7) What kinds of creatures occur in this world?
The animals that occur alongside your characters are an important part of your world. These include the creatures they eat, the ones they train and make use of, and what they might keep as pets or companions.
Some important questions to ask about creatures in your world are:
1) Does your story depend on clearly defined creatures that occur in the real world? Are there horses? Chickens? Snakes? Dogs? Cats?
2) Is it a mix of real animals and mythical animals?
3) Are all the creatures in your world made up in your head?
It's important to ask these questions because if you're using creatures that you've created and no one else has ever seen or heard of you have to be able to describe them in such a way that your readers can picture them in their heads. Of course they won't see exactly what you see, but they'll get a close consensus.
If you're using real life animals, whether mixing them with mythical/created creatures or not you don't have to worry as much. A chicken is a chicken whether it's being gobbled down by a chimera or a lion. A horse is a horse whether an elf is riding it or a human.
Mythical creatures tend to be a mix as to how you write them into a story. Most everyone knows what a dragon or unicorn looks like. Even a chimera you could get away with little detail about it and still have most all your readers know what you are talking about. But, what about a Baku? What the heck is that? Well, in Japanese mythology the Baku is a great tapir with the body of a horse, the head of a lion, and the legs and paws of a tiger (Element Encyclopedia of Magical Creatures pg. 55). Yeah, I hear Baku and I picture that. XD So even if you're using established mythical creatures you may need to add a bit of description so your readers know what you are talking about.