Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Prokaryote
open-in-new
<p>A prokaryote is a <a href="/facts/Unicellular_organism/9PQsRuHU">single-celled organism</a> whose <a href="/facts/Cell_(biology)/bLM9UQvy">cell</a> lacks a <a href="/facts/Cell_nucleus/D7sFRa3c">nucleus</a> and other <a href="/facts/Membrane-bound_organelle/vhDFnGbs">membrane-bound organelles</a>. The word <i>prokaryote</i> comes from the <a href="/facts/Ancient_Greek/LIK7NlUh">Ancient Greek</a> πρό (<i>pró</i>), meaning 'before', and κάρυον (<i>káruon</i>), meaning 'nut' or 'kernel'. In the earlier <a href="/facts/Two-empire_system/28zQoSBM">two-empire system</a> arising from the work of <a href="/facts/%25C3%2589douard_Chatton/cUC39kWo">Édouard Chatton</a>, prokaryotes were classified within the empire Prokaryota. However, in the <a href="/facts/Three-domain_system/np75fPUv">three-domain system</a>, based upon <a href="/facts/Molecular_phylogenetics/FysplHP5">molecular phylogenetics</a>, prokaryotes are divided into two <a href="/facts/Domain_(biology)/RpP6V7n6">domains</a>: <a href="/facts/Bacteria/wC8xSCsU">Bacteria</a> and <a href="/facts/Archaea/Adxh0aHw">Archaea</a>. A third domain, <a href="/facts/Eukaryote/SkwyPLMA">Eukaryota</a>, consists of organisms with nuclei. </p><p>Prokaryotes <a href="/facts/Evolution/qE5amP6a">evolved</a> before eukaryotes, and lack nuclei, <a href="/facts/Mitochondria/ErHqrdJ1">mitochondria</a>, and most of the other distinct organelles that characterize the eukaryotic cell. Some unicellular prokaryotes, such as <a href="/facts/Cyanobacteria/S8bKxIU9">cyanobacteria</a>, form <a href="/facts/Colony_(biology)/b5QfltwY">colonies</a> held together by <a href="/facts/Biofilm/zg93x2w4">biofilms</a>, and large colonies can create multilayered <a href="/facts/Microbial_mat/qVfYYzvW">microbial mats</a>. Prokaryotes are <a href="/facts/Asexual_reproduction/HpovW0VS">asexual</a>, reproducing via <a href="/facts/Fission_(biology)/9Ed5vUr6">binary fission.</a> <a href="/facts/Horizontal_gene_transfer/FPyUIsf2">Horizontal gene transfer</a> is common as well. </p><p>Molecular phylogenetics has provided insight into the interrelationships of the three domains of life. The division between prokaryotes and eukaryotes reflects two very different levels of cellular organization; only eukaryotic cells have an <a href="/facts/Nuclear_membrane/IwRQ5BVL">enclosed nucleus</a> that contains its <a href="/facts/DNA/nB89Iauz">DNA</a>, and other membrane-bound organelles including mitochondria. More recently, the primary division has been seen as that between Archaea and Bacteria, since eukaryotes may be part of the archaean clade and have multiple <a href="/facts/Homology_(biology)/muctKlyT">homologies</a> with other Archaea. </p><p>Prokaryotic cells are generally smaller and similar than eukaryotic cells. Prokaryotic cells do not enclose their genetic material within a nucleus. </p>