population

In biology and ecology, a group of organisms of one species, living in a certain area. The organisms are able to interbreed. It also refers to the members of a given species in a community of living things. The area can be small. For example, one can refer to the population of duckweed (a small floating plant found on the surface of ponds) on a pond. Since the pond is a habitat, one can consider the population of duckweed in a habitat and forming part of the community of plants and animals there. However, it is also possible to use the term population for all the organisms of one species in a large geographical area, for example the elephant population in Africa. It could also be used to describe all the organisms of that species on Earth, for example the world population of humans. Population sizes in habitats change over a period of time. The timescale may be daily, seasonal, or there may be changes over the years.

The success of an organism can be determined by measuring the size of a population or by measuring biomass. Measuring the size of a population is quite difficult and requires careful sampling of the habitat and careful calculation to estimate population size. It is rarely possible to count directly all the individuals in a population. Typically, sampling techniques require random sampling to get a fair estimate of the population and may use equipment such as quadrats (a way of defining a square sampling area of a certain size). However, these techniques have their limitations – for example, animals move around and may also be difficult to find. Species may also be difficult to identify. There may not be time to take a large enough sample to make the estimate accurate.

population

The number of people living in a specific area or region, such as a town or country, at any one time. The study of populations, their distribution and structure, resources, and patterns of migration, is called demography. Information on population is obtained in a number of ways, such as through the registration of births and deaths. These figures are known as ‘vital statistics’. However, more detailed information on population distribution, population density, and change is necessary to enable governments to plan for education, health, housing, and transport on local and national levels. This information is usually obtained from censuses (population counts), which provide data on sex, age, occupation, and nationality.

The word census comes from a Latin word meaning to count or assess, and the censuses conducted by the Romans were mainly for purposes of tax and the recruitment of armies. Nowadays, censuses are carried out by most countries on a regular basis; in the USA a census has been taken every ten years since 1790. In Europe the first national censuses were taken in 1800 and 1801 and provided population statistics for Ireland, Italy, Spain, and the UK, and for the cities of Berlin, London, Paris, and Vienna. A census of the population of New York was also taken at that time. Most countries in the world have taken at least one census within the last decade.

Urban population growth The increasing industrialization of Europe and North America in the 19th and 20th centuries, together with the mechanization of agriculture, caused large numbers of people to move from rural areas to the ever-expanding cities in search of work. This migration of people to urban areas created vast changes in population distribution and population density. Today, the majority of Western populations live in cities and only about 5% in rural areas.

Shifting population patterns Improvements in living standards, education, health care, and social welfare have resulted in a fall in birth rate and a fall in death rate, particularly infant mortality rate. One of the most significant trends in modern industrialized nations has been the decline in fertility, which is explained in socioeconomic terms by the theory of demographic transition. The combined effect of the decrease in fertility and the decline in mortality rates has resulted in a state of population equilibrium similar to that existing in pre-industrialized populations. These shifts in population patterns and characteristics of regional population changes can be summarized in a population pyramid, or illustrated with the use of histograms and bar charts.

Increased global population In the less industrialized nations of Africa, Asia, and South America, a decline in death rates did not come about until the mid-20th century and, since this was not matched by a corresponding decrease in birth rates, the overall population of low-income countries increased rapidly in the latter part of the 20th century. Since the poorer nations also tend to be the most highly populated to begin with, this caused the global population to soar. Between 1990 and 1995 the world population increased by 1.7% a year, and the elderly population by 2.7%. In mid-2000 the world population was 6.1 billion and increasing at the rate of 77 million per year. According to a UN low variant projection, the world population will be at least 7.9 billion by 2050, 9.3 billion by a mid-range projection, or 10.9 billion by high-range forecasts.

Population control By 2000, the population of the developed nations was 1.2 billion people, compared to 4.9 billion people in the developing countries. In September 1994 a UN international conference on population and development was attended by politicians from 150 countries. It emphasized the importance of improving the position of women for effective population control, and of improving sex education and contraception, particularly in the less industrialized countries. Since the early 1950s, India has taken the lead among developing nations to control its population growth with government-sponsored family planning programs. However, in April 2001, it became the second country after China with a population of over 1 billion. China, with its one-child family policy, is struggling to control the rising numbers of its huge population. The majority of developing nations now have governments that support some form of family planning program.

Population statistics Serious population studies date from the end of the 18th century, and demography as a discipline is considered to have begun with the development by the British economist Thomas Malthus of his theory of population growth, and the publication in 1798 of his pamphlet ‘Essay on the Principle of Population’. The growth of the behavioural sciences in the 20th century, and the development of computer sciences, stimulated and aided demographic research. In the 21st century, the key issues for demographers, economists, and governments are the limiting and stabilization of growth in the world population.

population

In statistics, the universal set from which a sample of data is selected. The chief object of statistics is to find out population characteristics by taking samples.