An exam begins when I hand out the first test. After that, you may not talk, except quietly to me, and you may not consult any written materials without prior permission. In a lab exam, you may not look at any questions except those at your current station. When I assign grades, though, I want them to be based on your own effort. If two people turn in substantially identical answers, no amount of explaining is going to convince me not to give both papers a zero.
Plagiarism is a serious offense.
The University provides for punishments than can include expulsion, and the Biological Sciences Department aggressively prosecutes cheating. I don't enjoy arguing points on tests and I tend to be very hard-nosed about such things, so if you want to argue, make sure you know what you are talking about first. It's not fair to you or anyone else in the class if I reevaluate someone's grade and revise it upward without being able to revise yours and everyone else's grades as well. I expect you to complete the course requirements. If you miss an assignment without a legitimate reason, you will receive zero points for it.