Though both are unicellular, bacteria doesn't possess a nucleus or cell organelles, except ribosomes, whereas amoebas possess a well-defined nucleus and all essential cell organelles.
Explanation:
Eukaryotes and prokaryotes have the most significant difference between them. Eukaryotes have organelles that are membrane-bound and have a nucleus. Prokaryotes do not have these specific features. Eukaryotes can be both multicellular and unicellular and prokaryotes are unicellular.
Bacteria are an example of prokaryotes as it doesn’t have nucleus and organelles that are membrane bound. As it is small in shape it can function without organelles. Amoeba is an example of eukaryotic cell as it is unicellular and has all necessary organelles and has a nucleus.