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