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Disturbance and Succession NOTES
I. Disturbance
• An event that causes loss of life in a community
• Measured by scale, intensity, and frequency
• Moderate disturbance can increase diversity in
communities
II. Population Growth (post-disturbance
and otherwise)
Carrying Capacity: maximum population size
an ecosystem can sustain
Limiting Factor/ Resource: factors that
influence carrying capacity
limiting factors
# of
organis
ms
carrying capacity
r-strategists
K-strategists
time
III. Ecological Succession
Many species of organisms in an area is a community.
community
1. An existing______________of
is
organisms
replaced by a different community over periods of
time ranging from a few decades to thousands of
years.
Secondary succession
Primary succession
Climax stage
K-strategists
III. Ecological Succession
Later seral stages
Early seral stages
r-strategists
Mid seral stages
Pioneer species
III. Ecological Succession
2. Disturbance/ uninhabited area
lichens, (produce acids to break down rocks),In primary
succession
produce a thin soil,
only
mosses, (change soil) ,
weeds, grasses, (pioneer species),
perennial herbs,
shrubs,
trees,
insects,
birds,
animals
III. Ecological
Succession
3. Climax community –
stable collection of
organisms – which reach
a stage
stable
more
than those that preceded.
Nature of the climax
community depends on
climate: varies from
rainforest to shrubland to
grassland, etc.
III. Ecological Succession
4. Trends in many successions
Change in community structure: Replacement
of opportunistic, early-stage (r-strategists) with
late-stage (K-strategists)
Increased nutrients available.
Increased biomass (living material)
Increase in diversity (especially with small,
regular disturbances)
Increased complexity (i.e. in food web)
Increased stability between photosynthesis
(producers) and respiration (consumers)