Is a virus alive? Why or why not?

Question

Does it exhibit characteristics of life?

Answer 1

Most virologists will tell you that viruses are alive and meet all the important criteria of life:


There are 7 characteristics of life: homeostasis, organization, metabolism, growth, adaptation, response to stimuli, and reproduction.

Homeostasis - many bacteria don't maintain a stable internal environment, are they dead?

Organization - Viruses are organized, have you ever seen a crystal structure of a virion

Metabolism - no

Growth - yes virus particles grow and mature in the host cell

adaptation (evolution) - very much yes

response to stimuli - Viruses respond to stimuli, just not the stimuli you think of naturally. Viruses modulate their reproduction and life cycles based on the "stimuli" in the host cell

Reproduction - agreed yes

So the only characteristic that viruses fail to qualifiy as alive for is metabolism, and it could easily be argued that metabolism is the least important and most arbitrar characteristic of living organisms since viruses do a fine job of gathering energy from their environment (host cell).

Answer 2

No it is not alive. It cannot reproduce itself without the genetic machinery of a living cell, since it has either DNA or RNA, but never both. It also does not respond to stimuli, as a virus just sort of floats around in the air and lands wherever the wind blows it. A virus also does not consume organic material, nor does it photosynthesize, as it needs no energy.

It can exhibit some of the characteristics of life, such as bacteriophage's ability to "inject" its genetic material into a cell through its membrane, which is a form of movemement. It also has a protein coat in its capsid, similar to an outer membrane, and has genetic material composed of nucleic acids.

However, since it cannot reproduce itself, it is considered to be 'not alive'.

Answer 3

The difficult part of this question is defining life.
The standard, simple definition of life is:
Any self-replicating chemical system which undergoes darwinian evolution. By this definition, virii are alive.

However, as with most science, things get complicated and that definition is a pretty simple one. So there is some debate as to whether virii is alive or not, depending on where you draw the line of life.

Answer 4

Virus' are alive, but their not. It depends on what you consider "alive". If you mean active and moving, then yes they are. Some people beg to differ though because they are just herditary material.

Answer 5

I have argued this all the time with professors: I think that viruses should be considered living, even though the scientific community as a whole classifies viruses as non-living only because they require a host in order to reproduce. Ridicules !

Perhaps they are just smarter and more sinister than other microorganisms.

Answer 6

It's an exception to the cell theory and not consider a "living organism."

Answer 7

Must be alive, otherwise Heaven would be overcrowded with virus souls... there's so many of them.

Answer 8

according to most defnitions of life its not because they are not made of cells and do not contain dna.

Answer 9

it depends on your opinion of what is "alive"
for example, an unborn child. some say it is not alive, yet others say it is.