Transcript Ecological Succession

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Succession means…
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act or process of following in order, sequence
Ecological succession means…
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Predictable and orderly changes in the structure of an
ecological community over time
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Ecosystems responding/changing due to
natural and human disturbances
In ecosystems community dynamics change as
older organisms die out and new ones move in
PRIMARY
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Growth occurs on
newly exposed surfaces
where no soil exists
Ex. Surfaces of volcanic
eruptions
SECONDARY
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Growth occurring after
a disturbance changes a
community without
removing the soil
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For example, new land created by a volcanic
eruption is colonized by various living organisms
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Disturbances responsible can include cleared and
plowed land, burned woodlands
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Pioneer species
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First species to populate an area
Climax community
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Mature stable community achieved over time which
does not undergo further succession
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Activity:
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Work with others at your table to individually
create a flow chart summarizing the steps of
ecological succession in this ecosystem
 use information from pgs 96-97
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What are the major phases of succession?
What changes occur?
What types of organisms are involved?
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Due Tuesday
Interview a family member or neighbor about
succession in your neighborhood
Have grassy or overgrown areas been
developed?
Have farms, parks or lots returned to their
previous wild state?
Over what period of time did changes occur?
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How many people are in this room?
What is the area of the room in square meters?
How many people are there per square meter?
Population density =
number of individuals
unit area
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There are 1500 bullfrogs living in a pond that
covers an area of 3 square kilometers. What is
the density of the bullfrog population?
Population density =
number of individuals
unit area
Population density =
1500 bullfrogs
3 square km
Population density = 500 bullfrogs per square km
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Density
Geographic distribution
Growth rate
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Number of
individuals per unit
area
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i.e. plants, animals,
etc.
May be a lot of
variation
depending upon
species and
ecosystem
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Factors affecting size: number of births, number of
deaths, and number of individuals entering and
leaving the population
Immigration vs. emigration
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Migration
Im – like in
E – like exit
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Under ideal conditions with
unlimited resources, a
population will grow
exponentially
Reproduce at a constant
rate
Ex. Initial bacterial growth,
2-4-8-16-32-64…etc.
J shaped curve
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Available resources
decline, growth slows,
stops following a period
of exponential growth
S shaped curve
Carrying capacity
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Max number individuals of
a population that an
environment can support
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Limiting factors = factors causing population
growth to decrease
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Ex. Competition, predation, parasitism, disease,
climate extremes, human disturbances
Density- Dependent
Density - Independent
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Limiting factor depending on population size
Population density reaches certain level
Ex. factors include: competition, predation,
parasitism and disease
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regulate populations according to the
population density.
Specific example: a boom in the wolf
population makes wolves start eating squirrels
in addition to rabbits. This causes a more
dramatic decrease in the squirrel population
than previous records indicate.
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Affect populations regardless of size
Ex. factors include weather, natural disasters,
seasonal cycles and human activities
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factors acting randomly, with reference to
the population density, to regulate
population size.
Specific example = freezing weather and heavy snow.
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During winter, either or both of these abiotic factors can cause
the population of moose to drop. With fewer moose on the
island, the population of wolves also may decrease, because the
wolves' primary food source becomes harder to find.