Which one of the following organisms is not an eukaryote?

Explanation

1. Paramecium caudatum: Paramecium caudatum is a eukaryotic organism. Eukaryotes are characterized by having a true nucleus enclosed within a membrane, and Paramecium fits this description.2. Escherichia coli: Escherichia coli, commonly known as E. coli, is a prokaryotic organism. It is a bacterium, which means it lacks a true nucleus and other membrane-bound organelles. Instead, its genetic material is found in a single circular chromosome in the cytoplasm.3. Euglena viridis: Euglena viridis is a eukaryotic organism. It is a single-celled organism with a well-defined nucleus and other membrane-bound organelles, which are characteristics of eukaryotes.4. Amoeba proteus: Amoeba proteus is also a eukaryotic organism. Like Paramecium and Euglena, it possesses a true nucleus enclosed by a nuclear membrane, confirming its classification as a eukaryote.So, among the options provided, Escherichia coli is the one that is not a eukaryote. It is a prokaryotic bacterium.