What are the examples of unicellular organisms?

The origins of unicellular organisms can be traced back to 3.8 billion years. Examples of unicellular organisms include amoeba, bacteria, unicellular fungi, unicellular protists, and cyanobacteria. An amoeba is a type of eukaryotic protozoan that predominantly exists in all freshwater environments. Its shape is not fixed and is instead determined by environmental conditions. Bacteria are found in every environment on the planet, and exist in various shapes such as rod, spiral, and spherical forms. Bacteria are a type of prokaryotic cell and lack a nucleus. Some bacteria have adapted to survive in even the harshest conditions such as in the Earth’s core. Cyanobacteria, also known as blue-green algae, exhibit characteristics of bacteria and algae. These bacteria utilize photosynthesis to make food. Unicellular fungi are also known as yeasts and possess a cell wall, making them eukaryotes. Fungi are found in most habitats on earth. Unicellular protists include protozoa, which are found in soil or water globally. They vary in size, shape, cellular structure, and mode of nutrition. Protozoa can be found in the body as part of the normal flora or as a cause of illnesses.