Eukaryote
Eukaryotes
Fossil range: Proterozoic - Recent
Ostreococcus is the smallest known free living eukaryote with an average
size of 0.8 µm.
Scientific classification
Domain:
Eukaryota
Whittaker & Margulis,1978
Kingdoms
Animalia - Animals
Fungi
Amoebozoa
Plantae - Plants
Chromalveolata
Rhizaria
Excavata
Alternative phylogeny
• Unikonta
•
• Metazoa
• Mesomycetozoa
• Choanozoa
• Eumycota
• Amoebozoa
• Bikonta
• Apusozoa
• Rhizaria
• Excavata
• Archaeplastida
• Chromalveolata
A eukaryote (IPA: /juːˈkæriɒt/ or /juːˈkærioʊt/) is an or-
ganism whose cells are organized into complex struc-
tures enclosed within membranes. Most living organ-
isms, including all animals, plants, fungi, and protists,
are eukaryotes. The defining membrane-bound struc-
ture that differentiates eukaryotic cells from prokaryot-
ic cells is the nucleus. The presence of a nucleus gives
these organisms their name, which comes from the
Greek ευ (eu, "good", "true") and κάρυον (karyon,
"nut"). Many eukaryotic cells contain other membrane-
bound organelles such as mitochondria, chloroplasts and
Golgi bodies.
Cell division in eukaryotes is different from organ-
isms without a nucleus (prokaryotes). It involves separ-
ating the duplicated chromosomes, through movements
directed by microtubules. There are two types of divi-
sion processes. In mitosis, one cell divides to produce
two genetically identical cells. In meiosis, which is re-
quired in sexual reproduction, one diploid cell (having
two instances of each chromosome, one from each par-
ent) undergoes recombination of each pair of parental
chromosomes, and then two stages of cell division, res-
ulting in four haploid cells (gametes). Each gamete has
just one complement of chromosomes, each a unique
mix of the corresponding pair of parental chromosomes.
Eukaryotes appear to be monophyletic, and so make
up one of the three domains of life. The two other do-
mains, bacteria and archaea, are prokaryotes, and have
none of the above features.
Cell features
Eukaryotic cells are typically much larger