Transcript Chapter 5: “How Ecosystems Work”

Chapter 5
How Ecosystems Work
Lake Victoria
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Freshwater lake in Africa
Formerly home to ≈ 400 species of cichlids
1960: Nile perch
introduced
1990: water hyacinth
invaded
Today, ecological
imbalance; why?
What Is Ecology?
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Literally study of one’s “house”
Interactions
Two components
 Biotic
 Abiotic
Broadest biological field of study
Ecological Organization
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Organism
Population
Community
Ecosystem
Landscape
Biosphere
Positive and Negative
Feedback Loops
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Feedback Loop
 circular process
Positive Feedback Loop
 change becomes more pronounced
Negative Feedback Loop
 change is reduced or inhibited
Landscape Ecology
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Studies the connections
among ecosystems
Ecosystem engineers
 Organisms that
create or modify
habitat
 How are grizzly
bears ecosystem
engineers?
Goals Of Ecologists
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Understand how ecosystems function
Make connections: landscape ecology
Connections among ecosystems
 Grizzly Bears
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Energy
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Capacity or ability to do work
Flows through ecosystems
Why do organisms need energy?
Different kinds
Potential energy
Kinetic energy
First Law of Thermodynamics
Energy cannot be
created or
destroyed
 Energy can be
changed from one
form to another
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Second Law of
Thermodynamics
When energy is changed from one form
to another, some is degraded into heat
 Heat is a less usable form of energy
 Increases entropy in the universe
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Ecosystem Composition
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Producers
Consumers
Decomposers
Producers
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Make their own food
Photosynthesis
Examples?
6CO2 + 6H2O + ------> C6H12O6 + 6O2
Consumers
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Feed on other things
Herbivores
Carnivores
Omnivores
Detrivores
Decomposers
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Break down dead organisms and waste
products
Examples?
Energy Flow
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Energy passes from one organism to the
next
Trophic level: each step in this flow of
energy
Food chain: straight path
Food web
 Interconnected food chains
 More realistic than food chain; why?
Food Chain
Biological Production
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Net Primary Production: amount of plant
mass generated by photosynthesis and
that remains after cellular respiration
Biomass: total amount of organic matter
NPP is measured by tracking the changes
in biomass over time
(NPP = B2 –B1)
Food
Web
Biogeochemical Cycles
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Matter cycles through ecosystems
Five cycles
Carbon
 Hydrologic (water)
 Nitrogen
 Sulfur
 Phosphorus
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Carbon Cycle
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Essential component for life
Gas (CO2) in atmosphere
Several forms in ocean
Can take a long time—think fossil fuels
Photosynthesis
CO2
Cellular respiration
Sugar
CO2
Carbon Cycle
Hydrologic Cycle
Ocean
Atmosphere
Land
Ocean
Nitrogen Cycle
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Proteins, DNA
Atmosphere is 78% N2
Five steps
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Nitrogen fixation
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Nitrification
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Assimilation
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Ammonification
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Denitrification
Nitrogen Fixation
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Specialized bacteria
Split atmospheric nitrogen and combine it
with hydrogen
Nitrogen Cycle
Phosphorus Cycle
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No atmospheric component
Phosphates used in DNA and ATP
(chemical energy)
Phosphates move through the food chain
Land
Organism
Organism
Land
Phosphorus Cycle
Ecological Niche
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Everything about an organism
 Adaptations
 Use of resources
 Lifestyle
 Habitat
Ecological Niche
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Two species cannot occupy the same
niche: why?
Resource partitioning
 Reduces niche overlap
 Reduces competition
Resource Partitioning At Work!
Species Interactions
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No species lives in complete isolation
Symbiosis
 Intimate relationship between members
of at least 2 species
 Mutualism, commensalism, parasitism
 Result of coevolution
Other interactions
 Predation, competition
Mutualism
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Both species benefit
Commensalism
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One species benefits, other not affected
Parasitism
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Parasite benefits, host is “harmed”
Ectoparasites & endoparasites
Species Interactions
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Predation: consumption of one species by
another
Coevolution: “arms race”
Avoiding Predators
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Mechanical defenses
Social groups
Camouflage
Protective chemicals
Species Interactions
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Competition: two or more organisms
attempting to use the same resource
Intraspecific vs. interspecific
Keystone Species
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Crucial to maintenance of an ecosystem
Loss affects many other
species
Examples?
What are the differences
between a keystone,
umbrella or flagship
species?
Adaptive Ecosystem
Management
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Ecosystem Management: meeting the goals or
objectives of the biotic community and their
associated abiotic components
Adaptive Ecosystem Management:
 developed by C.S. Holling and Carl J. Walters,
University of B.C., 1970
 acknowledges the uncertainty and the need
for managers to learn while they manage
 passive and active
Eco Canada Career Focus
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Consider a career as
an ecologist
Ecologists study the
relationships
between living
things and their
environments
Case Study: Human
Appropriation of Net Primary
Productivity (HANPP)
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HANPP : indicator of are of land an the
amount of biomass consumed by humans
Valuable indicator of “human domination of
ecosystems” on a global scale
Many countries are consuming an excess of
100% of locally available NPP
Case Study: Human
Appropriation of Net Primary
Productivity (HANPP)