animal classification and evolution arguments

[mr friendly guy]

Forgive my lack of biology knowledge if this seems obvious.

One of the examples of evolution trotted out as been the breeding of different breed of dogs, eg say the bulldog by selective breeding. One of the typical creationist response has been that while its still a dog, not a new species so it doesn't count.

Now the obvious response I give has been that speciation doesn't need to occur for evolution to occur.

However, what I want to know, are dogs counted above the species level. For example dogs, wolves, foxes etc fit into the family canidae (?sp). After the family level, follows genus then species. Do dogs themselves fit into the genus level?

Basically if dogs are classified in biology above the species level, a new breed of dog can be a new species even though its still a dog.

[AMX]

Nope.
If anything, it could be argued that "dogs" are below species level (since they can successfully interbreed with wolves; ergo both dogs and wolves should be counted as one species, so "dog" refers only to part of that species).

[Elfdart]

Forgive my lack of biology knowledge if this seems obvious.

One of the examples of evolution trotted out as been the breeding of different breed of dogs, eg say the bulldog by selective breeding. One of the typical creationist response has been that while its still a dog, not a new species so it doesn't count.

Now the obvious response I give has been that speciation doesn't need to occur for evolution to occur.

However, what I want to know, are dogs counted above the species level. For example dogs, wolves, foxes etc fit into the family canidae (?sp). After the family level, follows genus then species. Do dogs themselves fit into the genus level?

Basically if dogs are classified in biology above the species level, a new breed of dog can be a new species even though its still a dog.

Dogs are classified as either the species Canis familiaris or as a subspecies of wolf: Canis lupus familiaris. Either way, they fall under the genus Canis. I think that if there were no bulldogs bred by humans, but one were found in the woods by scientists, it most likely would not be included among the subspecies (dogs), species (wolves) and possibly not even in the genus Canis until DNA tests proved otherwise.

Nope.
If anything, it could be argued that "dogs" are below species level (since they can successfully interbreed with wolves; ergo both dogs and wolves should be counted as one species, so "dog" refers only to part of that species).

The problem is the fact that grey wolves, red wolves, and coyotes can interbreed and produce fertile offspring. Another problem is that as the Canidae show, nature doesn't always fit into neat, orderly man-made categories. The Linnaean system is an excellent shorthand for classifying animals, but there are holes in it. It is most useful as a rough outline of the animal and plant kingdoms. But there is a certain point at which you can tell a wolf from a coyote, or a tiger from a leopard, or a zebra from a donkey.

If the various breeds of dogs or other domestic animals were found naturally in the wild, they would almost certainly be classified as different subspecies of wolf, with the least wolfish ones classified as separate species (Pekingese, terriers, Chihuahuas). This is why classifying fossil animals is so dicey. All you have to go by is the skeleton. Fossil lions and tigers would be lumped together (actually they have been already), while the different dog skeletons would be split off into different species.

[Darth Wong]

I always point out that Darwin explained a century and a half ago in "Origin of Species" that the distinction between "variation" and "species" is blurry at best, and is often just a function of an arbitrarily subjective determination of how much different two animals can be while still belonging to the same species. In extreme cases there is intersterility, but there are plenty of species which can theoretically mate but are still regarded as separate species. Lions and tigers for example.

[Darth Servo]

Case in point: try breeding a Saint Bernard with a Chihuahua.

[wolveraptor]

Bah, that's just a mechanical difficulty. Besides, it it didn't seem to stop this guy.

But seriously, you could stick sperm from a St Bernard into a Chihuahua's uterus. She might die giving birth, though, if the babies turn out to be too large. Still, they would be viable offspring, so Chihuahuas and Bernards can breed.

For everyone's information, lion and tiger hybrids can only produce fertile female offspring, so there is still a good justification for keeping them in different species.

[Darth Servo]

Bah, that's just a mechanical difficulty. Besides, it it didn't seem to stop this guy.

But seriously, you could stick sperm from a St Bernard into a Chihuahua's uterus. She might die giving birth, though, if the babies turn out to be too large. Still, they would be viable offspring, so Chihuahuas and Bernards can breed.

For everyone's information, lion and tiger hybrids can only produce fertile female offspring, so there is still a good justification for keeping them in different species.

So if they need human intervention, they clearly represent a picture where the distinction between variation and species is starting to blurr.

Biologists consider trees that blossom in different monts different species even though a human can preserve the pollen from one and fertilize the flowers from the other later.

[Darth Servo]

ghost edit: note, I'm not saying the largest and smallest doge are different species. They clearly could easily interbreed indirectly with each other with a medium sized dog. However, it is an example of the process midway in action. There are species of snakes that have several populations spread over a large geographical area. Populations next to each other can interbreed easily while populations on the extreme opposite ends of the chain cannot.