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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

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10

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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