tronvillain

The only apparent connection between the replicators of the RNA World and viruses is that some viruses use RNA as their genetic material. Other than that, it is not apparent that they have any similarity whatsoever. Personally, I'm not a fan of the purely RNA World.

Francois Tremblay

Standard definitions of life are flawed because they obviously exclude a lot of cases that we consider "living". Babies cannot reproduce, for example (it's always surprised me how many people miss that). We just have to accept that we have no precise definition of life.

Personally I like to stay in the simple realm of "self-moving or not", even though this also leads to counter-intuitive propositions (ex. a ventilator is alive). I treat it probably like our prehistoric ancestors did, as an indicator of how something can surprise us (for example, a ventilator is more surprising than a plant).

[ January 29, 2002: Message edited by: Franc28 ]</p>

RyanS2

Just one question that has me curious, and that is obligatory reproduction. A virus is supposed to go into a foreign cell and replicate itself. Does this go against the view of every living thing supposed to be only able to produce its' own offspring?

[ January 28, 2002: Message edited by: RyanS2 ]</p>

MortalWombat

I don't quite follow what you mean about "obligatory reproduction." The virus is just using the cell's own machinery to replicate itself. If you step on a nail and get a bacterial infection, the bacterium is using materials from your body for building blocks and energy to reproduce. There are even certain types of bacteria that can only grow inside a host cell. How is this any different?

tronvillain

It is different by virtue of the method by which it is achieved. You said it yourself - a virus is replicated by the cell, and a cell replicates itself. Of course, I don't have any idea what RyanS2 is talking about either.

MortalWombat

Not all cells replicate. Neurons, for example, don't replicate, and herpes simplex virus does a fine job of making more copies of themselves inside neurons.

tronvillain

While true, that has no relation to the difference I was referring to. You asked "How is this any different" and I explained.

Lannergard

Babies are just humans in a non-reproducing phase. No organism can reproduce all the time. At the cellular level, however, reproduction takes place in the baby continually.

Lannergard

Actually I think #5 seem superfluous. If the author had a good reason to include it, maybe it could be modified to "different from non-living surroundings" or something.

Francois Tremblay

Why yes, that was my point. As I said, considering such stringent criterias is futile.


Of course the cells in a baby are alive, I never said otherwise (in fact, since reproduction implies some kind of movement, that's implied in my definition also).