Prokaryotes are organisms without a nucleus.

Answer

**Step-by-Step Text Solution:**

1. **Definition of Prokaryotes**: Prokaryotes are defined as organisms that do not have a true nucleus. This means that their genetic material is not enclosed within a membrane-bound nucleus.

2. **Cell Structure**: Prokaryotes are typically unicellular organisms. This means that they consist of a single cell, which is a fundamental unit of life.

3. **Absence of Nuclear Membrane**: In prokaryotic cells, the genetic material (DNA) is located in a region called the nucleoid, which is not surrounded by a nuclear membrane. This is a key characteristic that distinguishes prokaryotes from eukaryotes, which do have a membrane-bound nucleus.

4. **Classification of Prokaryotes**: In the three-domain system of biological classification, prokaryotes are divided into two main domains:
- **Bacteria (Eubacteria)**: This domain includes most of the common bacteria.
- **Archaea (Archaeobacteria)**: This domain includes organisms that often live in extreme environments and have distinct biochemistry and genetics compared to bacteria.

5. **Conclusion**: Based on the above points, we can conclude that the statement "Prokaryotes are organisms without a nucleus" is indeed correct.

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