To be a biologist, you can't just like animals, you have to also love science. You're going to spend a lot of time writing papers and grants, performing statistics, reading (and reading, and reading...), teaching, etc. Just liking animals isn't enough.
My advice to anyone considering a career in biology is to work in a lab as an undergraduate. That's how I started out. You'll find out pretty quickly if research is the right thing for you. It can be quite a bit of hard work. Also, consider that for most types of research you'll end up having to sacrifice some of the animals that you love. It can be avoided if you stick to only certain topics, but most people don't think of that before they start studying amphibians.
I will give you my boring life story as an example
When I was an undergraduate, all I wanted to do was be a vet. I knew I wanted to work with animals and I thought that was the only way I could do it. After working for two miserable years on graveyard shifts at an animal hospital, I decided that it definitely wasn't for me.
Fortunately I started working for a lab on campus, maintaining their axolotl colony. I enjoyed it as mindless work. Then I got to help on an experiment looking at Ambystoma genetics. I enjoyed that even more. I decided I wanted to go to grad school and be a 'herpetologist'. Yep, I was young and stupid.
I applied to labs I found interesting and I got into one that was focused on courtship behavior in plethodontid salamanders. I moved to a new state and started my Masters degree. I ended up working on chameleon behavior (rather than salamanders), but what I did still fit in with the major theme of the lab. In two years, I had a Master's degree (and a husband
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The most important thing to keep in mind when applying to graduate schools for the sciences is that you're not looking at a particular school so much, but a particular professor who is working on projects that you find interesting. There's some leeway, but generally you'll have more freedom as a grad student to choose your own projects if you enter a lab in a basic science department (evolutionary biology, botany, zoology) as opposed to a molecular department (micro, cell biology, etc). And don't 'just apply': you've got to contact the professor, talk to him/her, visit the lab, to have the best shot.
Anyway, I really enjoyed grad school. It was a lot of work - you're basically taking classes, teaching, and doing your own research. You're expected to teach right away (unless you're on a research fellowship), even if you have no experience. If you're in a science department, your tuition will usually be covered and you'll be paid a 'stipend': around $16,000 a year. It's enough to live on.
I got my Master's and went on to get a PhD - basically same procedure as before. For a PhD, you're expected to come up with a number of connected projects that you write up for your dissertation. You're expected to publish papers in research journals. You teach. You take classes. You do research. Most programs say they expect you to finish in 5 years, but it will probably take you 6. I worked on lizard behavior, and my dissertation was a mix of field work and lab work.
You should consider your research projects carefully: Do you really want to work with an animal you 'love' when your project might require you to kill a large number of those animals? Even if your actual experiment causes no harm to the animals, many institution guidelines require you to destroy the animals at the end of your study. If you want to do fieldwork, how hard is it to find and work with your creature? It's something to think about.
Right now, I'm working as a postdoctoral fellow. I make about $30,000 a year and I'm 32 years old. It will be at least another year before either I or my husband can apply for a faculty position. That's another thing to consider about going into biology: you will be 'poor' for a good long time. You will also have to move to where the jobs are - it's not something you can just do anywhere. If you're interested in a research position, you'll also have to fight for grant money constantly. You must always be publishing. You really, really have to love the science.
Anyway, I don't mean to seem down on it - I love biology! But just consider the time and effort needed in the field. If you have any questions about anything, I'd be happy to answer them.