Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. The most characteristic membrane bound structure is the nucleus. This feature gives them their name, (also spelled "eucaryote,") which comes from the Greek ευ, meaning good/true, and κάρυον, meaning nut, refering to the nucleus. In the nucleus the genetic material, DNA, is arranged in chromosomes. Many eukaryotic cells also contain membrane-bound organelles such as mitochondria, chloroplasts and Golgi bodies. Eukaryotes often have unique flagella made of microtubules in a 9+2 arrangement.
Finally, cell division involves a complex way of separating the duplicated chromosomes, which is also mediated by complexly choreographed arrangements of microtubules. There are two methods. In mitosis one cell divides to produce two genetically identical cells. In meiosis, which is required in sexual reproduction, one diploid cell (having two copies of each chromosome, one from each parent) undergoes a process of recombination between each pair of parental chromosomes, and then two stages of cell division, resulting in four haploid cells (gametes) each of which has only a single complement of chromosomes, each one being a unique mix and match of the corresponding pair of parental chromosomes.
Eukaryotes appear to be monophyletic and thus make up one of the three domains of life. The two other domains: bacteria and archaea (prokaryotes (without a nucleus)) share none of the above features, though the eukaryotes do share some aspects of their biochemistry with the archaea, and as such, are grouped with the archaea in the clade Neomura.
Animals, plants, and fungi are mostly multicellular, while many sorts of protist are unicellular.