Population density: the number of organisms per unit of area
Population dispersion: the pattern of spacing of a population within an area, such as clumping in herds, or living solitarily, due primarily to the availability of resources such as food
Density dependent factors: any factor in the environment that depends on the number of members in a population per unit area. These factors are usually biotic, such as predation, disease, parasites, and competition. For example, the numbers of wolf and moose populations on Isle Royale were dependent on each other.
Density independent factors: factors in the environment that do not depend on the number of members of a population per unit area. These factors are usually abiotic, such as weather, flooding, extreme heat or cold, tornadoes. For example, a forest fire may destroy many trees; the building of a dam will cause changes in water flow and temperature, which affect populations.
Population growth rate: how fast a given population grows (natality and mortality, emigration and immigration)
Exponential growth model: (also called geometric growth) how a population would grow assuming there are no environmental constraints.
Logistic growth model: growth that occurs when a population’s growth slows or stops following exponential growth, at the population’s carrying capacity. When birth rate is less than death rate, or when emigration exceeds immigration.
Carrying capacity: the maximum number of individuals in a species that an environment can support for the long term. Limits include energy, oxygen, nutrients, and water available.
R-strategists: rate strategy of reproduction in which organisms produce as many offspring as possible in a short amount of time, and spend little or no energy raising them; they tend to have short lifespans. This is an adaptation for living in an environment where fluctuation factors occur, such as availability of food or changing temperatures, density-independent factors. They do not usually maintain their population near carrying capacity
K-strategists: Carrying-capacity strategists are adapted to environments that are fairly predictable. They prduce fewer offspring that have a better chance of survival due to the energy, time, and resources invested in raising them. They tend to have longer lifespans. These populations are usually controlled by density-dependent factors.
Demography is the study of human population size, density, distribution, movement, and birth and death rates.
Demographic transition is when a population changes from having high birth and death rates to low birth and death rates. This has been seen in industrially developed countries.
Zero population growth is when the birth rate equals the death rate.
Age structure is another characteristic of populations. It is the number of males and females in each of 3 age groups: pre-reproductive, reproductive, post-reproductive.
Carrying capacity is the maximum number of individuals that an environment can support for the long term; limited by energy, water, nutrients, and oxygen.