An eukaryote is an organism with complex cells, or a single cell with complex structures. In these cells the genetic material is organized into chromosomes in the cell nucleus.
Animals, plants, algae and fungi are all eukaryotes. There are also eukaryotes amongst single-celled protists. In contrast, simpler organisms, such as bacteria and archaea, do not have nuclei and other complex cell structures. Such organisms are called prokaryotes.
The eukaryotes are often treated as a superkingdom, or domain.
Eukaryotes evolved in the Proterozoic eon. The oldest known probable eukaryote is Grypania, a coiled, unbranched filament up to 30 mm long. The oldest Grypania fossils come from an iron mine near Negaunee, Michigan. The fossils were originally dated as 2100 million years ago, but later research showed the date as about 1874 million years ago. Grypania lasted into the Mesoproterozoic era.
Another ancient group is the acritarchs, believed to be the cysts or reproductive stages of algal plankton. They are found 1400 million years ago, in the Mesoproterozoic era.p57
The classification of the Eukaryota is under active discussion, and several taxonomies have been proposed. Modern versions disagree about the number of kingdoms. It carrys DNA as well as it is an organism.