**Prokaryotes and Eukaryotes:**

Prokaryotes and eukaryotes are two basic types of cellular organisms. The main difference between these two types lies in the organization of their cells. Prokaryotes are single-celled organisms that lack a true nucleus and other membrane-bound organelles, whereas eukaryotes are multicellular organisms that possess a true nucleus and various membrane-bound organelles.

**Prokaryotes:**

Prokaryotes are a group of microorganisms that include bacteria and archaea. They are characterized by the absence of a true nucleus and other membrane-bound organelles. Prokaryotic cells are much smaller and simpler compared to eukaryotic cells.

**Bacteria:**

Bacteria are one type of prokaryote. They are single-celled microorganisms that can be found in a wide range of environments. Bacteria have a simple cellular structure and lack a nucleus. Their genetic material is contained in a single circular chromosome located in the nucleoid region of the cell.

Bacteria play crucial roles in various ecological processes. They can be found in soil, water, air, and even in the human body. While some bacteria are harmful and can cause diseases, others are beneficial and help in nutrient cycling, decomposition, and even in human digestion.

**Chlamydomonas, Amoeba, and Spirogyra:**

Chlamydomonas, Amoeba, and Spirogyra are not prokaryotes. They are all eukaryotes.

- Chlamydomonas: Chlamydomonas is a single-celled green alga. It belongs to the group of eukaryotes and possesses a nucleus and other membrane-bound organelles. Chlamydomonas is commonly found in freshwater environments.

- Amoeba: Amoeba is a genus of single-celled eukaryotic organisms. It belongs to the group of protists and is characterized by its ability to form temporary extensions of its cytoplasm called pseudopodia. Amoebas can be found in various habitats such as soil, freshwater, and marine environments.

- Spirogyra: Spirogyra is a filamentous green alga. It is also a eukaryotic organism with a true nucleus and other membrane-bound organelles. Spirogyra is commonly found in freshwater environments and forms green mats or strands in ponds, lakes, and slow-flowing streams.

**Conclusion:**

In summary, among the given options, only bacteria are prokaryotes. Bacteria are single-celled microorganisms that lack a nucleus and other membrane-bound organelles. Chlamydomonas, Amoeba, and Spirogyra, on the other hand, are eukaryotes and possess a true nucleus and other membrane-bound organelles.