Hi everyone,
I’m not very knowledgeable about science, so I’m struggling to understand the notion that viruses aren’t “alive”, and the robot analogies people use. I understand that they don’t have some of the characteristics (cells, ability to reproduce), but my mind can’t wrap itself around the notion that they’re like objects. Can you please give some examples that could explain this in a way that is accessible to someone who isn’t very advanced in the subject?
Thanks
EDIT: wow thanks so much guys for so many amazing replies!!!
In: 29
There are many instances of thousands, or even millions of year old viruses that were resurrected. Not many living things can stay dormant for that long.
Also, while viruses do reproduce, they don’t do other functions of living things like eat and even when they reproduce, it’s asexual cloning using host cells.
I like to think of it more like a spectrum
On the “definitely not alive” side, we have stuff like rocks.
Then we have the typical definition of life on the other.
Viruses are sort somewhere in the middle. Doesn’t meet the definition of life, but it’s closer to life than a rock is.
>Hi everyone,
>I’m not very knowledgeable about science, so I’m struggling to understand the notion that viruses aren’t “alive”, and the robot analogies people use. I understand that they don’t have some of the characteristics (cells, ability to reproduce), but my mind can’t wrap itself around the notion that they’re like objects. Can you please give some examples that could explain this in a way that is accessible to someone who isn’t very advanced in the subject?
>Thanks
I feel like you’ve created kind of a [false dichotomy](https://en.wikipedia.org/wiki/False_dilemma) for yourself. I don’t fully understand what you mean by “they’re like objects” but I’d guess from the context of your whole post you’re trying to say something like “it’s not alive so it’s basically a piece of rock”. That’s not the case. “Alive” is just a very very **very** special category of things and just because most things are “not alive” does not mean “all not alive things are the same”. There are objects that are blue and there are objects that aren’t, but that doesn’t mean all objects that *aren’t* blue are alike. They just share the characteristic of not being in the category “blue” – that’s it.
Don’t think of a virus as a rock, it isn’t. If you’re trying to wrap your head around why it *is* like a rock then this is the reason you’re failing!
A virus is too simple to exhibit the complex behavior of a living system. It is a container for genetic material with one function, to plug into a cell and replicate. A cell assembles multiple structures within itself. If you were to break it down further, those individual parts by themselves wouldn’t be “alive” either.
A robot could be made quite complex to move and react to the enviroment, but an individual processor within it can’t do those things.
it is a self-replicating organic machine. It contains a code of more copies of itself. Because it isn’t alive it cannot make those copies, so it injects the code (or recipe?) for itself into living things. Those recipes are made by the cells with produces more of the organic machines. Sometimes those machines also produce or contain toxins.
The question is embarrassing for biologists, because it really is a matter of definition.
A very thorough definition of “being alive” (at least on Earth) would be composed of the following (simplified) points:
– being a cell, or being composed of cells
– being able to “use” outside source of energy to grow and maintain yourself
– being able to reproduce in way that your “species” will subjected to Darwinian evolution
Now, viruses do not check the two first points. However, the first point is often considered to be an arbitrary addition to the definition that just happens to be true to everything consensually called “alive” on Earth.
The second point really is the crux of the issue for viruses: by themselves, they are not able to “use energy” (they do not have a metabolism), and many people consider this to be a fundamental point of “being alive”.
But saying that they do not belong to the realm of life isn’t really true either, because not only do they check the third point, they also very often and strongly interact, at the genetic and evolutionary level, with entities we consensually call “alive” (bacteria, animals, plants, etc…).
So, they are a kind of middle-point in the definition of live, and depending on what you choose to include in “life”, you might include them or not. Fully including or excluding them is very difficult, hence the embarrassement for biologists…
Personally, I consider this question to be rather moot, once you’ve realised which part of the definition above they check or not. Then it “just” (it’s a bit more complicated really) becomes a matter of arbitrary threshold.
Maybe rather than objects, another way you could think of viruses is that they’re like ideas. It’s more like a recipe than a rabbit or a rock.
Viruses don’t reproduce themselves. They’re little packets of information, all saying “make more of me.” They come into contact with living things carrying this instruction: “make more of me”
Not every animal can read every recipe, but those that can understand it say “sure, I’ll make more of you.”
Then we sneeze them out, poop them out, or otherwise send them on their way, where the new copies *we’ve* made can come into contact with other recipients.
Living things adapt to our environments, make more of ourselves, and generally “do things.” Viruses don’t do things, hence their object-likeness. They’re just instructions
They get categorized as “not really alive” because they don’t do things that most living things do, such as eating, breathing, reproducing (at least, unassisted), or producing usable chemical energy.
It’s just a definitional question. They’re not alive because we’ve decided that they don’t meet some criteria. But the real question is “how do we define what is “alive”?”. There’s less difference between animate and inanimate than most people want to admit.
ELIA5: Viruses are considered to not be alive because they can’t duplicate themselves without the help of other organisms, and they don’t make their own energy.
In-depth: The definition of life is fluid so there is no definite distinction between something being alive and not alive. Generally, scientists consider life to have 7 characteristics:
1. Order and structure
2. Reproduction
3. Growth and development
4. Energy utilization
5. Maintenance of homeostasis
6. Response to external stimuli
7. Adaptation to external pressures
Viruses definitely are ordered, respond to stimuli, and adapt to external pressures. As viruses require a host to reproduce, utilize energy, and grow/mature, they are not considered to be alive. They also have no innate mechanisms to maintain homeostasis (though their capsid could be considered to maintain a homeostasis). One could counter that obligate intracellular bacteria also require a host to reproduce; however, these bacteria can grow, make and use energy, and maintain homeostasis on their own.
Life is a spectrum; however, our language only allows for the binary “alive” or “not alive” so a line must be drawn for this distinction. Viruses straddle that line which makes them so interesting
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