Here's why:

* Eukaryotic cells have a true nucleus that contains their genetic material (DNA). They also have other membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, etc.

* Prokaryotic cells lack a nucleus and other membrane-bound organelles. Their DNA is located in a region called the nucleoid.

Animal cells are complex and have a variety of structures and functions that are characteristic of eukaryotic cells.