Hi avni.m! I'm really glad you loved Hopkins during your visit! Personally, I feel that people are in fact very supportive of each other. I haven't come across a single person who was not willing to help me if I needed it. I find that it is very hard to survive my classes unless I have a group of friends and classmates to work with since the work load is very rigorous and comes in large amounts. In high school, a lot of the time my teachers discouraged working with others so that we would become more independent and self sufficient. However, at Hopkins, many of the professors encourage group work since our quality of learning can greatly improve by teaching each other and catching each other's mistakes. It is also great preparation for the real world since we will often find ourselves having to cooperate and work with others. So I wouldn't say there is a "cut throat" environment where people are reluctant to help others.
Ironically, a competitiveness still exists among many students, but it does not arise from any lack of ability to help each other out (because again, everyone here is very helpful). Instead, it arises from the way many classes are structured. In many large lecture classes (like chemistry, calculus, physics, etc.), we are graded based on a curve and standard deviation. In other words, a student's final grade in the class is not solely determined by his/her individual performance, but is also dependent on the performances of everyone else. But even with this grading policy, students at Hopkins are NOT out to get each other. They are simply striving to be the best they can. And because everyone is striving to be the best they can, there comes a misconception that Hopkins is "cut throat".
If you are up for all the hard work, then Hopkins is a great place to be. Believe me, you will learn a lot in your classes! Luckily, studying and being in class is only half of what your days will consist of here. You will have plenty of time as a Biology major to get involved with other things, such as clubs/organizations, sports, research, etc. And there will be plenty of time (if you are good at time management) to just hang out with friends or go out on the weekends! Hope this helped and good luck with your decision:)