# population pyramid

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## pop·u·la·tion pyr·a·mid

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.

## population

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.

**binomial population**

see binomial population.

**population cartogram**

a map of populations.

**case population**

see case population.

**closed 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.

**comparison population**

see comparison population.

**contiguous p's**

the populations are separated but have a common border. Some diseases are very difficult to restrain from spreading from one population to the next.

**control population**

see control population.

**population density**

see population density.

**experimental population**

the population in which the experiment, or trial, is being conducted.

**finite population**

one capable of total examination by census.

**genetic population**

see deme.

**genetically defined population**

one in which the ancestry of the animals in it is known.

**population genetics**

deals with the frequency of occurrence of inherited characteristics in a population.

**infinite population**

cannot be examined as a total population because they may never actually exist but are capable of statistical importance.

**population limitation**

restricting the growth of an animal population by desexing, by culling or by managemental means of interfering with reproduction.

**population mean**

the mean of the population.

**population numbers**

see population size (below).

**open population**

one in which immigration in and out is unrestrained.

**parent population**

the original population about which it is hoped to make some inferences by examination of a sample of its constituent members.

**population proportion**

the percentage of the population that has the subject characteristics.

**population pyramid**

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).

**risk population**

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.

**population size**

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).

**stable population**

a population which has constant mortality and fertility rates, and no migration, therefore a fixed age distribution and constant growth rate.

**target population**

in epidemiological terms the population from which an experimenter wishes to draw an unbiased sample and make inferences about it.

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