What makes a virus non living

Facebook Twitter Pinterest. Partner Login. An Educational Blog. Is a Virus Living or Non-Living? Part 1 by Erica Mitchell March 12 9 Comments.

Are viruses alive? What are viruses made of? These microscopic infectious agents are the culprits of numerous human ailments, as well as animal and plant diseases. They have been around for millennia, and have left a path of destruction in their wake. Just how do we become infected with a virus, and what weapons do we have against these villains? We will answer those questions in our next post. Search this site on Google Search Google.

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More on:. Jake Port Jake Port contributes to the Cosmos explainer series. More from:. Jake Port. Read science facts, not fiction Make a donation. Go to mobile version. Although it is a single cell, it can generate energy and the molecules needed to sustain itself, and it can reproduce.

But what about a seed? A seed might not be considered alive. Yet it has a potential for life, and it may be destroyed. In this regard, viruses resemble seeds more than they do live cells. They have a certain potential, which can be snuffed out, but they do not attain the more autonomous state of life. Another way to think about life is as an emergent property of a collection of certain nonliving things.

Both life and consciousness are examples of emergent complex systems. They each require a critical level of complexity or interaction to achieve their respective states. A neuron by itself, or even in a network of nerves, is not conscious—whole brain complexity is needed. The enucleated cell is akin to the state of being braindead, in that it lacks a full critical complexity.

A virus, too, fails to reach a critical complexity. So life itself is an emergent, complex state, but it is made from the same fundamental, physical building blocks that constitute a virus. Approached from this perspective, viruses, though not fully alive, may be thought of as being more than inert matter: they verge on life.

In fact, in October, French researchers announced fi ndings that illustrate afresh just how close some viruses might come. Didier Raoult and his colleagues at the University of the Mediterranean in Marseille announced that they had sequenced the genome of the largest known virus, Mimivirus, which was discovered in The virus, about the same size as a small bacterium, infects amoebae.

Sequence analysis of the virus revealed numerous genes previously thought to exist only in cellular organisms. Some of these genes are involved in making the proteins encoded by the viral DNA and may make it easier for Mimivirus to co-opt host cell replication systems. Impact on Evolution Debates over whether to label viruses as living lead naturally to another question: Is pondering the status of viruses as living or nonliving more than a philosophical exercise, the basis of a lively and heated rhetorical debate but with little real consequence?

I think the issue is important, because how scientists regard this question infl uences their thinking about the mechanisms of evolution. Viruses have their own, ancient evolutionary history, dating to the very origin of cellular life. For example, some viral- repair enzymes—which excise and resynthesize damaged DNA, mend oxygen radical damage, and so on— are unique to certain viruses and have existed almost unchanged probably for billions of years.

Nevertheless, most evolutionary biologists hold that because viruses are not alive, they are unworthy of serious consideration when trying to understand evolution. They also look on viruses as coming from host genes that somehow escaped the host and acquired a protein coat. In this view, viruses are fugitive host genes that have degenerated into parasites. And with viruses thus dismissed from the web of life, important contributions they may have made to the origin of species and the maintenance of life may go unrecognized.

Indeed, only four of the 1, pages of the volume The Encyclopedia of Evolution are devoted to viruses. Of course, evolutionary biologists do not deny that viruses have had some role in evolution. But by viewing viruses as inanimate, these investigators place them in the same category of infl uences as, say, climate change.

Such external infl uences select among individuals having varied, genetically controlled traits; those individuals most able to survive and thrive when faced with these challenges go on to reproduce most successfully and hence spread their genes to future generations. But viruses directly exchange genetic information with living organisms—that is, within the web of life itself. A possible surprise to most physicians, and perhaps to most evolutionary biologists as well, is that most known viruses are persistent and innocuous, not pathogenic.

These viruses have developed many clever ways to avoid detection by the host immune system— essentially every step in the immune process can be altered or controlled by various genes found in one virus or another.