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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 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 conde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stabilization Pond
Waste stabilization ponds (WSPs or stabilization ponds or waste stabilization lagoons) are ponds designed and built for wastewater treatment to reduce the organic content and remove pathogens from wastewater. They are man-made depressions confined by earthen structures. Wastewater or "influent" enters on one side of the waste stabilization pond and exits on the other side as "effluent", after spending several days in the pond, during which treatment processes take place. Waste stabilization ponds are used worldwide for wastewater treatment and are especially suitable for developing countries that have warm climates. They are frequently used to treat sewage and industrial effluents, but may also be used for treatment of municipal run-off or stormwater. The system may consist of a single pond or several ponds in a series, each pond playing a different role in the removal of pollutants. After treatment, the effluent may be returned to surface water or reused as irrigation water (or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Lagoon
Facultative lagoons are a type of waste stabilization pond used for biological treatment of industrial and domestic wastewater. Sewage or organic waste from food or fiber processing may be catabolized in a system of constructed ponds where adequate space is available to provide an average waste retention time exceeding a month. A series of ponds prevents mixing of untreated waste with treated wastewater and allows better control of waste residence time for uniform treatment efficiency. Fundamentals First pond The facultative lagoon in the pond sequence functions like the primary clarifier of a conventional sewage treatment system. Heavy solids will settle to the bottom of the lagoon, and lighter solids will float. This facultative lagoon lacks the sludge removal capability of a primary clarifier, so a population of anaerobic organisms will colonize accumulated sludge on the bottom of the lagoon. The surface area of the lagoon should be large enough to provide an atmospheric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Biped
A facultative biped is an animal that is capable of walking or running on two legs (bipedal), as a response to exceptional or discretionary (facultative) circumstances, while normally walking or running on four limbs or more. In contrast, obligate bipedalism is where walking or running on two legs is the primary method of locomotion. Facultative bipedalism has been observed in several families of lizards and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, gorillas, bonobos and chimpanzees. Several dinosaur and other prehistoric archosaur species are facultative bipeds, most notably ornithopods and marginocephalians, with some recorded examples within sauropodomorpha. Different facultatively bipedal species employ different types of bipedalism corresponding to the varying reasons they have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport. In lizards, it has been debated whether ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Anaerobe
A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus'' spp., ''Escherichia coli'', ''Salmonella'', ''Listeria'' spp., '' Shewanella oneidensis'' and ''Yersinia pestis''. Certain eukaryotes are also facultative anaerobes, including pupfish, fungi such as ''Saccharomyces cerevisiae'' and many aquatic invertebrates such as nereid polychaetes. It has been observed that in mutants of '' Salmonella typhimurium'' that underwent mutations to be either obligate aerobes or anaerobes, there were varying levels of chromatin-remodeling proteins. The obligate aerobes were later found to have a defective DNA gyrase subunit A gene ('' gyrA''), while obligate anaerobes were defective in topoisomerase I (''topI''). This indicates that topoisomerase I and its associated relaxation of chromosomal DNA is requi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterochromatin
Heterochromatin is a tightly packed form of DNA or '' condensed DNA'', which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes. Because it is tightly packed, it was thought to be inaccessible to polymerases and therefore not transcribed; however, according to Volpe et al. (2002), and many other papers since, much of this DNA is in fact transcribed, but it is continuously turned over via RNA-induced transcriptional silencing (RITS). Recent studies with electron microscopy and OsO4 staining reveal that the dense packing is not due to the chromatin. Constitutive heterochromatin can affect the genes near itself (e.g. position-effect variegation). It is usually repetitive and forms structural functions such as centromeres or telomeres, in addition to acting as an attractor for other gene-expression or repression signals. Facultativ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anaerobic Organism
An anaerobic organism or anaerobe is any organism that does not require oxygen, molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environment. Anaerobes may be unicellular (e.g. protozoans, bacteria) or multicellular. Most fungi are obligate aerobes, requiring oxygen to survive. However, some species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes; for these species, anaerobic respiration is used because oxygen will disrupt their metabolism or kill them. The sea floor is possibly one of the largest accumulation of anaerobic organisms on Earth, where microbes are primarily concentrated around Hydrothermal_vent, hydrothermal vents. These microbes produce energy in absence of sunlight or oxygen through a process called chemosynthesis, whereby inorganic compounds such as hydrogen gas, hydrogen sulfide or ferrous ions are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Heterochromatin
Heterochromatin is a tightly packed form of DNA or '' condensed DNA'', which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes. Because it is tightly packed, it was thought to be inaccessible to polymerases and therefore not transcribed; however, according to Volpe et al. (2002), and many other papers since, much of this DNA is in fact transcribed, but it is continuously turned over via RNA-induced transcriptional silencing (RITS). Recent studies with electron microscopy and OsO4 staining reveal that the dense packing is not due to the chromatin. Constitutive heterochromatin can affect the genes near itself (e.g. position-effect variegation). It is usually repetitive and forms structural functions such as centromeres or telomeres, in addition to acting as an attractor for other gene-expression or repression signals. Facultative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wetland Indicator Status
Wetland indicator status denotes the probability of individual species of vascular plants occurring in freshwater, brackish and Salt marsh, saltwater wetlands in the United States. The wetland status of 7,000 plants is determined upon information contained in a list compiled in the National Wetland Inventory undertaken by the U.S. Fish and Wildlife Service and developed in cooperation with a federal inter-agency review panel (Reed, 1988). The National List was compiled in 1988 with subsequent revisions in 1996 and 1998. The wetland indicator status of a species is based upon the individual species' occurrence in wetlands in 13 separate regions within the United States. In some instances the specified regions contain all or part of different floristic provinces and the tension zones which occur between them. While many Obligate Wetland (OBL) species do occur in permanently or semi-permanently flooded wetlands, there are also a number of obligates that occur in temporary or seasona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Parasite
A facultative parasite is an organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. Examples of facultative parasitism occur among many species of fungi, such as family members of the genus '' Armillaria''. ''Armillaria'' species do parasitise living trees, but if the tree dies, whether as a consequence of the fungal infection or not, the fungus continues to eat the wood without further need for parasitic activity; some species even can ingest dead wood without any parasitic activity at all. As such, although they also are important ecological agents in the process of nutrient recycling by microbial decomposition, the fungi become pests in their role as destructive agents of wood rot. Similarly, green plants in genera such as ''Rhinanthus'' and '' Osyris'' can grow independently of any host, but they also act opportunistically as facultative root parasites of neighboring green plants. Among animals, facultati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obligate
{{wiktionary, obligate As an adjective, obligate means "by necessity" (antonym '' facultative'') and is used mainly in biology in phrases such as: * Obligate aerobe, an organism that cannot survive without oxygen * Obligate anaerobe, an organism that cannot survive in the presence of oxygen * Obligate air-breather, a term used in fish physiology to describe those that respire entirely from the atmosphere * Obligate biped, Bipedalism designed to walk on two legs * Obligate carnivore, an organism dependent for survival on a diet of animal flesh. * Obligate chimerism, a kind of organism with two distinct sets of DNA, always * Obligate hibernation, a state of inactivity in which some organisms survive conditions of insufficiently available resources. * Obligate intracellular parasite, a parasitic microorganism that cannot reproduce without entering a suitable host cell * Obligate parasite, a parasite that cannot reproduce without exploiting a suitable host * Obligate photoperiod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
