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Ecological PrinciplesEcological PrinciplesEcologyEcology
• Ecology = the study of the interaction of organismswith their environments.
• It involves understanding biotic and abioticfactors influencing the distribution andabundance of living things.
• The word "ecology" coined from Greek word"oikos", which means "house" or "place to live”.
• Ecology = the study of the interaction of organismswith their environments.
• It involves understanding biotic and abioticfactors influencing the distribution andabundance of living things.
• The word "ecology" coined from Greek word"oikos", which means "house" or "place to live”.
The Scope of EcologyThe Scope of Ecology
• population growth• competition between species• symbiotic relationships• trophic (=feeding) relationships• origin of biological diversity• interaction with the physical environment
• population growth• competition between species• symbiotic relationships• trophic (=feeding) relationships• origin of biological diversity• interaction with the physical environment
Population GrowthPopulation GrowthExample of a Single-Celled Organism
That Doubles Each GenerationExample of a Single-Celled Organism
That Doubles Each Generation
GenerationGeneration
123456789
10
123456789
10
Population SizePopulation Size
1248
163264
128256512
1248
163264
128256512
0
100
200
300
400
500
600
Pop
ulat
ion
Siz
e
0 1 2 3 4 5 6 7 8 9 10 11 12
Generation
ExponentialPopulation
Growth
ExponentialPopulation
Growth
Effects of Different IntrinsicGrowth Rates (r)
Effects of Different IntrinsicGrowth Rates (r)
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Influence of the Carrying Capacity (K)on Population Growth
Influence of the Carrying Capacity (K)on Population Growth
Density-DependentVersus
Density-IndependentFactors Influencing Population Size
Density-DependentVersus
Density-IndependentFactors Influencing Population Size
Density-Dependent FactorsDensity-Dependent Factors
• limiting resources (e.g., food & shelter)• production of toxic wastes• infectious diseases• predation• stress• emigration
• limiting resources (e.g., food & shelter)• production of toxic wastes• infectious diseases• predation• stress• emigration
Density-Independent FactorsDensity-Independent Factors
• severe storms and flooding• sudden unpredictable severe cold spells• earthquakes and volcanoes• catastrophic meteorite impacts
• severe storms and flooding• sudden unpredictable severe cold spells• earthquakes and volcanoes• catastrophic meteorite impacts
K-Selected SpeciesK-Selected Species
• Poor colonizers• Slow maturity• Long-lived• Low fecundity• High investment in care for the young• Specialist• Good competitors
• Poor colonizers• Slow maturity• Long-lived• Low fecundity• High investment in care for the young• Specialist• Good competitors
r-Selected Speciesr-Selected Species
• Good colonizers• Reach sexual maturity rapidly• Short-lived• High fecundity• Low investment in care for the young• Generalists• Poor competitors
• Good colonizers• Reach sexual maturity rapidly• Short-lived• High fecundity• Low investment in care for the young• Generalists• Poor competitors
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Competition Among SpeciesCompetition Among Species
Ecological Niche ConceptEcological Niche Concept• Ecological niche = the "role" a species "plays" in
the ecosystem.• Contrast the ecological niche with the "habitat"
which is the physical environment in which theorganism lives.
• The ecological niche of a species, therefore,includes not just the species’ habitat, but also theways in which it interacts with other species andthe physical environment.
• Ecological niche = the "role" a species "plays" inthe ecosystem.
• Contrast the ecological niche with the "habitat"which is the physical environment in which theorganism lives.
• The ecological niche of a species, therefore,includes not just the species’ habitat, but also theways in which it interacts with other species andthe physical environment.
Competitive Exclusion PrincipleCompetitive Exclusion Principle
• No two similar species occupy the same nicheat the same time.
• Possible outcomes of competition– extinction of one species– resource partitioning: splitting the niche– character displacement: two similar species
evolve in such a way as to become different fromeach other by accentuating their initial minordifferences
• No two similar species occupy the same nicheat the same time.
• Possible outcomes of competition– extinction of one species– resource partitioning: splitting the niche– character displacement: two similar species
evolve in such a way as to become different fromeach other by accentuating their initial minordifferences
Extinction of One SpeciesExtinction of One Species
Resource PartitioningResource Partitioning
CharacterDisplacement
CharacterDisplacement
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Predator-Prey RelationshipsPredator-Prey Relationships
Outcomes of Predator-PreyInteractions
Outcomes of Predator-PreyInteractions
• offset oscillations in the population sizes ofthe predator and prey
• coevolution of predator and prey
• offset oscillations in the population sizes ofthe predator and prey
• coevolution of predator and prey
Oscillations in Predator and PreyPopulations
Oscillations in Predator and PreyPopulations
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Keystone SpeciesKeystone Species
A species whose presence in the communityexerts a significant influence on the
structure of that community.
A species whose presence in the communityexerts a significant influence on the
structure of that community.
Sea Otters ofCalifornia Kelp BedsSea Otters ofCalifornia Kelp Beds
Keystone SpeciesKeystone Species
Sea Stars of the Rocky Intertidal ZoneSea Stars of the Rocky Intertidal Zone
Keystone SpeciesKeystone SpeciesKeystone SpeciesKeystone Species
Algal turf farming by the PacificGregory (Stegastes fasciolatus)Algal turf farming by the PacificGregory (Stegastes fasciolatus)
SymbiosisSymbiosis
“Living Together”“Living Together”
Types of SymbiosisTypes of Symbiosis
• Mutualism– Both the symbiont and host benefit.
• Commensalism– The symbiont benefits with little effect on
the host.
• Parasitism– The symbiont benefits to the detriment of
the host.
• Mutualism– Both the symbiont and host benefit.
• Commensalism– The symbiont benefits with little effect on
the host.
• Parasitism– The symbiont benefits to the detriment of
the host.
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MutualismMutualism
Ecological SuccessionEcological Succession
The progressive change in thespecies composition of an
ecosystem.
The progressive change in thespecies composition of an
ecosystem.
Ecological SuccessionEcological Succession
Climax StageClimax Stage
Bare SubstrateBare Substrate
Colonizing StageColonizing Stage
Successionist StageSuccessionist Stage
Ecol
ogic
al S
ucce
ssio
nEc
olog
ical
Suc
cess
ion
Primary SuccessionVersus
Secondary Succession
Primary SuccessionVersus
Secondary Succession
Primary ProductivityPrimary Productivity
• Photosynthesis– Involves the use of light energy in the
conversion of inorganic carbon intoorganic carbon.
– Photosynthetic organisms include:terrestrial plants, seaweeds,phytoplankton, blue-green algae, andzooxanthellae.
• Photosynthesis– Involves the use of light energy in the
conversion of inorganic carbon intoorganic carbon.
– Photosynthetic organisms include:terrestrial plants, seaweeds,phytoplankton, blue-green algae, andzooxanthellae.
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Primary ProductivityPrimary Productivity
• Chemosynthesis– Involves the use of energy released by
the catalysis of certain inorganicreaction to convert inorganic carboninto organic carbon.
– Chemosynthetic organisms include:hydrothermal vent bacteria.
• Chemosynthesis– Involves the use of energy released by
the catalysis of certain inorganicreaction to convert inorganic carboninto organic carbon.
– Chemosynthetic organisms include:hydrothermal vent bacteria.
Primary ProductivityPrimary Productivity
• Gross Primary Productivity (GP)– The rate of production of organic matter from
inorganic materials by autotrophic organisms
• Respiration (R)– The rate of consumption of organic matter
(conversion to inorganic matter) by organisms.
• Net Primary Productivity (NP)– The net rate of organic matter produced as a
consequence of both GP and R.
• Gross Primary Productivity (GP)– The rate of production of organic matter from
inorganic materials by autotrophic organisms
• Respiration (R)– The rate of consumption of organic matter
(conversion to inorganic matter) by organisms.
• Net Primary Productivity (NP)– The net rate of organic matter produced as a
consequence of both GP and R.
Primary ProductivityPrimary Productivity
NP = GP + RNP = GP + R
Note that R is a negative value because itresults in the reduction of organicmatter.
Note that R is a negative value because itresults in the reduction of organicmatter.
Primary Productivity of DifferentEcosystems
Primary Productivity of DifferentEcosystems
Energy and Materials ThroughEcosystems
Energy and Materials ThroughEcosystems
Energy Useby an
Herbivore
Energy Useby an
Herbivore
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Trophic LevelsTrophic Levels
• 1st Trophic Level = Primary Producers• 2nd Trophic Level = Herbivores or Primary
Consumers• 3rd Trophic Level and Higher = Carnivores
or Secondary (or higher) Consumers• Highest Trophic Level = Top Carnivore• Decomposers
• 1st Trophic Level = Primary Producers• 2nd Trophic Level = Herbivores or Primary
Consumers• 3rd Trophic Level and Higher = Carnivores
or Secondary (or higher) Consumers• Highest Trophic Level = Top Carnivore• Decomposers
Some Feeding TypesSome Feeding Types• Algal Grazers and Browsers• Suspension Feeding• Filter Feeding• Deposit Feeding• Benthic Animal Predators• Plankton Pickers• Corallivores• Piscivores• Omnivores• Scavengers
• Algal Grazers and Browsers• Suspension Feeding• Filter Feeding• Deposit Feeding• Benthic Animal Predators• Plankton Pickers• Corallivores• Piscivores• Omnivores• Scavengers
Simple FoodChains
Simple FoodChains A Food WebA Food Web
Energy Flow Through EcosystemsEnergy Flow Through Ecosystems Energy and Biomass PyramidsEnergy and Biomass Pyramids
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Biogeochemical CyclesBiogeochemical Cycles
The Carbon CycleThe Carbon Cycle
carbon dioxidecarbon dioxide
inorganic-C
plantsplants
organic-C
animalsanimals
organic-C
decomposersdecomposers
organic-C
death
death
eating
photosynthesis
respiration
respiration
respiration
The Nitrogen CycleThe Nitrogen Cycle
animalsanimals
organic-N
decomposersdecomposers
organic-N
death
deat
h
eating
nitratenitrate
inorganic-N
plantsplants
organic-N
inorganicnitrogen uptake
metabolism
nitratenitrate
inorganic-N
ammoniaammonia
inorganic-N
nitritenitrite
inorganic-N
molecular nitrogenmolecular nitrogen
inorganic-N
metabolism
metabolism
metabolism
Biogeochemical CyclesBiogeochemical Cycles
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