Ecology of Populations

Ecology of Ecology of PopulationsPopulationsDay #1:Introduction to Day #1:Introduction to

EcologyEcology

Niche Discussion

Modern BiologyModern Biology

Pages 359-360Pages 359-360

What is the What is the common theme for common theme for

ecology?ecology?•““Interconnectedness”Interconnectedness”

– Nothing exists by itself.Nothing exists by itself.– Interdependence.Interdependence.– All living organisms interact with; All living organisms interact with;

• Other organismsOther organisms• Physical factorsPhysical factors

Key Words:Key Words:InterdependenceInterdependence

• Biosphere Biosphere is is broadest broadest of all.of all.– All areas All areas

that that support support life.life.

Modern Modern BiologyBiology

Pages 361-362Pages 361-362

What are the levels What are the levels of organization of organization

found in the found in the environment?environment?

Key Words:Key Words:BiosphereBiosphere

• Biomes are Biomes are large areas of large areas of the Earth.the Earth.– Common abiotic Common abiotic

conditions in the conditions in the area.area.




Pages 361-362Pages 361-362

Key Words:Key Words:BiomesBiomes

EcosystemsEcosystems– All organisms All organisms

and non-living and non-living environment environment in a given in a given area.area.

– Can be any Can be any size.size.




Pages 361-362Pages 361-362

Key Words:Key Words:EcosystemsEcosystems

• CommunitiesCommunities– All interacting All interacting

organisms in an organisms in an area.area.

– Includes all Includes all speciesspecies




Pages 361-362Pages 361-362

Key Words:Key Words:CommunitiesCommunities

• PopulationsPopulations– All members All members

of a species of a species living in one living in one area.area.




Pages 361-362Pages 361-362

Key Words:Key Words:PopulationPopulation

• OrganismOrganism– Simplest Simplest

level of level of organization organization in ecology.in ecology.




Pages 361-362Pages 361-362

Key Words:Key Words:PopulationPopulation

Ecology of Ecology of PopulationsPopulations

Day #2:Ecology of OrganismsDay #2:Ecology of Organisms

How doHow do organisms organisms

interact with their interact with their environment?environment?

• Environmental Environmental factors;factors;– AbioticAbiotic– BioticBiotic

• InteractionsInteractions– Abiotic - abioticAbiotic - abiotic– Abiotic - bioticAbiotic - biotic– Biotic - bioticBiotic - biotic


Pages 363-365Pages 363-365

Key Words:Key Words:AbioticAbiotic

BioticBiotic

• Abiotic factors Abiotic factors always change,always change,

• Organisms must Organisms must tolerate abiotic tolerate abiotic changes.changes.

• All organisms All organisms have a range of have a range of tolerance.tolerance.




Pages 363-365Pages 363-365

Key Words:Key Words:Tolerance CurveTolerance Curve

• Tolerance Tolerance curves shows curves shows how well a how well a species species tolerates tolerates abiotic abiotic changes.changes.




Pages 363-365Pages 363-365

• AcclimationAcclimation– Not adaptationNot adaptation– How organisms How organisms

react to react to changing changing abiotic abiotic conditions.conditions.

– Ex: You and Ex: You and altitudealtitude




Pages 363-365Pages 363-365

Key Words:Key Words:acclimationacclimation

• ConformersConformers– Change with the Change with the

environment.environment.– Ex: Reptiles and Ex: Reptiles and

body temperature.body temperature.

• RegulatorsRegulators– Maintain steady Maintain steady

internal conditions.internal conditions.

– Ex: MammalsEx: Mammals




Pages 363-365Pages 363-365

Key Words:Key Words:ConformerConformer

RegulatorsRegulators

• Escaping Escaping unfavorable unfavorable conditions.conditions.– MigrationMigration– HibernationHibernation– DormancyDormancy




Pages 363-365Pages 363-365

Key Words:Key Words:DormancyDormancy

MigrationMigration


Day #3: Energy Transfer in Day #3: Energy Transfer in EcosystemsEcosystems

Producers Are Producers Are Essential To An Essential To An

EcosystemEcosystem• Energy flows through

ecosystems.

• Producers use energy to produce organic molecules..

• Autotrophs– Use energy to produce

carbohydrates.– Most use

photosynthesis.– A few use

chemosynthesis..


Pages 366Pages 366

Key Words:Key Words:ProducersProducers

ChemosynthesisChemosynthesis

Organic moleculesOrganic molecules

What is What is Productivity?Productivity?

• Gross Primary productivity:– The rate at which

producers capture energy.

– Equal to all of the carbohydrates produced using photosynthesis.

– Referred to as biomass.


Pages 366Pages 366

Key Words:Key Words:biomassbiomass

Gross Primary Gross Primary ProductivityProductivity

How is How is Productivity Productivity Measured?Measured?

• Net Primary Productivity.

– Measured as g/m2/year.

– All organic material in an ecosystem is referred to as biomass (dry organic mass).

– All stored energy in the ecosystem.

– Rate at which biomass accumulates is NPP.


Pages 366Pages 366

Key Words:Key Words:Net Primary ProductivityNet Primary Productivity

Dry Organic MassDry Organic Mass

ConsumersConsumers

• Consumers are heterotrophs.– Obtain energy by

consuming organic molecules.• Herbivores• Carnivore• Omnivore• Detritivore• Decomposers


Pages 370Pages 370

Key Words:Key Words:DetritusDetritus

DecomposersDecomposers

Energy Energy FlowFlow

• Energy is transferred from organism to organism.

• Trophic level is the feeding position in community.

• Trophic levels:– 1st level = producers– 2nd level = herbivores– 3rd level = carnivore– 4th level = second carnivore


Pages 368-369Pages 368-369

Key Words:Key Words:Trophic LevelTrophic Level

How is Energy Lost in Ecosystems?


Pages 368-369Pages 368-369

Food Food ChainsChains

• A single pathway of energy through the ecosystem.

• 5% of sun’s energy is preserved in the producers.

• Approximately 10% of energy is preserved in each transfer..


Pages 368-369Pages 368-369

Food WebsFood Webs

• Several food Several food chains chains interlinked.interlinked.

• Better shows Better shows energy flow in energy flow in an ecosystem.an ecosystem.


Pages 368-369Pages 368-369

Why Do We Find Just a Why Do We Find Just a Few Hawks In An Few Hawks In An

Ecosystem?Ecosystem?


Pages 368-369Pages 368-369

• The niche– The way of

life.– The role in the

environment– Includes all

interactions in ecosystem.

– Generalist Vs specialist

What factors might be What factors might be included in the artic wolf’s included in the artic wolf’s

niche?niche?

What is a What is a specie’s niche?specie’s niche?


Pages 365Pages 365

Key Words:Key Words:generalistsgeneralists

specialistsspecialists

• Modern BiologyModern Biology• Pages 371-372Pages 371-372Ecology of Ecology of

OrganismsOrganisms

• Niche Differences– A species niche

can change over time.

– Generalists have very broad niches

– Specialists have very specific niches. Why is it an advantage for the adult

to feed on a different food source than the larva?


Day #4:Measuring PopulationsDay #4:Measuring Populations

Properties of Properties of PopulationsPopulations

• Population sizePopulation size– Determined Determined

by:by:• actual countactual count• samplingsampling

How many How many populations are populations are

shown here?shown here?


Pages 381-384Pages 381-384

Properties of Properties of PopulationsPopulations

• Population Population DensityDensity– Expressed as:Expressed as:– # of # of

Individuals/area.Individuals/area.

How would low density effect How would low density effect the condor population?the condor population?


Pages 366-369Pages 366-369

Key Words:Key Words:Population densityPopulation density

Population dispersionPopulation dispersion

Properties of Properties of PopulationsPopulations• Population

dispersion– Clumped– Uniform– Random

• Depends viewing scale in many cases.

Could redwood trees demonstrate Could redwood trees demonstrate all three dispersions in different all three dispersions in different

conditions?conditions?


Pages 366-369Pages 366-369

Population Population DynamicsDynamics

• Dynamics means changing over time.

• Change is due to:– Birth rate.– Death (mortality) rate.– Immigration– Emmigration

What industry (business) pays close attention to this type of

data?


Pages 383-389Pages 383-389


• Survivorship curvesSurvivorship curves– Type IType I– Type IIType II– Type IIIType III

Is survivorship type related to Is survivorship type related to number of offspring produced?number of offspring produced?


Pages 383-389Pages 383-389


• Age structureAge structure

What information can you get from this chart?What information can you get from this chart?


Pages 383-389Pages 383-389

Population Population GrowthGrowth

• Population growth rate is size change over time.– Growth can be negative

or positive.

• Depends on any of four factors– Birth rate– death rate– Emmigration &

immigationWhat two events might have led What two events might have led to the rapid increase in human to the rapid increase in human

populations?populations?


Pages 383-389Pages 383-389

Exponential Exponential Growth Growth CurveCurve

• Populations grow more Populations grow more rapidly as they rapidly as they increase in size.increase in size.

• ““J” curve.J” curve.• Demonstrates species Demonstrates species

biotic potential.biotic potential.• Unlimited resources.Unlimited resources.• Only occurs in rare Only occurs in rare

cases.cases.

Can this growth curve occur for Can this growth curve occur for long periods of time? Whylong periods of time? Why


Pages 383-389Pages 383-389

Logistic Logistic Growth Growth CurveCurve

• Same as exponential for short time.

• Growth slows and finally levels out.

• Known as “S” curve.• Carrying capacity has

been reached.

What resource most likely causes What resource most likely causes this curve to flatten out?this curve to flatten out?


Pages 383-389Pages 383-389

Comparison of Expoential and Logistic Comparison of Expoential and Logistic Growth CurvesGrowth Curves


Day #5:Measuring PopulationsDay #5:Measuring Populations

Factors that Limit Factors that Limit Population GrowthPopulation Growth• Causes growth to be

something less than biotic potential.

• Referred to as limiting factors– Density dependent

• Limits on resources.• Disease

– Density independent• Weather• Fire

Why so Why so many many

rabbits in rabbits in Australia?Australia?


Pages 383-389Pages 383-389

Factors that Limit Factors that Limit Population GrowthPopulation Growth


Pages 383-389Pages 383-389

Dangers of Small Dangers of Small PopulationsPopulations

• Leads to:– Lack of genetic

variation.– Inbreeding.– Lower birth rates.– Susceptible to

extinction.

Do zoos solve the problems of small populations?


Pages 383-389Pages 383-389

• Fundamental niche– Full range of

interactions in ecosystem.

– All potential resources

– Theoretical niche as if no other organisms present

Why is the realized niche shown above smaller than the

fundamental niche?


Pages 363-365Pages 363-365

Key Words:Key Words:Fundamental nicheFundamental niche

Realized nicheRealized niche

How is a fundamental How is a fundamental niche different from a niche different from a

realized niche?realized niche?

• Modern BiologyModern Biology• Pages 371-372Pages 371-372Ecology of Ecology of

OrganismsOrganisms

• Realized niche– All resources

actually used.– Competition with

other organisms limits fundamental niche.

– Something less than the fundamental niche.

Which species out competes the other Which species out competes the other species regarding niche?species regarding niche?

Why is there not a mixture of the two species in the Why is there not a mixture of the two species in the overlap area?overlap area?

What strategies help the finches to survive?

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Ecology of Populations