About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.
It seemed to me that all of us have different ideas about viruses. (Living, non-living or what else...) I thought that the things we discussed in ' Exceptions of characteristics of life' is getting a little bit OUT of the topic.
So we can discuss all about viruses here.
To be honest I do not have so many detailed info about viruses. And wonder if you can inform me...
A virus in its simplicity is a protein shell carrying a little bit of RNA. This RNA carries instructions only to take command of another organism's cells' nuclei and reproduce original copies of viruses.
Where the idea that viruses are not living comes from the wording in the most accepted definition of life...part of which says "All life is composed of cells." A protein shell is not a lipid bilayer, and thus not a shell. By textbook definition, a virus is not alive.
However, in all other areas of biology, we take exceptions to every rule. The debate here is should we make exception to the most basic rule that our entire science is founded on?
Of course I know how viruses are defined in books. I was asking the people's opinion or doubts.
Personally, it seems to me that viruses are a form between living and non-living. OK all scientists have an idea.
But should we just accept them without any logical thinking?
What is there to talk about viruses - poison, why don't you start us of in a specific direction...
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
Read and understood...but I do not accept it. Please take not that while I am fairly progressive, I still base my ideas on accepted knowledge in the biological community. Some places may be teaching that life must contain DNA or RNA. However...the most widely accepted and used definition of life says that if there is no DNA present in a sample of tissue, it is not life.
Furthermore, even if the definition of life were to be changed to include RNA...viruses would SILL fail to make the list of life. The definition of life also stipulates that all life is made of cells. A virus is not made of any cell. Cell membranes are complex phospholipids and proteins bound to them. Viruses have simple protein shells, and therefore are not cells.
Point Three: "Cells must arise from other cells." This also is included in the definition of life. Viruses do not divide through mitosos, as all true cells do. They invade true cells and reprogram them to manufacture new viruses. Not unlike human organisms building robots, aye?
Any virus in the family Retroviridae that has RNA as its nucleic acid and uses the enzyme reverse transcriptase to copy its genome into the DNA of the host cells chromosomes. Many cancers in vertebrates are caused by retroviruses.
(from: http://www.biology-online.org/dictionary.asp )
Viruses are really simple. They contain genetic information in the form of RNA or DNA, they have a protein shell called the capsid, and sometimes (depending on which virus) the capsid itself is contained within a phospholipid membrane called the viral envelope. The phospholipid used to create this envelope is actually stolen from the plasma membrane of the host cell that created the virus.
Viruses are not considered to be alive because they cannot metabolize or carry out reproductive processes on their own. In order to reproduce, they MUST hijack the cellular machinery of a host.
I looked in a my 9-th grade book an it said at the lesson at viruses: "They are at the limit between living and non-living, therefor are named infectious entites"
This makes sence to me
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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