I was just reading a great paper on the over use of the Student's t-test in many biological studies. The author surveyed a collection of studies from the journal "Behavioral Ecology" (published by Oxford University Press) and found that many utitlized some form of the Student's t-test. This test should only be used when the variances of the two populations are identical (or nearly identical). When this does not hold true, the Student's t-test actually does very poorly, as shown by the increased number of Type 1 and 2 errors.
I think as biologists, we often neglect to make sure that the tests we use are appropriate and that we need to stop treating these tests as one-size-fits-all-blackboxes.
The paper, entitled "The unequal variance t-test is an underused alternative to Student's t-test and the Mann-Whitney U test" by Graeme D. Ruxton. The paper can be accessed here: http://beheco.oxfordjournals.org/cgi/content/full/17/4/688