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

The definition of life is kinda blurry. There are plenty of definite yeses, tons of definite nos, and a fair number of “depends on how you wrote your definition”. Our current definition of life includes the following pieces, which must all be met:

Growth

Reproduction

Homeostasis (does it self-regulate its internal environment)

Metabolism (does it use materials and energy from its environment)

Ability to react to the environment

Complex organization

Adaptation over generations

All of these are required for something to be defined as living.

Let’s start with something that doesn’t have any of these characteristics, then look at some things that have some of the characteristics but don’t quite make the cut.

A rock is not living. It does not grow, reproduce, self-regulate, use energy or material from its environment, react to the environment, adapt, or have a complex organization.

Fire is not alive. Fire grows, reproduces, and uses energy and material from its environment, but it does not adapt, respond to environment, or have any complex organization.

Computers are not alive. Computers have complex organization, self-regulate somewhat (with fans, low battery mode, automatic virus scans, etc.), they take energy from the environment (though not new material), they respond to the environment (when you click on stuff and cat pictures appear), and it has a pretty complex organization, but it does not grow, reproduce, or adapt on its own.

Transposons are genes which copy themselves and insert the copy into a new spot in a cell’s genome. They are not alive. They reproduce and they adapt, but they do not have complex organization, grow (rather, they are made by parts of the cell), or self-regulate and saying that the cellular machinery copying and inserting the transposon is the transposon’s metabolism would be a stretch.

Viruses are the same as transposons except for a protein coating that lets viruses leave the cell they started in. They are not very complex and they don’t really self-regulate unless you count the fact that the protein shell keeps the DNA or RNA separated from the outside environment until it hits a suitable cell membrane. It does not use energy or material from the environment—all energy needed comes from the cell when the cell makes the pieces of the virus.