Glossary Pseudergate A false worker; among termites, a temporarily nonreproductive individual serving the colony in nutrition, construction, or brood care, which results from a late, reversible deviation from the pathways to the imago and is characterized by reduced wing buds compared to nymphs of the same stage Pseudocoelom A body cavity (coelom) not lined with a mesodermal epithelium Pseudoextinction The disappearance of a species from the fossil record due not to the death of all its members but rather to an evolutionary change that results in it being reclassified as a new species Psychrophile An organism that grows better at low temperature or that requires low temperature for growth Such a condition is psychrophily Public good A good whose consumption is both nonrival and nonexcludable That is, one person’s consuming it does not preclude another (a rival) from doing so, and the provider of the good cannot exclude those who have not paid for it Examples of public goods are clean air, a fireworks display, or a lighthouse Compare PRIVATE GOOD Pull of the recent A term reflecting the fact that recently formed rock is more accessible and offers better preserved fossils; this may produce a bias toward the conclusion that diversity has increased toward the present time Puna An ecosystem of the high Andean mountains, found above the tree line from Bolivia to southern Peru It has four distinct ecological regions: wet, dry, thorny, and desert The dominant vegetation types vary from grassland/shrublands to desert Punctuated equilibrium The morphological stasis of fossil species over long periods of time, punctuated by seemingly abrupt speciation and morphological change Purebred An animal that is a member of a recognized livestock breed, as determined by pedigree records, geographical location, or knowledge of the breeding structure of the herd or flock Pure culture An organism growing in the absence of all other organisms PVA Population viability analysis Pycnocline The water layer in which density changes most rapidly with depth and separates the surface mixed layer from the deeper waters Quasispecies Hierarchically ordered populations of mutants resulting from erroneous copying of a genotypic ancestor Whole mutant distributions behave like single species and are subjected to natural selection Quaternary The past million years (approximately) of Earth’s history, including the Pleistocene and Holocene (or Recent) epochs, particularly characterized by the extreme fluctuations in global temperature patterns that produced the ice ages See also LATE QUATERNARY Queens and kings A term for females and males that actively reproduce in a colony Quiescence A state of dormancy in which inhibition of development depends directly on environmental factors R0 The basic reproductive ratio of a parasite or pathogen For a microparasite, this describes the number of new infections generated by a single infected host entering an entirely susceptible population For a macroparasite, R0 is the 529 number of adult offspring produced by a single adult parasite over its lifespan Radiation All the species descended from a single common ancestor; tends to be a more diverse group in comparison with others of a similar age Radiative forcing A measure used to express and compare the potential of contemporary climate system changes (vs preindustrial ones) to perturb the Earth’s energy balance; reported in watts per square meter (W/m2) A positive radiative forcing tends to warm the Earth’s surface, and a negative one tends to cool the surface Radiocarbon dating The dating of organic matter in geological samples using as the standard the radioactive decay of Carbon-14, which has a half-life of about 5, 750 years When a plant or animal dies it has approximately the same level of Carbon-14 as the atmosphere, but this decreases from that point onward By dating tree rings of known age, and other methods, radiocarbon determinations can be calibrated Radula In mollusks, a ribbon-like structure bearing transverse rows of small ‘‘teeth,’’ typically used to collect food and move it into the mouth Rainshadow A less rainy sector on the leeward side of mountains and protected valleys, caused by descending warm air masses Rami See CAUDAL RAMI Range The extent of the area in which a given organism or species is found See rangeland Range core See CORE RANGE Range expansion The process in which a species spreads into new areas (usually new regions, rather than local-scale movements) due to natural dispersal, though the expansion may be assisted by human-mediated changes to the environment The concept can be applied to both native and alien species Rangeland Land on which the potential native vegetation is predominately grasses, grass-like plants, forbs, or shrubs Rangelands include prairies, marshes, tundra, wet meadows, savannas, shrubland steppe, chaparral, desert grasslands, and woodlands Range periphery The marginal parts of the distribution of a species Range state A country in which an animal is found Rank-abundance curve A plot of the number of individuals in each species ordered by their rank, starting with the most abundant species and ending with the most rare Rapoport effect A pattern in which the size of a species’ geographic range increases toward higher latitudes [Named for the Argentinean ecologist Eduardo Rapoport, who observed this pattern.] Also known as Rapaport’s rule Rare A classification for species with small populations globally that are not presently listed as endangered or vulnerable, but are at risk because of their limited population size Rarefaction A statistical interpolation method of rarefying or thinning a reference sample by drawing random subsets of individuals (or samples), in order to standardize the comparison of biological diversity on the basis of a common number of individuals or samples rDNA See RECOMBINANT DNA