population pyramid(redirected from Christmas tree graph)
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graphic representation of the age and gender composition of a population, constructed by computing the percentage distribution of the population in each age and sex class.
all of the animals in a specifically defined area considered as a whole. The population may also be defined in modes other than geography, e.g. the cow population, a species specification, the nocturnal bird population.
see binomial population.
a map of populations.
see case population.
e.g. closed herd or flock; a population into which no introductions are permitted, including artificial insemination or embryo transfer; the population is genetically and/or hygienically isolated.
see comparison population.
the populations are separated but have a common border. Some diseases are very difficult to restrain from spreading from one population to the next.
see control population.
see population density.
the population in which the experiment, or trial, is being conducted.
one capable of total examination by census.
genetically defined population
one in which the ancestry of the animals in it is known.
deals with the frequency of occurrence of inherited characteristics in a population.
cannot be examined as a total population because they may never actually exist but are capable of statistical importance.
restricting the growth of an animal population by desexing, by culling or by managemental means of interfering with reproduction.
the mean of the population.
see population size (below).
one in which immigration in and out is unrestrained.
the original population about which it is hoped to make some inferences by examination of a sample of its constituent members.
the percentage of the population that has the subject characteristics.
a graphic presentation of the composition of a population with the largest group forming the baseline, the smallest at the apex.
population at risk
see risk population (below).
the population which is composed of animals that are exposed to the pathogenic agent under discussion and are inherently susceptible to it. Called also population at risk. High or special risk groups are those which have had more than average exposure to the pathogenic agent.
actual counting of a total population, the census method, is not often possible in large animal populations. Alternatives are by various sampling techniques including area trapping, the trapping of all animals in an area, the capture-release-recapture method, the nearest neighbor and line transect methods,
The population size is expressed as the population present at a particular instant. Alternatively it can be expressed as an animal-duration expression when the population is a shifting one and it is desired to express the population size over a period (e.g. cow-day).
a population which has constant mortality and fertility rates, and no migration, therefore a fixed age distribution and constant growth rate.
in epidemiological terms the population from which an experimenter wishes to draw an unbiased sample and make inferences about it.