Chapter 36 Population Ecologycoachshannon.weebly.com/uploads/3/0/1/1/30116035/... · 36.1 Population ecology is the study of how and why populations change. ... 1210 8 6 4 2 0 2 4

Copyright © 2009 Pearson Education, Inc.

PowerPoint Lectures for

Biology: Concepts & Connections, Sixth Edition

Campbell, Reece, Taylor, Simon, and Dickey

Chapter 36 Population Ecology

Lecture by Brian R. Shmaefsky


Introduction: A Tale of Two Fishes

Population ecology is concerned with

– Changes in population size

– Factors that regulate populations over time

It helps explain the biodiversity of an environment


Ecologists learn the structure and dynamics of natural populations

With this information they are better equipped to

– Develop sustainable food sources

– Assess the impact of human activities

– Balance human needs with the conservation of biodiversity and resources

Introduction: A Tale of Two Fishes


POPULATION STRUCTURE AND DYNAMICS


36.1 Population ecology is the study of how and why populations change

Population

– A group of individuals of a single species that occupy the same general area

Individuals in a population

– Rely on the same resources

– Are influenced by the same environmental factors

– Are likely to interact and breed with one another


A population can be described by the number and distribution of individuals

Population dynamics is the interactions between

– Biotic and abiotic factors

It is the cause of variation in population sizes

– A population increases through birth and immigration

– Death and emigration out of an area decrease the population

36.1 Population ecology is the study of how and why populations change


36.2 Density and dispersion patterns are important population variables

Population density is the number of individuals of a species per unit area or volume

Examples of population density

– The number of oak trees per square kilometer in a forest

– The number of earthworms per cubic meter in forest soil

Ecologists use a variety of sampling techniques to estimate population densities


Within a population’s geographic range, local densities may vary greatly

The dispersion pattern of a population refers to the way individuals are spaced within their area


Video: Flapping Geese (clumped)

Video: Albatross Courtship (uniform)

Video: Prokaryotic Flagella (Salmonella typhimurium) (random)

36_02AFlappingGeese_SV.mpg

36_02AFlappingGeese_SV.mpg

36_02BAlbatrossCourtship_SV.mpg

36_02BAlbatrossCourtship_SV.mpg

36_02CSalmonellaFlagella_SV.mpg

36_02CSalmonellaFlagella_SV.mpg


The dispersion pattern of a population refers to the way individuals are spaced within their area

Dispersion patterns can be

– Clumped

– Uniform

– Random



In a clumped pattern individuals are grouped in patches



In a uniform pattern individuals are equally spaced in the environment



In a random pattern of dispersion, the individuals in a population are spaced in an unpredictable way



36. 3 Life tables track survivorship in populations

Life tables track survivorship over the life span of individuals in a population

Survivorship curves plot the proportion of individuals alive at each age

– Type I

– Type II

– Type III

Percentage of maximum life span

Perc

en

tag

e o

f su

rviv

ors

(lo

g s

cale

)

0 50 1000.1

1

10

100

III

II

I


36.4 Idealized models predict patterns of population growth

Exponential growth model

– The rate of population increases under ideal conditions

– Calculated using the equation G = rN

– G is the growth rate of the population

– N is the population size

– r is the per capita rate of increase

Time (months)

Po

pu

lati

on

siz

e (

N)

0 1 2 3 4 5 6 7 8 9 10 11 120

50

100

150

200

250

300

350

400

450

500


Logistic growth model

– This growth model takes into account limiting factors

– Limiting factors are environmental factors that restrict population growth

– Formula


(K N)G = rN

K

Year

Bre

ed

ing

male

fu

r seals

(th

ou

san

ds)

1915 1925 1935 19450

2

4

6

8

10

Year

1915 1925 1935 1945

Bre

ed

ing

male

fu

r seals

(th

ou

san

ds)

0

2

4

6

8

10


Idealized models describe two kinds of population growth

– Exponential growth

– Logistic growth


Time

Nu

mb

er

of

ind

ivid

uals

(N

)

0

K

G = rN

G = rN(K – N)

K


36.5 Multiple factors may limit population growth

The logistic growth model

– Population growth slows and ceases as population density increases

– Increasing population density results in a decrease in birth rate, an increase in death rate, or both

Density of females

Clu

tch

siz

e

0 10 20 30 40 50 60 70 802.8

3.0

3.2

3.4

3.6

3.8

4.0


Abiotic factors may reduce population size before other limiting factors become important


Apr May Jun Jul Aug Sep Oct Nov Dec

Nu

mb

er

of

ap

hid

s

Exponentialgrowth

Suddendecline


Most populations fluctuate in numbers


Time (years)

Nu

mb

er

of

fem

ale

s

1975 1980 1985 1990 1995 20000

20

40

60

80


36.6 Some populations have “boom-and-bust” cycles

Some populations fluctuate in density with regularity

Boom-and-bust cycles

– Food shortages

– Predator-prey interactions

Lynx

Snowshoe hare

Lyn

x p

op

ula

tio

n s

ize

(th

ou

sa

nd

s)

Ha

re p

op

ula

tio

n s

ize

(th

ou

san

ds)

Year

1850 1875 1900 19250

40

80

120

160

0

3

6

9


36.7 EVOLUTION CONNECTION: Evolution shapes life histories

Life history

– Series of events from birth to death

r/K selection

– r-selective traits

– K-selective traits

Males Females

Experimentaltransplant ofguppies

Predator: Killifish; preysmainly on small guppies

Guppies:Larger atsexual maturitythan those inpike-cichlid pools

Pools with killifish,but no guppies priorto transplant

Predator: Pike-cichlid preys mainly on large guppies

Guppies: Smaller at sexual maturity thanthose in killifish pools11 years

later

Ma

ss

of

gu

pp

ies

at

ma

turi

ty (

mg

)

40

80

120

160

200

67.5 76.1

161.5185.6

Ag

e o

f g

up

pie

sa

t m

atu

rity

(d

ays

)

Males Females

20

40

60

80

100

48.558.2

85.792.3 Control:

Guppies from poolswith pike-cichlidsas predators

Experimental:Guppies transplantedto pools with killifishas predators

Predator: Killifish; preysmainly on small guppies

Experimentaltransplant ofguppies

Guppies:Larger atsexual maturitythan those inpike-cichlid pools

Pools with killifish,but no guppies priorto transplant

Predator: Pike-cichlid preys mainly on large guppies

Guppies: Smaller at sexual maturity thanthose in killifish pools

Males Females

Mass o

f g

up

pie

sat

matu

rity

(m

g)

Males Females

40

80

120

160

200

67.5 76.1

161.5185.6

Ag

e o

f g

up

pie

sat

matu

rity

(d

ays)

20

40

60

80

100

48.558.2

85.792.3

Control:Guppies from poolswith pike-cichlidsas predators

Experimental:Guppies transplantedto pools with killifishas predators

11 yearslater


36.8 CONNECTION: Principles of population ecology have practical applications

Sustainable resource management

– Maximum sustained yield

1960

Yie

ld (

tho

usan

ds o

f m

etr

ic t

on

s)

1970 1980 1990 20000

100

200

300

400

500

600

700

800

900


THE HUMAN POPULATION


36.9 The human population continues to increase, but the growth rate is slowing

Human population is expected to continue increasing for several decades

95% of the increase is in developing nations

1500

Year

Population increase

Total population size

To

tal p

op

ula

tio

n (

in b

illio

ns

)

1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 20500

2

4

6

8

10

20

40

60

80

100

An

nu

al

inc

rea

se

(in

millio

ns

)

Year

Birth rateDeath rate

Rate of increase (r)

1900 19501925 1975 2000 2025 2050

0

10

20

30

40

50

Bir

th o

r d

eath

rate

per

1,0

00 p

op

ula

tio

n


Population momentum of Mexico

36.9 The human population continues to increase, but the growth rate is slowing

0 1 2 3 4 55 4 3 2 1 0 1 2 3 4 55 4 3 2 1

1980

Age

Male Female

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4

Population in millions

Total population size = 68,347,479



FemaleMale

2005 2030

FemaleMale



0 1 2 3 4 55 4 3 2 1

Age

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4

5 4 3 2 1 0 1 2 3 4 5

Population in millionsTotal population size = 68,347,479

1980

Male Female

5 4 3 2 1 0 1 2 3 4 5

Age

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4



FemaleMale

2005

5 4 3 2 1 0 1 2 3 4 5

Age

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4

2030

FemaleMale



36.10 CONNECTION: Age structures reveal social and economic trends

Age structure diagram

– Reveals a population’s growth trends

Age1980

Birth years Male Female

2005 2030

Birth years Male Female Birth years Male Female80+ before 1900 before 1926 before 1951

1951-551926-301901-190575-7970-74 1906-10 1931-35 1956-60

1961-651936-401911-1565-6960-6455-59

1916-20 1941-45 1966-701971-751946-501921-25

50-54 1926-30 1951-55 1976-801981-851956-601931-3545-49

40-44 1936-40 1961-65 1986-901991-951966-701941-4535-39

30-34 1946-50 1971-75 1996-20002001-051976-801951-5525-29

20-24 1956-60 1981-85 2006-102011-151986-901961-6515-19

10-14 1966-70 1991-95 2016-202021-251996-20001971-755-9

0-4 1976-80 2001-2005 2026-30

12 10 8 6 4 2 0 2 4 6 8 10 12



12 10 8 6 4 2 0 2 4 6 8 10 1212 10 8 6 4 2 0 2 4 6 8 10 12


1980Age Birth years Male Female80+

75-7970-74

before 19001901-19051906-10

65-69 1911-1560-64 1916-2055-59 1921-2550-54 1926-3045-49 1931-3540-44 1936-4035-39 1941-4530-3425-2920-24

1946-501951-55

1956-6015-19 1961-6510-14

5-90-4

1966-701971-751976-80

12 10 8 6 4 2 0 2 4 6 8 10 12


Age

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4


12 10 8 6 4 2 0 2 4 6 8 10 12


before 19261926-30

1931-351936-40

1941-451946-50

1951-551956-601961-65

1966-701971-751976-80

1981-851986-901991-95

1996-20002001-2005

2005

Age

80+75-7970-7465-6960-6455-5950-5445-4940-4435-3930-3425-2920-2415-1910-14

5-90-4


12 10 8 6 4 2 0 2 4 6 8 10 12


2030

before 19511951-55

1956-601961-651966-701971-75

1976-801981-85

1986-901991-95

1996-20002001-052006-102011-152016-202021-252026-30


36.11 CONNECTION: An ecological footprint is a measure of resource consumption

U.S. Census Bureau projection

– 8 billion people within the next 20 years

– 9.5 billion by mid-21st century


Ecological footprint helps understand resource availability and usage

The United States has a

– Big ecological footprint

– Large ecological deficit

36.11 CONNECTION: An ecological footprint is a measure of resource consumption

NorthAmerica

EuropeAsia

Africa

> 5.4 global ha per person

3.6–5.4 global ha per person



< 0.9 global ha per person

Insufficient data

SouthAmerica

Australia

Few large offspring,

low mortality

until old age

Many small

offspring,

high mortality

Percentage of maximum life span

Pe

rce

nta

ge

of

su

rviv

ors

III

II

I

G = rN(K N)

K

Time

Bir

th o

r d

eath

rate

III IVI II


You should now be able to

1. Explain the factors that determine the characteristics of a population

2. Describe exponential growth and the factors that produce logistic growth of a population

3. Explain the limiting factors that influence population growth

4. Distinguish between r- and K-strategies

5. Describe and give examples of the different types of life histories


6. Explain the factors the determine human population growth

7. Describe the concept of ecological footprint

You should now be able to

Documents

Chapter 36 Population Ecologycoachshannon.weebly.com/uploads/3/0/1/1/30116035/... · 36.1 Population ecology is the study of how and why populations change. ... 1210 8 6 4 2 0 2 4