Amoebas are single-celled microorganisms belonging to the phylum Amoebozoa. They are known for their shape-shifting ability, characterized by their ability to alter their cell shape and move by means of pseudopodia (singular: pseudopodium), which are temporary, finger-like projections of the cell membrane. Amoebas are a diverse group of protists, and they can be found in various aquatic environments, soil, and even in some animals as parasites.
Some key features of amoebas include:

1. Shape and Movement: As mentioned, amoebas lack a fixed shape and can change their form. They use pseudopodia to move and engulf food particles, such as bacteria and smaller microorganisms.
2. Nutrition: Amoebas are primarily heterotrophic, meaning they obtain their nutrients by engulfing and digesting other microorganisms. They are considered phagocytic feeders.
3. Reproduction: Amoebas can reproduce both asexually and sexually. Asexual reproduction often occurs through a process called binary fission, where the cell divides into two identical daughter cells. Sexual reproduction, when it occurs, typically involves the exchange of genetic material between two amoebas.
4. Habitats: Amoebas can be found in a wide range of environments, including freshwater ponds, streams, and soil. Some amoebas are also found in extreme environments, such as hot springs and acidic lakes.
5. Amoebic Diseases: While most amoebas are harmless, some species can cause diseases in humans and animals. The best-known example is Entamoeba histolytica, which causes amoebic dysentery.
6. Research: Amoebas have been used in scientific research, particularly as model organisms for studying cell biology and genetics.

Overall, amoebas are fascinating microorganisms with a range of adaptations that allow them to thrive in diverse habitats and play important roles in ecosystems.