The present disambiguation page holds the title of a primary topic, and an article needs to be written about it. It is believed to qualify as a broad-concept article. It may be written directly at this page or drafted elsewhere and then moved over here. Related titles should be described in Facultative, while unrelated titles should be moved to Facultative (disambiguation).
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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 for plants
- Facultative anaerobe, an organism that can use oxygen but also has anaerobic methods of energy production. It can survive in either environment
- 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 parasite, a parasite that can complete its life cycle without depending on a host
- 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