Regulation of Population Size

• Once a population reaches its maximum size in a given environment, the numbers will not remain constant, but fluctuate within narrow boundaries due to changes in environmental resistance
• If the population numbers increase beyond carrying capacity, the environmental resistance (limiting factors) will increase and result in a decrease in numbers
• If the population numbers decrease below the carrying capacity, the environmental resistance will decrease and the population numbers will increase
• A stable population is a population where numbers fluctuate around the carrying capacity
• When population numbers far exceed the carrying capacity, the habitat will most likely by damaged, resulting in a decrease in the carrying capacity of the environment; this is called an unstable population
• The environment can no longer sustain the population and the numbers will decrease; it may even become extinct

  
• We already know that the sum of limiting factors that form environmental resistance, play a huge role in the regulation of the population size
• Limiting factors increase or take effect when the population numbers increase and are also called the density dependent factors
• An increase in population numbers results in a greater demand for food and water, causing increased competition, which limits reproduction
• An increase in population numbers results in a decrease in living space, which has a negative effect of the rate of reproduction due to stress
• An increase in population numbers results in a shortage of shelter which increases exposure to adverse weather conditions and predators and leads to a decrease in numbers
• An increase in population numbers results in an increase in predation because there is more food available for predatos
• An increase in population numbers results in easier spread of diseases and parasites as the population density is higher
• An increase in population numbers results in an accumulation of waste that may poison the environment
• There are also factors that regulate the population size, regardless of size or density of the population; these limiting factors are called density independent factors
• Density independent factors include extreme changes in temperature, natural disasters
• Density independent factors usually cause a drastic decline in population numbers. Such a population could possibly recover if the habitat has not been damaged or changed beyond recovery
• Density dependent factors: factors that take effect when population size or density increases. Larger the population, greater the effect of these factors
• Density independent factors: factors that limit the size of a population regardless of the density of the population. Often can't be controlled