I had thoughts about going into zoology, marine biology or botany when I was a teen, but as a lazy, rebellious and irresponsible student I didn't have the kinds of marks or course background a university would require for applicants to science programs (amusingly, I am now a teacher).
Now that I'm 30 I suppose I could get into such a program as a mature student, but my time is occupied with work and family. I will compromise with my young dreams by becoming a farmer in the future (will be inheriting my wife's family farm in Northern Japan once her parents retire, and will soon be moving there to learn the business).
That said, I'd like to give you some advice. Anything that people tell you is impossible is exceedingly worth doing. Example: everyone told me I was a fool for planning to move to Japan, offering me "helpful" lists of examples of why it would never work out. I have now lived in Japan for four years, and had effectively achieved my life's goal while in my 20s. I will likely be here for the rest of my days and have nothing but opportunities going into the future.
If your dream is to start a zoo then that is what you will have to do. Expect it to be hard work, full of surprises and disappointments and people throwing barriers at you at every step. In spite of all that, however, think of the reward if you succeed - not only to yourself but to the animals you could help to conserve.
Good luck! Show everyone else that they do not control your future.
