NOTE: if you come across terms you don't understand, plz scroll down. I have included a term-list there.
The definition of life is too long to post here, check it out on the link. Why is this definition so long? It's easy: exceptions. Our planet houses such a biodiversity that everytime they make an all-included definition, a (new) species pops up from which we're sure it's an animal, but misses one key in the chain that makes it life. In order to make a correct definition it expands everytime, again and again.
quite an understatement
Let's look at what a virus is as an object.
That's what science has been debating about for a long time now. I won't clear it out with one post But I'd like to clarify it to you guys.Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms.
These are 2 of the more standard viruses out there. As you see they look a bit like moonlanders (especially the 2nd one). That isn't surprising.
(don't look at how crappy the img is, did it in paint )
As you see, the viron (name of one virus molecule) actually 'lands' on this great 'orb' which represents a cell in your body. I'll guide you through the process.
1. This is the evul viron, seeking a good host. No, not a site-hosting company . A host is a living organism in which a parasite (such as a virus) can live, and eat from.
2. The ship has landed. The virus now clamps it's little clawlike tentacles into little tentacles on the outside of your cell to get a good grip for the next phase.
3. In this phase the viron pushes itself through the membrane of the cell with brute force, and injects it's DNA into your cell (a viron can also contain only RNA, but for the sake of simplicity, we'll keep to DNA). Notice that the other viron, the on the right, just uses a sort of needle.
4-5. The DNA reaches the core of the cell and infiltrates it. In this core lies the most important part of the cell: your DNA. The viron's DNA pushes itself between yours and assumes control over the cell. It starts redirecting everything in the cell: it orders the cell to make new virons. Many new virons.
6. After a while, there is no space left for the new virons to go, but they keep coming, so eventually, the cell bursts open, and the young virons are cast out into the cruel world to go find a new host.
Not a nice scene now is it?
Next: the symptoms of life. If a supposed organism shows these signs, it's alive. So they say.
These 7 signs are as follows:
Theme #1 - Cells
From Dictionary.com:
Biology. The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semipermeable cell membrane.
Here we come across the first flaw. It says: ...capable of independent functioning... which is not the case with a virus. He has to use a host-cell in order to do things like a normal cell.
Theme#2 - Organization
This means to say that living organisms have a basic structure. Like an energy provider, a command centre, etc.
This is partly true with a viron. They have a nuclei (the core, containing DNA), but nothing else. So there is only a commando centre. So well, they are organised, as one big structure.
Theme#3 - Energy Use
'Living matter acquires matter and energy from the external environment and converts it into different forms.'
ripped from Oceans Online.
Well, this certainly is a DON'T. That exactly why viruses need hostcells, they can't make energy for themselves.
Theme#4 - Homeostasis
'Living matter maintains some type of homeostasis.'
This one is universally accepted. Homeostasis is the property of an open system, especially living organisms, to regulate its internal environment so as to maintain a stable condition. Well, this one we can also cross out on our list. As a matter of fact, a viron has a very minimalistic internal environment.
Theme#5 - Growth
Does a virus grow? Well, if you see a car being built -piece by piece is being put on- and consider that the 'growth' of the car to adulthood, then yes, a viron can grow. But as I see it virons are mainly assembled.
Theme#6 - Reproduction
'Living matter reproduces and passes on genetic material as a blueprint for growth and subsequent reproduction'
Well these babies produce allright. They produce so well we are being killed in the process.
Theme#7 - Evolution
'Living matter evolves.'
Yes, a virus can evolve. Look at the recent 'SARS'. Or ****, to stay closer at home (**** = flu, your average home-garden-kitchen virus). SARS originally only affected pigs and animals of the like, until it evolved slightly and could acces humans. And **** shows signs that they are becoming more and more resistant to anibiotics, the big medicine that stopped great **** epidemics. So yes, a virus can certainly evolve.
Lacking 4 of the 7 needed signs, I'd say that it is not really alive. But then again, the most important of these characteristics of life are containing DNA and evolving, in which viruses excellently succeed.
If I had to put it in my own words:
Virons are like zombies are to men. Not with a free will, not with the capability to make food for itself, and needing a host (like a human) to survive, but still with the few vital signs of life.
NOTE: zombies need to eat human flesh in order to 'stay alive'. (Never really figured out why )
Terms:
Viron: A microscopic object consisting out of an outer membrane, an inner membrane and a core with DNA/RNA
Virus: A collective noun for a specific group of virons.
DNA: A long spiralled string of specific proteins that is the blueprint of your body. It describes exactly how you look and what kind of curve your nose has. It is in every cell of your body. If you could take one DNA-string out of a cell and stretch it out, it would be around 2 metres in length (6.6 feet). Surprising, no ?
RNA: Similar to DNA, but not quite the same. It is also a a string of proteins, but one of the main functions of RNA is to copy genetic information from DNA and then translate it into proteins. In virons it is like a copy of DNA that never existed.
URLS:
Physics forum
Wikipedia
And some other site I couldn't remember
Hope this makes maybe somewhat clearer, plenty to debate still!
