Chapter 12 Lecture 4 Flashcards
what is population growth rate influenced by
the proportions of individuals in different age, size, and life history classes
what does a population’s growth rate depend on
the proportion of individuals in each age class
the weakness of both the exponential and geometric growth models
birth and death rates are assumed to be uniform over all members of the population
age structure of the population
the proportion of individuals in a population belonging to each age class
two populations with identical birth and death rates at corresponding ages will grow at different rates if they have different
age structures
age structure pyramids with broad bases indicate
a growing population
pyramids with narrow bases indicate
a declining population
pyramids with straight sides indicate
a stable population
type I survivorship curve
depicts a population that experiences low mortality early in life and high mortality later in life (bears)
type II curve
a population that experiences constant mortality throughout its life span
type III curve
depicts a population with high mortality early in life and high survival later in life
what do most populations exhibit
a survivorship curve that combines features of type I and type III curves
what is the growth rate of an age-structured population the sum of
the growth rates owing to individuals in each age class weighted by the proportion in the population
why is the usefulness of the exponential growth formula limited
one can’t determine natality (birth) and mortality (death) rates at every age, since an individual remains a particular age for only an instant
How do demographers get around the problem with the exponential growth formula
by dividing populations into age classes, to which they can assign probabilities of giving birth and dying
