Population is the count of all the organisms that both belong to the same species and reside in the same geographical area. The region that is used to define the populace is really that inter-breeding is possible between any pair inside the area and much more probable than cross-breeding with individuals using their company areas. Normally breeding is substantially more common within the area than across the border.
In sociology, population refers to a collection of human beings. Demography is a sociological discipline which entails the statistical study of human populations. This article refers mainly to human population.
In population genetics a population is a set of organisms in which any pair of members can breed together. This implies that all members belong to the same species and live near each other
 Human population
As of 17 April 2011, the world population is estimated by the United States Census Bureau to be 6.913 billion.
According to papers published by the United States Census Bureau, the world population hit 6.5 billion (6,500,000,000) on 24 February 2006. The United Nations Population Fund designated 12 October 1999 as the approximate day on which world population reached 6 billion. This was about 12 years after world population reached 5 billion in 1987, and 6 years after world population reached 5.5 billion in 1993. The population of some countries, such as Nigeria and China is not even known to the nearest million, so there is a considerable margin of error in such estimates
Population growth increased significantly as the Industrial Revolution gathered pace from 1700 onwards. The last 50 years have seen a yet more rapid increase in the rate of population growth due to medical advances and substantial increases in agricultural productivity, particularly beginning in the 1960s, made by the Green Revolution. In 2007 the United Nations Population Division projected that the world's population will likely surpass 10 billion in 2055. In the future, world population has been expected to reach a peak of growth, from there it will decline due to economic reasons, health concerns, land exhaustion and environmental hazards. There is around an 85% chance that the world's population will stop growing before the end of the century. There is a 60% probability that the world's population will not exceed 10 billion people before 2100, and around a 15% probability that the world's population at the end of the century will be lower than it is today. For different regions, the date and size of the peak population will vary considerably.
The population pattern of less-developed regions of the world in recent years has been marked by gradually declining birth rates following an earlier sharp reduction in death rates. This transition from high birth and death rates to low birth and death rates is often referred to as the demographic transition
Human population control is the practice of artificially altering the rate of growth of a human population. Historically, human population control has been implemented by limiting the population's birth rate, usually by government mandate, and has been undertaken as a response to factors including high or increasing levels of poverty, environmental concerns, religious reasons, and overpopulation. While population control can involve measures that improve people's lives by giving them greater control of their reproduction, some programs have exposed them to exploitation.
Worldwide, the population control movement was active throughout the 1960s and 1970s, driving many reproductive health and family planning programs. In the 1980s, tension grew between population control advocates and women's health activists who advanced women's reproductive rights as part of a human rights-based approach. Growing opposition to the narrow population control focus led to a significant change in population control policies in the early 1990s.
 Population and Environment
Between 1960 and 1999, Earth's population doubled from three billion to six billion people. This reflected good news for humanity: child mortality rates plummeted, life expectancy increased, and people were on average healthier and better nourished than at any time in history. However, during the same period, changes in the global environment began to accelerate: pollution heightened, resource depletion continued, and the threat of rising sea levels increased.
 Land Use
Fulfilling the resource requirements of a growing population ultimately requires some form of land-use change, in order to provide for the expansion of food production through deforestation, to intensify production on already cultivated land, or to develop the infrastructure necessary to support increasing human numbers. During the past three centuries, the amount of Earth's cultivated land has grown by more than 450 percent, increasing from 2.65 million square kilometers to 15 million square kilometers. A related process, deforestation, is also critically apparent: A net decline in forest cover of 180 million acres took place during the 15-year interval 19801995, although changes in forest cover vary greatly across regions. Whereas developing countries experienced a net loss of 200 million acres, developed countries actually experienced a net increase, of 20 million acres.
 Population and food security
As we pass the 7 billion milestone, and go on to 9 billion or more by 2050, we face a “perfect storm” of future needs for food, energy and water. There are already 600 million people today who can’t count on eating tomorrow. The United Nations defines food security as "all people at all times having both physical and economic access to the basic food they need." For approximately 2 billion people throughout the world, this security is anything but guaranteed. Food security is a complicated issue that is susceptible to many forces.
Hunger experts are seeking out large-scale responses, including stepping up commercial agricultural techniques by introducing genetically modified rice and related products into the region. Other more localized efforts by universities and organizations are providing training in sustainable techniques for traditional farming families and minority ethnic groups.