Chapter 57 -- Dynamics of Ecosystems

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Chapter 57 – Dynamics of Ecosystems

Trophic levels

Nutrient flow

Energy Flow

Biodiversity

Productivity

Question

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 Ecosystems

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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)

Chapter 57 -- Dynamics of Ecosystems

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What happens to the energy as it passes through an ecosystem?

Question

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Why are food chains relatively short?

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FoodChain 1

Foodchain 2Food Chain

What do ‘ecological pyramids’ show?

energy

numbers

biomass

Inverted pyramids?

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Food webs

How much disruption can a food web withstand?

What is a “Keystone species”?

e.g., CA sea otterImportance to Kelp ForestsConflicts with shellfish industry

-- crabs, abaloneSurge of sea urchins

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Carbon cycle

How do nutrients flow throughecosystems?-- Biogeochemical Cycles

Carbon cycle

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Do all essential nutirents flow through biogeochemcal cycles?

Limiting nutrients

Key steps ofThe N cycle

Roles of

Microorganisms

Plants

Animals

Environmentalissues

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 growthin Yellowstone with wolves

Bottom-up effects

Disruption of producers

Human impacts

Adadpted fromRipple WJ and Bescht RL (2007) Restoring Yellowstone’s aspen with wolves. Biological Conseravation 138: 514-519http://www.cof.orst.edu/leopold/papers/Restoring%20Yellowstone%20aspen%20with%20wolves.pdf

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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

Biomes to microscopic

Simple to complex

Of great longevity to the ephemeral

Familiar to bizarre

Redwood canopy

Vernal pool