I recommend taking the test in your case. However, do not take advantage ETS's offer to send your scores to four schools for free unless you know for a fact you will do well. Then, if you are pleased with your scores, send them out to the schools that you think might have an interest (to show your strength in biology). It may cost you a bit more money this way, but it could be worth it.
I took the GRE subject biology and only regret it in hindsight because I was not pleased with my score.