Here's why:

* Prokaryotes are single-celled organisms that lack a membrane-bound nucleus and other membrane-bound organelles. Their genetic material (DNA) is located in a region called the nucleoid, which is not enclosed by a membrane.

* Eukaryotes, on the other hand, have cells with a true nucleus that contains their DNA, as well as other membrane-bound organelles.

Examples of prokaryotes include bacteria and archaea.