Chapter 5Chapter 5PopulationsPopulations

Section 5-2Section 5-2

Limits To GrowthLimits To Growth

Limiting FactorsLimiting Factors

Cause Population Growth to Cause Population Growth to DECREASE!DECREASE!

CompetitionCompetition PredationPredation Parasitism & DiseaseParasitism & Disease Climate ExtremesClimate Extremes Human DisturbancesHuman Disturbances

Density Dependent Factors:differ with the biome/environmentAmount foodDiseaseCompetitionParasitesVersus Independent:Abiotic factorsHabitat disruption

Density-Dependent FactorsDensity-Dependent Factors

Are Limiting Factors that depend Are Limiting Factors that depend on increased population size on increased population size

(density) for activation.(density) for activation.

competition competition predationpredation

parasitism diseaseparasitism disease

CompetitionCompetition

Between different species is a Between different species is a major force behind major force behind

evolutionary changeevolutionary changeResults in the formation ofResults in the formation of

NICHESNICHES

CompetitionCompetition

PredationPredation

Predator/Prey RelationshipPredator/Prey Relationship Balances, Stabilizes PopulationsBalances, Stabilizes Populations Wolves & MooseWolves & Moose

50 kg Wolf needs 2700 kg Moose 50 kg Wolf needs 2700 kg Moose per yearper year

Average Moose is 385 kgAverage Moose is 385 kg How many Moose need to be How many Moose need to be eaten each year?eaten each year?

PredationPredation

2700/385 = 7.01 Moose per Year2700/385 = 7.01 Moose per Year

A pack of 8 wolves will kill how A pack of 8 wolves will kill how many Moose per year?many Moose per year?

Parasitism & DiseaseParasitism & Disease

Weaken HostWeaken Host

Makes Host Susceptible Makes Host Susceptible To PredationTo Predation

May Kill Host.May Kill Host.

Density-Independent FactorsDensity-Independent Factors

Affect population regardless of Affect population regardless of size.size. Unusual WeatherUnusual Weather Natural DisastersNatural Disasters Seasonal CyclesSeasonal Cycles Human ActivitiesHuman Activities

DamsDamsClear CuttingClear Cutting

Density-Independent FactorsDensity-Independent Factors

Result in crash in Result in crash in population sizepopulation size

May result in May result in extinction extinction

What sort of limiting factor is seen here?

Density dependent!

What sort of limiting factor is seen here?

Density independent