chapter 53

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PowerPoint® Lecture Presentations for

Biology Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Chapter 53Chapter 53

Population Ecology

Demography - study of the vital statistics of a population and how they change over time

Fig. 53-3

Births

Births and immigrationadd individuals toa population.

Immigration

Deaths and emigrationremove individualsfrom a population.

Deaths

Emigration

Density - number of individuals per unit area or volume

Fig. 53-4

(a) Clumped

(b) Uniform

(c) Random

Dispersion - pattern of spacing among individuals within the boundaries of the population

influenced by resource availability and behavior

Territoriality

absence of strong attractions or repulsions

Life table - age-specific summary of the survival pattern of a population

Cohort - group of individuals of the same age

Age (years)20 4 86

10

101

1,000

100

Nu

mb

er o

f su

rviv

ors

(lo

g s

cale

)

Males

Females

Survivorship curve - graphic way of representing life table data

Fig. 53-6

1,000

100

10

10 50 100

II

III

Percentage of maximum life span

Nu

mb

er

of

su

rviv

ors

(lo

g s

ca

le)

I

Table 53-2

Reproductive table (fertility schedule) -age-specific summary of the reproductive rates


Concept 53.2: Life history traits are products of natural selection

• Life history - traits that affect schedule of reproduction and survival:

– age at which reproduction begins

– How often the organism reproduces

– How many offspring are produced during each reproductive cycle

• Life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organism

Fig. 53-7

•Semelparity (aka big-bang reproduction) - reproduce once and die

•Highly variable or unpredictable environments

•Iteroparity (aka repeated reproduction) produce offspring repeatedl)

•dependable environments


“Trade-offs” and Life Histories

• Organisms have finite resources, which may lead to trade-offs between survival and reproduction

• Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce

• Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established

• In animals, parental care of smaller broods may facilitate survival of offspring

Fig. 53-9

(a) Dandelion

(b) Coconut palm

Fig. 53-12

2,000

1,500

1,000

500

00 5 10 15

Number of generations

Po

pu

lati

on

siz

e (N

)

Exponentialgrowth

1.0N=dN

dt

1.0N=dN

dt

K = 1,500

Logistic growth1,500 – N

1,500

Fig. 53-13b

Nu

mb

er

of Daphnia

/50

mL

0

30

60

90

180

150

120

0 20 40 60 80 100 120 140 160

Time (days)

(b) A Daphnia population in the lab


The Logistic Model and Life Histories

• Life history traits favored by natural selection may vary with population density and environmental conditions

• K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density

• r-selection, or density-independent selection, selects for life history traits that maximize reproduction


Population Change and Population Density

• In density-independent populations, birth rate and death rate do not change with population density

• In density-dependent populations, birth rates fall and death rates rise with population density

Fig. 53-15

(a) Both birth rate and death rate vary.

Population density

Density-dependentbirth rate

Equilibriumdensity

Density-dependentdeath rate

Bir

th o

r d

eath

ra

tep

er c

ap

ita

(b) Birth rate varies; death rate is constant.

Population density

Density-dependentbirth rate

Equilibriumdensity

Density-independentdeath rate

(c) Death rate varies; birth rate is constant.

Population density

Density-dependentdeath rate

Equilibriumdensity

Density-independentbirth rate

Bir

th o

r d

eath

ra

tep

er c

ap

ita


Density-Dependent Population Regulation

• Density-dependent birth and death rates are an example of negative feedback that regulates population growth

• They are affected by many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors

• In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate


Territoriality

• In many vertebrates and some invertebrates, competition for territory may limit density

• Cheetahs are highly territorial, using chemical communication to warn other cheetahs of their boundaries

• Oceanic birds exhibit territoriality in nesting behavior

Fig. 53-17

(a) Cheetah marking its territory

(b) Gannets


Disease and Predation

• Population density can influence the health and survival of organisms

• In dense populations, pathogens can spread more rapidly

• As a prey population builds up, predators may feed preferentially on that species


Population Dynamics

• The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size

• Long-term population studies have challenged the hypothesis that populations of large mammals are relatively stable over time

• Weather can affect population size over time

Fig. 53-20

Snowshoe hare

Lynx

Nu

mb

er

of

lyn

x(t

ho

us

an

ds

)

Nu

mb

er

of

ha

res

(th

ou

sa

nd

s)

160

120

80

40

01850 1875 1900 1925

Year

9

6

3

0

•Changes in predation pressure can drive population fluctuations

•Some populations undergo regular boom-and-bust cycles

Fig. 53-21

AlandIslands

EUROPE

Occupied patchUnoccupied patch5 km

˚Metapopulations - groups of populations linked by immigration and emigration

Rapid growthAfghanistan

Male Female Age AgeMale Female

Slow growthUnited States

Male Female

No growthItaly

85+80–8475–7970–74

60–6465–69

55–5950–5445–4940–4435–3930–3425–2920–2415–19

0–45–9

10–14

85+80–8475–7970–74

60–6465–69

55–5950–5445–4940–4435–3930–3425–2920–2415–19

0–45–9

10–14

10 10 8 866 4 422 0Percent of population Percent of population Percent of population

66 4 422 08 8 66 4 422 08 8

One important demographic factor in present and future growth trends is a country’s age structure

Fig. 53-26

Less indus-trialized

countries

Indus-trialized

countries

60

50

40

30

20

10

0 0

20

40

80

Lif

e ex

pec

tan

cy (

year

s)

Infa

nt

mo

rtal

ity

(dea

ths

per

1,0

00 b

irth

s)

Less indus-trialized

countries

Indus-trialized

countries

60

Fig. 53-27

Log (g carbon/year)

13.49.85.8

Not analyzed

http://www.myfootprint.org/http://www.footprintnetwork.org/en/index.php/GFN/page/personal_footprint/

Ecological footprint - aggregate land and water area needed to sustain the people of a nation

http://www.myfootprint.org/

http://www.footprintnetwork.org/en/index.php/GFN/page/personal_footprint/

http://www.footprintnetwork.org/en/index.php/GFN/page/personal_footprint/

chapter 53

Documents