Maybe I've just had good experiences, but I've never noticed gender biases or class differences in the biological sciences. (OKay, so I've known some phds who were absolutely terrible to any people in their labs... and I think that was just they were mean people that would torture anyone they could get away with torturing, even if it was fellow phds who wouldn't stand up for themselves) Yes, most of the tenured professors tend to be old men, but most of them at this point don't have a choice in taking women seriously. My graduate school class was 13 females. We did have 1 token male, but he was doing the 1 year certificate program to try to get into med school. And old men professors seem to not have too much problems with ending up with a lab full of smart females that look up to them as a mentor.
But, I was always taken seriously and my opinions sought - as a high school student working in a military lab, a college student in a lab, as a grad student or as a post-doc. And I can't say that I ever really observed class differences, but then I've never been the top of the chain. As a grad student or post-doc, you're pretty aware that you need to be in the lab technicians good graces. But lab technicians, high school or college students, etc. were always invited to sit in on meeting about a project they were working on, and they were listened to - because they were the ones actually doing the work.
I won't say that I'm not disgruntled with the whole academia, post-doc, etc - but it's not about being female or not being taken seriously because of my level or anything like that.