I have a lot of cool extra curriculars, but the only science related activity i have is the science club at my school. I also have SAT subject scores in math II and biology m to submit, and a high school junior and senior schedule that has many classes concentrated in math and the sciences. will I be at a disadvantage if I dont have a lot of sciencey activities when I apply to WashU, or any school as a bio major for that matter?? Does WashU prefer to have students that are more involved in science?
No I think as long as you have good scores you will be fine! Good luck with everything 
If you don’t have a lot of science activities, be prepared to explain clearly why you want to major in biology. Colleges want some evidence of interest in the subject that you plan to pursue there.
I disagree with rdeng. Even for a selective college like WUSTL, they want you to demonstrate a pattern of initiative and academic potential. They don’t need you to “explain” why you want to be a bio major w/o bunches of science ECs. They accept that the explanation is simple as “I want to study biology”.
They don’t require “evidence” – that’s baloney, IMHO
I also disagree. Lots of people get into WashU without science EC’s. You also don’t need to know your major when you apply so there is no need to justify why you are majoring in something that doesn’t match your EC’s.
I don’t think it will be an issue for you at all. It sounds like you have strong and interesting ECs. And you have the math and science SATII scores and an academic schedule which show your commitment to the STEM field.
And from what I have heard from multiple admissions officers, schools don’t pay a whole lot of attention to intended major unless you are applying for a specific program like an engineering school, a business school etc. The reason for this is that half of the students apply undecided and half of those who apply with an intended major end up changing it while in college.
thanks everyone!
If OP wants to pursue a scholarship at WUSTL, there are essay questions pertaining to this:
“Why have you chosen to study the academic discipline associated with the scholarship program you are seeking? You may include comments about both your academic interests and your professional/career goals.”
“Describe a biology or chemistry reading or research project in which you have recently been engaged or that you would like to undertake. (If you choose to discuss a large research project in which you participated, do so in a manner that will permit the Moog Committee to assess your own contributions.) For the Fossett Pathfinder Fellowship, you should focus your essay on environmental sustainability.”
Having an experience/background to talk about, which inspired you to pursue biology, (Soft Evidence) or some science activities that you did, any awards, competitions that you joined, science fair etc. (hard evidence) will be very helpful in writing these essays.
The OP asked about getting into WashU, not getting scholarships.
Just going to throw this out there… while it may not matter for Biology so much, if you apply to a niche school at WashU you better be prepared to show that you have some interest in the topic.
For example, if you apply to Sam Fox you better have a portfolio (even though it’s not required). Conversely, if you’re applying to engineering, if your only EC’s are art-related (just a simple example), it’s going to raise some red/yellow flags to the admissions committee.
And I know this for a fact. I’ve heard this from several admissions reps AND they’ve written it out very clearly in APAP resources.
So @me29034 's comment that “You also don’t need to know your major when you apply so there is no need to justify why you are majoring in something that doesn’t match your EC’s.” isn’t entirely true in all cases.