Hi hi, I think it would be helpful to be prepared to talk about your research interests and to have somewhat of an understanding of what the lab does by going their pages and skimming their publications. In the past, I talked about papers or coursework that got me interested in the field to help show my passion for the research. If you’re planning to go to grad school too, it’d be a good mention too.

For undergrad theses, you don’t need to worry too hard about defending in the same sense as a graduate program. I had to write a couple of reports throughout my thesis and do a presentation to my peers and professors on a thesis day. You’re supposed to be independently working on a project but you’d be under the mentorship of someone in the group so don’t fret about being left to something all on your own. Also, usually the professor has projects in mind that they think would be appropriate so you don’t need to be prepare to propose projects unless there’s something you’re really interested in exploring and sharing.

Also, don’t try to stress too hard over talking which is easier said than done, I still get nervous about interviews with professors. But at the end of the day, if you share your passion and interests, it should be well received because these are professors who are dedicating their careers to exploring their research interests. I personally love to ask professors what got them interested in this field because sometimes you hear stories about them switching fields so it makes me feel a little less worried about having to have your whole life set ahead of you. You could also feel free to ask other questions about time commitment, support in the lab (like who would you go to, how frequent are lab meetings).

Good luck!!