What is Life?

I particularly enjoyed this nerdy video, and took the poll definitions from it. I’m curious how others would respond.

What is Life?
  • Organization, Growth, Reproduction, Metabolism, Homeostasis, Response, Adaptation
  • At least a majority of the above
  • Metabolism and Homeostasis
  • A self-sustaining chemical system capable of Darwinian evolution
  • A thing that actively prevents entropy from increasing within itself
  • Something else

0 voters

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Leaning more towards metabolism and homeostasis. I don’t think evolution, nor even reproduction is a requirement for life, as that would imply a neutered cat isn’t alive. It seems to me a universal property of living systems is the ability to take compounds from the environment and then rebuilt it’s own constituents (and from this derive the energy required to maintain homeostasis within some threshold). This metabolism, combined with homeostasis, seems to me to be what makes something alive. If these two conditions aren’t met, it is dead.


@Rumraket, do the giant viruses muddy the waters a bit for you? Here is a paper on metagenomic analysis of ~500 Nucleo-Cytoplasmic Large DNA Viruses.


Overall our findings reveal that giant viruses encode complex metabolic capabilities with evolutionary histories largely independent of cellular life, strongly implicating them as important drivers of global biogeochemical cycles.

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Definitely. I also think it’s hard to narrow down exactly the point at which, for example, a multicellular organism is dead. As more and more of the cells in it’s body gradually lose the capacity to maintain homeostasis (suppose it’s starving to death), at what point do we say it is dead?
We could even pose the question concerning a single cell. Must all metabolic reactions in a cell have ceased for it to be considered dead? We can contrast the extremes at both ends of the spectrum and say somewhere between them must lie the “point of death”, but I can’t get around thinking the exact point must be an arbitrary point of convention.

There’s also a similar problem of metabolic and reproductive rates. I can imagine, at least in principle, a sort of bacterium with a metabolism so slow it would for all intents and purposes appear dead to us, with some reactions taking years or even decades. A bacterium that takes a century to undergo binary fission? Such an organism would be practically impossible to culture, and by any extant measure considered inviable. Yet it could basically have a lifecycle so long it would be indistinguishable from inert organic matter.

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Table 1 in this article is thought-provoking:

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Humans love to draw sharp dividing lines. Nature, not so much.

A pertinent observation when it comes to understanding life, and evolution.


Hmmm yes, it could be questioned whether endospores are alive.

If we look at the Cats individual cells would you think differently about reproduction?

Thanks for answering. I liked the physicist answer, of course. :grinning: If something isn’t active it is also dead.

I don’t think so. But it’s an interesting question, and I think that relates to the question of metabolic rate. If the rate at which cells are dying (because the cat is for example starving) is greater than the rate at which they can be replaced, the cat is in the process of dying, even though technically it’s cells are still capable of reproducing. But of course, the cat might still be considered alive for an extended period of time even as it moves ever closer to death.

I could imagine that literally all the cat’s cells have lost the capacity to reproduce, and yet the cat remains alive for a short time. I think blood cells have a very high rate of replacement, so I imagine a cat that can replace no cell in it’s body would only have hours left to live. And yet, for some portion of that remaining time I would probably consider it alive.

I think the relationship between life, non-life, metabolism, and reproduction is ultimately really weird, and we can imagine many counter-intuitive states and edge-cases that might defy our definitions (and defy our intuitions). I think, in the end, this highlights the fact that there is no true boundary at the physical, molecular level, and that “life” is really just an emergent property of particular complex systems of “dead” physics, and that where we put the dividing line will always be rather arbitrary.


Thank you for the quiz. Life is nothing on that list. I see that biologists, and the host of other scientific disciplines are still unable to separate what life “does” from what it “is”. Everything there is a descriptor only. What life is is a mystery to science, even Creation science. But whatever it is, it comes from God alone.

Given the choices, the last choice is the most accurate.

I figured someone would say that. :blush: We have an intuitive sense because we were created. Personally I think that the sun was high on his list of “alive” things in the video because people are taught /assume life comes from the sun.

I liked the entropy definition in terms of a scientific definition.

I chose “Actively prevents entropy”, but that alone isn’t enough, otherwise a growing crystal might be alive. Imperfect growth or reproduction plus selection implies adaptation. Preservation and reproduction of information.

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Yes, I think life has information.

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