Ecology and Population Dynamics: Key Concepts
Ecology and Population Dynamics
Ecology: A discipline of biology that studies the interrelations among living things and their environments.
Ecosystem
The interacting system that encompasses a community and its nonliving, physical environment. Compare with community.
Community
An association of populations of different species living together in a defined habitat with some degree of interdependence. Compare with ecosystem.
Population
A group of organisms of the same species that live in a defined geographic area at the same time.
Population Dynamics
The study of changes in populations, such as how and why population numbers change over time.
Population Crash
An abrupt decline in the size of a population.
Population Density
The number of individuals of a species per unit of area or volume at a given time.
Natality
The rate at which individuals produce offspring; the average per capita birth rate.
Mortality
The rate at which individuals die; the average per capita death rate.
Migration
The periodic or seasonal movement of an organism (individual or population) from one place to another, usually over a long distance. See dispersal
Emigration
The movement of individuals out of a population.
Immigration
The movement of individuals into a population. Compare with emigration.
Growth Rate (r)
The rate of change of a population’s size on a per capita basis. Formula: r = b – d, where b = birth rate and d = death rate.
Exponential Population Growth
The accelerating population growth that occurs when optimal conditions allow a constant per capita growth rate. Compare with logistic population growth. Formula: dn/dt = rn
Logistic Population Growth
Population growth that initially occurs at a constant rate of increase over time (i.e., exponential) but then levels out as the carrying capacity of the environment is approached. Compare with exponential population growth. Formula: dn/dt = rn(k-n/k)
Carrying Capacity (K)
The largest population that a particular habitat can support and sustain for an indefinite period, assuming there are no changes in the environment.
Intrinsic Rate of Increase (rmax)
The theoretical maximum rate of increase in population size occurring under optimal environmental conditions. Also called biotic potential.
Environmental Resistance
Unfavorable environmental conditions, such as crowding, that prevent organisms from reproducing indefinitely at their intrinsic rate of increase.
Density-Dependent Factor
An environmental factor whose effects on a population change as population density changes; tends to retard population growth as population density increases and enhance population growth as population density decreases. Compare with density-independent factor.
Density-Independent Factor
An environmental factor that affects the size of a population but is not influenced by changes in population density. Compare with density-dependent factor.
Survivorship
The probability that a given individual in a population or cohort will survive to a particular age; usually presented as a survivorship curve.