1. What cycle is illustrated in this picture?
2. What are the key processes in the cycling of this
element?
3. How could human population growth affect this cycle?
Population Growth Patterns and
Ecological Succession
• Population density
is expressed as a
ratio that describes
a direct relationship
between two
quantities.
• What do you think
the relationship for
calculating
population density
is?
# of individuals = population
Area they occupy density
Population Density
• Ex: If scientists sampling
a population of deer
counted 200 individuals
in an area of 10 square
kilometers, what would
the density be?
• 20 deer/square km
• What might a decrease
in the density of a deer
population over a
specific time period tell
scientists about the
habitat in the area?
• Resources might be
depleted, the
community may have
changed due to factors
such as a new predator
Population Dispersion Patterns
• How might individuals of a
population be dispersed
throughout their habitats?
• What dispersion pattern is displayed
in our classroom?
• What dispersion pattern is displayed
in the cafeteria?
•
http://video.nationalgeographic.com
/video/animals/mammalsanimals/bats/weirdest-bats-swarmsurvive/
•
This satellite photo shows the
uniform distribution of termite
mounds in Africa’s Savanna
•
Each mound stands at the center of
floral productivity
•
The highly regular spatial pattern of
fertile mounds generated by termites
increases overall levels of ecosystem
production
•
Termites bring coarse particles into
the fine soil. The coarse particles
allow water to infiltrate the soil. Also,
elevated levels of nitrogen and
phosphorus were found to be
associated near the mounds
Survivorship Curves
• What does a survivorship
curve show?
– # of surviving members
over time
• How might it explain the
reproductive strategies of
a species?
– Large amount of offspring,
few survive / smaller
amount of offspring- more
parental care
Population Growth Patterns
• Immigration
– Movement of
individuals into a
population from
another population
• Emigration
– Movement of
individuals out of a
population and into
another population
WHAT DETERMINES POPULATION
GROWTH?
Exponential Growth
Logistic Growth
Population growth is a function of the environment
The rate of growth is determined by the amount of resources
available
Other Factors that Affect Population
Growth
• Carrying Capacity
– The maximum number of
individuals of a particular
species that the
environment can
consistently support
• When could carrying
capacity change?
– When the environment
changes
• What is the carrying
capacity of humans?
– It depends on how we use
our resources
What factors affect the carrying capacity of an
environment for a population?
• Limiting Factors
• Density-Independent
• Density-Dependent limiting factor
– Environmental factors
Limiting factors
– Factors affected by the that limit a population’s
number of individuals in growth regardless of the
density
a given area
• Competition
• Predation
• Parasitism/Disease
• Unusual weather
• Natural disasters
• Human activities
What is Earth’s Carrying Capacity?
• http://www.youtube.
com/watch?v=sc4Hx
PxNrZ0
Ecological Succession
• From clean to cluttered
• A gradual process
Ecological Succession
• After an ecosystem experiences a catastrophe and begins to re-grow, the
space re-forms itself through “succession”
• Succession = the sequence of biotic changes that regenerate a damaged
community or create a community in a previously uninhabited area
Ecological Succession
• Primary Succession
– Establishment &
development of an ecosystem
in a previously uninhabited
area
• Ex: Glacier Bay National Park in
Alaska- as glaciers recede,
primary succession is observed
– Begins with bare rock
– “Pioneer species” are the first
organisms to live in this
previously uninhabited area
• Typically lichens and mosses
• Secondary Succession
– Reestablishment of a
damaged ecosystem
where soil remains intact
Secondary Succession as a result of
Fires
• The Fire of 1910
• Largest forest fire in American
history
• Burned 3 million acres across 3
states- Washington, Idaho,
Montana
– Almost as large as the state of
Connecticut
• Hot and dry summer led to 1,000
to 3,000 fires burning across
these states in August
• August 20th- cold front blows in
and brings “hurricane” winds that
turn thousands of fires into one
or two “blazing infernos”
• Many towns were completely
destroyed by the fire
• The U.S. Forest Service was
shaped after this fire