1. Organisms composed of prokaryotic cells are classified into 2 main groups: archaea and bacteria
2. A primitive organism or lower organism is the one which has a simple body structure and ancient body design or features that have not changed much over a period of time
3. Prokaryotes are primitive cells, without a nucleus or membrane bound organelles, has DNA located in a "nuclear area", but the DNA is not bound inside the nucleus as in Eukaryotes.
So,prokaryotes are called primitive organisms