A eukaryote is a type of organism whose cells contain a nucleus and other membrane-bound organelles. This group includes a wide variety of life forms, such as animals, plants, fungi, and protists. Eukaryotic cells are generally larger and more complex than prokaryotic cells, which lack a nucleus. Eukaryotes reproduce through processes like mitosis and meiosis, allowing for genetic diversity. They can be unicellular, like yeast, or multicellular, like humans and oak trees. The presence of a nucleus enables eukaryotic cells to organize their genetic material more efficiently, supporting complex functions and development.