work (or “ironed out,” as my grandmother was wont to describe such carcasses) has achieved a remarkable and sudden increase in entropy. It has accelerated sooner than expected to a more probable state. Scavengers and decay microbes will see to the rest. One of the corollaries of the second law bids us not to expect that ‘possum to spontaneously reassemble on the asphalt and head out for another can conquest. This is the irreversibility of increasing entropy in a defined system — reflected in the phenomemon of “time’s arrow,” for those with more of a physics bent.
The concept of entropy, that ultimate increase in disorder, has become another straw man to gleefully torch by opponents of evolution, and even by those hoping for an outside hand in the “miracle of life” itself. Any animal — take you or me for example — began life as a single fertilized cell, the zygote. Through successive cell divisions and growth, we increased order BIGLY, until arriving at our current magnificent state of high order and omniscience.
And what about those crazy claims that species have generally increased in complexity over evolutionary-geological time, from the first unicellular prokaryotes to the miracle of Tom Brady? Take THAT, Darwinists! Entropy says NO! Ergo, an almighty hand must intervene.
Those darn laws of thermodynamics seem pretty iron, at least down here on this mortal coil, which is news I hate to break to all you endless growth and sky’s-the-limit fans out there. So iron, in fact, that they inspired what has come to be called (tongue firmly in cheek) Ginsberg’s theorem: You can’t win; you can’t break even; you can’t even get out of the game.
This same concept of the inevitability of entropy pops up for me in many situations. Recently I had a brief discussion with a friend about controlling nonnative, invasive species, now regarded as an essential action for conserving biodiversity, especially in some areas. My friend’s response was blunt: “Fighting invasive species is like battling thermodynamics. You can never win, but will always lose.”
That set me back on my heels at the moment, and I left it without response. On slow digestion, which is usually the case for the slow-witted like me, a thorough response would have been, Correct. You can’t win against thermodynamics. But tell me, do you plan to run up the white flag and stop eating today? We will never be rid of many, many invasive species. But the literature is rife with inspiring examples of conservationists who have either eliminated or controlled invasives, bringing the native species and food webs they support roaring back. Shall we tell them to give it up?
Of course not, any more than I’ll give up that pulled pork I smell in the crock pot right now.
So, what’s all this about a great moment of revelation, then? For me, it happened in an undergraduate cell biology class, more than four decades(!) ago. My professor was delivering her standard lecture series on cellular metabolism, complete with calculations of available free energy. She wore her trademark open-collar dress shirt and plaid suit jacket, along with a unique delivery that cut quite an impression in the classroom. Her final summation held the revelation. She ended the unit with that same nagging question: How do living cells, and by extension multicellular organisms, defy that iron entropy law? How are they able to increase order through time?
The answer was both succinct and memorable: “Cells increase order by decreasing the order of their surroundings.” The concrete among us call that “eating.” I still have the notebook with that line scrawled out in the jagged hybrid print-cursive, self-taught stenography of old school note-taking:
Cells ↑ order by ↓ “ surroundings
There were no pauses for writing verbatim sentences. You had to get it while it was hot and brush up later with fellow classmates or the professor. Alas, the lost art of note taking!
Now, the revelation part. It wasn’t a revelation in the film short sense. Venus never popped fully formed out of a clam shell. No instant gratification of deep understanding. I’m sure I didn’t understand much at the time about free energy, except to see that some bookkeeping was involved. And I never really conceptually grasped entropy either, until years of reading and teaching later. To be honest, I’m sure I still don’t understand entropy that deeply. I’m not a molecular biologist or thermodynamicist. But I grok it well enough now to ‘splain some things to my introductory biology students.
These days, that simple phrase springs back to life like clockwork. It eventually bolstered a more mature understanding of concepts like “energetic coupling” in cellular metabolism. There’s still no such thing as a free lunch, but for every reaction that increases molecular order, like building a glucose molecule, there must be some external energy source to power it. That energy can be sunlight, in the case of plant sugar biosynthesis, or it can be harvested through coupling to a separate, entropy-increasing (“exergonic”) reaction, whose released energy powers the energy-requiring task of building something more complex (“endergonic”). Those “power reactions” themselves are fueled by constant input of molecules from without, the building blocks of the food we ate. Photosynthesis and respiration, the circle of life…
Thus do living cells, organisms, populations, and species defy the iron law of entropy, if only temporarily. Some day that solar furnace will wink out, and that will be all she wrote for your stock portfolio.
Time to consider bonds?
I’ll close with some reflection on why this was a “great revelation” for me in the first place. What made it so? Why did that short, scrawled line in a notebook itself defy entropy to lodge in my brain long enough to eventually bear fruit?
Now comes the opinion part. There were two essential ingredients to my eventual entropy revelation. The first was bringing a curious mind to the classroom. That was all on me, and it’s still an essential component of any effective teaching and learning arrangement. But it’s only half of the equation, maybe even less than half. The other secret ingredient was the delivery of that summary line by a dedicated, admittedly somewhat quirky, but most of all enthusiastic teacher. Revelation in a lecture, yes; as hard as that may seem now to believe, and even if it was only the germ of later growth.
That mix of personal attributes for delivery cannot be taught to green instructors in any simple or enduring way. And yet I think most of us who survived education can identify similar moments of inspiration, that perhaps didn’t fully take hold until later, sometimes much later. They are always tied to individual personalities who remain vivid by association. My own teaching career has been a constant effort to provide memorable substance for students, often failing, always revising, and starting over. There are multiple paths to good teaching; this is one of them.
The next time you see a squarshed squirrel on the road, check whether it’s fresh or not. I have a killer recipe for squirrel and dumplings, free to anyone who wants to advance their own fight against entropy.