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Lecture Presentation
Anne Gasc
Hawaii Pacific University and
University of Hawaii–Honolulu Community College
BIOLOGY OF HUMANSConcepts, Applications, and Issues
Fifth Edition
Judith Goodenough Betty McGuire
24Human Population,
Limited Resources,
and Pollution
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Human Population, Limited Resources, and
Pollution
OUTLINE:
Population Changes
Patterns of Population Growth
Environmental Factors and Population Size
Earth’s Carrying Capacity
Human Impacts on Earth’s Carrying Capacity
Global Climate Change
Looking to the Future
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Population Changes
Population size
Births increase population size
Deaths decrease population size
Birth rate
Number of births per a specified number of individuals in the
population during a specific time
Example: 20 births per 1000 individuals per year
The age at which a female has her first offspring has a
dramatic impact on the rate at which a population grows
This is the most important factor in determining a female’s
reproductive potential
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Population Growth Rate
Death rate
Number of deaths per a specified number of individuals
in the population during a specific time
Example: eight deaths per 1000 individuals per year
Growth rate
Difference between the birth rates and death rates of a
population
Example: (Births Deaths)/1000 (20 8)/1000 1.2%
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Population Growth Rate
Size of the starting population affects how quickly
new individuals will be added
At the same growth rate, the larger the size of the
starting population, the more individuals produced
Age structure
Relative number of individuals of each age
Important because only individuals within a certain
age range can reproduce
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Figure 24.2 Age structures of Afghanistan, the United States,
and Canada.
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Immigration and Emigration
Individuals also can be added to a population by
immigration
Arrival of individuals from other populations
Individuals also can be lost from a population by
emigration
Exodus of individuals from a population
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Immigration and Emigration
Web Activity: Age Structure and Population Growth
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Patterns of Population Growth
Exponential growth
Unrestricted growth at a constant rate
Occurs in environments with plenty of resources and
adequate waste removal
J-shaped growth curve
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Patterns of Population Growth
Carrying capacity
Number of individuals of a given species that a
particular environment can support for a prolonged
period
Determined by many factors:
Availability of resources (food, water, space)
Ability to remove wastes
Predation pressure
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Patterns of Population Growth
Logistic growth
Growth slows as population approaches carrying
capacity and eventually levels off
S-shaped growth curve
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Patterns of Population Growth
Web Activity: Human Population Growth
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Figure 24.3 Population growth is often restrained by environmental
factors.
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Figure 24.4 The human population has grown steadily throughout
most of human history.
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Environmental Factors and Population Size
Environmental factors regulate population size
Density-independent regulating factors
Events that cause death that are not related to
population density
Natural disasters such as hurricanes, earthquakes, and
fires
Density-dependent regulating factors
Events that have a greater impact on the population as
conditions become more crowded
Food scarcity
Disease
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Earth’s Carrying Capacity
Earth’s carrying capacity for humans depends on
Natural constraints such as resource availability
Human activities and choices
Estimates range from 5 to 20 billion people
In mid 2010, there were 6.8 billion people on Earth
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Human Impacts on Earth’s Carrying Capacity
Ecological footprint
A measure of the amount of productive land and
water required to support a person or population
based on consumption levels
Calculation of an ecological footprint includes
everything that is consumed and the corresponding
waste removal
More affluent people or populations typically have
larger ecological footprints
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Figure 24.6 Ecological footprint.
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Agricultural Advances
The green revolution
Development of high-yield varieties of crops and use
of modern cultivation methods
Benefit: increased crop production
Costs: requires more energy and causes more
environmental damage
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Figure 24.7 Desertification.
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Depletion of Resources
Depletion of resources
Desertification
Overfarming and overgrazing transform marginal farmland
into desert
Soil erosion
Deforestation
Removal of trees without replacing them
Tropical forests most affected
Results in decline in soil fertility
Overfishing
Leading to depleted fish populations
Worldwide, 70% of fisheries are overexploited
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Figure 24.8 Deforestation.
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Water Shortage
Water shortages
97% of Earth’s water is in the oceans
Freshwater scarcity is an emerging crisis
Water footprint
Indicator of direct and indirect water use by a person,
locality, or nation
Direct use
Water use at home
Indirect use
Water used to produce goods and services
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Water Shortage
Irrigation
Benefit: allows crops to grow in areas that would
otherwise be barren
Cost: salinization
Irrigation water contains dissolved minerals that stay in
the soil
When water evaporates from the soil, salts accumulate
Worldwide, salinization destroys the fertility of 5000 km2
(1930 mi2) of irrigated land each year
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Water Shortage
Steps to reduce water shortages
Reduce water use
Raise the price of water
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Pollution
Water pollution
Surface water: mercury, PCBs, fertilizers
Groundwater: leaks from underground tanks and septic
systems
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Ozone Pollution and Ozone Depletion
Ozone: gas, O3
Can be an air pollutant at Earth’s surface (component of
photochemical smog)
Naturally produced ozone is an essential part of the
stratosphere: shields Earth from excessive UV radiation
Ozone depletion: chlorofluorocarbons (CFCs) are the
primary culprit responsible for the destruction of the ozone
layer in the stratosphere
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Figure 24.9 The thinning of the ozone layer.
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Global Climate Change
Climate describes a region’s average temperature,
precipitation, humidity, solar radiation, etc.
Global climate change
Changes in Earth’s climate patterns
Two key conclusions of Intergovernmental Panel on
Climate Change (IPCC)
Global climate is getting warmer
Most of the increase in global temperature is due to
human activity that releases greenhouse gases into
the atmosphere
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Global Warming and Greenhouse Gases
Greenhouse gases include
Carbon dioxide
Methane
Nitrous oxides
CFCs
Trap heat in the atmosphere
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Figure 24.10 Greenhouse gases promote global warming.
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Figure 24.11 The concentration of CO2 in the atmosphere has
been increasing for many years.
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Global Warming and Greenhouse Gases
Possible consequences of global warming
Melting polar ice caps cause rising sea levels
Flooding of coastal cities
Warmer oceans
Changing weather patterns
Warmer oceans may fuel more hurricanes
Altered distribution of climax communities
Negative impacts on human health
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Carbon Footprint
Carbon footprint is a measure of the amount of CO2
entering the atmosphere due to a person’s or a
nation’s daily activities
Important to reduce your individual (direct) carbon
footprint and for nations to reduce the global carbon
footprint
Reducing reliance on fossil fuels is key
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Figure 24.12 Possible causes of global climate change.
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Looking to the Future
Our future depends on the decisions we make today
Humans must realize that Earth’s resources are
limited and must be shared with all living things
Requires changes in the way governments and
businesses operate and the ways in which individuals
think
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Looking to the Future
Humans are a small part of a large ecosystem
We must find ways to work within natural laws to
preserve ecosystem Earth and its biodiversity
Jane Goodall’s optimism about our future is
based on
Human brain
Resilience of nature
Energy and enthusiasm of young people
Indomitable human spirit
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You Should Now Be Able To:
Understand population changes
Know the patterns of population growth
List environmental factors and population size
Define Earth’s carrying capacity
Understand human impacts on Earth’s carrying
capacity
Explain global climate change
Look to the future!