Download Population Ecology - West Windsor

POPULATION
ECOLOGY
WHAT IS A POPULATION?
A group of individuals of the same species
occupying a given area
Can be described by demographics
Vital statistics such as size, density,
distribution, and age structure
SOME CHARACTERISTICS OF
POPULATIONS
Density and Distribution
Number of individuals in
some specified area of
habitat
Crude density
information is more
useful if combined with
distribution data
Determining Population Size
• Direct counts are most accurate but
seldom feasible
• Can sample an area, then extrapolate
• Capture-recapture method is used for
mobile species
Assumptions in
Capture-Recapture
• Marking has no effect on mortality
• Marking has no effect on likelihood to being
captured
• There is no immigration or emigration
between sampling times
GROWTH RATES OF POPULATIONS
EXPONENTIAL GROWTH
Population size
expands by ever
increasing increments
during successive
intervals
The larger the
population gets, the
more individuals there
are to reproduce
J curve
Growth Rates of Populations
Logistic Growth
• As size of the population increases, rate of reproduction
decreases
• When the population reaches carrying capacity, population
growth ceases
Maximum
number of
individuals
that can be
sustained
in a
particular
habitat
S curve
Growth Rates of Populations
Overshooting Capacity
• Population may
temporarily increase
above carrying capacity
• Overshoot is usually
followed by a crash;
dramatic increase in
deaths
Boom and Bust Curve
WHICH OF THE FOLLOWING IS A CURVE
SHOWING THE GROWTH RATE OF THE
HUMAN POPULATION?
A. S curve
B. J curve
C. Boom and Bust Curve
D. None of the above, humans are
unique.
FACTORS THAT EFFECT POPULATION
GROWTH
Limiting Factors
Any resource that is in short supply
Which determines the
Carrying capacity of that population
Maximum number of individuals that can be
sustained in a particular habitat
Can be
Density dependent – factors that are effected
by the population density
Density independent – factors that are NOT
affected by the populations
Density-Dependent Controls
• Logistic growth equation deals with
density-dependent controls
• Limiting factors become more intense as
population size increases
• Disease, competition, parasites, toxic
effects of waste products
Density-Independent Controls
• Factors unaffected by population density
• Natural disasters or climate changes affect
large and small populations alike
WHICH OF THE FOLLOWING IS A
DENSITY INDEPENDENT FACTOR THAT
WILL AFFECT THE POPULATION OF DEER
IN NJ?
A. Tsunami
B. Tick infections
C. Cold winters
D. Number of males in the population
E. None of the above
HOW DO DIFFERENT SPECIES INTERACT
WITH EACH OTHER?
SYMBIOSIS
Parasitism
Commensalism
Mutualism
Succession
Change in the composition
of species over time
Pioneer Species
• Species that colonize barren habitats
• Lichens, small plants with brief life cycles
• Improve conditions for other species who
then replace them
Types of Succession
• Primary succession new environments
• Secondary succession communities were destroyed or
displaced
PRIMARY SUCCESSION IN ALASKA’S
GLACIER BAY REGION
 Begins where nothing
ever grew before
 Primary species are
those that can withstand
conditions like extreme
heat, light, nutrient poor
Soil
Ex. Lichens, moss
Fig. 40-18a, p.716
Fig. 40-18b, p.716
Fig. 40-18c, p.716
Fig. 40-18d, p.716
Fig. 40-31b, p.727
SECONDARY SUCCESSION
Anything that decimates
the landscape and
succession must begin
again. Ex. Volcanic
erruptions, fire, floods,
Clear cutting and human
interference.
Fig.
4019a,
p.717
SUCCESSION IS RAPID
 Soil is present and so are some
seeds that withstood the calamity.
Fig.
4019b
,
p.7
17
Climax Community
• Stable array of species that persists
relatively unchanged over time
• Succession does not always move
predictably toward a specific climax
community; other stable communities may
persist