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Evidence of Evolution

Selecting for different traits over hundreds of years of breeding has caused different dog breeds to have distinctive characteristics. (Dog breeds from left to right: top row- Alaskan Malamute, Basset Hound, Llasa Apsa; middle row- Beagle puppy, Shar Pei, Chow; bottom row- Pekinese, Tibetan Terrier, Pug.)
Click on image for full size
Courtesy of Corel Photography

Dog Breeds: An Example of Artificial Selection

Darwin developed his theory in part because of his study of how dogs and pigeons were bred. He knew several breeders of dogs and asked them how they selected certain traits. According to the American Kennel Club, there are over 150 different dog breeds, from tiny Chihuahuas to giant Great Danes, but they are the same species (Canis familiaris) and all are descendants of wolves.
  • A species is a group of individuals that can reproduce with one another, producing offspring that are able to reproduce.
  • A breed is a group of domestic animals within a species whose appearance has been determined by artificial selection over many generations. An individual of one breed will be able to successfully reproduce with an individual of another breed, but both breedsí distinctive characteristics can be lost, this makes a mixed breed animal.

Breeders taught Darwin how they selected certain characteristics and how they ensured that those characteristics made it into the next generation. Thatís how different dog breeds are made. If a breeder wanted a dog with a curly coat, he or she would allow curly-coated dogs to breed and not allow them to breed with straight-coated dogs. In nature, the most well-adapted animals are more likely to survive and reproduce, but in dog breeding, the dogs with the desirable characteristics are allowed to reproduce by the breeders.

Last modified May 16, 2005 by Lisa Gardiner.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF