ObjectiveObjective Explain how population sizes are Explain how population sizes are

regulated.regulated.

Key TermsKey Terms

PopulationPopulation

DispersionDispersion

Growth rateGrowth rate

Reproductive potentialReproductive potential

Carrying capacityCarrying capacity

What Is a Population?What Is a Population? Group of organisms of the same speciesGroup of organisms of the same species

live in the same area live in the same area interbreedinterbreed

Organisms usually breed with members Organisms usually breed with members of their own population.of their own population.

PopulationsPopulations ““Population” refers to the group as a Population” refers to the group as a

whole or the size - number of whole or the size - number of individuals (members) in the group.individuals (members) in the group.

PopulationsPopulations Population DensityPopulation Density - number of - number of

members that live in a specific area.members that live in a specific area.

PopulationsPopulations Dispersion - Dispersion -

distribution of distribution of organisms in a organisms in a populationpopulation ClumpedClumped UniformUniform RandomRandom

Growth RateGrowth Rate Population change over time can be Population change over time can be

represented by:represented by:

Growth RateGrowth Rate Changes when birth rates and death Changes when birth rates and death

rates increase or decrease. rates increase or decrease. Can be positive, negative, or zero.Can be positive, negative, or zero.

Growth RateGrowth Rate Positive – average number Positive – average number

of births of births >> average average number of deathsnumber of deaths

Negative - average number Negative - average number of births of births << average average number of deathsnumber of deaths

Zero - average number of Zero - average number of births = average number births = average number of deathsof deaths

Population sizes usually stay Population sizes usually stay the samethe same

Certain factors control the Certain factors control the sizes of populations (limiting sizes of populations (limiting factors).factors).

• spacespace• diseasedisease• immigration/emigrationimmigration/emigration• predators and parasitespredators and parasites

Growth RateGrowth Rate

Reproductive PotentialReproductive Potential The maximum number of offspring a The maximum number of offspring a

specific organism can produce.specific organism can produce. Depends upon Depends upon

fecundityfecundity fertilityfertility gestationgestation

Reproductive PotentialReproductive Potential Increases when individuals Increases when individuals

produce more offspring at a timeproduce more offspring at a time reproduce more oftenreproduce more often reproduce earlier in lifereproduce earlier in life

• shortens generation time – average age of shortens generation time – average age of reproductionreproduction

Reproductive PotentialReproductive Potential Small organisms have short Small organisms have short

generation times generation times can reproduce after few hours/few dayscan reproduce after few hours/few days populations grow quicklypopulations grow quickly

Reproductive PotentialReproductive Potential Large organisms reach reproductive Large organisms reach reproductive

age after years age after years have a much lower reproductive have a much lower reproductive

potentialpotential populations grow slowlypopulations grow slowly

Exponential GrowthExponential Growth A large number of A large number of

individuals is added individuals is added to the population to the population each generation. each generation.

Numbers increase Numbers increase by a certain factor by a certain factor (usu. 2).(usu. 2).

Occurs in nature Occurs in nature with plenty of with plenty of resources and no resources and no predators.predators.

Only the best adapted members of a Only the best adapted members of a population will survive and population will survive and reproduce. reproduce.

Characteristics of a population may Characteristics of a population may evolve over time.evolve over time.

Limits to Population GrowthLimits to Population Growth

Carrying CapacityCarrying Capacity Largest population an environment Largest population an environment

can support at any time.can support at any time. Population can increase beyond this Population can increase beyond this

number but cannot stay elevatednumber but cannot stay elevated

Carrying CapacityCarrying CapacityEstimated by average population Estimated by average population sizes or by observing population sizes or by observing population crashes after a certain size has been crashes after a certain size has been exceeded.exceeded.

Resource LimitsResource Limits

Resource LimitsResource Limits Carrying capacity is reached when Carrying capacity is reached when

species consume a resource at the species consume a resource at the same rate that the resource is same rate that the resource is produced.produced. resource consumption = resource creationresource consumption = resource creation

That natural resource is called a That natural resource is called a limiting resource.limiting resource. FoodFood WaterWater LightLight

Resource competition Resource competition increases as increases as population population approaches carrying approaches carrying capacity.capacity.

Competition within a Competition within a population is part of population is part of the pressure of the pressure of natural selection.natural selection.

Competition Within a Competition Within a PopulationPopulation

Members of a species may compete Members of a species may compete indirectly for social dominance or for a indirectly for social dominance or for a territory.territory.

A territory is an area defended by one or A territory is an area defended by one or more individuals against other individuals.more individuals against other individuals. space space sheltershelter foodfood matesmates breeding sitesbreeding sites

Competition Within a Competition Within a PopulationPopulation

Causes of death in a population may Causes of death in a population may be density dependent or density be density dependent or density independent.independent.

Population RegulationPopulation Regulation

Population RegulationPopulation Regulation

Density dependent Density dependent cause of death - cause of death - deaths occur more deaths occur more quickly in a quickly in a crowded population crowded population than in a sparse than in a sparse population.population. Limiting factorsLimiting factors PredationPredation EmigrationEmigration

Population RegulationPopulation Regulation

Population RegulationPopulation Regulation Density independent cause of death Density independent cause of death

– some of the population can die – some of the population can die regardless of the population’s regardless of the population’s density.density. Severe weather Severe weather Natural disastersNatural disasters

Do Now/Objective – separate Do Now/Objective – separate paper…Hand In (4 min)paper…Hand In (4 min)

Do all living organisms interact in the Do all living organisms interact in the same way?same way?

List the different ways organisms List the different ways organisms interact with each other.interact with each other.

NicheNiche Ecological role of an organismEcological role of an organism

where it makes its homewhere it makes its home resources it needs to surviveresources it needs to survive how it interacts with other organismshow it interacts with other organisms

A niche includes an organism’s A niche includes an organism’s habitat. habitat. habitat is an area within an ecosystem.habitat is an area within an ecosystem.

Niche MapNiche Map

All organisms use their habitats in a unique way.All organisms use their habitats in a unique way.

Think about your niche (where you fit into your Think about your niche (where you fit into your community) and answer:community) and answer:

• Where do you gather your favorite resources?Where do you gather your favorite resources?

• Who do you compete or cooperate with?Who do you compete or cooperate with?

• Where do you live and where do you hang out?Where do you live and where do you hang out?

• Do you spend certain parts of the day in certain places?Do you spend certain parts of the day in certain places?

Draw a niche bubble map that shows how your use Draw a niche bubble map that shows how your use your habitat. INCLUDE 4+ interactions and your habitat. INCLUDE 4+ interactions and describedescribe those interactions on your maps. those interactions on your maps.

Key TermsKey Terms

NicheNiche

CompetitionCompetition

PredationPredation

ParasitismParasitism

MutualismMutualism

ComensalismComensalism

SymbiosisSymbiosis

Species InteractionSpecies Interaction Five main types of interactions:Five main types of interactions:

• CompetitionCompetition• PredationPredation• ParasitismParasitism• MutualismMutualism• CommensalismCommensalism

CompetitionCompetition Organisms try to use the same Organisms try to use the same

limited resourcelimited resource Members of the same species Members of the same species

competecompete they require the same resources they require the same resources they occupy the same niche they occupy the same niche

Indirect CompetitionIndirect Competition

Species can compete Species can compete even if they never even if they never come into direct come into direct contact with each contact with each other.other.

Adaptations to CompetitionAdaptations to Competition Members of different species Members of different species

sometimes compete (niche overlap)sometimes compete (niche overlap) each species use some of the same each species use some of the same

resources in a habitat.resources in a habitat.

Adaptations to CompetitionAdaptations to Competition

Law of Competitive ExclusionLaw of Competitive Exclusion No two species can occupy the same No two species can occupy the same

niche (competing for the same niche (competing for the same resources) at the same time indefinitelyresources) at the same time indefinitely

Adaptations to CompetitionAdaptations to CompetitionThe species will often divide up the The species will often divide up the niche niche

by areaby area

by time of useby time of use

Adaptations to CompetitionAdaptations to Competition Niche restriction - each species uses Niche restriction - each species uses

less of the niche than they are less of the niche than they are capable of using. capable of using. Actual niche may be smaller than Actual niche may be smaller than

potential niche.potential niche.

Adaptations to CompetitionAdaptations to Competition

PredationPredation One species kills and eats the other One species kills and eats the other

speciesspecies predatorpredator preyprey

PredatorsPredators

Some predators Some predators eat only specific eat only specific types of prey.types of prey. sizes of both sizes of both

populations have a populations have a direct relationshipdirect relationship

ParasitismParasitism

An organism lives An organism lives in or on another in or on another organism to feed organism to feed on the other on the other organism organism parasiteparasite host host

Parasitism vs. PredationParasitism vs. Predation Parasites depend on their hosts; Parasites depend on their hosts;

usually don’t kill them.usually don’t kill them. The host is often weakened or The host is often weakened or

diseased by the parasite.diseased by the parasite.

SymbiosisSymbiosis Relationship where two different Relationship where two different

organisms benefit from each otherorganisms benefit from each other MutualismMutualism CommensalismCommensalism

MutualismMutualism

Relationship between two species where Relationship between two species where both species benefit.both species benefit.

CommensalismCommensalism Relationship between two organisms Relationship between two organisms

where one organism benefits and the where one organism benefits and the other is unaffected.other is unaffected.

CoevolutionCoevolution Can occur with species in symbiotic Can occur with species in symbiotic

relationships. relationships. species may evolve adaptations that species may evolve adaptations that

improve the benefits to each member.improve the benefits to each member.

Species InteractionsSpecies InteractionsInteractioInteractio

n Typen TypeSpecies Species

AA

(harmed (harmed or or

benefitebenefited)d)

Species BSpecies B

(harmed (harmed or or

benefitedbenefited))

DescriptionDescription Your own Your own exampleexample

1.1. CompetitionCompetition

HarmedHarmed HarmedHarmed Both parties Both parties struggle for a struggle for a

limited resourcelimited resource

Coyote and kit fox Coyote and kit fox both hunting both hunting kangaroo ratkangaroo rat

2.2.

3.3.

4.4.

5.5.