Questions for "How did the stickleback lose its fins?"

After reading the article "How did the stickleback lose its fins?"By David Perlman, Chronicle Science Editor, April 15, 2004. ©2004 San Francisco Chronicle, answer these question in complete sentences in your journal.

1. How long are sticklebacks?
2. Why don't freshwater sticklebacks have pelvic fins?
3. Why do the saltwater sticklebacks have those sharp fins?
4. What is the Pitx1 gene known to be involved with ?
5. What is a gene (two parts to the answer)?
6. What does it mean to cross-breed the fish?
7. What do the damaged forms of the Pitx1 gene cause in mice?
8. Pelvic fins are to sticklebacks as _____ _____ are to four-legged animals.
9. Pectoral fins are to sticklebacks as _____ are to four-legged animals.
10. What is adaptive radiation? (Hint: it has nothing to do with X-rays or Uranium)
11. These genetic changes in the freshwater sticklebacks happened within the last ______ years.
12. Scientists from how many countries were involved in this study?