Thanks, Allison. I was just pottering around on the website when up came your question! So since I thought I knew the answer I posted it. But remember this is a math site, so biology questions are not strictly appropriate for this site. There are websites that deal with the other sciences, if you want to have a look around.
Nevertheless, I was happy to be of help to you on this occasion (I'm not a biologist, by the way!).