Download Population density: the number of organisms per unit of area

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.