Description of Eukaryota
The eukaryotes are one of the three major domains of cellular life. The eukaryotes are distinct because many cellular functions are sequestered into compartments that are separated from the cytoplasm by fluid lipo-protein membranes. The largest compartment in most cells is the nucleus - from which the group gets it name (karyon is greek for nut). The nucleus contains much of the cellular DNA, usually in multiple histone-rich chromosomes. Eukaryotes are rich in cytoskeletal proteins (e.g. the tubulin that forms microtubules or actin that forms microfilaments) and motility proteins (such as dynein, myosin, spasmin = caltractin = centrin). Cytoskeletal proteins provide shape to cells as well as anhcor and link cell components. Motility proteins help organelles move within the cells, facilitate cell and nuclear division, or move cells. Most eukaryotes contain mitochondria that derived from an ancient symbiosis with a bacterial lineage. Algae and plants contain chloroplasts derived from a symbiosis with a blue green algal lineage. Multicellularity (co-existence of functionally different cells with the same genome) has arisen many times within the estimated 2 billion year history of eukaryotes. The most familiar multicellular forms are the animals, plants and fungi. With almost 2,000,000 described species, eukaryotes are the most diverse of the cellular life forms. About one third of the species are equally distributed among fungi, plants and protists, the remaining two thirds are animals. Link to Eukaryotes in the Tree of Life project.