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In population genetics and population ecology, population size (usually denoted N) is a countable quantity representing the number of individual organisms in a population. Population size is directly associated with amount of genetic drift , and is the underlying cause of effects like population bottlenecks and the founder effect . [ 1 ]
Population control may involve culling, translocation, or manipulation of the reproductive capability. The growth of a population may be limited by environmental factors such as food supply or predation. The main biotic factors that affect population growth include: Food – both the quantity and the quality of food are important. The ...
The effective population size (N e) is the size of an idealised population that would experience the same rate of genetic drift as the real population. [1] Idealised populations are those following simple one- locus models that comply with assumptions of the neutral theory of molecular evolution .
The environment can directly affect the survival of a small population. Some detrimental effects include stochastic variation in the environment (year to year variation in rainfall, temperature), which can produce temporally correlated birth and death rates (i.e. 'good' years when birth rates are high and death rates are low and 'bad' years when birth rates are low and death rates are high ...
It focuses on how populations are distributed across space, the factors influencing these distributions, and the implications for resources, environment, and societal development. This branch of geography integrates demographic data with spatial analysis to understand patterns such as population density, urbanization, and migration trends.
In ecology, a population is a group of organisms of the same species which inhabit the same geographical area and are capable of interbreeding. [2] [3] The area of a sexual population is the area where interbreeding is possible between any opposite-sex pair within the area and more probable than cross-breeding with individuals from other areas.
Absolute increase in global human population per year [1] Population growth is the increase in the number of people in a population or dispersed group. The global population has grown from 1 billion in 1800 to 8.2 billion in 2025. [2] Actual global human population growth amounts to around 70 million annually, or 0.85% per year.
Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.