Life is defined as being able to undergo metabolism, growth, reproduction, and adaptation to the environment and being alive is defined as being FULL of activity. So it is possible to have life but not be 'alive'. A bear in hibernation, though not being able to grow and reproduce, would still exhibit a minimum amount of metabolism. It's just that adaptation has been prioritized as of the moment to ensure its survival. Fungal and bacterial spores are considered dormant but though growth and development have stopped, the fundamental metabolic processes remain in play, keeping them viable (having the ability to grow, expand, and develop). Viruses are obligate intracellular parasites, not exhibiting metabolism. A bear needs to hibernate to conserve energy, but in viruses, energy conservation has become so efficient (considering that they have co-evolved with every known living thing since time immemorial) to the point that they don't need to metabolize outside of a host cell to remain viable. Even the dormant fungal and bacterial spores need to keep some metabolic processes going in order to remain viable. I am inclined to think that Evolution has given viruses a choice (at a particular evolutionary crossroad) and that they chose not to metabolize when outside of a host cell. The phrase 'unable to metabolize outside of a host' seems to me to be a bit of an understatement. Helminthic parasites survive outside the host cell for the amount of time it takes to digest what they took and/or to look for another host. Viruses are able to find hosts without wasting energy (ex. HIV travels through secretions). Furthermore, viruses replicate inside the host, using the host's energy, while most helminthic parasites replicate outside of their host, using their own. In these examples, viruses are more 'alive' than the 'living' helminthic parasites, the metabolizing dormant microbial spores, and the fat-consuming bear in hibernation, because I do not see how wasting energy can be an evidence of having 'life' and it be attributed to being 'alive.' Yes, viruses are very much alive.
i think they contain the genetic material and can use very efficently use the metabolism of the host to produce thousands of copies in single cell and so they can make identical copies of them.
so they have the genetic material
they have the abality to produce similar virus particles
so we can say them as living particles.
i agree with DonLine and he beautifully elaborate the topic that viruses are alive and indeed they are alive, because they produce similar virus particles very efficiently and contain the genetic material that is the most fundamental characteristic of living things.
Didn't think you guys would agree...whew!!! Haha! Any other takers?
Can't believe anyone is still adding to this thread. Viruses are not alive. If you study pathology not biology you will clearly see what the differences between organism and infectious agent (even disease causing agent i.e. chemical) are.
Consider Wikipedia's article on Virus especially the section on origins and lifeform debate. ---> [Only registered users see links. ]
Note the comments on retro-evolution of parasitic cell inside larger cell, escaped genes, simplified pre-life self-replicating molecule.
A virus (from the Latin virus meaning toxin or poison) is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Each viral particle, or virion, consists of genetic material, DNA or RNA, within a protective protein coat called a capsid. The capsid shape varies from simple helical and icosahedral (polyhedral or near-spherical) forms, to more complex structures with tails or an envelope. Viruses infect cellular life forms and are grouped into animal, plant and bacterial types, according to the type of host infected.
It has been argued whether viruses are living organisms. Some consider them non-living as they do not meet the criteria of the definition of life. For example, unlike most organisms, viruses do not have cells. However, viruses have genes and evolve by natural selection. They have been described as organisms at the edge of life.
this debate is continue all over and its true that some scientist consider them live because of producing progeny virus particles and they contain the genetic mateiral that is fundamental property of life.
and some say that they are non-living because they dont have a true cellular organization, they dont grow in size, dont produce progeny outside a living system and dont metabolize any energy.
but this debate is still continue.
i myself introduce a term of semi-life for virus because they have some living and some non-living characteristics.
but if somebody ask me, then they are more live in my view point.
thanks to all for nice discussion on this topic