extinction

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extinction

 [eks-ting´shun]
in psychology, the disappearance of a conditioned response as a result of its not being reinforced; also, the process by which the disappearance is accomplished. See also conditioning.

ex·tinc·tion

(eks-tingk'shŭn),
1. In behavior modification or in classical or operant conditioning, a progressive decrease in the frequency of a response that is not positively reinforced; the withdrawal of reinforcers known to maintain an undesirable behavior.
2. Synonym(s): absorbance
[L. extinguo, to quench]

extinction

(ĭk-stĭngk′shən)
n.
1.
a. The act of extinguishing: The extinction of the fire took several hours.
b. The condition of being extinguished: mourned the extinction of her dreams.
2. The fact of being extinct or the process of becoming extinct: the extinction of the passenger pigeon; languages that are in danger of extinction.
3. Psychology A reduction or a loss in the strength or rate of a conditioned response when the unconditioned stimulus or reinforcement is withheld.
4. Physiology A gradual decrease in the excitability of a nerve to a previously adequate stimulus, usually resulting in total loss of excitability.

extinction

Psychiatry A facet of operant–classical conditioning, in which the conditioned response is weakened and eventually disappears by nonreinforcement. See Operant conditioning, Respondent conditioning, Sensory extinction.

ex·tinc·tion

(eks-tingk'shŭn)
1. In behavior modification or classical or operant conditioning, a progressive decrease in the frequency of a response that is not positively reinforced.
See: conditioning
2. Synonym(s): absorbance.
[L. extinguo, to quench]

extinction

  1. the act of making EXTINCT or the state of being extinct.
  2. the elimination of an allele of a gene in a population, due to RANDOM GENETIC DRIFT or to adverse SELECTION pressures.
  3. any periodical, catastrophic event resulting in a species or larger taxonomic group dying out abruptly at a particular point in geological history. Such extinctions are thought to be cyclical, occurring every 28.4 million years, and have been attributed to cosmic activity such as showers of large asteroids or comets, though neither the periodicity nor its causes are at present universally accepted.
References in periodicals archive ?
Thus, ENM represents a powerful tool for characterizing ecologic and geographic distributions of species across real-world landscapes.
The number of species within a region is called species richness.
The exact status of species, as sentinels or spreaders, and precise migratory pattern may help explain any inconsistencies that arise from considering all species at equal risk for transmission.
There are as many definitions of species as there are authors who have written about them.
University of California at Davis evolutionary biologist Geerat Vermeij concluded in a 1991 Science article: "Invasion usually results in the enrichment of biotas [the total flora and fauna] of continents and oceans." In layman's terms, introducing species tends to raise the total number of species living in a given ecosystem, not decrease it.
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But even more telling are the statistics not included in those USFWS figures: the tally of species that are gone, presumably, forever.
Although few in number, the plight of these trees represents most of the causes of species decline: habitat loss or alteration, introduced diseases and pests, commercial exploitation and development, over-collecting, and a naturally small geographic range.
Now imagine choosing among thousands of species. Plants and animals.
The accompanying Figure shows that the new species clusters with the monophyletic relapsing fever group of species rather than with the LB group species.
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