Multicellular organism

multicellularmulticellular organismsmulticellularitymulticellular lifeevolution of multicellularitycomplex lifemulti-celledmulti-celled organismmulti-cellular organismcolonial theory
Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.wikipedia
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Organism

organismsflora and faunaliving organisms
Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.
Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi; or unicellular microorganisms such as protists, bacteria, and archaea.

Unicellular organism

unicellularsingle-celled organismsingle-celled
Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells.

Cell (biology)

cellcellscellular
Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.
Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or multicellular (including plants and animals).

Algae

algaalgalfilamentous algae
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium.
Included organisms range from unicellular microalgae, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length.

Brown algae

brown algaPhaeophyceaebrown
However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants.
The brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere.

Eukaryote

Eukaryotaeukaryoticeukaryotes
However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants.
Unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue.

Red algae

Rhodophytared algared
However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants.
The majority of species (6,793) are found in the Florideophyceae (class), and mostly consist of multicellular, marine algae, including many notable seaweeds.

Fungus

Fungifungalnecrotrophic
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants. It evolved repeatedly for Chloroplastida (green algae and land plants), once or twice for animals, once for brown algae, three times in the fungi (chytrids, ascomycetes and basidiomycetes) and perhaps several times for slime molds and red algae.
Growth of fungi as multicellular structures consisting of somatic and reproductive cells—a feature independently evolved in animals and plants —has several functions, including the development of fruit bodies for dissemination of sexual spores (see above) and biofilms for substrate colonization and intercellular communication.

Dictyostelium

dictyostelium lacteumDictyostelium.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium.
Members of the order are Protista of great theoretical interest in biology because they have aspects of both unicellularity and multicellularity.

Embryophyte

land plantsland plantEmbryophyta
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants.
Embryophytes are complex multicellular eukaryotes with specialized reproductive organs.

Yeast

yeastsbrewer's yeastbudding yeast
Fungi are predominantly multicellular, though early diverging lineages are largely unicellular (e.g., Microsporidia) and there have been numerous reversions to unicellularity across fungi (e.g., Saccharomycotina, Cryptococcus, and other yeasts).
Yeasts are unicellular organisms that evolved from multicellular ancestors, with some species having the ability to develop multicellular characteristics by forming strings of connected budding cells known as pseudohyphae or false hyphae.

Cell type

cell typescell-typecell-types
Animals have evolved a considerable diversity of cell types in a multicellular body (100–150 different cell types), compared with 10–20 in plants and fungi.
A multicellular organism may contain a number of widely differing and specialized cell types, such as muscle cells and skin cells in humans, that differ both in appearance and function yet are genetically identical.

Animal

Animaliaanimalsmetazoa
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants. This is inexact, as living multicellular organisms such as animals and plants are more than 500 million years removed from their single-cell ancestors.
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia.

Mycetozoa

myxomycetesMyxomycotaslime molds
It evolved repeatedly for Chloroplastida (green algae and land plants), once or twice for animals, once for brown algae, three times in the fungi (chytrids, ascomycetes and basidiomycetes) and perhaps several times for slime molds and red algae.
Dictyostelids are used as examples of cellular communication and differentiation, and may provide insights into how multicellular organisms develop.

Somatic cell

somatic cellssomaticvegetative cell
In some multicellular groups, which are called Weismannists, a separation between a sterile somatic cell line and a germ cell line evolved.
A somatic cell (from the Greek σῶμα sôma, meaning "body") or vegetal cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell.

Prokaryote

prokaryoticprokaryotesprokaryotic cells
Multicellularity has evolved independently at least 25 times in eukaryotes, and also in some prokaryotes, like cyanobacteria, myxobacteria, actinomycetes, Magnetoglobus multicellularis or Methanosarcina.
Most explanations of co-operation and the evolution of multicellularity have focused on high relatedness between members of a group (or colony, or whole organism).

Embryo

embryosembryonalhuman embryos
This is what plant and animal embryos do as well as colonial choanoflagellates.
An embryo is an early stage of development of a multicellular organism.

Plant

Plantaeplantsflora
This is inexact, as living multicellular organisms such as animals and plants are more than 500 million years removed from their single-cell ancestors.
Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae.

Anatomy

anatomistanatomicalanatomically
Until recently, phylogenetic reconstruction has been through anatomical (particularly embryological) similarities.
The kingdom Animalia contains multicellular organisms that are heterotrophic and motile (although some have secondarily adopted a sessile lifestyle).

Francevillian biota

Francevillian Group FossilGaboniontaFrancevillian
The earliest fossils of multicellular organisms include the contested Grypania spiralis and the fossils of the black shales of the Palaeoproterozoic Francevillian Group Fossil B Formation in Gabon (Gabonionta).
The fossils are regarded as evidence of the earliest form of multicellular life.

Mitochondrion

mitochondriamitochondrialmitochondrial membrane
Although such symbiosis is theorized to have occurred (e.g., mitochondria and chloroplasts in animal and plant cells—endosymbiosis), it has happened only extremely rarely and, even then, the genomes of the endosymbionts have retained an element of distinction, separately replicating their DNA during mitosis of the host species.
Some cells in some multicellular organisms may, however, lack them (for example, mature mammalian red blood cells).

Cellular differentiation

differentiationcell differentiationdifferentiate
The mechanism of this latter colony formation can be as simple as incomplete cytokinesis, though multicellularity is also typically considered to involve cellular differentiation.
Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.

Protist

ProtistaprotistsProtoctista
However, it can often be hard to separate colonial protists from true multicellular organisms, as the two concepts are not distinct; colonial protists have been dubbed "pluricellular" rather than "multicellular".
In the classification system of Lynn Margulis, the term protist is reserved for microscopic organisms, while the more inclusive term Protoctista, or protoctist, is applied to a biological kingdom that includes certain large multicellular eukaryotes, such as kelp, red algae and slime molds.

Mitosis

mitoticmitosesmitotic division
Although such symbiosis is theorized to have occurred (e.g., mitochondria and chloroplasts in animal and plant cells—endosymbiosis), it has happened only extremely rarely and, even then, the genomes of the endosymbionts have retained an element of distinction, separately replicating their DNA during mitosis of the host species.

Colony (biology)

colonialcoloniescolony
Colonial organisms are the result of many identical individuals joining together to form a colony.
The subunits of colonial organisms can be unicellular, as in the alga Volvox (a coenobium), or multicellular, as in the phylum Bryozoa.