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Population Ecology_BIO 102


madelyn rios

on 8 June 2015

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Transcript of Population Ecology_BIO 102

Population Ecology
Overview of Population Ecology
Population Growth Models
Regulation of Population Growth
Applications of Population Ecology
A population is a group of individuals of a single species that occupy the same general area
Population size fluctuates as new individuals
are born,
immigrate into an area,
emigrate away, and
A density-dependent factor is a population-limiting factor whose effects intensify as the population increases in density
, or density-dependent selection, selects for life history traits that are sensitive to population density
Population ecology is used:
increase populations of organisms we wish to harvest,
decrease populations of pests, and
save populations of organisms threatened with extinction
Population density
is the number
of individuals of a species per unit of
area or volume
Example: oak trees per square kilometer (km2) in a forest
How do we
population density?

- track survivorship (the chance of an individual in a given population surviving to various ages)
- help to determine the most vulnerable stages of the life cycle.
Life tables
plot the number of individuals still alive at each age in the maximum life span and
are classified based upon the rate of mortality over the life span of an organism.
Survivorship curves
A population's pattern of suviorship is a key feature of its LIFE HISTORY
Opportunistic life history
take immediate advantage of favorable conditions and
typically exhibit a type III survivorship curve
Equilibrial life history
develop and reach sexual maturity slowly,
produce few, well-cared-for offspring,
are typically larger-bodied and longer-lived, and
typically exhibit a type I survivorship curve.
Compare & Contrast
An organism’s life history is the set of traits that affect the organism’s schedule of
Life history
Exponential population growth
Expansion of a population in an ideal and unlimited environment.
Exponential growth explains:
how a few rabbits can multiple into millions
rapid expansion after natural disasters
Logistic Population Growth Model
Occurs when the growth rate decreases as the population size approaches carrying capacity.
Intraspecific competition: competition between individuals of the same species for the same limited resources.
Interspecific competition: competition between individuals of different species for the same limited resources.
A density- independent factors are population-limiting factors whose intensity is unrelated to population density and include abiotic factors
, or density-independent selection, selects for life history traits that maximize reproduction
Population Cycles
Some populations have regular boom-and-bust cycles characterized byperiods of rapid, exponential growth followed by steep population declines.
Biological Control of Pests:
Invasive Species:
Burmese pythons
Sustainable Resource Management:Northern Atlantic cod fishery,
Conservation of Endangered Species:
The red-cockaded woodpecker
Mark & Recapture
s = sample of individuals that were randomly marked
n = second sample of individuals that are trapped
x = number of marked individuals captured
N = Population size

Table 1 Life Table for Belding’s Ground Squirrels (Spermophilus beldingi) at Tioga Pass, in the Sierra Nevada Mountains of California

Belding ground squirrel

Figure 5 Idealized survivorship curves: Types I, II, and III



Age (years)







Number of survivors (log scale)





Figure 4 Survivorship curves for male and female Belding’s ground squirrels

Exponential growth in the African elephant population of Kruger National Park, South Africa
Species that exhibit
, or big-bang reproduction, reproduce once and die

Species that exhibit iteroparity, or repeated reproduction, produce offspring repeatedly

The age structure of a population provides insight into the history of a population’s survival,
reproductive success, and/or
how the population relates to environmental factors.

Endangered Species Act
What is a Population ?
Full transcript