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NO, this isn't another abortion thread, this is a biology thread.

Currently we divide everyting we consider to be alive into three Domains-
Archea-Ancient bacteria
Prokaryota-Bacteria/animals with no nucleus
Eukaryota-Everything else

The problem is that this leaves viruses and prions out and no one is sure if they are alive by our definition or if they fit anywhere in this model.

Viruses containt DNA but they do not respire, feed, produce waste, or display any signs of life outside of a living medium
Prion's are just rogue, self replicating protiens.

So what do you think, are they alive?

Life is defined by simply being alive.

Viruses are not alive because they are unable to reproduce amongst themselves--they require a host cell to do so. Those other things you listed also keep viruses out of the bracket of life.

protolife?

MRS GREEN

Movement
Respiration
Sensitivity

Growth
Reproduction
Excretion
(Egestion)
Nutrition

Viruses are not organisms but bacteria are.

If they can evolve, possibly. But until then their just matter.

Originally posted by Darth Jello
protolife?

Perhaps. They still lack some very huge requirements in order to be considered life.

Life...? well, life is cool!! yeah,
I think it is cool when you know the meaning of life afterall.
the creator of heaven,earth and all things in this world.

Life is so wonderful living w/ Him *God

Originally posted by soulwinner
Life...? well, life is cool!! yeah,
I think it is cool when you know the meaning of life afterall.
the creator of heaven,earth and all things in this world.

Life is so wonderful living w/ Him *God

I think you're in the wrong class. This is Biology 101 not Theology 101.

hmm, would they be in an even greater division than domain then?
like with viruses and all other life being two separate branches coming from the same primordial ooze?

Originally posted by DiamondBullets
Perhaps. They still lack some very huge requirements in order to be considered life.
Can you give some examples?

Originally posted by Darth Jello
hmm, would they be in an even greater division than domain then?
like with viruses and all other life being two separate branches coming from the same primordial ooze?

No, cuz viruses lack a nucleus as well as all other organelles needed for respiration, waste production, and reproduction amoungst themselves. They display some charactaristics of life including genetic material, basic proteins and amino acids.

Some scientists actually debate that they are their own kingdom and those oddities make them very unique in their own right. I for one, think that claim is a bit of a stretch. I would put viruses, prions and cancers in the same category--they are rogue units that can only live by causing harm to a host. No they aint parasites--a tapeworm is a parasite. Those things are a whole 'nother ballgame.

Originally posted by Valharu
Can you give some examples?

respiration

waste production

lacking organelles

lacking the ability to reproduce without a foreign host

I don't consider alive and a life to be the same thing entirely.

"There's life on Mars." If you go there expecting to find malls and starbucks, you will be wrong. There are things there that are alive, though.

-AC

well, it wouldn't be a kingdom. it would be a new classification greater than that since none of the three domains can adiquetly house viruses. Any thoughts on prions?

Originally posted by Alpha Centauri
I don't consider alive and a life to be the same thing entirely.

Good for you!

Originally posted by Darth Jello
well, it wouldn't be a kingdom. it would be a new classification greater than that since none of the three domains can adiquetly house viruses. Any thoughts on prions?

Where a cancer is a rogue cell, a prion is a rogue protein. A similar process, but on a much smaller scale.

Originally posted by DiamondBullets
respiration

waste production

lacking organelles

lacking the ability to reproduce without a foreign host
Hmm. whats the point where something "dead" evolves into something "alive"?
If a virus reproduces, whether or not it needs a host, has the potential to be alive. And I repeat, Potential. I believe to even have the possibility makes any virus "alive".
Its flawed, but its the best Ive got.
Feel free to rip me to shreds.

but a cell is a living, eukariotic organism. a prion has no DNA, but replicates, and in case of things such as Kuru/mad cow disease seems to do quite a bit of damage to other protiens as it replicates by rearranging them.

Prions are evil. Prions cannot be destroyed by boiling, alcohol, acid, standard autoclaving methods, or radiation. In fact, infected brains that have been sitting in formaldehyde for decades can still transmit spongiform disease. Cooking your burger 'til it's well done won't destroy them either.

you have to breakdown the protiens. tempuratures in excess of 1000 C, high molarity acids or alkali, high level ultra violet light and just about any kind of nuclear radiation or concentrated particle beam (like a laser) should do it.

It doesn't matter. You could easily say non living material we are talking about has the foundations for life. Whether this happens I don't know. But to have the building blocks to survive and multiply suggests to me some kind of life. The real "living dead"?

I've been to a couple of exobiology conventions. And trust me, defining exactly WHAT life is, and when something is a live is not easy.

A conventional definition

Although there is no universal agreement or agreements on the definition of life, the generally accepted biological manifestations are that life exhibits the following phenomena:

1. Organization - Living things are comprised of one or more cells, which are the basic units of life.
2. Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
3. Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
4. Adaptation - Adaptation is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the individual's heredity.
5. Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. Plants also respond to stimuli, but usually in ways very different from animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasing its prey.
6. Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.

Originally posted by Darth Jello
NO, this isn't another abortion thread, this is a biology thread.

Currently we divide everyting we consider to be alive into three Domains-
Archea-Ancient bacteria
Prokaryota-Bacteria/animals with no nucleus
Eukaryota-Everything else

The problem is that this leaves viruses and prions out and no one is sure if they are alive by our definition or if they fit anywhere in this model.

Viruses containt DNA but they do not respire, feed, produce waste, or display any signs of life outside of a living medium
Prion's are just rogue, self replicating protiens.

So what do you think, are they alive?

Yes, they are alive. But as DiamondBullet said they need a host to do so

Life: that which deliberately makes more of itself.

I submit that the word "deliberately" serves the same function as the word "reasonable" as in "proof beyond a reasonable doubt." Both address gray areas in definitions we are trying to render black and white. We don't understand Life well enough yet to know if we can define it w/o referring to nonempirical elements, ie, a soul.

Originally posted by The Omega
I've been to a couple of exobiology conventions. And trust me, defining exactly WHAT life is, and when something is a live is not easy.

A conventional definition

Although there is no universal agreement or agreements on the definition of life, the generally accepted biological manifestations are that life exhibits the following phenomena:

1. Organization - Living things are comprised of one or more cells, which are the basic units of life.
2. Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
3. Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
4. Adaptation - Adaptation is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the individual's heredity.
5. Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. Plants also respond to stimuli, but usually in ways very different from animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasing its prey.
6. Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.

These are the criteria that are often looked to when deciding whether something is alive or not. Neither prions nor viruses are eligible for being considered alive.

A virus, in all actuality, is simply a few strands of DNA or RNA, a protective protein coat, and possibly a few enzymes so that its genetic material can be translated.
A virus is not organized; it is not even a single cell, and lacks mitochondria, cytoplasm, and other basic cellular units.
A virus does not have a metabolism; it can never perform any chemical reactions without the help of a host cell. This is why antibiotics do not work on viruses; antibiotics target and disrupt the metabolism, and with nothing to disrupt they do not work.
A virus never actually grows; it is put together using the instructions of another virus' DNA or RNA inside of a host cell.
A virus never adapts to its surroundings. It can force a host cell to adapt to surroundings by rupturing and the like, but the virus itself can not adapt in such a fashion. This statement also addresses response to stimuli.
A virus does not reproduce. It creates copies of itself through a host cell, and never actually goes through mitosis because, well, it's not a cell.

I will readily admit that I do not know much about Prions, so feel free to correct me on anything in the below section.
A prion, as I understand it, is simply a protein folded into a beta sheet, or perhaps a more complex form such as a tertiary or quaternary structure. Thus, it is not a cell and therefore lacks the required organization.
A prion is a protein. It doesn't carry out any chemical reactions; thus, it does not have a metabolism.
A prion cannot grow. Something that lacks any genetic material whatsoever simply cannot.
A prion is an abnormal form of a "prion protein" located in the brain. How is it possible for a protein to adapt to its environment?
Again, this does not even seem possible. It is a protein. I can't see how it could logically respond to stimuli in its environment. Folding from a beta sheet to a tertiary structure perhaps, but that isn't something that I would consider response to stimuli.
Prions are not known to reproduce themselves; they are created by cells not by each other.

Any questions?

No.

Originally posted by Adam_PoE
No.
I second that.

How do we define life? It dies and pays taxes, I think. But, if it doesn't do both, then it's debatable.

Originally posted by Darth Jello
NO, this isn't another abortion thread, this is a biology thread.

Currently we divide everyting we consider to be alive into three Domains-
Archea-Ancient bacteria
Prokaryota-Bacteria/animals with no nucleus
Eukaryota-Everything else

The problem is that this leaves viruses and prions out and no one is sure if they are alive by our definition or if they fit anywhere in this model.

Viruses containt DNA but they do not respire, feed, produce waste, or display any signs of life outside of a living medium
Prion's are just rogue, self replicating protiens.

So what do you think, are they alive?

prions are just some protein parts.. so a big no
and viruses... they're not able to carry out (?) methabolism outside the host cells... so it should be counted not as life, as well...

Cell theory says that all living things contain one or more cells. A virus =/= a cell. Virus=/=living thing.

n.b. =/=, not equal

Viruses do not follow the basic principle's of life (At least to our knowledge of them) but does that really mean they arent alive? They are the most basic moving form of organized matter but they are quite complex in themselves. I think they should be counted.

perhaps they are philosophically part of life, but biologically not alive.

Don't you just love paradoxes?

sure, like quantum mechanics