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Population Ecology
Objective: I will apply my knowledge of population
ecology to calculate populations based on field signs
Different Species Playing Different
Roles
Biological communities differ in the types and numbers
of species they contain and the ecological roles those
species play.
Species diversity: the number of different species it
contains (species richness) combined with the
abundance of individuals within each of those species
(species evenness).
Factors that determine species richness:
• Latitude
• Time
• Habitat size
Factors that Regulate Population Abundance
and Distribution
•
•
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Population size- the total number of individuals
within a defined area at a given time.
Population density- the number of individuals
per unit area at a given time.
Population distribution- how individuals are
distributed with respect to one another.
Population sex ratio- the ratio of males to females
Population age structure- how many individuals
fit into particular age categories.
Population
Distribution
Patterns
Competition
• Competition- the
struggle of individuals
to obtain a limiting
resource .
Resource Patitioning
Population Density and Population
Change: Effects of Crowding
A population’s density can affect how rapidly it can
grow or decline (density dependent factors)
•
Ex: biotic factors like disease
Some population control factors are not affected by
population density (density independent factors)
•
Ex: abiotic factors like weather
TYPES OF SPECIES
1. Native
2. Nonnative
3. Indicator
4. Keystone
5. Foundation species
Native: I was here
first!
1. Native: those that normally live and
thrive in a particular community.
2. Nonnative (Invasive) species: those
that migrate, deliberately or accidentally
introduced into a community.
Indicator Species:
Biological Smoke Alarms
3. Indicator Species – A species that serve as
early warnings of damage to a community or an
ecosystem.
• Ex: Presence or absence of trout species
because they are sensitive to temperature
and oxygen levels.
eystone Species: Major Players
4. Keystone species - a species that plays a role in its
community that is far more important than its relative
abundance might suggest.
•
Help determine the types and numbers of other
species in a community thereby helping Figures
to sustain
it.
7-4 and 7-5
Foundation Species:
Other Major Players
5. Foundation species can create and enhance
habitats that can benefit other species in a
community.
• Expansion of keystone species category.
• Elephants push over, break, or uproot trees,
creating forest openings promoting grass
growth for other species to utilize.
Theory of Island Biogeography
•
The theory that
explains that both
habitat size and
distance to nearest
mainland
determine species
richness.
• Idea that
immigration and
extinction will
reach equilibrium
• Proposed by Wilson
and MacArthur in mid1960s
Case Study: Exploding White-Tailed Deer
Populations in the United States
• Since the 1930s the white-tailed deer
population has exploded in the United States.
• Nearly extinct prior to their protection in
1920’s.
• Today 25-30 million white-tailed deer in U.S.
pose human interaction problems.
• Deer-vehicle collisions (1.5 million per year).
• Transmit disease (Lyme disease in deer
ticks).