In regular zoos, I often make (like just about every one else) a large savannah exhibit with all the non-attacking animals, then individual exhibits (with maybe one or two other combined ones) for the rest of the zoo. But I am working on a zoo with one large exhibit for each of the biomes (larger if that biome has more animals, like savannah, and less if it has fewer, like scrub). I then make smaller exhibits for the preditors (as an example, for Savannah I would have all the peaceful animals together, then another exhibit attatched with the lions and such). It's much more interesting, and guests love it. My favorite is perhaps the rainforest, when I have okapi, gorillas, chimps, lemurs, and several more downloaded animals all together.
And, no, I have no expansions. My latest game installment was either AA/EA or Age of Empires 3, and I chose AOE3.