Design of a database about Zoos
While you've done a pretty thorough job of following the textbook requirements, there are some practical considerations that you might or might not want to include, depending on the expectations of the assignment.  Some of these have to do with bad requirements.  I don't know if you would get extra marks or reduced marks for pointing these out.

Food quantity as an integer is probably not precise enough
Food quantities should have a unit of measure. Some foods will be dry, some will be liquid. Iguanas probably need a few grams of &quot;Iguana Chow&quot; whereas elephants will need multiple kilos of whatever they're eating.
Amounts of money should be stored as MONEY or another non-integer data type.
If your zoos are all over the place you might need to consider storing a currency with the monetary amount
Storing the age of a visitor is a mistake.  Visitors age between visits.  You're better off storing the date of birth of the visitor and calculating their age at each visit, since you know the date of the visits
In a real system, some of this information is going to be optional. Not everyone is going to tell you their date of birth.  Similarly, you may not know when your giant tortoise was born.
People's names, if they matter, are usually stored in more than one field (e.g. given name and family name)
It's highly unlikely that every animal will have a personal record of their dietary requirements. Some animals might, but for a lot of animals it might make more sense to store the requirements for all animals of a given species.
The fact that animal species is not accounted for in the model is kind of questionable, since you would think that most zoos would care about something like that