Fig. 52-2

Organismalecology

Populationecology

Communityecology

Ecosystemecology

Landscapeecology

Globalecology

Introduction to Ecology Populations

• Population ecology– Abundance– Dynamics Density, dispersion, demographics, interrelationships with other populations

Population density

• The number of individuals per unit area or volume

Fig. 52-1a, p. 1128

(a) Random dispersion

Pattern of dispersion

• Refers to how individuals are spaced relative to one another

Fig. 52-1b, p. 1128

(b) Clumped dispersion

Pattern of dispersion

• Patchiness in resources

• Family groups• Reduce risk of

predation

Fig. 52-1c, p. 1128

(c) Uniform dispersion

Pattern of dispersion

• Aggressive interactions

• Competition

Population dynamics

• 4 primary factors that influence population size– Births– Deaths– Immigration– Emigration

• How do these factors affect the rate at which populations change?

Fig. 53-3

Births

Births and immigrationadd individuals toa population.

Immigration

Deaths and emigrationremove individualsfrom a population.

Deaths

Emigration

Fig. 53-3

Births

Births and immigrationadd individuals toa population.

Immigration

Deaths and emigrationremove individualsfrom a population.

Deaths

Emigration

– The age at which reproduction begins– How often the organism reproduces– How many offspring are produced during each

reproductive cycle

• evolutionary outcomes reflected in the development, physiology, and behavior of an organism – based on trade-offs

Life History

Age (years)20 4 86

10

101

1,000

100

Num

ber o

f sur

vivo

rs (l

og s

cale

)

Males

Females

A survivorship curve is a graphic way of representing the data in a life table

relatively constant death rate

Fig. 53-6

1,000

100

10

10 50 100

II

III

Percentage of maximum life span

Num

ber o

f sur

vivo

rs (l

og s

cale

) I

Fig. 53-9

(a) Dandelion

(b) Coconut palm

Fig. 52-2, p. 1130

Num

ber o

f bac

teria

(N)

Hours

Dynamics - Population growth

r = unchecked population growth

Fig. 52-13, p. 1139

2006: 6.5 billion

Hum

an p

opul

ation

(bill

ions

)

Black Death

Time (years)

Fig. 52-3, p. 1131

Carrying capacity of the environment (K)

Num

ber o

f ind

ivid

uals

(N)

Time

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

• Density-dependent– Density of population alters the affect of an

environmental condition• Density-independent– Effect of an environmental factor is not affected

by the density of a population

Factors influencing population size

Density-dependent factors

• Competition – interaction in which individuals try to use the same resource– Intraspecific– Interspecific

Density-dependent factors

Density-independent factors

Metapopulations

• Environments are heterogeneous– Resources are patchy– Several small populations

rather than 1 large • Not all patches are equal

– Less desirable may result in lower b or higher d

– More productive may lead to higher b and lower d

Fig. 52-12, p. 1138