What Exactly Is A Species?

[Johnny Pneumatic]

We need a working defenition of this. How about usually unwilling to breed with another organism that is distinctly
genetically different for biological reasons.? When the rare breeding does occur the offspring are almost always sterile.
But there are those famous frogs that don't mate with another of a different mating call. That is their only difference. If they were forced to mate, fertile offspring would be produced. That is different than a KKK member being unwilling to mate with a African or Inuit. They are like that because of xenophobic input by their parents etc. not because of a build in biological unwillingness to mate. Remember to keep in mind species is a human construct. Just like planet, moon, math etc. If Luna was orbiting the sun on its own we'd call it a planet wouldn't we?
Is Pluto a planet? It is if we define planet as any mass made sphereoidal(or an oblate spheroid if it's spinning on its axis really fast) due to its own gravity and is not orbiting a much greater non star mass. I like that definition. I guess because it's mine.

 

[athon]

The 'virile offspring' definition has long been a point of contention, and as far as I know evolutionists and most biologists have hated it. It is so problemative that at best it is a high-school definition that makes nobody happy.

For instance, how do you use it to define speciation lines for asexual organisms?

There is a present trend to see speciation as a quantitative measure of genetic similarity. What the percentage is, nobody can agree. In molecular genetics, there's a drive to requalify prokaryotes according to a scale of similarity in terms of their genetic code. According to this frame of reference, a large number of bacteria have been reclassified completely. Some have even changed genera.

I'd imagine that this is where we will go in the future. The question is; how different genetically will an organism have to be before it is classified as a unique species?

Athon

 

[Dymanic]

Originally posted by athon

There is a present trend to see speciation as a quantitative measure of genetic similarity.

The question is; how different genetically will an organism have to be before it is classified as a unique species?

The problem gets worse the closer you get to an actual speciation event (which is unfortunate since this is often what is of most interest). Logically, we expect speciation to be traceable to a single individual, but such a hypothetical individual's status as the founding member of a new species is more a historical fact than a biological one.

The definition we're using now may be as good as it gets.

 

[Hellbound]

This link Describes the four most common definitions of species, and list speciation events observed within each.

 

[exarch]

Originally posted by athon
I'd imagine that this is where we will go in the future. The question is; how different genetically will an organism have to be before it is classified as a unique species?

I recall the number "1.6%" or something in this regard. Can't remember where that was from. Or perhaps it's merely the genetic difference between monkeys and us

 

[phildonnia]

There's a huge debate among dog owners concerning the distinction between wolves and dogs.

Many states and municipalities have laws prohibiting the ownership of any dog containing wolf genes, yet as owners of these lovable furballs point out, they are biologically identical.

The species were originally called Canis Lupus and Canis Familiaris, but they have apparently recently changed, to Canis Lupus Lupus, Canis Lupus Familiaris, Canis Lupus Dingo, etc.

 

[Soapy Sam]

If the chromosome counts don't match , the chance of viable interbreeding is low among plants and lower still among mammals, but hybrids do happen, occasionally fertile.(Breadwheat for example). A species is a group of related creatures which do not, habitually, breed outwith that group.

Of course, until the actually try, we can't know if they can or not.

In short, it's a working definition.