You will be fine, you are not the first kid to get a c+ or a B- on a hard class, will it effect you getting into a ivy, maybe , but usually your essay is a really important part of your package, much more importantly is why did you get the C+, do you understand what you need to change so it does not happen again, also it would help if you nailed the Bio AP test, it would help you explain the class grade vs the test grade.Good luck