Community Ecology, Population Ecology, and the Human Population

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Community Ecology, Population Ecology, and the
Human Population

• Chapter 4

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4-1 What Roles Do Species Play in Ecosystems?

• Concept 4-1A Each species plays a specific
  ecological role called its niche.
• Concept 4-1B Any given species may play one or
  more of five important rolesnative, nonnative,
  indicator, keystone, or foundation rolesin a
  particular ecosystem.

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Each Species Plays a Unique Role in Its Ecosystem

• Ecological niche, niche
• Pattern of living
• Generalist species
• Broad niche
• Specialist species
• Narrow niche

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Case Study Cockroaches Natures Ultimate
Survivors

• Cockroaches
• Generalists
• High reproductive rates
• Giant panda and tiger salamanders
• Specialists
• Low reproductive rates

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Niches Can Be Occupied by Native and Nonnative
Species

• Native species
• Nonnative species invasive, alien, or exotic
  species
• May spread rapidly
• Not all are villains

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Indicator Species Serve as Biological Smoke Alarms

• Indicator species
• Can monitor environmental quality
• Trout
• Birds
• Butterflies
• Frogs

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Case Study Why Are Amphibians Vanishing? (1)

• Habitat loss and fragmentation
• Prolonged drought
• Pollution
• Increase in UV radiation
• Parasites
• Viral and fungal diseases
• Climate change
• Overhunting
• Nonnative predators and competitors

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Case Study Why Are Amphibians Vanishing? (2)

• Importance of amphibians
• Sensitive biological indicators of environmental
  changes
• Adult amphibians
• Important ecological roles in biological
  communities
• Genetic storehouse of pharmaceutical products
  waiting to be discovered

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Keystone, Foundation Species Determine Structure,
Function of Their Ecosystems

• Keystone species
• Pollinators
• Top predator
• Foundation species
• Create or enhance their habitats, which benefit
  others
• Elephants
• Beavers

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Case Study Why Should We Protect Sharks?

• Keystone species
• Eat dead and dying fish in the ocean
• Strong immune systems
• Wounds do not get infected
• Almost never get cancer
• Could help humans if we understood their immune
  system

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How Do Species Interact?

• Concept 4-2 Five types of species
  interactionscompetition, predation, parasitism,
  mutualism, and commensalismaffect the resource
  use and population sizes of the species in an
  ecosystem.

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Species Interact in Five Major Ways

• Interspecific Competition
• Predation
• Parasitism
• Mutualism
• Commensalism

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Most Species Compete with One Another for Certain
Resources

• Competition
• Competitive exclusion principle

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Some Species Evolve Ways to Reduce Competition

• Resource partitioning
• Reduce niche overlap
• Use shared resources at different
• Times
• Places
• Ways

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Most Consumer Species Feed on Live Organisms of
Other Species (1)

• Predators may capture prey by
• Walking
• Swimming
• Flying
• Pursuit and ambush
• Camouflage
• Chemical warfare

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Most Consumer Species Feed on Live Organisms of
Other Species (2)

• Prey may avoid capture by
• Camouflage
• Chemical warfare
• Warning coloration
• Mimicry
• Deceptive looks
• Deceptive behavior

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Some Species Feed off Other Species by Living on
or in Them

• Parasitism
• Parasite-host interaction may lead to coevolution

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In Some Interactions, Both Species Benefit

• Mutualism
• Nutrition and protection relationship
• Gut inhabitant mutualism

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In Some Interactions, One Species Benefits and
the Other Is Not Harmed

• Commensalism
• Epiphytes
• Birds nesting in trees

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4-3 How Do Communities and Ecosystems Respond to
Changing Environmental Conditions?

• Concept 4-3 The structure and species
  composition of communities and ecosystems change
  in response to changing environmental conditions
  through a process called ecological succession.

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Communities and Ecosystems Change over Time
Ecological Succession

• Natural ecological restoration
• Primary succession
• Secondary succession

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Some Ecosystems Start from Scratch Primary
Succession

• No soil in a terrestrial system
• No bottom sediment in an aquatic system

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Some Ecosystems Do Not Have to Start from
Scratch Secondary Succession (1)

• Some soil remains in a terrestrial system
• Some bottom sediment remains in an aquatic system
• Ecosystem has been
• Disturbed
• Removed
• Destroyed

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Some Ecosystems Do Not Have to Start from
Scratch Secondary Succession (2)

• Primary and secondary succession
• Tend to increase biodiversity
• Increase species richness and interactions among
  species
• Primary and secondary succession can be
  interrupted by
• Fires
• Hurricanes
• Clear-cutting of forests
• Plowing of grasslands
• Invasion by nonnative species

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Succession Doesnt Follow a Predictable Path

• Traditional view
• Balance of nature and a climax community
• Current view
• Ever-changing mosaic of patches of vegetation
• Mature late-successional ecosystems
• State of continual disturbance and change

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4-4 What Limits the Growth of Populations?

• Concept 4-4 No population can continue to grow
  indefinitely because of limitations on resources
  and because of competition among species for
  those resources.

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Populations Can Grow, Shrink, or Remain Stable

• Population size governed by
• Births
• Deaths
• Immigration
• Emigration
• Population change
• (births immigration) (deaths
  emigration)

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No Population Can Grow Indefinitely J-Curves
and S-Curves (1)

• Biotic potential
• Low
• High
• Intrinsic rate of increase (r)
• Individuals in populations with high r
• Reproduce early in life
• Have short generation times
• Can reproduce many times
• Have many offspring each time they reproduce

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No Population Can Grow Indefinitely J-Curves
and S-Curves (2)

• Size of populations limited by
• Light
• Water
• Space
• Nutrients
• Exposure to too many competitors, predators or
  infectious diseases

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No Population Can Grow Indefinitely J-Curves
and S-Curves (3)

• Environmental resistance
• Carrying capacity (K)
• Exponential growth
• Logistic growth

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When a Population Exceeds Its Habitats Carrying
Capacity, Its Population Can Crash

• Carrying capacity not fixed
• Reproductive time lag may lead to overshoot
• Dieback (crash)
• Damage may reduce areas carrying capacity

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Species Have Different Reproductive Patterns

• r-Selected species, opportunists
• K-selected species, competitors

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4-5 What Factors Influence the Size of the Human
Population?

• Concept 4-5A Population size increases because
  of births and immigration and decreases through
  deaths and emigration.
• Concept 4-5B The average number of children born
  to women in a population (total fertility rate)
  is the key factor that determines population
  size.
• Concept 4-5C The numbers of males and females in
  young, middle, and older age groups determine how
  fast a population grows or declines.

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Human Population Growth Continues but It Is
Unevenly Distributed (1)

• Reasons for human population increase
• Movement into new habitats and climate zones
• Early and modern agriculture methods
• Control of infectious diseases through
• Sanitation systems
• Antibiotics
• Vaccines

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Human Population Growth Continues but It Is
Unevenly Distributed (2)

• Population growth in developing countries is
  increasing 15 times faster than developed
  countries
• By 2050, 97 of growth will be in developing
  countries
• Should the optimum sustainable population be
  based on cultural carrying capacity?

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The Human Population Can Grow, Decline, or Remain
Fairly Stable

• Population change
• Births fertility
• Deaths mortality
• Migration
• Population change
• (births immigration) (deaths emigration)
• Crude birth rate
• Crude death rate

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Women Are Having Fewer Babies but Not Few Enough
to Stabilize the Worlds Population

• Fertility rate
• Replacement-level fertility rate
• Total fertility rate (TFR)

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Case Study The U.S. Population Is Growing Rapidly

• Drop in TFR in U.S.
• Rate of population growth has slowed
• Population still growing and not leveling off
• Fourfold increase since 1900
• Changes in lifestyle in the U.S. during the 20th
  century

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Several Factors Affect Birth Rates and Fertility
Rates (1)

• 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

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Several Factors Affect Birth Rates and Fertility
Rates (2)

• Infant mortality rate
• Average age of a woman at birth of first child
• Availability of legal abortions
• Availability of reliable birth control methods
• Religious beliefs, traditions, and cultural norms

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Several Factors Affect Death Rates (1)

• Life expectancy
• Infant mortality rate
• Why are people living longer and fewer infants
  dying?
• Increased food supply and distribution
• Better nutrition
• Medical advances
• Improved sanitation

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Several Factors Affect Death Rates (2)

• U.S. infant mortality rate high due to
• Inadequate health care for poor women during
  pregnancy and their infants
• Drug addiction among pregnant women
• High birth rate among teenagers

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Migration Affects an Areas Population Size

• Economic improvement
• Religious freedom
• Political freedom
• Wars
• Environmental refugees

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Case Study The United States A Nation of
Immigrants

• Historical role of immigration in the U.S.
• Legal immigration
• Illegal immigration

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Populations Made Up Mostly of Young People Can
Grow Rapidly

• Age structure categories
• Prereproductive ages
• Reproductive ages
• Postreproductive ages

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We Can Use Age-Structure Information to Make
Population and Economic Projections

• Baby boomers
• Job market when they retire

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Populations Made Up of Mostly Older People Can
Decline Rapidly

• Slow decline
• Manageable
• Rapid decline
• Severe economic problems
• Severe social problems

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Populations Can Decline from a Rising Death Rate
The AIDS Tragedy

• 25 million killed by 2008
• Many young adults die loss of most productive
  workers
• Sharp drop in life expectancy
• International community called upon to
• Reduce the spread of HIV through education and
  health care
• Financial assistance and volunteers

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4-6 How Can We Slow Human Population Growth?

• Concept 4-6 Experience indicates that the most
  effective ways to slow human population growth
  are to encourage family planning, to reduce
  poverty, and to elevate the status of women.

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Core Case Study Are There Too Many of Us? (1)

• Estimated 2.4 billion more people by 2050
• Are there too many people already?
• Will technological advances overcome
  environmental resistance that populations face?
• Should populations be controlled?

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Core Case Study Are There TooMany of Us? (2)

• Will growing populations cause increased
  environmental stresses?
• Infectious diseases
• Biodiversity losses
• Water shortages
• Traffic congestion
• Pollution of the seas
• Climate change

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As Countries Develop, Their Populations Tend to
Grow More Slowly

• Demographic transition stages
• Preindustrial
• Transitional
• May lead to a demographic trap
• Industrial
• Postindustrial

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Planning for Babies Works

• Family Planning
• Responsible for a 55 drop in TFRs
• In developing countries
• Expansion of program
• Include teenagers, sexually active unmarried
  women, and men
• Slow and stabilize population growth
• Invest in family planning
• Reduce poverty
• Elevate the social and economic status of women

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Empowering Women Can Slow Population Growth

• Education
• Paying jobs
• Human rights without suppression
• For poor women the only holiday is when you are
  asleep

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Case Study Slowing Population Growth in China
the One-Child Policy

• Encourages fewer children
• Gender imbalance
• Fast-growing economy
• Face serious resource and environmental problems

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Case Study Slowing Population Growth in India

• Population control gender bias
• Poverty
• Malnutrition
• Environmental problems