Download 4-1

SUSTAINING THE
MILLER/SPOOLMAN
EARTH | G. TYLER MILLER | SCOTT E. SPOOLMAN
11e
4
Community Ecology,
Population Ecology,
and the Human
Population
© Cengage Learning 2015
4-1 What Roles Do Species Play in
Ecosystems?
• Each species plays a role in its ecosystem
– Ecological niche (niche)
• Species’ way of life in a community: everything that
affects survival and reproduction, e.g., sunlight,
water, space, food, predators, and temperature
– Generalist species
• Broad niches: wide range of tolerance
– Specialist species
• Narrow niches: narrow range of tolerance
© Cengage Learning 2015
Black skimmer
seizes small fish
at water surface
Flamingo
feeds on
minute
organisms
in mud
Stepped Art
Fig. 4-1
Brown pelican
dives for fish,
Avocet sweeps bill
which it locates through mud and
from the air
surface water in
search of small
crustaceans,
insects, and seeds
Scaup and other
diving ducks
feed on
mollusks,
crustaceans,
and aquatic
vegetation
Louisiana
heron wades
into water to
seize small
fish
Herring
gull is a
Ruddy
tireless
turnstone
scavenger
searches
Dowitcher probes
under shells
deeply into mud in
and pebbles
search of snails,
for small
marine worms, and
invertebrates
small crustaceans
Oystercatcher feeds
on clams, mussels,
and other shellfish
into which it pries
its narrow beak
Knot (sandpiper)
picks up worms
and small
crustaceans left
by receding tide
Piping plover
feeds on insects
and tiny
crustaceans on
sandy beaches
Case Study: The Giant Panda—A Highly
Endangered Specialist
• 1,600 to 3,000 giant pandas in the wild
– Most in China
• Specialist species
– Requires bamboo stalks and leaves as food
• Low reproductive rate
• Threats
– Limited range of bamboo forests
– Poaching
© Cengage Learning 2015
Species Can Play Four Major Roles within
Ecosystems
• Native species
• Nonnative species (invasive, alien, and
exotic species)
• Indicator species
• Keystone species
© Cengage Learning 2015
Indicator Species Serve as Biological
Smoke Alarms
• Indicator species
– Provide early warning of damage to a
community
– Widespread
– Affected quickly by environmental changes
– Examples:
• Birds
• Butterflies
• Some amphibians
© Cengage Learning 2015
Science Focus: Why Are Amphibians
Vanishing?
• Natural and human-caused factors
− Parasites
− Viral and fungal
diseases
– Increases in UV
radiation
– Pollution
− Parasites
– Overhunting
− Habitat loss and
fragmentation
– Nonnative
predators and
competitors
− Prolonged drought
© Cengage Learning 2015
Keystone and Foundation Species Play
Critical Roles in Their Ecosystems
• Keystone species
– Roles have a large effect on the types and
abundances of other species
• Pollinators
• Top predators
– Vulnerable to extinction
• Loss of a keystone species can lead to population
crashes and other species’ extinctions
© Cengage Learning 2015
Case Study: Why Should We Protect
Sharks?
• Keystone species
• Shark studies could help save human lives
– Sharks rarely get cancer
– Highly effective immune system
• Three largest species
– Plant-eaters
• 100 million sharks killed every year
– Among most vulnerable and least protected
© Cengage Learning 2015
4-2 How Do Species Interact?
• Species interact in five major ways
– Interspecific competition
• Resource partitioning
– Predation
– Parasitism
– Mutualism
– Commensalism
© Cengage Learning 2015
Blackburnian BlackWarbler
throated
Green
Warbler
Cape
May
Warbler
Baybreasted
Warbler
Resource partitioning
Fig. 4-2
Yellowrumped
Warbler
Most Consumer Species Feed on
Organisms of Other Species
• Predation
– Predator–prey relationships
– Plays a role in evolution by natural selection
– Predators play an important ecological role
© Cengage Learning 2015
Some Species Feed off Other Species by
Living on or in Them
• Parasitism
• Parasite is usually much smaller than the
host
• Parasite rarely kills the host
– In some cases, parasites help to keep the
hosts’ populations in check
+
© Cengage Learning 2015
-
In Some Interactions, Both Species Benefit
•
•
•
•
•
Mutualism
Nutrition and protection relationship
Gut inhabitant mutualism
Mutual exploitation
Example: clownfish and sea anemones
© Cengage Learning 2015
+
+
In Some Interactions, One Species
Benefits and the Other Is Not Harmed
• Commensalism
• Example: epiphytes attach to the trunks of
large trees in tropical forests
+ 0
© Cengage Learning 2015
4-3 How Do Communities and Ecosystems
Respond to Changing Conditions?
• Communities and ecosystems change
over time: ecological succession
– Primary succession
– Secondary succession
• Primary succession and secondary
succession
– Tend to increase biodiversity and interactions
among species
© Cengage Learning 2015
Lichens and
Exposed mosses
rocks
Fig. 4-4
Small herbs
and shrubs
Heath mat
Jack pine,
black spruce,
and aspen
Balsam fir,
paper birch,
and white
spruce forest
community
Annual
weeds
Stepped Art
Fig. 4-5
Perennial
weeds and
grasses
Shrubs and
small pine
seedlings
Young pine forest
with developing
understory of oak
and hickory trees
Mature oak and hickory
forest
4-4 What Limits the Growth of
Populations?
• Populations can grow, shrink, or remain
stable
– Population change =
(births + immigration) – (deaths + emigration)
• Biotic potential
• Intrinsic rate of increase
– Population growth rate with unlimited
resources
© Cengage Learning 2015
Populations Can Grow, Shrink, or Remain
Stable
• Limiting factors
– Physical or chemical environmental conditions
• Environmental resistance
– All factors that act to limit the growth of a
population
• Carrying capacity
– Maximum population a given habitat can
sustain
© Cengage Learning 2015
Number of sheep (millions)
2.0
1.5
1.0
Population
overshoots
carrying capacity
Carrying
capacity
Population
recovers and
Population runs stabilizes
Exponential out of resources
growth
and crashes
.5
1800
Fig. 4-6
Environmental resistance
1825
1850
1875
Year
1900
1925
When a Population Exceeds Its Habitat’s
Carrying Capacity It Can Crash
• A population exceeds the area’s carrying
capacity
– Population crash (dieback)
– Damage may reduce area’s carrying capacity
• Area’s carrying capacity
– Can rise or decline seasonally and from year
to year
© Cengage Learning 2015
Population
overshoots
carrying
capacity
Number of reindeer
2,000
1,500
Population
crashes
1,000
500
0
Fig. 4-7
Carrying
capacity
1910
1920
1930
Year
1940
1950
Species Have Different Reproductive
Patterns
• Opportunist species
– Many, usually small, offspring
– Little or no parental care
– Massive deaths of offspring
– Examples: algae, bacteria, and insects
© Cengage Learning 2015
Species Have Different Reproductive
Patterns
• Competitor species
– Reproduce later in life
– Small number of offspring with long life spans
– Young offspring develop inside their mothers
– Long time to maturity
– Protected by parents and potentially groups
– Examples: elephants, whales, and humans
© Cengage Learning 2015
4-5 What Factors Influence the Size of the
Human Population?
• Human population growth continues but it
is unevenly distributed
– Reasons for human population increase
• Movement into new habitats and climate zones
• Emergence of early and modern agriculture
methods
• Control of infectious diseases through sanitation
systems, antibiotics, and vaccines
© Cengage Learning 2015
Human Population Growth Continues but It
Is Unevenly Distributed
• World population is growing exponentially
– Rate of 1.2 percent a year
– Projected population by 2050: 9.6 billion
– More-developed countries (2012):
0.1 percent yearly growth rate
– Less-developed countries (2012):
1.5 percent yearly growth rate
• Least equipped to deal with rapid growth
© Cengage Learning 2015
World population (in billions)
Population in less-developed countries
Population in more-developed countries
Year
Fig. 4-9
Fig. 6-3, p. 123
Women Having Fewer Babies but Not Few
Enough to Stabilize the World’s Population
• Fertility rate
• Replacement-level fertility rate
– Rate is higher in less-developed countries
• Total fertility rate (TFR)
– Plays a key role in determining population
size
How many children does a woman need
to have to keep the population the same?
© Cengage Learning 2015
Case Study: The U.S. Population—
Third-Largest and Growing
• Population still growing
– 76 million in 1900
– 310 million in 2010
• Drop in TFR in U.S.
– Population growth rate has slowed
• The U.S. has the world’s largest total and
per capita ecological footprint
© Cengage Learning 2015
Births per woman
Fig. 4-11
Baby boom
(1946–64)
Replacement
level
47 years
Life expectancy
77 years
Married women working
outside the home
8%
81%
15%
High school
graduates
83%
10%
Homes with flush
toilets
Homes with
electricity
Living in
suburbs
Hourly manufacturing job
wage (adjusted for inflation)
Homicides per
100,000 people
Stepped Art
Fig. 4-12
98%
2%
99%
10%
52%
$3
1900
2000
$15
1.2
5.8
Several Factors Affect Birth Rates and
Fertility Rates
•
•
•
•
•
Children as part of the labor force
Cost of raising and educating children
Availability of private and public pension
Urbanization
Educational and employment opportunities
for women
© Cengage Learning 2015
Several Factors Affect Birth Rates and
Fertility Rates
• Availability of legal abortions
• Availability of reliable birth control methods
• Religious beliefs, traditions, and cultural
norms
© Cengage Learning 2015
Several Factors Affect Death Rates
• Life expectancy
– U.S. ranks 32nd among nations
• Infant mortality rate
– Based on live births that die in first year
– Impacted by undernutrition and malnutrition
– U.S. ranks 44th among nations due to
• Inadequate health care for poor women during
pregnancy and for infants after birth
• Drug addiction among pregnant women
© Cengage Learning 2015
Migration Affects an Area’s Population
Size
• Immigration and emigration
• Reasons for movement
– Economic
– Religious
– Ethnic
– Political
– Wars
– Environmental
© Cengage Learning 2015
World population (in billions)
Science Focus: Projecting Population
Change
UN high-fertility variant (2008 revision)
U.S. Census Bureau (2008 update)
UN medium-fertility variant (2008 revision)
IIASA (2007 update)
UN low-fertility variant (2008 revision)
Year
Fig. 4-B
Population Age Structure Can Affect
Growth or Decline
• Age structure categories
– Prereproductive ages (0-14)
– Reproductive ages (15-44)
– Postreproductive ages (45 and older)
• Seniors (ages 65+)
– Fastest-growing age group in the U.S.
© Cengage Learning 2015
Male
Female
Expanding Rapidly
Guatemala Nigeria
Saudi Arabia
Prereproductive
ages 0–14
Fig. 4-13
Male
Female
Expanding Slowly
United States
Australia China
Reproductive
ages 15–44
Male
Female Male
Stable Japan
Italy Greece
Female
Declining Germany
Bulgaria Russia
Postreproductive
ages 45–85+
Fig. 6-11, p. 131
Case Study: The American Baby Boom
Growing senior population: the graying of
America
Fig. 4-14
Populations Made Up of Mostly Older
People Can Decline Rapidly
• Severe effects
– Fewer adults working and paying taxes to
support an increasing elderly population
• Countries facing rapid decline
– Japan, Russia, Germany, Bulgaria, Hungary,
Ukraine, Serbia, Greece, Portugal, and Italy
© Cengage Learning 2015
Some Problems with Rapid
Population Decline
Can threaten economic growth
Labor shortages
Less government revenues with fewer
workers
Less entrepreneurship and new
business formation
Less likelihood for new technology
development
Increasing public deficits to fund higher
pension and health-care costs
Pensions may be cut and retirement age
increased
Fig. 4-15
4-6 How Can We Slow Human Population
Growth?
• Is the earth overpopulated? An important
controversy
– Can the world provide an adequate standard
of living for a projected 2.5 billion more people
by 2050 without causing widespread
environmental damage?
• Population regulation
– Opponents and proponents
© Cengage Learning 2015
Birth rate and death rate
(number per 1,000 per year)
Stage 1
Preindustrial
Stage 2
Transitional
Population
grows very
slowly because
of a high
birth rate
(to compensate
for high infant
80 mortality) and a
70 high death rate
Stage 3
Industrial
Population grows rapidly
because birth rates are high and
death rates drop because of
improved food production and
health
Stage 4
Postindustrial
Population growth
slows as both birth
and death rates
drop because of
improved food
production, health,
and education
Population growth
levels off and then
declines as birth
rates equal and
then fall below
death rates
Total population
60
Birth rate
50
40
30
Death rate
20
10
0
Low
Increasing
Very high
Decreasing
Growth rate over time
Stepped Art
Fig. 4-17
Low
Zero
Negative
Empowering Women Helps to Slow
Population Growth
• Factors that decrease total fertility rates
– Education
– Paying jobs
– Rights supported
• Women’s roles
– Do most of the domestic work and child care
– Provide unpaid health care within families
• Bottom-up change in taking charge
© Cengage Learning 2015
Family Planning Can Provide Several
Benefits
• Educational and clinical services
– Responsible for a 56 percent drop in TFRs in
less-developed countries (1960-2012)
• Issues in less-developed countries
– 42 percent of all pregnancies unplanned,
26 percent end with abortion
– Many couples lack access to family planning
© Cengage Learning 2015
Is It Possible to Reduce Population
Growth?
• United Nations’ Conference on Population
and Development goals by 2015
– Provide universal access to family planning
and reproductive health care
– Improve health care for infants, children, and
pregnant women
– Implement national population policies
– Improve the status of women
© Cengage Learning 2015
Is It Possible to Reduce Population
Growth?
• Goals by 2015
– Increase the involvement of men in
child-rearing
– Sharply reduce poverty
– Sharply reduce unsustainable patterns of
production and consumption
© Cengage Learning 2015
Case Study: India’s Attempts to Slow Its
Population Growth
• Projected 1.69 billion people by 2015
– Most populous country
• Problems: poverty, malnutrition,
environmental degradation
• Factors for larger families
– Poor couples want many children
• Work and care for parents in old age
– Bias toward having male children
© Cengage Learning 2015
Case Study ─ Slowing Population Growth
in China: the One-Child Policy
• Projected 1.4 billion people by 2026
• Promotes one-child families
– Free sterilization, contraceptives, and abortion
• Fast-growing economy since 1980
– Rapidly growing middle class
– Need for more environmentally sustainable
economic development
• Concerns regarding the graying of China
© Cengage Learning 2015