biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

, a colony is composed of two or more

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...

individuals living in close association with, or connected to, one another. This association is usually for mutual benefit such as stronger defense or the ability to attack bigger prey. Colonies can form in various shapes and ways depending on the organism involved. For instance, the bacterial colony is a cluster of identical cells (clones). These colonies often form and grow on the surface of (or within) a solid medium, usually derived from a single parent cell. Colonies, in the context of development, may be composed of two or more unitary (or solitary) organisms or be

modular Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a s ...

organisms. Unitary organisms have determinate development (set life stages) from

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

to adult form and individuals or groups of individuals (colonies) are visually distinct. Modular organisms have indeterminate growth forms (life stages not set) through repeated iteration of genetically identical modules (or individuals), and it can be difficult to distinguish between the colony as a whole and the modules within. In the latter case, modules may have specific functions within the colony. In contrast, solitary organisms do not associate with colonies; they are ones in which all individuals live independently and have all of the functions needed to survive and reproduce. Some organisms are primarily independent and form

facultative {{wiktionary, facultative Facultative means "optional" or "discretionary" (antonym '' obligate''), used mainly in biology in phrases such as: * Facultative (FAC), facultative wetland (FACW), or facultative upland (FACU): wetland indicator statuses ...

colonies in reply to environmental conditions while others must live in a colony to survive ( obligate). For example, some

carpenter bee Carpenter bees are species in the genus ''Xylocopa'' of the subfamily Xylocopinae. The genus includes some 500 bees in 31 subgenera. The common name "carpenter bee" derives from their nesting behavior; nearly all species burrow into hard plant m ...

s will form colonies when a dominant hierarchy is formed between two or more nest foundresses (facultative colony), while

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

s are animals that are physically connected by living tissue (the

coenosarc In corals, the coenosarc is the living tissue overlying the stony skeletal material of the coral. It secretes the coenosteum, the layer of skeletal material lying between the corallites (the stony cups in which the polyps sit). The coensarc is comp ...

) that contains a shared

gastrovascular cavity The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into a ...

Colony types

Social colonies

Unicellular 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. Organisms fall into two general categories: prokaryotic organisms and ...

and

multicellular A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...

unitary organisms may aggregate to form colonies. For example, *

Protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

s such as

slime mold Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mul ...

s are many unicellular organisms that aggregate to form colonies when food resources are hard to come by, as together they are more reactive to chemical cues released by preferred prey. *

Eusocial Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generat ...

insects like

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...

s and

honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current co ...

s are multicellular animals that live in colonies with a highly organized social structure. Colonies of some social insects may be deemed

superorganism A superorganism or supraorganism is a group of synergetically interacting organisms of the same species. A community of synergetically interacting organisms of different species is called a holobiont. Concept The term superorganism is used m ...

s. *

Animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s, such as humans and

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s, form breeding or nesting colonies, potentially for more successful mating and to better protect offspring. ** The

Bracken Cave Bracken Cave is the summer home to the largest colony of bats in the world. An estimated 20 million Mexican free-tailed bats roost in the cave from March to October making it the largest known concentration of mammals. The cave is located in sou ...

is the summer home to a colony of around 20 million

Mexican free-tailed bat The Mexican free-tailed bat or Brazilian free-tailed bat (''Tadarida brasiliensis'') is a medium-sized bat native to the Americas, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been ...

s, making it the largest known concentration of mammals.

Modular organisms

Modular organisms are those in which a genet (or genetic individual formed from a sexually-produced

) asexually reproduces to form genetically identical clones called

ramet A clonal colony or genet is a group of genetically identical individuals, such as plants, fungi, or bacteria, that have grown in a given location, all originating vegetatively, not sexually, from a single ancestor. In plants, an individual in s ...

s. A clonal colony is when the ramets of a genet live in close proximity or are physically connected. Ramets may have all of the functions needed to survive on their own or be interdependent on other ramets. For example, some

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

s go through the process of pedal laceration in which a genetically identical individual is asexually produced from tissue broken off from the anemone's pedal disc. In plants, clonal colonies are created through the propagation of genetically identical trees by

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

s or

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...

s. Colonial organisms are

clonal colonies A clonal colony or genet is a group of genetically identical individuals, such as plants, fungi, or bacteria, that have grown in a given location, all originating vegetatively, not sexually, from a single ancestor. In plants, an individual in s ...

composed of many physically connected, interdependent individuals. The subunits of colonial organisms can be unicellular, as in the alga ''

Volvox ''Volvox'' is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. It forms spherical colonies of up to 50,000 cells. They live in a variety of freshwater habitats, and were first reported by Antonie van Leeuwenhoek in 1700 ...

'' (a coenobium), or

, as in the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

. The former type may have been the first step toward multicellular

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

s. Individuals within a multicellular colonial organism may be called

modules Broadly speaking, modularity is the degree to which a system's components may be separated and recombined, often with the benefit of flexibility and variety in use. The concept of modularity is used primarily to reduce complexity by breaking a s ...

, or

zooid A zooid or zoöid is a single animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zoo ...

s. Structural and functional variation ( polymorphism), when present, designates ramet responsibilities such as feeding, reproduction, and defense. To that end, being physically connected allows the colonial organism to distribute nutrients and energy obtained by feeding zooids throughout the colony. The

hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specializ ...

Portuguese man o' war The Portuguese man o' war (''Physalia physalis''), also known as the man-of-war, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or blue bottle, which is ...

is a classic example of a colonial organism, one of many in the taxonomic class.

Microbial colonies

A microbial colony is defined as a visible cluster of

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s growing on the surface of or within a solid medium, presumably cultured from a single cell. Because the colony is clonal, with all organisms in it descending from a single ancestor (assuming no

contamination Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination W ...

), they are genetically identical, except for any

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...

s (which occur at low frequencies). Obtaining such genetically identical organisms (or pure strains) can be useful; this is done by spreading organisms on a culture plate and starting a new stock from a single resulting colony. A

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

is a colony of

s often comprising several species, with properties and capabilities greater than the aggregate of capabilities of the individual organisms.

Life history

Individuals in social colonies and modular organisms receive benefit to such a lifestyle. For example, it may be easier to seek out food, defend a nesting site, or increase competitive ability against other species. Modular organisms' ability to reproduce asexually in addition to sexually allows them unique benefits that social colonies do not have. The energy required for sexual reproduction varies based on the frequency and length of reproductive activity, number and size of offspring, and parental care. While solitary individuals bear all of those energy costs, individuals in some social colonies share a portion of those costs. Modular organisms save energy by using asexual reproduction during their life. Energy reserved in this way allows them to put more energy towards colony growth, regenerating lost modules (due to predation or other cause of death), or response to environmental conditions.

References