Okay, so this is part 2 in my three part series on your first teaching experience in graduate school. If you haven't read, or at least seen part 1, go do that! I'll wait.
Let's talk about the second type of class you might be expected to teach. This time, we'll talk about what to do when you get thrust into a class where you're not familiar whatsoever with the material, unlike the introductory biology class.
Type of class #2: Upper division lab section
Less common of an occurrence than a lower division lab section, you might be tasked with being a TA for an upper science division lab section. This is exciting for a few reasons, and comes with a ton of benefits that your introductory science class didn't, but it also carries a few new challenges.
The easy parts (strengths)
Most often, the students involved in these classes have (or should have at least) a much deeper understanding of basic biology/chemistry/physics than your freshman or sophomore undergrads. Therefore, it stands to reason that you shouldn't have to explain elementary concepts to them when leading them in lab, meaning you can focus deeply on the new, interesting, and more in depth topics. This, however, also leads to a difficulty, which I'll explain later on. Buuuuut, despite that, this means that you can have higher level conversations with these students and not worry about "dumbing things down", which sometimes makes teaching way more straightforward.
I will place a caveat here and say that not all students will remember all of their basic material (I mean come on, did you remember every step of the krebs cycle after 3 years of not talking about it?). This means that you should cut some slack to the students on not remembering absolutely EVERYTHING in previous classes, while also expecting a certain level of recall. This is a delicate line to toe, and every lab section will be different.
The difficult parts (weaknesses)
The hard part that I alluded to earlier on is that upper division courses differ sometimes significantly from university to university. This means that even if you took O-chem at your college in Idaho, you might not necessarily be familiar with some of the material covered or lab techniques performed in a much larger/smaller university in South Carolina. This all requires you to have a certain level of outside-of-class responsibility. You will inevitably need to take more time outside of class to ask the primary professor questions on lab techniques, safety, and just general material of the course. This is ESPECIALLY true if you've never taken the class before in undergrad (for example, I had to teach an upper division microbiology lab while never having taken a formal microbiology course in college).
This can be scary, because you can feel like you have to play catch-up and constantly work outside of class to be one step ahead of the students, but that's exactly the point. One. Step. Ahead. You don't have to know everything about every class period or lab section for the entire term, you just have to be prepared on a weekly basis, which isn't too daunting at all once you get in the groove of it.
My tips for succeeding
I have a few simple tips for succeeding in this type of section.
1. Be comfortable with staying in communication with your primary professor in the class. They are your point person for ensuring that you understand the material clearly. If you have any doubt that you might not fully understand the lab content enough to communicate it well to your students, make sure you reach out and ask questions! You don't want to compromise the students' education because of your lack of preparation.
2. Be stern about your expectations with students on remembering basic material. Let's be real, progress in class is going to go so much faster if everyone has a relatively high recollection of basic science. It's important to make this point clear to your students that you have expectations. Be sincere to special accommodations to students who might need them, but also don't be a push-over and teach tons of extra basic material to students who should be doing some extra work outside of class. We've all been there, we've all had to review basics again, and you're not superman/woman. You can't teach it all effectively.
3. Just say "I don't know" if you truly don't know something. This is the BIGGEST tip I think I will give to anyone in any of these sections. Whatever you do, just be honest with students if you don't know the answer to a question. The worst thing you can do is lead a student astray by answering something completely wrong when you had no idea what the answer actually was. Just simply say that you don't know, and that you can ask the professor for clarification. The students will appreciate this so much more than if you just gave an answer that had no real merit to it.
Well, there you go! My next/last section to this three part series will cover upper division discussion sections, which are very similar to upper division lab sections.
I could say more about specifically what to do in lab sections, but that is going to differ greatly between professor, university, and class type. Some profs might hold weekly lab prep sessions, others might give you a handout, and some might even just teach it themselves and have you as moral support to help with pipetting and other various tasks. It just depends. Most faculty won't leave you in the dark, however, because they know just how difficult your first experiences teaching can be.
Good luck out there!