You may find it hard to take pictures from desired angles. If you like photography like me, this is probably frustating. To fix this, use raised paths or the high wire ride. Then, just jump in or get up to them and SNAP!

In wetland exhibits, you can have hippos and flamingoes.
In addition to the ones mentioned by malicious_angel_82, you can put gemsboks in desert exhibits.
In tropical exhibits, you can have chimps, gorillas, crested gibbons, and orangutans.
In addition to the ones mentioned by malicious_angel_82, you can put thompsons gazelles in savannah exhibits.
In addition to the ones mentioned by malicious_angel_82, you can put spectacled bears in temperate exhibits.

When you do combine exhibits, make sure the food, houses, and toys are shared by most of the animals. If an animal has needs that are rare, like the crested gibbons only sleeping on raised platforms and tree trunks, make sure to pick the one that isn't in common with any other animal in the exhibit. This way, they will have access to their specific needs that may otherwise be used by teh other animals.

First, when choosing a campaign, you can hold the up button on your keyboard to increase the amount of starting money.

To save money, start with a small exhibit for any animal. Keep increasing by a little. This way, you won't have to waste money on useless fencing.

If you've ever had a black rhino, you may notice that, even though you put a water trough in the exhibit, they still get thirsty. They will paw the ground for water. If they do this, then you need to put some shallow savannah water in the in the exhibit and remove the trough with water. This works for any animal that is big enough to have their shoulders above the water. They may not paw for water like the rhino, but it will save you money when you can put some water in their exhibit instead of buying a trough.

Give any animal that can have some food dish that is elivated that food dish. They will get sick less often.

The Breeding Center doesn't help with non-endangered animals and only helps the animals to mate. Once the animal is pregnant, the Breeding Center helps no more.

See Ya!

Put more than 1 species of animal in an exhibit. This makes your guests more amused and keeps them more happy because they have more to see. Also they sometimes comment on how they think it's great that two different species can live together. I have writen a list below of animals you can put together.

Savannah
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Giraffe, Zebra, Ostrich and Giant Sable Antalope

Temperate Rainforest
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Giant Panda, Red Panda, Koala and Common Peafowl

Grassland
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American Bison and Prezwalski's Wild Horse

Tundra
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Penguin, Polar Bear and Caribou

Desert
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Fennec Fox, Dromedary Camel and Scimitar Horned Oryx

I haven't figured out if you can put the any of the other animals together but makes sure you don't put any more animals than I have listed in each exhibit. Happy Tycoonin'!