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A population pyramid (age structure diagram) or " age-sex pyramid " is a graphical illustration of the distribution of a population (typically that of a country or region of the world) by age groups and sex; it typically takes the shape of a pyramid when the population is growing. [1] Males are usually shown on the left and females on the right ...
Population pyramids of developed and developing nations, showing how increased lifespan and changes in fertility alter the population. Each bar represents an age category and its percent of the total population, with males to the left and females to the right.
An ecological pyramid (also trophic pyramid, Eltonian pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed to show the biomass or bioproductivity at each trophic level in an ecosystem. A pyramid of energy shows how much energy is retained in the form of new biomass from each trophic level, while a pyramid ...
In demography, demographic transition is a phenomenon and theory which refers to the historical shift from high birth rates and high death rates to low birth rates and low death rates, as societies attain more technology, education (especially of women) and economic development. [1] The demographic transition has occurred in most of the world ...
On April 1, 2020, the United States had a population of 331,449,281, according to the 2020 United States census. [ 31 ] The following demographic statistics are from the CIA World Factbook estimated as of 2018 [update], [ 5 ] unless otherwise indicated. Graphs are unavailable due to technical issues.
A biomass pyramid shows the amount of biomass at each trophic level. A productivity pyramid shows the production or turn-over in biomass at each trophic level. An ecological pyramid provides a snapshot in time of an ecological community. The bottom of the pyramid represents the primary producers . The primary producers take energy from the ...
A trophic pyramid (a) and a simplified community food web (b) illustrating ecological relations among creatures that are typical of a northern Boreal terrestrial ecosystem. The trophic pyramid roughly represents the biomass (usually measured as total dry-weight) at each level. Plants generally have the greatest biomass.
The Demography of the World Population from 1950 to 2100. Data source: United Nations — World Population Prospects 2017. Demography (from Ancient Greek δῆμος (dêmos) 'people, society' and -γραφία (-graphía) 'writing, drawing, description') [1] is the statistical study of human populations: their size, composition (e.g., ethnic group, age), and how they change through the ...