Here's why:

* Eukaryotes are organisms whose cells have a membrane-bound nucleus that contains their genetic material (DNA).

* Prokaryotes, on the other hand, are organisms whose cells lack a nucleus and other membrane-bound organelles. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

So, animals, plants, fungi, and protists are all eukaryotes because their cells contain a nucleus.