The proportions of a population in each age class.
carrying capacity
The maximum population size that can be supported indefinitely by the environment; the concept of a carrying capacity is represented by the term K in the logistic equation (Equation 9.7).
cohort life table
A life table in which the fate of a group of individuals born during the same time period (a cohort) is followed from birth to death.
density-dependent
Of or referring to a factor that causes birth rates, death rates, or dispersal rates to change as the density of the population changes. Compare density-independent.
density-independent
Of or referring to a factor whose effects on birth and death rates are independent of population density. Compare density-dependent.
doubling time (td)
The number of years it takes a population to double in size.
ecological footprint
The total area of productive ecosystems required to support a population.
exponential growth
Change in the size of a population of a species with continuous reproduction by a constant proportion at each instant in time. Compare geometric growth.
exponential population growth rate (r)
A constant proportion by which a population of a species with continuous reproduction changes in size at each instant in time; also called the intrinsic rate of increase. Compare geometric population growth rate.
fecundity
The average number of offspring produced by a female while she is of age x (denoted Fx in a life table).
finite rate of increase
See geometric population growth rate.
geometric growth
Change in the size of a population of a species with discrete reproduction by a constant proportion from one discrete time period to the next. Compare exponential growth.
geometric population growth rate (λ)
A constant proportion by which a population of a species with discrete reproduction changes in size from one discrete time period to the next; also called the finite rate of increase. Compare exponential population growth rate.
intrinsic rate of increase
See exponential population growth rate.
life table
A summary of how survival and reproductive rates in a population vary with the age of individuals; in species for which age is not informative or is difficult to measure, life tables are often based on the size or life history stage of individuals.
logistic growth
Change in the size of a population that is rapid at first, then decreases as the population approaches the carrying capacity of its environment.
net reproductive rate (R0)
The mean number of offspring produced by an individual in a population during its lifetime.
population regulation
A pattern of population growth in which one or more density-dependent factors increase population size when numbers are low and decrease population size when numbers are high.
stable age distribution
A population age structure that does not change from one year to the next.
static life table
A life table that records the survival and reproduction of individuals of different ages during a single time period.
survival rate
The proportion of individuals of age x that survive to be age x + 1 (denoted Sx in a life table).
survivorship
The proportion of individuals that survive from birth (age 0) to age x (denoted lx in a life table).
survivorship curve
A graph that is based on survivorship data (lx) and that plots the number of individuals from a hypothetical cohort (typically, of 1,000 individuals) that will survive to reach different ages.
type I survivorship curve
A survivorship curve in which newborns, juveniles, and young adults all have high survival rates and death rates do not begin to increase greatly until old age.
type II survivorship curve
A survivorship curve in which individuals experience a constant chance of surviving from one age to the next throughout their lives.
type III survivorship curve
A survivorship curve in which individuals die at very high rates when they are young, but those that reach adulthood survive well later in life.
