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THE ECOSYSTEM
2.6 Changes
Assessment Statements
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2.6.1 Explain the concepts of limiting factors and
carrying capacity in the context of population
growth.
2.6.2 Describe and explain S- and J- population
curves.
2.6.3 Describe the role of density-dependent and
density-independent factors, and internal and
external factors, in the regulation of populations.
2.6.4 Describe the principles associated with
survivorship curves including, K- and r-strategists.
Assessment Statements Cont.
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2.6.5 Describe the concept and processes of
succession in a named habitat.
2.6.6 Explain the changes in energy flow, gross
and net productivity, diversity, and mineral cycling
in different stages of succession.
2.6.7 Describe factors affecting the nature of
climax communities.
2.6.1 Explain the concepts of limiting factors and
carrying capacity in the context of population growth.
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Limiting Factors – Factors
that limit the distribution
or numbers of a
particular population.
They are environmental
factors that slow down
population growth.
Usually involve an
optimal range, with
upper and lower
tolerances.
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Temperature
Water
Nutrient Availability
2.6.1 Explain the concepts of limiting factors and
carrying capacity in the context of population growth.
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Carrying capacity–
the number of
organisms or size of
population that an
area or ecosystem
can support
sustainably over a
long period of time.
2.6.2 Describe and explain S- and J- population curves.
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S-population curve: Three
Stages
Exponential growth stage
– population grows at
increasingly rapid rate
Transitional phase –
continues to grow, but
slows considerably
Plateau or stationary
phase – number of
individuals stabilizes and
population growth
stabilizes
2.6.2 Describe and explain S- and J- population curves.
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J-population curve:
Only has the
exponential growth
stage. Growth is
initially slow and
becomes increasingly
rapid. It does not
slow down.
2.6.3 Describe the role of density-dependent and densityindependent factors, and internal and external factors, in the
regulation of populations.
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Density-dependent –
factors that lower the
birth rate or raise the
death rate as a
population grows in size.
Operate as negative
feedback mechanisms.
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Examples: resources,
space, disease,
parasitism, and
predation
2.6.3 Describe the role of density-dependent and densityindependent factors, and internal and external factors, in the
regulation of populations.
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Density-independent –
factors that lower the
birth rate or raise the
death rate irrespective
of population density.
 Examples:
Natural
disasters, and long
term climate change.
2.6.3 Describe the role of density-dependent and densityindependent factors, and internal and external factors, in the
regulation of populations.
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Internal factors include
density-dependent fertility
or size of breeding
territory.
External factors include
predation or disease.
Physical environmental
factors: water and nutrient
availability, and
temperature
Biological environmental
factors: Predation, and
competition.
2.6.4 Describe the principles associated with survivorship curves
including, K- and r-strategists.
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K-strategists species:
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Grow and mature slowly
Produce few large
offspring
Stable environments
r-strategists species:
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Grow and mature quickly
Produce many small
offspring
Disturbed or new
environments
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Those that lie between are
called C-strategists
2.6.4 Describe the principles associated with survivorship curves
including, K- and r-strategists.
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K-strategists survivorship
curve:
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Almost all survive potential
lifespan, and then die
almost simultaneously
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Salmon and humans
r-strategists survivorship
curve:
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Most die at a very young
age, but those that survive
are likely to live a very
long time
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Turtles and oysters
2.6.5 Describe the concept and processes of succession
in a named habitat.
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Succession – Orderly
process of change over
time in a community
divided into stages
called serals
Zonation – The
arrangement or
patterning of plant
communities or
ecosystems into bands in
response to change,
over a distance, in some
environmental factor.
2.6.5 Describe the concept and processes of succession
in a named habitat.
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Primary Succession –
Succession on
previously uncolonized
substrate
Secondary Succession
– Succession where a
previous community
has been disturbed
2.6.6 Explain the changes in energy flow, gross and net
productivity, diversity, and mineral cycling in different stages
of succession.
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Pioneer community –
Earliest seral stage
Early Stages of
Succession:
 Gross
Productivity: low
 Respiration loss: low
 Net Productivity: high
 System: Growing
 Biomass: Accumulating
2.6.6 Explain the changes in energy flow, gross and net
productivity, diversity, and mineral cycling in different stages
of succession.
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Climax community –
Final seral stage
Final Stages of
Succession:
 Gross
Productivity: high
 Respiration loss: high
 Net Productivity: near
0
 Production/Respiration
Ratio: Near 1
2.6.7 Describe factors affecting the nature of climax
communities.
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Climax community features:
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Greater biomass
Higher levels of diversity
Favorable soil conditions
Lower pH
Taller and longer-living plant
species
More K-strategists or fewer rstrategists
Greater community complexity
and stability
Greater habitat diversity
Steady-state equilibrium
Plagioclimax – interrupted
succession