Cross Breeds

Why are there so many types of dogs/cats, but most other species have just the one type?

For example a Shih Tsu looks absolutely nothing like a Great Dane, but they are both dogs. A Giraffe is a giraffe. Elephants have a few species, but they all look alike.

Public Comments

1. I would say that it is the opposite.
2. Dogs and cats were bread and cross bread by people to exaggerate or diminish specific traits. Giraffes and elephants were not to the same degree or for as long.
3. The same thing is true of sheep, goldfish, domestic cattle, pigeons, . . . almost any domesticated animal that has been subjected to selective breeding.
4. Because of human influence. Most animals form one breeding pool and they evolve as a group to better fit their environment. If two groups get split apart, like african and indian elephants, then each evolves to fit its niche and eventually they diverge enough to be separate species, but as long as they have access to breed together, they don't. Then humans come in and add another element - deliberate breeding. If you live in Siberia, you want a dog who thrives in the cold and can pull a sled, so the humans pick the dogs best at those things and breed them together and kill off the undesired dogs. At the same time the the hunters in coastal England may want a dog that can swim and find ducks, and breed for those traits. So humans create all the different breeds of dogs and cats, but haven't completely isolated them nearly completely enough or long enough to cause them to diverge into different species. You can see some of the same in other human-domesticated animals, like cattle and horses (not to mention to a lesser degree in humans themselves where breeding may be based on conscious, culturally determined cosmetics that have little to do with survivability).. A Tennessee walker is very different from a Clydesdale.
5. although people claim selective breeding is the only reason, i find this impossible to believe. There is no way ancient dogs could be bred to become a chihuaua and a great dane and everything in between simply by selective breeding. If you started with a population of 10000 poodles and you had 10,000 years to create every variety of dog from those poodles, it would never work. You would have to breed out curly hair, you would have to add spots, pointy ears, huge size, tiny size, wooly fur short hair, etc.
6. With domestication of the wolf, people bred together animals with traits they wished to be prominent.... to the point of today really ruining many breeds of dogs. Bull dogs--French and English-- today look nothing at all what they looked like 100 years ago... the breeders bred sister to brother, and sire to daughter, resulting in runts, mutations, deformed heads, and twisted limbs. All dogs were meant to be athletes. Such is now no longer the case. And dog show judges are as guilty as the breeding clubs. The case of the King Charles Spaniel (Google this one...King Charles Spaniel + genetic disease) Here's the link: http://www.greatdogs.co.uk/Syringomyelia.html is so bad that these poor animals have now an inherited condition in the brain case that causes horrid pain. Bully dogs now have arthritis by age 3 or 4, and can barely breathe. And the heads are now so large, pups are delivered by c-section. The peke is in no better shape...some have to undergo throat surgery since with in- breeding, the face is so far pushed in the throat tissue collapses!!!. Any time people start to breed for what they call a "standard, the breed" is in trouble. Bassets have ears way too long, and drooping lower lids make the eyes constantly dry, and open to infection. As well, these hugely long backs and short misshapen legs as well give them arthritis before age 5...Doxies are in the same boat with spines too long. They are cripples before age 4. And it is not only in dogs, but horses too..... Google: Quarter Horse + Impressive + genetic disease, and read about that one. Here's a great link for this one: http://www.vgl.ucdavis.edu/services/hypp.php No one knew that Impressive carried a mutation, until his babies started showing up with the condition. I promise you, you never in your life saw a more gorgeous Quarter Horse that this one. He was jaw dropping in his muscling....and how that muscle occurred was part of his problem. Anyway, I could go on and on about what has happened to pure breds of any animal... Moral of story???? buy or get a cross bred dog, and do your research before you buy any horse with Impressive bloodlines. Hope you learned something interesting today.
7. its not only dogs or cats who have many types but there are also many other types of monkey's which are also chimps,apes etc. also there are horses who have many types such as stallions,ponies
8. Dogs and cat breeds are the result of artificial selection. The varieties are maintained by people who fancy different varieties. Since dogs and cats in captivity do not have to compete with members of their own species for survival and reproduction, the different varieties can be maintained indefinitely by owners who fancy these breeds and will feed and raise them while protecting them from predators. In the wild, morphological variation within a species is limited by a number of factors. Sexual selection, for example, may limit how different a male (or female) may look or sound before it will be rejected as suitable mates by individuals of the same species. Females may not recognize a male that does not look, sound or smell like typical males of the same species and refuse to mate with him. Natural selection also may act against individuals that are too small, too slow, too big, or too fast, if it limits their ability to survive and reproduce. A sloth that moves too fast, for example, may get spotted by an eagle and eaten before it can reproduce. A cheetah that is too slow, for example, may not be able to catch enough to eat. An elephant that is too big, for example, may die of a heat stroke in hot weather. A giraffe that is too short, for example, may be killed by lions who can reach its neck. A frog that is not well camourflaged (e.g. an albino) may be caught and eaten before it can reach sexual maturity. In captivity, freed from natural selection, an albino frog may be artificially selected and bred for many different generations.