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Dog variety (and other animals)

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calum1
265508.  Fri Jan 25, 2008 4:31 pm Reply with quote

Only clocked this episode on UKTV Gold tonight. Mr Fry stated they did not know why dogs showed so much variation, however, I was taught it was simply to do with the fact a puppy looks wildly different to a full-grown dog (i.e. wolf).

Therefore, selective breeding merely had to stunt various features to produce the varieties seen today, coupled with various amounts of inbreeding to allow expression of dormant/recessive genes.

 
Flash
265649.  Fri Jan 25, 2008 8:49 pm Reply with quote

I think it's a bit more complicated than that, Calum; the diversity of dog breeds is a well-known enigma in genetic science circles. And if your explanation (which I don't really understand - don't nearly all juveniles look unlike adults of the same species?) was right, then why doesn't it work for cats?

 
Sadurian Mike
288518.  Sun Mar 02, 2008 1:21 am Reply with quote

Flash wrote:
I think it's a bit more complicated than that, Calum; the diversity of dog breeds is a well-known enigma in genetic science circles. And if your explanation (which I don't really understand - don't nearly all juveniles look unlike adults of the same species?) was right, then why doesn't it work for cats?

Don't be silly, Flash.

Cats don't have puppies.

 
calum1
288529.  Sun Mar 02, 2008 1:46 am Reply with quote

Sorry my reply is so late and not necessarily ‘coherent’.

No, many juveniles look remarkably similar to the adult form, including cats, though they still do manage to have a surprisingly large amount of variety. A quick search on the internet will find plenty examples of what I have said regarding dogs. A genetic ‘disease’ is able to stunt the growth of juvenile physical features – short legs, snouts ears, bodies etc.

The colours and hair types are more likely due to recessive/dominant/mutated/dormant genes being previously masked and inbreeding allowing their expression. Natural selection would not favour certain patterns or colours though the genes can still be present within a population. A good example is carp, in the wild they range from a olive to black, with occasional coloured offspring, a few generations of inbreeding these coloured varieties produces a vast array of colours.

The QI animal book alludes to the same things I have said, highlighting experiments with foxes showing similar outcomes in 20 or so generations. Bearing in mind dogs have had between 10000 – 17000 years of selective breeding.

 
Flash
288585.  Sun Mar 02, 2008 5:25 am Reply with quote

I still don't really understand that point that's being made about juveniles looking or not looking like adults, though I see that you are not the only one who's making it. The post below is one of my own, and it mentions the issue (though I still don't understand it, for all that).

That aside, we weren't addressing the relatively trivial issue of colour variation so much as the huge range covered by dog varieties: chihuahuas are the same species as St Bernards.

Quote:
The 400+ breeds of dog are all members of the same species, a species which is unique in the variety of forms it can take. Darwin speculated that this tendency might be because dogs were descended from various different canid ancestors (wolves, jackals, coyotes, etc) but modern techniques have established that all dog breeds are actually descended from gray wolves, with the morphological split probably occurring about 135,000 years ago (although the first archaelogical evidence is only 12,000 years old). Their variety certainly owes a lot to human intervention in selective breeding, but even so the reasons why the dog is such a uniquely malleable species are not well understood.

Quote:
what accounts for breeders' runaway success? How, for example, could Louis Doberman, a German dog-pound keeper active in the late 1800s, take German pinschers, Rottweilers, Manchester terriers, and possibly pointers and, in just 35 years, create the Doberman pinscher? Such rapid change would seem to fly in the face of the Darwinian transmutation of species, a process typically thought to operate over thousands or even millions of years.

Part of the reason lies in what happens when you cross two breeds. "Whenever you hybridize, instead of getting an average between the two types, you quite often get something that I call 'phylogenetically bizarre,'" Coppinger says. "Which means you've never seen that form before in evolutionary terms." Breeders build on those novel traits, winding up with the stubby legs of the dachshund or the rumpled-rug features of the shar-pei.

Another part of the reason is that dogs' bodies, particularly their skulls, undergo a major transformation between newborn and adult. (The skulls of newborn cats, by contrast, are already of adult proportion, which, along with less zealous breeding, may be one reason why the domestic cat is not nearly as motley as its household nemesis.)


From an interesting article at:
http://www.pbs.org/wgbh/nova/dogs/potpourri.html

 
beeblebum
661815.  Mon Jan 25, 2010 3:47 pm Reply with quote

did fry say the only animal
because poutry as a lot of different size birds from 12inches tall to 36inches
and some 1 pound to 14 pound


fail

 
Ameena
661876.  Mon Jan 25, 2010 6:45 pm Reply with quote

Different sizes and feather-patterns, yes, but a chicken still looks like a chicken, even if it looks different to another type of chicken - you'd still see enough similarities to think they were the same species. But you could put a husky, a wolf, and a Yorkshire terrier together and quite logically think that the husky and the wolf were the same species, while the Yorky was some other entirely different species.

 
bobwilson
661918.  Mon Jan 25, 2010 10:22 pm Reply with quote

You could put Tony Blair next to a human and think he was human too. Appearances can be deceptive.

 
beeblebum
662192.  Tue Jan 26, 2010 3:14 pm Reply with quote

Ameena wrote:
Different sizes and feather-patterns, yes, but a chicken still looks like a chicken, even if it looks different to another type of chicken - you'd still see enough similarities to think they were the same species. But you could put a husky, a wolf, and a Yorkshire terrier together and quite logically think that the husky and the wolf were the same species, while the Yorky was some other entirely different species.


they all have 4 legs a tail and cock there legs etc

if you compair a shamo to a silky you will have to chang your oppinion
they all came from jungle fowl and have been breed for different things ie eating,fighting,laying,ornimental,some have naked necks some have no parsons nose,some have tail feather 8 feeet long,what your saying is if it cant fly its a chicken

 
Ameena
662303.  Tue Jan 26, 2010 5:53 pm Reply with quote

Lol umm...no, actually, you know what, I don't think I'll bother.
Chickens are all roughly the same size and shape (give or take a bit). Two different breeds of dog could easily be confused for two different species by someone who didn't know any better.

 
Flash
662318.  Tue Jan 26, 2010 7:08 pm Reply with quote

Beeblebum - we do take your point, but our point is this: in appearence, a chihuahua is to a Great Dane as a bantam is to an ostrich - but the dogs are the same species. Breed them together and you'd get viable offspring.

 
Alfred E Neuman
662356.  Wed Jan 27, 2010 2:11 am Reply with quote

Ameena wrote:
Lol umm...no, actually, you know what, I don't think I'll bother.


I suspect you're not the only one who thought about it though. :-)

 
beeblebum
662470.  Wed Jan 27, 2010 7:09 am Reply with quote

have you conpaired a silky to a shamo and look at ga don as well,

 
Hornet
662491.  Wed Jan 27, 2010 7:47 am Reply with quote

From a Google Image search (I know nothing about chickens).

Silky:



Shamo:



The difference seems to be comparable to, for example, a sheep:



and a goat:



...which are clearly different species.

Oh, and as this is my first post, hello everyone.

 
beeblebum
662497.  Wed Jan 27, 2010 7:58 am Reply with quote

apart from the silkys 10inches tall and is under 1lb and the shamo is 3 feet tall and 13/14 pound
i mean a kiwi look more related to a silky than a shamo does
are you getting my point the different shape size and look of birds
they all came from the red jungle fowl
i know dogs can be hundreds of pounds apart and feet apart in hight
but youve got to look at pultry in the same lines

 

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