Unregulated Population Growth
vertical (static) life table
horizontal (cohort) life table
: net reproductive rate
T: mean generation time
Geometric Population Growth
: annual rate of increase
Exponential Population Growth
population doubling time
Key Points of Lecture 9.
Populations are groups of reproductive individuals living together in the same area and
isolated from other groups
The environmental conditions that will enable an individual to maintain critical
functions are broader than those that will maintain an individual organism which are
broader than those that will support a population of the species.
The young are frequently
most susceptible to harsher environmental conditions and successful reproduction is the
critical element of sustaining a population.
Species may be adapted to a subset of available conditions – specialization for specific
conditions (heat or cold tolerance)
Different measures of population size: a.
Total counts for sedentary or large
organisms with small population sizes, b.
subsamples for large populations using
quadrats (sedentary organisms like plants) or capture/ recapture (cryptic or highly mobile
R/C = M/N
Mark/ recapture methods assume random catch, equal mortality between marked and
unmarked, and marks not lost
Dispersion is the spatial pattern of individuals in the population: Clumped is most
common and is associated with a resource, microclimate, or a beneficial behavior,
Uniform next most common and is associated with a direct and frequently antagonistic
interaction among individuals.
Random least common and assumes uniformity in the
environment and lack of behavioral interactions.
How fast does a population grow?
births and immigration
deaths and emigration
We will restrict most of our discussion of population growth to
immigration or emigration.
..or the rates are so small to be inconsequential!
How fast a population will grow depends on the
of the population.
a high proportion of females in a reproductive age range will grow more rapidly than
one composed mostly of post-reproductive and pre-reproductive individuals.
structure is important
Will return to this when we discuss humans.
Parameters that are important:
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