Facultative

Facultative means "optional" or "discretionary" (antonym obligate), and is used mainly in biology. It is seen in topics including:

Facultative anaerobe, an organism that can use oxygen but also has anaerobic methods of energy production.
Facultative biotroph, an organism, often a fungus, that can live as a saprotroph but also form mutualisms with other organisms at different times of its life cycle.
Facultative biped, an animal that is capable of walking or running on two legs as well as walking or running on four limbs or more, as appropriate
Facultative carnivore, a carnivore that does not depend solely on animal flesh for food but also can subsist on non-animal food. Compare this with the term omnivore
Facultative heterochromatin, tightly packed but non-repetitive DNA in the form of Heterochromatin, but which can lose its condensed structure and become transcriptionally active
Facultative lagoon, a type of stabilization pond used in biological treatment of industrial and domestic wastewater
Facultative necrophage, an animal that feeds on carrion but retains the traits needed to find and consume other food sources
Facultative parasite, a parasite that can complete its life cycle without depending on a host
Facultative parthenogenesis, a rare biological term for when a species can switch between sexual reproduction and parthenogenesis
Facultative photoperiodic plant, a plant that will eventually flower regardless of night length but is more likely to flower under appropriate light conditions.
Facultative saprophyte, lives on dying, rather than dead, plant material
Wetland indicator status for plants can include facultative (FAC), facultative wetland (FACW), and facultative upland (FACU) to distinguish types that appear in multiple regions

Facultative

See also