PowerLecture: Chapter 25

1
PowerLectureChapter 25

• Ecology and
• Human Concerns

2
Learning Objectives

• Understand how materials and energy enter, pass
  through, and exit an ecosystem.
• Describe how communities are organized, how they
  develop, and how they diversify.
• Understand the various trophic roles and levels.
• Diagram the principal biogeochemical cycles.
• Learn the language associated with the study of
  population ecology.

3
Learning Objectives (contd)

• Understand the factors that affect population
  density, distribution, and change.
• Understand the meaning of logistic growth.
• Know the problems associated with the growth of
  human populations. Tell which factors have
  encouraged growth in some cultures and limited
  growth in others.
• Understand the magnitude of pollution problems in
  the United States.

4
Learning Objectives (contd)

• Examine the effects modern agricultural
  techniques have on different ecosystems.
• Describe how our use of fossil fuels and nuclear
  energy affects ecosystems.

5
Impacts/Issues

• The Human Touch

6
The Human Touch

• At one time as many as 15,000 people lived on
  Easter Island.
• The tiny island could not support this many
  people.
• Crop yields declined soil nutrients were
  depleted.
• Large statues were erected to appease the gods.
• The population dwindled and then disappeared as
  people turned against each other.

7
Video Easter Island
CLICKTO PLAY

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

8
How Would You Vote?

• To conduct an instant in-class survey using a
  classroom response system, access the Polls
  Clicker Questions from the PowerLecture main
  menu.
• Are you willing to pay extra for green
  products?
• a. Yes, I would be willing to pay more for
  sustainable products.
• b. No, I would not be willing to pay more for
  green products.

9
Section 1

• Some Basic Principles
• of Ecology

10
Some Basic Principles of Ecology

• The biosphere encompasses the earths crust,
  atmosphere, and waters that support life a biome
  is one of the major realms of life, such as
  deserts or rain forests.

Figure 25.1
11
Animation Major Biomes
CLICKTO PLAY
12
Animation Terrestrial Biomes
CLICKTO PLAY
13
Some Basic Principles of Ecology

• Ecology is the study of the interactions of
  organisms with one another and with the physical
  environment.
• A habitat is the place where a species normally
  lives it is characterized by distinctive
  physical features and vegetation.
• Humans live in disturbed habitats, places we have
  modified to suit our own purposes.
• A community is the collection of all the
  populations in a given habitat.

14
Some Basic Principles of Ecology

• The niche refers to a range of physical and
  biological conditions under which a species can
  live and reproduce.
• Specialist species have narrow niches.
• Generalists have broad ranges of habitats and
  niches.

15
Some Basic Principles of Ecology

• An ecosystem consists of one or more communities
  interacting with one another and with the
  physical environment.
• Communities
• of organisms
• make up the
• biotic, or
• living, portions
• of an
• ecosystem.

Figure 25.2
16
Some Basic Principles of Ecology

• Succession is the orderly progression of species
  changes that leads to a climax community.
• In primary succession, changes begin when pioneer
  species colonize a barren habitat.
• In secondary succession, a community
  reestablishes itself toward a climax state after
  a disturbance.

Figure 25.3
17
Animation Two Types of Ecological Succession
CLICKTO PLAY
18
Animation Levels of Organization
CLICKTO PLAY
19
Video Frogs Galore
CLICKTO PLAY

• From ABC News, Biology in the Headlines, 2005 DVD.

20
Section 2

• Feeding Levels and Food Webs

21
Feeding Levels and Food Webs

• Many ecosystems exist, but they are all similar
  in structure and function.
• Producers (autotrophs) capture sunlight energy
  and incorporate it into organic compounds.
• All other organisms in an ecosystem are consumers
  (heterotrophs) that depend on energy stored in
  the tissues of producers.

22
Fig 25.4, p. 456
energy input from sun
Producers
Nutrient Cycling
Consumers
energy lost (mainly heat)
23
Feeding Levels and Food Webs

• Herbivores eat plants (primary consumers).
• Carnivores eat animals (secondary or tertiary
  consumers).
• Omnivores eat a variety of organisms.
• Decomposers include fungi, bacteria, and small
  invertebrates that extract energy from the
  remains or products of organisms.
• Ecosystems require energy and nutrient input to
  continue to function.
• Energy is generally lost from the system as heat
  some nutrients can also be lost.

24
Animation Energy Flow
CLICKTO PLAY
25
Animation The Role of Organisms in an Ecosystem
CLICKTO PLAY
26
Feeding Levels and Food Webs

• Energy moves through a series of ecosystem
  feeding levels.
• Trophic levels (feeding levels) represent a
  hierarchy of energy transfers.
• Level 1 (closest to the energy source) consists
  of primary producers, level 2 is composed of
  herbivores, and levels 3 and above are
  carnivores.
• Decomposers and omnivores such as humans feed on
  organisms from all levels.

27
Animation Trophic Levels in a Simple Food Chain
CLICKTO PLAY
28
Animation Prairie Trophic Levels
CLICKTO PLAY
29
Feeding Levels and Food Webs

• Food chains and webs show who eats whom.
• A linear sequence of who eats whom in an
  ecosystem is called a food chain simple chains
  are rarely found in nature.
• Cross-connecting food chains make up food webs in
  which the same food resource is often part of
  more than one food chain.

30
In-text Fig, p. 466
Marsh Hawk
Upland Sandpiper
Garter Snake
Cutworm
Plants
31
In-text Fig, p. 466
Marsh Hawk
Upland Sandpiper
Garter Snake
Cutworm
Stepped Art
Plants
32
Animation Categories of Food Webs
CLICKTO PLAY
33
Animation Prairie Food Web
CLICKTO PLAY
34
Fig 25.5, p. 467
Marsh Hawk
Higher Feeding Levels A variety of carnivores,
omnivores, and other consumers. Many feed at
more than one level all the time, seasonally,
or when an opportunity presents itself
Crow
Upland Sandpiper
Garter Snake
Frog
Weasel
Coyote
Badger
Spider
Second Feeding Level Primary consumers
(herbivores)
Ground Squirrel
Clay-colored Sparrow
Earthworms, Insects (e.g.) Grasshoppers, Cutworms
Pocket Gopher
Prairie Vole
First Feeding Level Primary producers
Grass
35
Animation Rainforest Food Web
CLICKTO PLAY
36
Section 3

• Energy Flow
• through Ecosystems

37
Energy Flow through Ecosystems

• Producers capture and store energy.
• Primary productivity is the total rate of
  photosynthesis (trapping of energy) for the
  ecosystem during a specified interval.
• How much energy is trapped depends on many
  factors.
• The number of individual plants and the relative
  balance between trapping energy and expending
  energy to produce new plants.
• Environmental factors such as availability of
  mineral nutrients, rain fall, and temperature.

38
Earths Primary Productivity
Figure 25.6
39
Energy Flow through Ecosystems

• Consumers subtract energy from ecosystems.
• An ecological pyramid describes the energy
  relationships in an ecosystem.
• Primary producers form the base.
• Successive tiers of consumers are found above
  them.

40
Energy Flow through Ecosystems

• Ecological pyramids can be of two basic types
• Biomass is the combined weight of all of an
  ecosystems organisms at each level of the
  pyramid a biomass pyramid can be right-side
  up, with producers outnumbering consumers, or
  upside-down, which is the opposite.
• An energy pyramid reflects the trophic structure
  more accurately because it is based on energy
  losses at each level energy pyramids are always
  right-side up.

Figure 25.7a
41
Fig 25.7a, p.468
1.5
third-level carnivores (gar, large-mouth bass)
11
second-level consumers (fishes, invertebrates)
37
first-level consumers (herbivorous fishes,
turtles, invertebrates)
5
primary producers (algae, eelgrass, rooted
plants)
809
decomposers (bacteria, crayfish)
42
Fig 25.7a, p.468
Stepped Art
43
Decomposers
5,060
top carnivores
21
carnivores
383
herbivores
3,368
producers
20,810
Fig 25.7b
44
Section 4

• Biogeochemical Cycles
• An Overview

45
Biogeochemical Cycles

• Biogeochemical cycles describe the movement of
  nutrients from the environment to organisms and
  then back to the environment that serves as a
  reservoir for them.
• Cycling is slowest through the reservoir.
• The amount of nutrient being recycled through
  major ecosystems is greater than the amount
  entering or leaving in a given year.
• Inputs to an ecosystems nutrient reserves are by
  precipitation, metabolism, and rock weathering
  outputs include losses by runoff.

46
geochemical cycle
nutrient reservoirs in environment
consumers (herbivores, carnivores, parasites)
fraction available to ecosystem
primary producers
decomposers
Fig 25.8, p. 469
47
Biogeochemical Cycles

• There are three categories of biogeochemical
  cycles
• In the global water cycle, oxygen and hydrogen
  move as water molecules.
• In the atmospheric cycles, elements such as
  carbon and nitrogen move in gaseous phase.
• In sedimentary cycles, solid, non-gaseous
  nutrients move from land to the seafloor and back
  to land through geological uplifting this is a
  very slow cycle.

48
Section 5

• The Water Cycle

49
The Water Cycle

• The hydrologic cycle (water cycle) encompasses
  water in the oceans, atmosphere, and land.
• The ocean serves as the main water reservoir.
• Evaporation moves water into the lower atmosphere
  where it returns to Earth as precipitation.

50
Animation Hydrologic Cycle
CLICKTO PLAY
51
Fig 25.9, p. 470
atmosphere
precipitation onto land 111,000
wind-driven water vapor 40,000
evaporation from land plants (transpiration) 71,00
0
precipitation into ocean 385,000
evaporation from ocean 425,000
surface and groundwater flow 40,000
ocean
land
52
The Water Cycle

• Water moves nutrients in or out of ecosystems.
• A watershed funnels rain or snow into a single
  river.
• Plants absorb nutrients to prevent their loss by
  leaching.

53
Section 6

• Cycling Chemicals from the Earths Crust

54
Cycling Chemicals from the Earths Crust

• There are two phases in the phosphorus cycle
• In the geochemical phase, phosphorus moves from
  land to sediments in the seas and back to the
  land over long periods of time.
• In the much more rapid ecosystem phase, plants
  take up the phosphorus from the soil it is then
  transferred to herbivores and carnivores, which
  excrete it in wastes and their own decomposing
  bodies thus returning the phosphorus to plants.

55
Cycling Chemicals from the Earths Crust

• Excessive phosphorus compounds in runoff water
  can lead to eutrophication of lakes and streams,
  characterized by explosive growth of algae and
  weeds.

56
Animation Phosphorus Cycle
CLICKTO PLAY
57
Fig 25.10, p. 471
Fertilizer
mining
excretion
Guano
agriculture
uptake by autotrophs
weathering
uptake by autotrophs
Dissolved in Soil Water, Lakes, Rivers
weathering
Land Food Webs
Marine Food Webs
Dissolved in Ocean Water
death, decomposition
death, decomposition
sedimentation
settling out
leaching, runoff
Rocks
Marine Sediments
uplifting over geologic time
58
Section 7

• The Carbon Cycle

59
The Carbon Cycle

• In the carbon cycle, sediments and rocks hold
  most of the carbon carbon moves also through the
  oceans, soil, atmosphere, and biomass.
• Carbon enters the atmosphere as CO2 produced by
  aerobic respiration, fossil-fuel burning, and
  volcanic eruptions.

60
The Carbon Cycle

• Carbon in the ocean occurs as bicarbonate and
  carbonate carbon dioxide in the ocean is carried
  to deep storage reservoirs on the seafloor.

Figure 25.12
61
Fig 25.12, p. 473
Warm, less salty, shallow current
Cold, salty, deep current
62
The Carbon Cycle

• Carbon is removed from the atmosphere and the
  ocean by photosynthesizers and shelled organisms
  carbon is held for different periods of time in
  different ecosystems.
• Decomposition of buried carbon compounds millions
  of years ago caused the formation of fossil fuels
  (natural gas, petroleum, and coal).
• Burning of fossil fuels puts extra amounts of
  carbon dioxide into the atmosphere, an occurrence
  that may lead to global warming.

63
Animation Carbon Cycle
CLICKTO PLAY
64
The Carbon Cycle
Figure 25.11
65
Fig. 25.11a, p. 472
diffusion between atmosphere and ocean
Bicarbonate and Carbonate Dissolved in Ocean Water
combustion of fossil fuels
Terrestrial Rocks
photosynthesis
aerobic respiration
Marine Food Webs, producers consumers,
decomposers
Soil Water (dissolved carbon)
death, sedimentation
incorporation into sediments
uplifting over geologic time
sedimentation
leaching, runoff
Marine Sediments, Including Formations with
Fossil Fuels
66
Fig. 25.11b, p. 473
Atmosphere
combustion of fossil fuels
combustion of wood (for cleaning land or for
fuel)
aerobic respiration
photosynthesis
sedimentation
Land Food Webs producers, consumers, decomposers
death, burial, compaction over geologic time
Peat, Fossil Fuels
67
Section 8

• Global Warming

68
Global Warming

• The greenhouse effect.
• Molecules of gases such as carbon dioxide, water,
  ozone, and others act like a pane of glass over
  the surface of the Earth.

Figure 25.14
69
Animation Greenhouse Gases
CLICKTO PLAY
70
Fig 25.14a2, p. 475
380
Carbon dioxide
360
Concentration (parts per billion)
340
320
300
1995
1960
1965
1970
1975
1980
1985
1990
Time (years)
71
Fig. 25.14b, p. 475
1200
CFCs
1000
800
Concentration (parts per trillion)
600
400
200
1980
1985
1995
1990
1998
1976
Time (years)
72
Fig. 25.14c, p. 475
1.80
Methane
1.70
Concentration (parts per billion)
1.60
1.50
1.40
1976
1998
1980
1985
1990
1995
Time (years)
73
Fig. 25.14d, p. 475
320
Nitrous oxide (N2O)
310
300
Concentration (parts per billion)
290
280
270
260
1976
1980
1985
1990
1995
1998
Time (years)
74
Global Warming

• Wavelengths of visible light easily pass downward
  to Earth, but infrared wavelengthsheatare
  impeded from passing back into space.
• The warming of the lower atmosphere is called the
  greenhouse effect.

Figure 25.13
75
Fig 25.13, p. 474
Increased concentrations of greenhouse
gases trap more heat near Earths surface. Sea
surface temperature rises, more water evaporates
into the atmosphere, and Earths surface
temperature rises.
c
76
Animation Greenhouse Effect
CLICKTO PLAY
77
Global Warming

• Global warming.
• Concentrations of greenhouse gases are increasing
  and may be at the highest levels they have been
  at for 420,000 to 20 million years.
• The result is a long-term rise in
  temperatureglobal warming irreversible climate
  changes are already underway, such as melting of
  the polar ice caps and retreating of glaciers.

78
Animation Carbon Dioxide and Temperature
CLICKTO PLAY
79
Global Temperature
Figure 25.15
80
Video Kyoto Protocol

• This video clip is available in CNN Today Videos
  for Environmental Science, 2004, Volume VII.
  Instructors, contact your local sales
  representative to order this volume, while
  supplies last.

81
Section 9

• The Nitrogen Cycle

82
The Nitrogen Cycle

• Gaseous nitrogen (N2) makes up about 80 of the
  atmosphere, which is the largest reservoir this
  form of nitrogen can only be brought into the
  nitrogen cycle by certain species of bacteria.
• In nitrogen fixation, bacteria convert N2 to
  ammonia, which is then used in the synthesis of
  proteins and nucleic acids to be assimilated into
  plant, then animal, tissues.

83
The Nitrogen Cycle

• Decomposition of dead nitrogen fixers releases
  nitrogen-containing compounds.
• Nitrification is a type of chemosynthesis where
  ammonia and ammonium ions are converted to
  nitrite nitrite is turned to nitrates by
  bacteria for uptake by plants.
• Denitrification is the release of nitrogen gas to
  the atmosphere by the action of bacteria.
• Nitrogen can be lost from ecosystems through
  leaching.

84
Animation Nitrogen Cycle
CLICKTO PLAY
85
Fig 25.16, p. 476
Consumers
Nitrogen gas in Atmosphere
Nitrogen Fixation by industry for agriculture
Food Webs on Land
uptake by autotrophs
uptake by autotrophs
excretion, death, decomposition
Fertilizers
Loss by Denitrification
Nitrate in Soil
Nitrogen Fixation by bacteria
Nitrogen-rich wastes, Remains in soil
Ammonification bacteria, fungi convert residues
to NH3 this dissolves to form NH4
Nitrification
Ammonia, Ammonium in Soil
Nitrate in Soil
loss by leaching
loss by leaching
Nitrification
86
Section 10

• Biological Magnification

87
Biological Magnification

• DDT is a synthetic organic pesticide that was
  first used during World War II in the fight
  against malaria and typhus after the war it
  continued to be used as a pesticide to control
  agricultural and forest pests.
• DDT is insoluble in water, but it is fat soluble.
• Vapor forms and small particles in water can
  carry DDT through an environment from the
  environment it can be absorbed into tissues.

88
Biological Magnification

• Biological magnification describes the increased
  concentration of slowly degradable substances in
  organisms as it is passed upward in a food chain.
• Each organism in a chain essentially assumes the
  absorbed DDT in each organism it feeds on lower
  in the chain.
• With DDT, organisms at the very top of the food
  chain, such as bald eagles and other predatory
  birds, suffered the most and some were pushed
  almost to extinction.

89
Biological Magnification

• DDT is banned in the US, but this is not true
  outside of the US.

Figure 25.18
90
Fig 25.17a, p. 477
DDT Residues (ppm wet weight of whole live
organism)
Ring-billed gull fledgling (Larus
delawarensis) Herring gull (Larus
argentatus) Osprey (Pandion haliaetus) Green
heron (Butorides virescens) Atlantic needlefish
(Strongylura marina) Summer flounder
(Paralychthys dentatus) Sheepshead minnow
(Cyprinodon variegatus) Hard clam (Mercenaria
mercenaria) Marsh grass shoots (Spartina
patens) Flying insects (mostly flies) Mud snail
(Nassarius obsoletus) Shrimps (composite of
several samples) Green alga (Cladophora
gracilis) Plankton (mostly zooplankton) Water
75.5 18.5 13.8 3.57 2.07 1.28
0.94 0.42 0.33 0.30 0.26 0.16 0.083 0.040
0.00005
Data for a Long Island, NY, estuary in 1967
91
Animation Pesticide Examples
CLICKTO PLAY
92
Section 11

• Human
• Population Growth

93
Human Population Growth

• The human population is growing rapidly.
• The world population reached the 6.3 billion mark
  in 2004.
• It took 2.5 million years for the worlds human
  population to reach 1 billion.
• It took less than 200 years for it to reach 6
  billion.
• The growth rate is determined mainly by the
  balance between births and deaths.
• The total fertility rate (TFR) is the average
  number of children born to a woman.
• Many developed countries have a TFR at or below
  2.1 (replacement rate), but some developing
  countries have a TFR two or three times this rate.

94
6
Estimated size by 10,000 years ago 5 million
5
4
By 1904 1 billion By 1927 2 billion By
1960 3 billion By 1974 4 billion By
1987 5 billion By 1999 6
billion Projected for 2050 8.9 billion
3
2
beginning of industrial, scientific revolutions
domestication of plants, animals 9000B.C. (about
11,000 years ago)
agriculturally based urban societies
1
BC AD
14,000
12,000
10,000
8,000
6,000
4,000
2,000
2,000
Fig. 25.19, p. 478
95
Animation Exponential Growth
CLICKTO PLAY
96
Human Population Growth

• Population statistics help predict growth.
• Demographics influence a populations growth and
  impact on ecosystems.
• Population size is the number of individuals in
  the populations gene pool.
• Population density is the number of individuals
  per unit of area or volume.
• Population distribution refers to the general
  pattern in which the population members are
  distributed, such as clustering in towns or
  cities.

97
Fig. 25.20a, p. 479
292 million
population in 2003
177 million
134 million
population in 2050 (projected)
351 million
211 million
206 million
population under age 15
21
30
44
population above age 65
13
Gold U.S. Brown Brazil Ivory Nigeria
6
3
2.0
total fertility rate
2.2
5.8
6.9 per 1,000 births
infant mortality rate
33 per 1,000 births
75 per 1,000 births
77 years
life expectancy
69 years
52 years
34,280
per capita income in 2001
7,070
800
98
Animation Current and Projected Population Sizes
by Region
CLICKTO PLAY
99
Human Population Growth

• Age structure defines the relative proportions of
  individuals of each age.
• The three categories are prereproductive,
  reproductive, and postreproductive.
• The reproductive base (prereproductive and
  reproductive members) for a human population will
  determine the future growth rate of a population.

Figure 25.21
100
Fig 25.21, p. 479
UNITED STATES
INDIA
101
Animation Age Structure Diagrams
CLICKTO PLAY
102
Animation U.S. Age Structure
CLICKTO PLAY
103
Section 12

• Natures Controls on Population Growth

104
Natures Controls on Population Growth

• The human population has been growing
  exponentially since the mid-1700s.
• There is a limit on how many people the Earth can
  sustain.
• The biotic potential of a population is its
  maximum rate of increase under idealnonlimitingc
  onditions.
• Limiting factors on population growth could
  include any essential resource that is in short
  supply such as food, water, or living space
  predation and pathogens can also be limiting.

105
Natures Controls on Population Growth

• The number of individuals that can be sustained
  by the resources in a given area is the carrying
  capacity.
• The carrying capacity can vary over time and is
  expressed graphically in the S-shaped curve
  pattern called logistic growth.

Figure 25.22
106
Fig 25.22, p. 480
initial carrying capacity
Number of individuals
new carrying capacity
TIME
A
B
C
D
E
107
Animation Demographic Transition Model
CLICKTO PLAY
108
Natures Controls on Population Growth

• Some natural population controls are related to
  population density.
• Density-dependent controls (such as diseases) are
  limiting factors that exert their effects with
  respect to the number of individuals present.
• Density-independent controls, such as natural
  disasters, tend to increase the death rate
  without respect to the number of individuals
  present.

109
Video People Explosion
CLICKTO PLAY

• From ABC News, Human Biology in the Headlines,
  2006 DVD.

110
Section 13

• Assaults on Our Air

111
Assaults on Our Air

• Pollutants are substances that adversely affect
  health, activities, or survival of a population.
• Air pollutants include oxides of carbon, sulfur,
  and nitrogen as well as CFCs.
• Over 700,000 metric tons of pollutants are
  released into the atmosphere every day in the
  United States alone.

112
Assaults on Our Air

• Pollutants may be trapped in the atmosphere to
  produce two types of smog
• Industrial smog is gray air found in industrial
  cities that burn fossil fuels.
• Photochemical smog is brown air found in large
  cities in warm climates for example, gases from
  car exhaust.
• Burning of fossil fuels produces oxide particles
  that can fall to the earth as acid rain.

113
Animation Thermal Inversion and Smog
CLICKTO PLAY
114
Animation Formation of Photochemical Smog
CLICKTO PLAY
115
Animation Acid Deposition
CLICKTO PLAY
116
Animation Effect of Air Pollution in Forests
CLICKTO PLAY
117
Assaults on Our Air

• The ozone layer has been damaged.
• Ozone (O3) in the lower stratosphere absorbs most
  of the ultraviolet radiation from the sun.
• Ozone thinning has produced an ozone hole over
  Antarctica in 2001 an ozone hole appeared over
  the Arctic.
• Chlorofluorocarbons (CFCs) seem to be the
  causeone chlorine atom can destroy 10,000
  molecules of ozone.

118
Assaults on Our Air

• While most CFC production is being phased out, it
  will take 100 to 200 years for the ozone layer to
  fully recover once all production and use ceases.

Figure 25.23
119
Animation How CFCs Destroy Ozone
CLICKTO PLAY
120
Video Clean Air Act
CLICKTO PLAY

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

121
Section 14

• Water, Wastes, and Other Problems

122
Water, Wastes, and Other Problems

• Problems with water are serious.
• Three out of four humans do not have enough clean
  water to meet basic needs.
• About one third of all food is raised on
  irrigated land, leading to salt buildup
  (salinization) and depletion of ground water
  systems.

Figure 25.24
123
Water, Wastes, and Other Problems

• Humans waste limited water supplies and pollute
  much of the remaining water through agricultural
  and industrial runoff even garbage and debris is
  dumped into our waterways.

124
Animation Stream Pollution
CLICKTO PLAY
125
Animation Threats to Aquifers
CLICKTO PLAY
126
Water, Wastes, and Other Problems

• Where will we put solid wastes and produce food?
• Finding enough space to bury our wastes is
  becoming a problem, and the dump sites can leak
  toxic materials into the soil and water.
• Almost one quarter of all the land on Earth is
  used for agriculture.
• The green revolution has increased crop yields
  but uses many times more energy and mineral
  resources.
• Large-scale desertification is caused by
  overgrazing on marginal lands.

127
Water, Wastes, and Other Problems

• Deforestation has global repercussions.
• Deforestation, the removal of all trees from
  large tracts of land, can reduce fertility,
  change rainfall patterns, increase temperatures,
  and increase carbon dioxide levels.

128
Water, Wastes, and Other Problems

• Clearing large tracts of tropical forests may
  have global repercussions due to leaching and
  shifting rates of evaporation and sunlight
  penetration.

Figure 25.25
129
Animation Effects of Deforestation
CLICKTO PLAY
130
Video Desertification in China
CLICKTO PLAY

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

131
Section 15

• Concerns about Energy

132
Concerns about Energy

• The Earth has abundant energy, but the net amount
  of energy left after subtracting the energy it
  costs to find, process, and deliver this energy
  is relatively small.
• Some forms of energy are renewable, such as solar
  energy coal and petroleum are examples of
  non-renewable energy.

Figure 25.26a
133
Concerns about Energy

• People in developed countries use far more energy
  per person than those in developing countries.

Figure 25.26b
134
Animation Energy Use
CLICKTO PLAY
135
Concerns about Energy

• Fossil fuels are going fast.
• Fossil fuels include oil, coal, and natural gas
  these sources represent the fossilized remains of
  ancient forests and organisms.
• Petroleum and natural gas reserves may be
  depleted during this century.
• Extraction and use of abundant reserves of coal
  are not environmentally attractive.

136
Concerns about Energy

• Can other energy sources meet the need?
• Nuclear power can produce electricity at
  relatively low cost, but there are risks.
• Meltdowns may release large amounts of
  radioactivity to the environment.
• Waste is so radioactive that it must be isolated
  for 10,000 years.
• Solar energy can be converted to the mechanical
  energy of wind to run turbines solar cells could
  be used to generate electricity for producing
  hydrogen gas.

137
Concerns about Energy

• Hybrid cars are currently available, which work
  on a combination of gasoline and the electricity
  from batteries.
• Fusion power has potential, but many obstacles
  make the technology a distant possibility.

138
Video Nuclear Energy
CLICKTO PLAY

• From ABC News, Environmental Science in the
  Headlines, 2005 DVD.

139
Section 16

• Loss of Biodiversity

140
Loss of Biodiversity

• Humans have become a major factor in the
  premature extinction of more and more species.
• Extinction is irreversible and greatly decreases
  biodiversity.
• Speciation cannot balance rapid extinction.

141
Animation Humans Affect Biodiversity
CLICKTO PLAY
142
Animation Biodiversity Hot Spots
CLICKTO PLAY
143
Loss of Biodiversity

• Tropical deforestation is the greatest source of
  extinction of species, followed closely by
  destruction of coral reefs.
• Loss of plant diversity directly hurts consumers
  by removing an important part of every food
  chain plant loss also affects our sources of
  natural medicines.
• The underlying causes of such destruction are
  human population growth and poor economic
  policies.

144
Animation Habitat Loss and Fragmentation
CLICKTO PLAY
145
Fig 25.29, p. 487
1620
1850
1850 (pocket only)
1990
146
Animation Resource Depletion and Degradation
CLICKTO PLAY
147
Loss of Biodiversity

• To end the trend, we must collectively fight to
  reduce deforestation, global warming, ozone
  depletion, and poverty.

Figures 25.27 and 25.28