Take a look on this research website:
http://www.pklifescience.com/
See your school's learning commons person, teacher or public library, for log in info.
Log in to the site, click on "Animals", then "Pets", then "Dogs".
There's lots of info, about lots of breeds and a good explanation about why dogs have hair - or fur.
Here are some games to help you understand more about Animal Adaptations or why animals have fur or claws or other things to help them survive.
Eco Kids - Animal Adaptations game
http://www.ecokids.ca/pub/eco_info/topics/climate/adaptations/index.cfm
National Geographic - Arctic Adventures game
http://magma.nationalgeographic.com/ngexplorer/0211/games/game.cgi