Population growth is the change in population over time, and can be quantified as the change in the number of individuals in a population using "per unit time" for measurement. In Biology a population is the collection of inter-breeding organisms of a particular Species; in Sociology The term population growth can technically refer to any species, but almost always refers to humans, and it is often used informally for the more specific demographic term population growth rate (see below), and is often used to refer specifically to the growth of the population of the world. Demographics or demographic data refers to selected population characteristics as used in government Marketing or opinion research or the Demographic profiles The world population is the total number of living Humans on Earth at a given time

Simple models of population growth include the Malthusian Growth Model and the logistic model. The Malthusian growth model, sometimes called the simple exponential growth model is essentially Exponential growth based on a constant rate of Compound interest The logistic map is a Polynomial mapping of degree 2, often cited as an archetypal example of how complex chaotic behaviour can arise from very simple

## Population growth rate

In demographics and ecology, Population growth rate (PGR) is the fractional rate at which the number of individuals in a population increases. Ecology (from Greek grc οἶκος oikos, "house(hold" and grc -λογία -logia) is the scientific study of In Mathematics, a fraction (from the Latin fractus, broken is a concept of a proportional relation between an object part and the object Specifically, PGR ordinarily refers to the change in population over a specific time period expressed as a percentage of the number of individuals in the population at the beginning of that period. In Mathematics, a percentage is a way of expressing a number as a Fraction of 100 ( per cent meaning "per hundred" This can be written as the formula: P = Poekt or equivalently,

$\mathrm{Growth\ rate} = \frac{(\mathrm{population\ at\ end\ of\ period}\ -\ \mathrm{population\ at\ beginning\ of\ period})} {\mathrm{population\ at\ beginning\ of\ period}}$

The most common way to express population growth is as a ratio, not as a rate. A ratio is an expression which compares quantities relative to each other The change in population over a time period is expressed as a percentage of the population at the beginning of the time period. That is:

$\mathrm{Growth\ ratio} = \mathrm{Growth\ rate} \times 100%$

A positive growth ratio (or rate) indicates that the population is increasing, while a negative growth ratio (or rate) indicates population decline. A growth ratio of zero indicates that there were the same number of people at the two times -- net difference between births, deaths and migration is zero. However, a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times. [1]

A related measure is the net reproduction rate. The net reproduction rate ( NRR) is the average number of daughters that would be born to a woman (or a group of women if she passed through her lifetime conforming to the age-specific In the absence of migration, a net reproduction rate of more than one indicates that the population of women is increasing, while a net reproduction rate less than one (sub-replacement fertility) indicates that the population of women is decreasing. Sub-replacement fertility is a Total fertility rate that is not high enough to replace an area's population

## Human population growth rate

Annual population growth rate in percent, as listed in the CIA World Factbook (2006 estimate). The World Factbook ( ISSN; also known as the CIA World Factbook) is an annual publication of the Central Intelligence Agency of the [2]

When population growth can exceed the carrying capacity of an area or environment the results end with overpopulation. The supportable Population of an Organism, given the food habitat, water and other necessities available within an environment is known as the environment's Overpopulation refers to a condition where an Organism 's numbers exceed the Carrying capacity of its Habitat. Spikes in human population can cause problems such as pollution and traffic congestion, though these can be addressed by technological and economic changes. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Conversely, such areas may be considered "underpopulated" if the population is not large enough to maintain an economic system (see population decline). An economic system is a System that involves the production, distribution and consumption of goods and services between Population decline is the reduction over time in a region's Census.

Globally, the growth rate of the human population has slowed down a little since its peak in the 1980s (see External Links), although the last one hundred years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity[3] made by the Green Revolution. The world population is the total number of living Humans on Earth at a given time All human societies have medical beliefs that provide explanations for birth, Death, and Disease. The Green Revolution refers to the transformation of Agriculture that began in 1945 at the request of the Mexican government to establish an agricultural research station to [4][5][6]

The actual annual growth in the number of humans fell from its peak of 87 million per annum in the late 1980s, to a low of 75 million per annum in 2002, at which it stabilised and has started to slowly rise again to 77 million per annum in 2007. Growth remains high in the Middle East, South Asia, Southeast Asia, Latin America, and primarily in Sub-Saharan Africa. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East. Sub-Saharan Africa is a geographical term used to describe the area of the African continent which lies south of the Sahara, or those African countries [7]

In some countries there is negative population growth (ie. net decrease in population over time), especially in Central and Eastern Europe (mainly due to low fertility rates) and Southern Africa (due to the high number of HIV-related deaths). Central Europe is the Region lying between the variously and vaguely defined areas of Eastern and Eastern Europe is a general term that refers to the Geopolitical region encompassing the easternmost part of the European continent. The total fertility rate ( TFR, sometimes also called the fertility rate, period total fertility rate (PTFR or total Southern Africa is the Southernmost Region of the African Continent, variably defined by Geography or Geopolitics. Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome Within the next decade, Japan and some countries in Western Europe are also expected to encounter negative population growth due to sub-replacement fertility rates. For a topic outline on this subject see List of basic Japan topics. Western Europe at its most general meaning means 'all the countries in the West of Europe ' Sub-replacement fertility is a Total fertility rate that is not high enough to replace an area's population

## See also

Population evolution in different continents. A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions The vertical axis is logarithmic and is millions of people. Definition and base Logarithmic scales are either defined for ratios of the underlying quantity or one has to agree to measure
Theoretical Human population increase from 10,000 BCAD 2000. Stone Age Paleolithic See also Paleolithic, Recent African Origin, Early Homo sapiens, Early human migrations "Paleolithic" 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar.