@alipanjwani: The SAT is a general education test. It doesn't apply to any specific field, but rather is for all college students and measures their general knowledge. Like any standardized test, it's really a measure of how well you take tests, and not necessarily how much you know.
Having said that, you can look at it as a general entrance exam. You can major in biology at any U.S. school offering the degree. You'll take the courses once you're accepted into the university itself, based in part on your SAT scores.
U.S. schools generally do not require specialized exams for entrance into particular undergraduate fields. You may take placement tests, which will then recommend you for certain core courses, like preliminary English, etc., but these are not necessary to be admitted to the university.
Many schools do have advanced honors programs to which you can apply for admission, but that's after you've already been accepted to the university.
As I said in an earlier comment, what you need to do is to contact the universities you're interested in for their requirements. Most universities have websites that will list their minimum requirements for admission, and checking there first will give you a good idea of what you need to be enrolled.