Hi Codename Gordon!
Personally I think yours is a good essay in terms of both grammar and logic. It is perfectly normal if you do not clearly agree or disagree with the statement. You have done a good job in demonstrating clearly both sides of the coin. The conclusion is very good, since it states your stand in a very reasonable way.
There are just some ideas I would like to share as reference for the 2nd paragraph. Actually exhibition is just one function of zoos. Zoos also are the places where scientists can study about animal behaviors and related subjects (and usually when an animal dies, they will perform operations on the body for scientific purposes). A zoo can be a very place to protect endangered animals and plants, too.
Overall I like your neat and clear essay very much. A 5.5/6.0 from me.