Here's why:

* Prokaryotic vs. Eukaryotic: Bacteria belong to a group called prokaryotes. Prokaryotes are characterized by the absence of a membrane-bound nucleus. Their genetic material (DNA) is located in a region called the nucleoid, but it's not enclosed within a separate membrane.

* Eukaryotes: In contrast, eukaryotes, which include animals, plants, fungi, and protists, have a well-defined nucleus that contains their DNA.