What grade you are in, or how long the teacher has been teaching, or whether or not you'll be making a profit off of it, has nothing to do with whether or not using someone else's with without citing the references is plagiarism. It is. Period.

Personally, I'd go talk to the professor and/or someone above him (department head maybe?) and tell them that you are offended that you are being instructed to plagiarize, and concerned that the students are being taught that it is ok to do so.

As far as your presentation, it sounds like you are off to a good start. I'd caution you to remember that most likely, your professor and the other students know NOTHING about snakes, and make sure you start out at a low level. You happened to mention something about a pinstripe not being able to be confused with a normal. Sure, to us, it can't be. But to an average person, it is a brownish snake, and they are likely to think it is normal. Albinos and pieds (as long as they aren't very low white) and any of the various white snakes are pretty much the only ones you can be sure will catch the attention of the clueless that hey, there is something different here.