Obligate
Encyclopedia
Obligate means "by necessity" (antonym facultative) and is used mainly in biology in phrases such as:
- Obligate aerobeObligate aerobeAn obligate aerobe is an aerobic organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to oxidize substances, like sugars or fats, in order to obtain energy. During respiration, they use oxygen as the terminal electron acceptor...
, an organism that cannot survive without oxygen - Obligate anaerobeObligate anaerobeObligate anaerobes are microorganisms that live and grow in the absence of molecular oxygen; some of these are killed by oxygen. -Metabolism:...
, an organism that cannot survive in the presence of oxygen - Obligate air-breather, a complex organism which obtains required oxygen directly from the atmosphere through respiration rather than extracting dissolved oxygen from water, as, for example, the South American lungfishSouth American lungfishThe South American lungfish, Lepidosiren paradoxa, is the single species of lungfish found in swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America. Notable as an obligate air-breather, it is the sole member of its family Lepidosirenidae...
- Obligate carnivore, a true carnivore solely dependent for survival on the nutrients found in animal flesh.
- Obligate intracellular parasiteObligate intracellular parasiteIntracellular parasites are parasitic microorganisms - microparasites that are capable of growing and reproducing inside the cells of a host.-Facultative:...
, a parasitic microorganism that cannot reproduce outside their host cell - Obligate parasiteObligate parasiteAn obligate parasite is a parasitic organism that cannot complete its life cycle without dependence on its host.-See also:*Obligate intracellular parasite*Parasitism*Parasitic plant*Facultative parasite...
, a parasite that cannot survive without its host - Obligate photoperiodic plant, a plant requiring long or short nights before flowering
- Obligate symbionts, organisms which can only live together in a symbiosisSymbiosisSymbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...