Sorry for the stupid question...

[Extirpator]

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I have heard this put two different ways from many reliable sources and I'm wondering if anyone could set me straight...

What is required for something to be considered a species?

While the majority of information I have read states something along the lines of "organisms that can mate with each other under natural conditions, and
this mating produces viable, fertile offspring" (from kaplan).... I have also heard (most recently from examcrackers) that there are additional requirements, since the previous definition would include such things as domesticated dogs reproducing with wolves... I'm also unsure of whether or not domesticated dogs vs. wolves are currently considered different species or not...

If I get a question like this I would really prefer not to be second guessing myself, so if someone knows for sure (or what would be sufficient for the DAT), I would appreciate the help. Thanks

 

[jrobb220]

hmm sounds like examcrackers sucks.

In order to be a species they have to be able to mate and produce viable offspring.

 

[Extirpator]

not really, because it is true. Two species of dogs/wolves can interbreed and produce viable offspring... I guess I'mjust wondering if there are other notable exceptions to this classic definition and which definition I should use when the time comes.

 

[PrivateJoker]

hmm sounds like examcrackers sucks.

In order to be a species they have to be able to mate and produce viable offspring.

That is correct. That is the absolute basic definition of a species.

Just because two species can interbreed and because gene flow is possible does not mean that it is feasible or that it will happen. This is why we have different species of similar animals. Dogs and wolves is a bad way to think about it because humans have selected certain traits between species and allow specialization and gene flow to occur.

Maybe a species of wolf in north america can breed with a species in siberia, but that doesn't mean gene flow between the two populations will ever happen due to their geographic barrier. Does that make sense?

Learn about the different types of speciation and that broad definition will make more sense.

 

[Extirpator]

That is correct. That is the absolute basic definition of a species.

Just because two species can interbreed and because gene flow is possible does not mean that it is feasible or that it will happen. This is why we have different species of similar animals. Dogs and wolves is a bad way to think about it because humans have selected certain traits between species and allow specialization and gene flow to occur.

Maybe a species of wolf in north america can breed with a species in siberia, but that doesn't mean gene flow between the two populations will ever happen due to their geographic barrier. Does that make sense?

Learn about the different types of speciation and that broad definition will make more sense.

What you just described is exactly what I'm referring to. The fact that geographic barriers preventing gene flow can be taken into account and thus the first definition no longer really holds up.

I just don't see how you can consider the "broad definition" (as you described it) to be valid once you take something like domesticated dogs vs. wolves into account.

I guess if I do get a question like this, I'll just go with the generic definition and hopes that's what they're looking for.

 

[PrivateJoker]

What you just described is exactly what I'm referring to. The fact that geographic barriers preventing gene flow can be taken into account and thus the first definition no longer really holds up.

I just don't see how you can consider the "broad definition" (as you described it) to be valid once you take something like domesticated dogs vs. wolves into account.

I guess if I do get a question like this, I'll just go with the generic definition and hopes that's what they're looking for.

How so? Just because you can interbreed two species does not mean that they are not still two species.

Geographical barriers, behavioral differences, reproductive barriers, niche space...can all be reasons why different species develop from a common ancestor, through natural selection over vast amounts of time.

Some species can still interbreed because their gene pools have not been evolving separately for a long enough time but there is no significant amount of gene flow between the two populations so each population evolves into separate species due to some sort of "reproductive isolation."

"organisms that can mate with each other under natural conditions, and
this mating produces viable, fertile offspring"

That is the definition you should go with. Review the different types of speciation as I suggested and I promise this will make perfect sense.

 

[Extirpator]

How so? Just because you can interbreed two species does not mean that they are not still two species.

I realize that 2 species can interbreed to produce fertile offspring, hence my confusion with that definition.

Geographical barriers, behavioral differences, reproductive barriers, niche space...can all be reasons why different species develop from a common ancestor, through natural selection over vast amounts of time.

Some species can still interbreed because their gene pools have not been evolving separately for a long enough time but there is no significant amount of gene flow between the two populations so each population evolves into separate species due to some sort of "reproductive isolation."

I actually know my speciation stuff farily well... the more you try and convince me, the more I feel that the definiation doesn't apply lol.

For example, sure speciation is a process by which reproductive isolation occurs, but they don't actually become different "species" until the said speciation (or isolation) has completely isolated their ability to produce viable offspring with each other. That's how I learned it anyway. Yet we classify things like dogs that can produce viable/fertile offspring with each other as different species.

"organisms that can mate with each other under natural conditions, and
this mating produces viable, fertile offspring"

I guess if you take the term "natural conditions" to include respective barriers it could make sense... but it hoenstly just seems way to vague of a definition imo to be used as widely as it is.

That is the definition you should go with. Review the different types of speciation as I suggested and I promise this will make perfect sense.

regardless, I'm just going to accept it as it is and use that definition.

Thanks for all your help.

 

[PrivateJoker]

Yes, "respective barriers" would be considered natural conditions. That is the basis for the theory of allopatric speciation.

Also don't confuse human interference with natural selection. Selecting of traits within dogs, derived from domestication of different species of wolves is artificial selection has has no place in the definition of a species. If anything what we have done is speed up/manipulate evolution by artificially selecting for certain traits and creating different breeds by doing so. We are pulling domesticated dogs away from wolves genetically by unnaturally selecting for certain traits.
In a way we are making genetic drift the decisive factor in "evolution" instead of the major decisive factor for evolution in nature, which is natural selection. Still, that is not a good way to think about it.

That definition makes sense and encompasses why a species is considered a species. If it doesn't make sense it is because you are not relating your knowledge how species evolve from common ancestors and why or how they might be separated by not only geological barriers but behavioral or physical barriers. Even if they eventually did overlap in their respective niches or given the opportunity to mate they would not produce viable offspring or the geneflow would not be significant to alter the two gene pools of the two species.

Sorry, I just wanted to explain so that no one else was confused by what we were discussing.

 

[Extirpator]

After reading your last post, I would say we're actually in agreement on the definition, I just didn't take "natural conditions" to include things like geographical barriers (which is one of the other factors that examcrackers referred to).

However, that having been said, the definition that the second poster gave (which is how it is commonly phrased) would not really be correct since it doesn't include a term like "under natural conditions."

So you definately answered my question. Thanks again.