First off, just like to say what most others here have said: This is quite an amazing educational flash game, love the concept of it all.
Second, the reason I didn't give you a 5th star. I first checked this out 2 or 3 days ago, glancing at a few things before deciding to start from the smallest, and go around a bit. I came upon the Earthworm, which said in the info something along the lines of "If you cut it in half, both will grow back to be their own earthworms".
Today I come back here to learn some more, only to see that there are a few MORE things added, and the Earthworm info on growing back was CHANGED to state how "only the head side has chance to regrow, and tail will die."
This changed the "fact" that I had learned from my previous visit, which of course only makes me wonder how much more can be slightly off fact wise.
I figured that perhaps somewhere you'd have a log of new additions, changes, and fixes for that matter...But I'm not seeing it anywhere (not that its that important, i suppose)... I guess final point is that the credibility is shattered, and I can only believe most of what is stated. All in all though, I don't expect perfection, and you've done a wonderful job at raising awareness for people on here. Great work overall!