You would think getting into grad school in one or another area of biology would be more or less the same. You might even think that if you went to a better undergrad university, had better grades, more research experience, better letters, and wrote careful essays you would be more likely to get admitted than someone weaker in all those things. But this is not always the case, so here I’ll explain why.
Graduate school is where you specialize. You learn lots of general concepts and tools, but you apply them to a very specific problem. Exactly how soon you specialize and how exact that specialization is varies by field in a lot of ways. Some of that variation is cultural and some is a natural outcome of different numbers of faculty.
If the field has lots of faculty, even well over a hundred, and the program admits only tens of students, then the odds you will find a fitting laboratory are high. Such departments are likely to admit in ways similar to undergrad, choosing the students with the best overall qualifications and not worrying about exactly which lab you will end up in too much. At Wash U this is likely to be the case for departments like neuroscience or cell biology with over a hundred people listed as faculty.
Ecology and evolution programs are quite different. We admit about as many people as we have faculty, so fit becomes an issue. Furthermore, undergrads coming in are more likely to have identified a subfield they like. If we have one person in that field and they are not taking grad students, or you are not their top two or so choice, you will not get in, no matter how amazing your record is. If you are really sure you want to study frog communication and our frog communication person is full, you will not get in (hypothetical example – we don’t have such a person).
What should you do about this? First of all, apply to multiple programs with great people in frog communication. Make it clear to them that this is what you want, communicate with them in advance, and make your strengths clear.Another option is to loosen up your requirements a bit. Maybe you want to study anything about frogs, or amphibians, or vertebrates. Or maybe you want to study anything about communication. Or maybe any area of field behavior would do. Or maybe you are like I was and had no real idea, or rapidly changing ideas. In these cases you might communicate with multiple professors and it might increase your chance of getting in. It is still essential to apply to multiple programs, including some large state universities where there are lots of ways of fitting in. After all, if we don’t have what you want, this would not be the right place for you.
If you really want to come to this university, say so. We get a certain number of interview slots and a certain number of admissions slots. We cannot know who will accept our offers. If you make it clear you will accept here, it will probably help you get in. But you can only do this to one university.