Community Ecology Populations
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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.
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