are pathogens alive?

[cameron marical]

i know that there are severall types of pathogens, but is one or more of them actually considered to be alive? if so, how? there so small, i thought that they can only be inconveniant shapes that get in the way. they have no mightocondria, and surely there too small to have any thought process that we know about{let alone any organs, or blood for that matter i beleive} so how could they be considered alive?

[Kaeroll]

In a word: "eeeeeeeyup!"

 

Viruses are a grey area, so I'll leave that to a biologist to sort out, but bacteria and fungi are very much alive. They lack mitochondria, too, but can produce energy by reactions at the cell membrane. They grow and multiply, require food, etc - all the hallmarks of a living system. Leave some bread out past its sell-by date, and tell me with a straight face that the greeny-white muck growing on it isn't alive.

 

As for intelligence... intelligence is not a criterion of life. It's not necessary for life. Life is, in essence, a self-sustaining, self-replicating chemical system. Viruses, requiring a host's systems to reproduce itself, is borderline. Bacteria and fungi are quite firmly alive, even if they are dumb.

 

Kaeroll

[jimmydasaint]

I don't know about viruses being borderline. They have genetic information protected from enzymatic degradation and seem to have found a way to propagate themselves from generation to generation quite well. If that isn't alive, I would be surprised.

Edited March 28, 2009 by jimmydasaint
Spelling error

[Kaeroll]

I don't know about viruses being borderline. They have genetic information protected from enzymatic degradation and seem to have found a way to propagate themselves from generation to generation quite well. If that isn't alive, I would be surprised.

Fair enough - I'm just going off my somewhat limited education in the matter. I was always told it's a matter of debate, so I won't press my point.

[Mokele]

I don't know about viruses being borderline. They have genetic information protected from enzymatic degradation and seem to have found a way to propagate themselves from generation to generation quite well. If that isn't alive, I would be surprised.

 

They can reproduce, but not on their own, and they don't have a metabolism. Prions, which are nothing more than a protein, fit the bill almost as well as viri do.

 

Thing is, "life" is like "species" - we've got a definition that works for most cases, but there's always challenging exceptions and nobody can ever agree on a 100% ironclad definition.

[cameron marical]

what about sperm? i know there alive, but how are they made? arent sperm cells produced from a bunch of nonliving factors?

[Mokele]

No, sperm are produced from cells in your body going through a special form of division called meiosis.

[cameron marical]

i thought it was mitosis.

 

off topic, but i was wondering. how many species are there that can reproduce asexually? and how does that work? thanks.

[Mokele]

Mitosis produces two identical cells. Meiosis produces 4 cells with 1/2 the usual genetic material, such as sperm and eggs. Thus when the sperm and egg combine, each contributes their half of the genetic material to get a full complement.

 

Most microbes (bacteria, archaea, protists) are asexual, and many plants and fungi can reproduce both sexually and asexually. In animals, sexual reproduction is the norm, but quite a few species can manage asexual reproduction too. Most of those are invertebrates, but a few vertebrates can do it too.

[CharonY]

Prions, which are nothing more than a protein, fit the bill almost as well as viri do.

 

Or if we want to talk about genetic information, there are mobile genetic elements like transposons and plasmids. For most intents and purposes viruses also are more considered mobile genetic elements rather than organisms. But essentially this applies:

 

Thing is, "life" is like "species" - we've got a definition that works for most cases, but there's always challenging exceptions and nobody can ever agree on a 100% ironclad definition.

[cameron marical]

i know what a plasmid is, but my definitions are a bit rusty, and ive just flat out never heard of a transpoon. mind informing me?

 

thanks.

[GDG]

i know what a plasmid is, but my definitions are a bit rusty, and ive just flat out never heard of a transpoon. mind informing me?

 

thanks.

 

Again, Wikipedia has a pretty good entry.

[J.C.MacSwell]

Mitosis produces two identical cells. Meiosis produces 4 cells with 1/2 the usual genetic material, such as sperm and eggs. Thus when the sperm and egg combine, each contributes their half of the genetic material to get a full complement.

 

Most microbes (bacteria, archaea, protists) are asexual, and many plants and fungi can reproduce both sexually and asexually. In animals, sexual reproduction is the norm, but quite a few species can manage asexual reproduction too. Most of those are invertebrates, but a few vertebrates can do it too.

 

That's pretty interesting. I was unaware they could do that when "necessary"- I did a Qwiki. It must be triggered when a female can't find a mate.

[Mokele]

AFAIK, it's never based on necessity, actually. Asexual vertebrates are asexual regardless of circumstances. The ability to switch back and forth seems beyond our abilities.

[cameron marical]

so cells go through mitosis for the body their in right? thats how they copy themselves? and meosis is for sexual reproduction?

[Mokele]

Yep.