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Chapter 5Chapter 5
Population EcologyPopulation EcologyCharateristics: geographical Charateristics: geographical
distribution, distribution, density and growthdensity and growth
Population DensityPopulation Density
Measures how crowded a population Measures how crowded a population isis
Unit examples?Unit examples?
City vs Suburbs vs RuralCity vs Suburbs vs Rural
Population DistributionPopulation Distribution
Three main waysThree main ways– ClumpedClumped– RandomRandom– Uniform/EvenUniform/Even
Most common? Rare?Most common? Rare?
Distribution patternsDistribution patterns
Population DynamicsPopulation Dynamics Birth rate = number of births over timeBirth rate = number of births over time Death rate = deaths over a period of Death rate = deaths over a period of
timetime Life expectancy = how long individuals Life expectancy = how long individuals
in pop. are expected to livein pop. are expected to live– Take a guess: life expectancy for men and Take a guess: life expectancy for men and
women in United Stateswomen in United StatesMen = 72 yearsMen = 72 yearsWomen = 76 yearsWomen = 76 years
Population Growth RatePopulation Growth Rate
Growth rate= change in population Growth rate= change in population size over timesize over time
Depends upon the following:Depends upon the following:– Birth Birth – DeathDeath– ImmigrationImmigration– EmigrationEmigration
Age StructuresAge Structures
Effects of AIDS on a PopulationEffects of AIDS on a Population
Questions- be ready to answerQuestions- be ready to answer
What is a rate?What is a rate? What is birth rate?What is birth rate? What is death rate?What is death rate? What are two additional factors that What are two additional factors that
cause a population to increase? cause a population to increase? Decrease?Decrease?
What does per capita or % annual What does per capita or % annual growth rate mean?growth rate mean?
Growth RateGrowth Rate
What is a rate?What is a rate?– Change over time Change over time – In math terms = slopeIn math terms = slope
What is birth rate? death rate?What is birth rate? death rate?– Number of births over a period of time Number of births over a period of time – Number of deaths over a period of timeNumber of deaths over a period of time
Growth RateGrowth Rate
Two factors that increase population Two factors that increase population growthgrowth– BirthsBirths– ImmigrationImmigration
Two factors that decrease population Two factors that decrease population growthgrowth– DeathsDeaths– EmmigrationEmmigration
Growth rateGrowth rate
% GROWTH RATE? - takes into account % GROWTH RATE? - takes into account total growth (births and immigration) total growth (births and immigration) minusminus decline (death and emmigration) decline (death and emmigration)– Change in growth over timeChange in growth over time
Look at fig 5-14 on page 132Look at fig 5-14 on page 132
What does ZPG mean?What does ZPG mean?– Zero population growthZero population growth
What years had the highest % growth What years had the highest % growth rate?rate?
PopulationGrowth
can be
represented bycharacterized by characterized by represented by
which cause a
Exponentialgrowth
Logisticgrowth
Fallinggrowth rate
S-shapedcurve
Limits ongrowth
No limits on growth
J-shapedcurve
Constantgrowth rate
Unlimitedresources
Section 5-1
Concept Map
Exponential Model for Exponential Model for Population GrowthPopulation Growth
Says that populations grow rapidly Says that populations grow rapidly after only a few generationsafter only a few generations
Bacteria follow this modelBacteria follow this model
Logistic ModelLogistic Model
Populations are limited by their Populations are limited by their environmentenvironment
Any factor that limits population Any factor that limits population growth is called a limiting factorgrowth is called a limiting factor
Limiting factors include things like Limiting factors include things like food, habitat availability, water, food, habitat availability, water, predatorspredators
Carrying Capacity (K)Carrying Capacity (K) The number of individuals the The number of individuals the
environment can support over a long environment can support over a long period of time.period of time.
This number is due to birth rates, This number is due to birth rates, death rates, and limiting factorsdeath rates, and limiting factors
Humans – how long?
HW – CH 5 Study Guides due HW – CH 5 Study Guides due Tues!Tues!
5–25–2 Limits to GrowthLimits to Growth
AA.. Limiting FactorsLimiting Factors
B.B. Density-Dependent FactorsDensity-Dependent Factors
1.1. ExtinctionExtinction
2. Competition2. Competition
3.3. PredationPredation
4.4. Parasitism and DiseaseParasitism and Disease
C.C. Density-Independent Density-Independent FactorsFactors
Section 5-2
Section Outline
Population FluctuationsPopulation Fluctuations
1.1. Density-independent factors- reduce Density-independent factors- reduce population by the same proportion population by the same proportion regardless of population size; ex. Cold regardless of population size; ex. Cold winter effects the squirrel populationwinter effects the squirrel population
– It doesn’t matter the size of the populationIt doesn’t matter the size of the population
2. Density-dependent factors- resource 2. Density-dependent factors- resource limits due to increase in population limits due to increase in population density; ex. Shortage of food due to too density; ex. Shortage of food due to too many deer in the area causes some deer many deer in the area causes some deer to starve. to starve.
Fluctuations Change the GraphFluctuations Change the Graph
ExtinctionExtinction
What if an organism went extinct?What if an organism went extinct? What would the graph look like? What would the graph look like?
What about small populations?What about small populations?
Very vulnerable to extinctionVery vulnerable to extinction Why is that?Why is that? InbreedingInbreeding Something bad happens in the Something bad happens in the
environment and too many die to environment and too many die to sustain the populationsustain the population
Ex. Cheetahs, sea otters, CA Ex. Cheetahs, sea otters, CA Condors, Siberian tigersCondors, Siberian tigers
60
50
40
30
20
10
01955 1960 1965 1970 1975 1980 1985 1990 1995
2000
1600
1200
800
400
0
2400
Moose Wolves
Section 5-2
Figure 5-7 Wolf and Moose Populations on Isle Royale
Human PopulationsHuman Populations
Human PopulationsHuman Populations
They have exploded over the last They have exploded over the last 1000 years1000 years
The death rates have decreased and The death rates have decreased and the birth rates have increased. This the birth rates have increased. This makes the overall growth rate makes the overall growth rate increase.increase.
Do you think that this current human Do you think that this current human population is sustainable?population is sustainable?
Do you think that we are way past our Do you think that we are way past our carrying capacity and it will go down?carrying capacity and it will go down?
Agriculturebegins
Plowingand irrigation
Bubonicplague
IndustrialRevolutionbegins
Section 5-3
Human Population Growth