Chapter 57

Chapter 57 – Dynamics of Ecosystems
Trophic levels
Nutrient flow
Energy Flow
Question
Biodiversity
Productivity
Chapter 57 -- Dynamics of
Ecosystems
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Ecologists categorize species based upon
their nutrients and energy sources
What are sources of energy?
heterotrophs
autotrophs
What are sources of nutrients?
producers
consumers
decomposers
What is the final fate of energy?
What happens to nutrients?
Chapter 57 -- Dynamics of
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Knowledge of food chains helps us to
understand ecosystem dynamics
In 1997, ~500,000 short-tailed shearwater birds
were found dead in the Bering Sea off Alaska.
What happened?
Climate shift
favored Ehux
Question
Chapter 57 -- Dynamics of
Ecosystems
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How do energy and nutrients move through an ecosystem?
Food chains
Trophic levels (feeding levels)
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Ecosystems
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What happens to the
energy as it passes
through an ecosystem?
Question
Chapter 57 -- Dynamics of
Ecosystems
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Why are food chains relatively short?
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Ecosystems
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What do ‘ecological pyramids’ show?
energy
numbers
biomass
Inverted pyramids?
Food Chain
Chapter 57 -- Dynamics of
Ecosystems
FoodChain 1
Foodchain 2
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Food webs
How much disruption can
a food web withstand?
What is a “Keystone species”?
e.g., CA sea otter
Importance to Kelp Forests
Conflicts with shellfish industry
-- crabs, abalone
Surge of sea urchins
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How do nutrients flow through
ecosystems?
-- Biogeochemical Cycles
Carbon cycle
Carbon cycle
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Do all essential nutirents flow through biogeochemcal
cycles?
Limiting
nutrients
Key steps of
The N cycle
Roles of
Microorganisms
Plants
Animals
Environmental
issues
Note: you are not responsible for the
individual steps of the phosphorus cycle,
but should have a general understanding
of the role of P-related issues.
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So why did DDT cause
ecological harm?
DDT and Bioaccumulation
Which types of
pollutants will
tend to bioaccumulate?
See page 1227
Question
Chapter 57 -- Dynamics of
Ecosystems
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How do disruptions to specific trophic
levels affect ecosystems?
Top down effects
Restoring aspen growth
in Yellowstone with wolves
Bottom-up effects
Disruption of producers
Adadpted from
Ripple WJ and Bescht RL (2007)
Restoring Yellowstone’s aspen with
wolves. Biological Conseravation 138:
514-519
http://www.cof.orst.edu/leopold/paper
s/Restoring%20Yellowstone%20aspen
%20with%20wolves.pdf
Human impacts
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How many organisms exist
within an ecosystem?
“Biodiversity”
Global diversity: 100 million???
What factors influence diversity?
-- productivity
-- climate
-- habitat heterogeneity
-- other species
Diversity ‘hot spots’
Question
Chapter 57 -- Dynamics of
Ecosystems
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Ecosystems are diverse in their
scale and dynamics
Redwood canopy
Biomes to microscopic
Simple to complex
Of great longevity to the ephemeral
Vernal pool
Familiar to bizarre
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Ecosystems
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