population ecology

Community Ecology

Populations

Patterns of Human Population Growth

Age structure diagrams Population profiles Graph the numbers of people in different age

groups in the population

Male Female

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Slow GrowthUnited States

AustraliaCanada

Male Female

Ages 0-14 Ages 15-44 Ages 45-85+

© 2004 Brooks/Cole – Thomson Learning

Zero GrowthSpain

AustriaGreece

Negative GrowthGermanyBulgariaSweden

Male Female Male Female

Ages 0-14 Ages 15-44 Ages 45-85+

© 2004 Brooks/Cole – Thomson Learning

6

100+

95-99

90-94

85-89

80-84

75-79

70-74

65-69

60-64

55-59

50-54

45-49

40-44

35-39

30-34

25-29

20-24

15-19

10-14

5-9

0-4

Male

Female

Percent of population 1900

Age

5 4 3 2 1 0 1 2 3 4 5 6

US Population Growth

100+

95-99

90-94

85-89

80-84

75-79

70-74

65-69

60-64

55-59

50-54

45-49

40-44

35-39

30-34

25-29

20-24

15-19

10-14

5-9

0-4

Male

Female

Percent of population 2000

Age

5 4 3 2 1 0 1 2 3 4 5

100+

95-99

90-94

85-89

80-84

75-79

70-74

65-69

60-64

55-59

50-54

45-49

40-44

35-39

30-34

25-29

20-24

15-19

10-14

5-9

0-4

Percent of population 2050

Age

4 3 2 1 0 1 2 3 4

Age Age

Females Males

1955

20 1612

84

48

1216

20

2420

1612

84

48

1216 20

24

Females Males

1985

Millions Millions

© 2004 Brooks/Cole – Thomson Learning

1955

Age

2420

1612

84

48

1216 20

20

Females Males

Age

Females Males

1955

2420

1612

84

48

1216 20

20

2035

MillionsMillions

© 2004 Brooks/Cole – Thomson Learning

2015

Changes in a Population

3 factors determine population changes births deaths migration

immigration emigration

Human Population Growth

J curve growth grows at a rate of about 80 million

yearly (r=1.3%)

Population Growth

Developing countries are expected to account

for 97% of the population added from

1950 to 2100

U.S. 310,728,519World 6,882,190,241

Economic Development

Trade-Offs

Good News Bad News

Global life expectancy doubled since 1950

Life expectancy 11 years less in developing countries than in

developed countries

Food production ahead of population growth since 1978

Harmful environmental effects of agriculture may limit future food

production

Infant mortality cut in half since 1955

Air and water pollution down in most developed countries since

1970

Number of people living in poverty dropped 6% since 1990

Infant mortality rate in developing countries over 8 times higher than in

developed countries

Air and water pollution levels in most developing countries too

high

Half of world’s people trying to live on less than $3

(U.S.) per day

Ecological Footprint

Humanity’s ecological footprint per person exceeds the earth’s biological capacity to replenish renewable

resources and absorb waste by about 15%!!!

What is your Footprint?

http://www.earthday.net/footprint/flash.html

Survivorship

three types of survivorship curves late loss (Type I)

have a high survival rate of the young, live out most of their expected life span and die in old age.

constant loss (Type II) relatively constant death rate throughout their life span -

death could be due to hunting or diseases.

early loss (Type III) have many young, most of which die very early in their

life.

Population Growth and Regulation carrying capacity (K)

determined byrenewable resources like water,

nutrients, and lightnonrenewable resources such as

space

Logistic growth: exponential growth when resources are unlimited and slowed growth as species approach carrying capacity of environment. Growth curve called an S-curve because of its

shape. Environmental resistance: factors that tend

to reduce population growth rates.

Strategies of Population Growth r-adapted species (adapted for high rates

of growth) Insects, rodents, marine invertebrates,

parasites, and annual plants K-adapted species (adapted for living at

or near carrying capacity) Wolves, elephants, whales, and primates

r- and K-Stratigies

Characteristics of contrasting reproductive strategies

r-adapted species K-adapted species

1.Short life 2.Rapid growth 3.Early maturity 4.Many small offspring 5.Little parental care or protection 6.Little investment in individual offspring 7.Adapted to unstable environment 8.Pioneers, colonizers 9.Niche generalists 10.Prey 11.Regulated mainly by extrinsic factors 12.Low trophic level

1.Long life 2.Slower growth 3.Late maturity 4.Fewer large offspring 5.High parental care and protection 6.High investment in individual offspring 7.Adapted to stable environment 8.Later stages of succession 9.Niche specialists 10.Predators 11.Regulated mainly by intrinsic factors 12.High trophic level

Community Structure

Individuals within a population can be distributed randomly, clumped together, or in highly regular patterns.

Communities in Transition

Ecological succession: process by which organisms occupy a site and gradually change environmental conditions by creating soil, shelter, and increasing humidity. Primary succession: community begins to

develop on a site previously unoccupied by living organisms.

Secondary succession: existing community is disrupted and a new one develops.