Chapter 52Chapter 52

Population EcologyPopulation Ecology

I. Population Density, Dispersion I. Population Density, Dispersion and Demographyand Demography

Dynamic biological processesDynamic biological processes– Birth rates/death rates; immigration/emigrationBirth rates/death rates; immigration/emigration– Patterns: Clumped, Uniform, RandomPatterns: Clumped, Uniform, Random

DemographyDemography– Life tablesLife tables– Survivorship curves (figures 52.4 and 52.5)Survivorship curves (figures 52.4 and 52.5)– Reproductive ratesReproductive rates

LE 52-2

Populationsize

Emigration

Deaths

ImmigrationBirths

LE 52-3

Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory.

Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.

Random. Dandelions grow from windblown seeds that land at random and later germinate.

II. Life History and Natural II. Life History and Natural SelectionSelection

Life history variablesLife history variables– When reproduction begins, how often, how When reproduction begins, how often, how

manymany

Life history diversityLife history diversity– Semelparity (Big bang reproduction)Semelparity (Big bang reproduction)– Iteroparity (Repeated reproductionIteroparity (Repeated reproduction

Trade offsTrade offs

LE 52-5

III

II

100

Percentage of maximum life span

Nu

mb

er o

f su

rviv

ors

(lo

g s

cale

)

0 50

1,000

100

10

1

I

LE 52-8

Most weedy plants, such as this dandelion, grow quickly and produce a large number of seeds, ensuring that at least some will grow into plants and eventually produce seeds themselves.

Some plants, such as this coconut palm, produce a moderate number of very large seeds. The large endosperm provides nutrients for the embryo, an adaptation that helps ensure the success of a relatively large fraction of offspring.

III. Exponential vs. Logistic GrowthIII. Exponential vs. Logistic Growth

ExponentialExponential– Unlimited resourcesUnlimited resources

LogisticLogistic– Carrying capacityCarrying capacity

LE 52-10

Year

Ele

ph

ant

po

pu

lati

on

8,000

4,000

6,000

2,000

019801960194019201900

LE 52-12

Number of generations

Po

pu

lati

on

siz

e (N

)

K = 1,5001,500

2,000

1,000

500

1510500

Logistic growth

Exponentialgrowth

= 1.0NdNdt

= 1.0NdNdt

1,500 – N

1,500

LE 52-13b

Time (days)

Nu

mb

er o

f Daphnia

/50

mL

180

0

90

20

60

400

60

150

120

A Daphnia population in the lab

30

80 100 120 140 160

LE 52-13c

Time (years)

Nu

mb

er o

f fe

mal

es80

1975 1980

40

19850

1990

60

A song sparrow population in its natural habitat

20

1995 2000

IV. Regulation of PopulationsIV. Regulation of Populations

Density-dependent and density-Density-dependent and density-independentindependent

Dynamics of population growth -> variationDynamics of population growth -> variation

Population cyclesPopulation cycles

LE 52-18

1960

Year

Mo

ose

po

pu

lati

on

siz

e

2,500

Steady decline probably caused largely by wolf predation

2,000

1,500

1,000

500

01970 1980 1990 2000

Dramatic collapse caused by severe winter weather and food shortage, leading to starvation of more than 75% of the population

LE 52-19

1960

Year

Co

mm

erci

al c

atch

(kg

) o

fm

ale

crab

s (l

og

sca

le)

730,000

100,000

10,000

1970 1980 19901950

LE 52-21

Year

Ha

re p

op

ula

tio

n s

ize

(th

ou

sa

nd

s)

1850

Snowshoe hare

01875 1900 1925

40

80

120

160

Ly

nx

po

pu

lati

on

siz

e(t

ho

us

an

ds

)

Lynx

0

3

6

9

V. Human PopulationV. Human Population

Figure 52.23Figure 52.23

RegionalRegional– Demographic transitionDemographic transition– Age structureAge structure

Global Carrying CapacityGlobal Carrying Capacity

LE 52-22

8000B.C.

Hu

man

po

pu

lati

on

(b

illi

on

s)

6

5

4

3

2

1

0

4000B.C.

3000B.C.

2000B.C.

1000B.C.

The Plague

0 1000A.D.

2000A.D.

LE 52-22

8000B.C.

Hu

man

po

pu

lati

on

(b

illi

on

s)

6

5

4

3

2

1

0

4000B.C.

3000B.C.

2000B.C.

1000B.C.

The Plague

0 1000A.D.

2000A.D.

LE 52-25

Rapid growthAfghanistan

AgeMale

Percent of population

Female

8 6 4 2 2 4 6 80

45–4940–4435–3930–3425–2920–2415–1910–14

5–90–4

85+80–8475–7970–7465–6960–6455–5950–54

Slow growthUnited States

AgeMale

Percent of population

Female

6 4 2 2 4 6 80

45–4940–4435–3930–3425–2920–2415–1910–14

5–90–4

85+80–8475–7970–7465–6960–6455–5950–54

8

Decrease Italy

Male

Percent of population

Female

6 4 2 2 4 6 808

LE 52-26

Infa

nt

mo

rtal

ity

(dea

ths

per

1,0

00 b

irth

s)

50

40

30

20

10

0Developedcountries

60

Developingcountries

Lif

e ex

pec

tan

cy (

year

s)

80

40

20

0Developedcountries

60

Developingcountries