The easiest way to do this would be to create a Boss tab under a bios Tab, and then turn on Human Friendly URLs.

If you can't do that, you can set up a Friendly URL rule in your Host Settings (if you have access) under Friendly Url settings.  Create a rule like ".*/bios/boss.aspx" which points to "~/Default.aspx?TabId=[Your TabId]".  Note that it's much easier to do if you end the link with .aspx (so that IIS will push the request through ASP.NET and the Friendly URL redirector).  If you can't have .aspx, you will need to create a directory for each link (i.e. a /bios/boss/ directory under your website's root), and then place the default.aspx page in there to create a default page that will get sent to ASP.NET by IIS.  You'll also need to add "/default.aspx" to your Friendly URL rule, since that will be the actual request as ASP.NET receives it.

Hope this helps,