why aren’t viruses “alive”?

Question

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

Answer 1

There’s a little bit of a divide in biology on what the definition of life is. Traditionally, living organisms need to fulfil all of the following traits:

Homeostasis (regulation of internal environment)

Organisation (composed of cell(s))

Metabolism (transforming energy to cell components)

Growth

Adaptation (evolutionary change)

Response to stimuli

Reproduction (create offspring)

A virus is dependent on its host for many of these processes and as such not really considered life. The problem with the above definition is that it doesn’t 100% fit biological life all the time. Think for example about a mule, they aren’t able to reproduce, but still living.

Even though a virus doesn’t have its own metabolism, it does adapt. It does reproduce, but only through a host. There are biologist that consider a virus alive (I belong to this camp). There is another definition that I feel better captures life and that is that life is capable of darwinian evolution. This includes viruses, but also includes some other things that either really are on the boundary of life (self replicating proteins) or beyond (ideas can be argued to be able to evolve and selected on; some ideas stick around and adapt while others go extinct, sort of similar to a virus).

In conclusion, no definition of life is perfect and once you come at the boundary of life some sort of arbitrary line is drawn. Whether that line is put before or after a virus, self replicating proteins or ideas has interesting philosophical implications, but is not that relevant for the rest of biology.