After the idea has spread from German Wikipedia to French, Polish, Dutch, Hebrew, Japanese and Danish ones, I made the first Wikiportal at En dedicated to Biology:
http://en.wikipedia.org/wiki/Wikipedia:Wikiportal/Biology
I hope more portals will follow and that participants of the biology-related WikiProjects will help :). Here's the main page for Wikiportals:
http://en.wikipedia.org/wiki/Wikipedia:Wikiportal