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3.1 What Is Ecology?
Lesson Objectives
Describe the study of ecology.
Explain how biotic and abiotic factors influence an ecosystem.
Describe the methods used to study ecology.
Lesson Summary
Studying Our Living Planet Ecology is the scientific study of interactions among
organisms and between organisms and their environment.
Earth’s organisms live in the biosphere. The biosphere consists of the parts of the planet
in which all life exists.
Ecologists may study different levels of ecological organization:
 Individual organism
 An assemblage of individuals that belong to the same species and live in the same area
is called a population.
 An assemblage of different populations that live together in an area is referred to as a
community.
 An ecosystem includes all the organisms that live in a particular place, together with
their physical environment.
 A group of ecosystems that have similar climates and organisms is called a biome.
Biotic and Abiotic Factors Ecosystems include biotic and abiotic factors.
A biotic factor is any living part of an environment.
An abiotic factor is any nonliving part of an environment.
Ecological Methods Ecologists use three basic methods of research: observation,
experimentation, and modeling:
Observation often leads to questions and hypotheses.
Experiments can be used to test hypotheses.
Modeling helps ecologists understand complex processes.
Studying Our Living Planet
1. What is ecology?
2. What does the biosphere contain?
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3. How are human economics and ecology linked?
Use the diagram to answer Questions 4–5
4. Label each level of organization on the diagram.
5. Explain the relationship between ecosystems and biomes.
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Biotic and Abiotic Factors
6. Use the terms in the box to fill in the Venn diagram. List parts of the environment that
consist of biotic factors, abiotic factors, and some components that are a mixture of both.
air
animals
bacteria
heat
mushrooms
plants
precipitation
soil
sunlight
Both
Biotic
Factors
Abiotic
Factors
Ecological Methods
7. Why might an ecologist set up an artificial environment in a laboratory?
8. Why are many ecological phenomena difficult to study?
9. Why do ecologists make models?
Apply the Big idea
10. What makes a planet living? Explain your answer by comparing Earth with Mars.
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4.1 Climate
Lesson Objectives
Differentiate between weather and climate.
Identify the factors that influence climate.
Lesson Summary
Weather and Climate Weather is the condition of Earth’s atmosphere at a particular
time and place. Climate is the average condition of temperature and precipitation in a region
over long periods.
Climate can vary over short distances.
These variations produce microclimates.
Factors That Affect Climate Climate is affected by solar energy trapped in the
biosphere, by latitude, and by the transport of heat by winds and ocean currents.
Temperature on Earth stays within a range suitable for life due to the greenhouse effect.
The greenhouse effect is the trapping of heat by gases in the atmosphere.
Earth’s curvature causes different latitudes to receive less or more intense solar energy.
The unequal distribution of the sun’s heat on Earth’s surface results in three main climate
zones: polar, temperate, and tropical.
Unequal heating of Earth’s surface also causes winds and ocean currents. Winds and
currents move heat and moisture through the biosphere.
Weather and Climate
1. How is weather different from climate?
2. What causes microclimates to form?
3. In the Northern Hemisphere, why are the south-facing sides of buildings often warmer
and drier than the north-facing sides?
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Factors That Affect Climate
VISUAL ANALOGY
For Questions 4–5, refer to the Visual Analogy comparing the
Earth’s atmosphere to a greenhouse.
4. What is the source of radiation for both the Earth’s atmosphere and the greenhouse?
5. What happens to sunlight that hits Earth’s surface?
For Questions 6–9, write the letter of the correct answer on the line at the left.
6. What effect do carbon dioxide and methane have on Earth’s temperature?
A. They trap heat in the atmosphere.
B. They release heat from the atmosphere.
C. They block heat from entering the ocean.
D. They block heat from reaching Earth’s surface.
7. How would the temperature on Earth change without the greenhouse effect?
A. The temperature at the equator would be warmer.
B. The temperature would stay the same.
C. It would be 30°C warmer.
D. It would be 30°C cooler.
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8. What causes solar radiation to strike different parts of Earth’s surface at an angle
that varies throughout the year?
A. Earth’s tilted axis
B. Earth’s erratic orbit
C. the moon’s orbit around Earth
D. solar flares on the sun’s surface
9. In which location is the sun almost directly overhead at noon all year?
A. the equator
B. the South Pole
C. the North Pole
D. North America
10. Complete the table about Earth’s three main climate zones.
Main Climate Zones
Climate Zone
Location
Climate Characteristics
Areas around North and
South poles
Between the polar zones and
the tropics
Near the equator
For Questions 11–14, write True if the statement is true. If the statement is false, change
the underlined word or words to make the statement true.
11. Patterns of heating and cooling result in ocean currents.
12. Warm air is less dense than cool air.
13. Surface water moved by winds results in ocean currents.
14. Deep ocean currents are caused by the sinking of warm water near the poles.
Apply the Big idea
15. Describe how a change in the temperature of an ocean current might affect the climate of
a nearby coastal area.
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4.2 Niches and Community Interactions
Lesson Objectives
Define niche.
Describe the role competition plays in shaping communities.
Describe the role predation and herbivory play in shaping communities.
Identify the three types of symbiotic relationships in nature.
Lesson Summary
The Niche Every species has its own tolerance, or a range of conditions under which it
can grow and reproduce. A species’ tolerance determines its habitat, the place where it lives.
A niche consists of all the physical and biological conditions in which a species lives and
the way the species obtains what it needs to survive and reproduce.
An organism’s niche must contain all of the resources an organism needs to survive. A
resource is any necessity of life, such as water, nutrients, light, food, or space.
Competition Competition occurs when organisms try to use the same limited resources.
Direct competition between species often results in one species dying out. This is the
basis of the competitive exclusion principle. This principle states that no two species can
occupy exactly the same niche in exactly the same habitat at the same time.
Competition helps to determine the number and type of species in a community.
Predation, Herbivory, and Keystone Species Predator-prey and herbivore-plant
interactions help shape communities.
Predation occurs when one organism (the predator) captures and eats another (the prey).
Herbivory is an interaction that occurs when an animal (the herbivore) feeds on
producers (such as plants).
Sometimes changes in the population of a single species, often called a keystone species,
can cause dramatic changes in the structure of a community.
Symbioses Symbiosis occurs when two species live closely together in one of three ways:
mutualism, commensalism, or parasitism.
In mutualism, both species benefit from the relation ship.
In parasitism, one species benefits by living in or on the other and the other is harmed.
In commensalism, one species benefits and the other is neither helped nor harmed.
The Niche
1. What is a niche?
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2. Give an example of resources a squirrel might need.
3. Three different warbler species live in the same tree. One species feeds at the top of the
tree, the second species feeds in the middle part of the tree, and the third species feeds at
the bottom of the tree. Do all three species occupy the same niche? Explain.
Competition
For Questions 4–8, write True if the statement is true. If the statement is false, change
the underlined word or words to make the statement true.
4. Competition occurs when organisms attempt to use the same resources.
5. Competition between members of the same species is known as
interspecific competition.
6. The competitive exclusion principle states that no two organisms can
occupy exactly the same niche in exactly the same habitat at exactly
the same time.
7. If two species of bacteria are grown in the same culture, one species
will always outcompete the other.
8. Members of the same species tend to divide resources instead of
competing over them.
Predation, Herbivory, and Keystone Species
Write the letter of the correct answer on the line at the left.
9. A lion eating a zebra is an example of
A. herbivory.
C. predation.
B. habitat destruction.
D. a keystone species.
10. A cow eating grass is an example of
A. herbivory.
C. habitat destruction.
B. predation.
D. a keystone species.
11. A keystone species is one that
A. eats a mixture of plants and animals.
B. is introduced into a community after a major disturbance.
C. causes the amount of diversity in a community to decrease.
D. helps to stabilize the populations of other species in the community.
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Symbioses
12. Complete the table about main classes of symbiotic relationships.
Main Classes of Symbiotic Relationships
Class
Description of Relationships
Mutualism
Commensalism
Parasitism
Match the example with the type of relationship. A relationship type may be used more
than once.
Example
Type of Relationship
13. a tick living on the body of a deer
14. a bee eating a flower’s nectar and picking up the
flower’s pollen
A. mutualism
B. commensalism
C. parasitism
15. a barnacle living on a whale’s skin
16. a tapeworm living in a person’s intestines
17. an aphid providing food to an ant in exchange for
protection
Apply the Big idea
19. How do keystone species illustrate the interdependence of organisms living in a
community? Give an example.
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4.3 Succession
Lesson Objectives
Describe how ecosystems recover from a disturbance.
Compare succession after a natural disturbance with succession after a human-caused
disturbance.
Lesson Summary
Primary and Secondary Succession The series of predictable changes that occurs
in a community over time is called ecological succession. Over the course of succession, the
number of different species usually increases.
Primary succession begins in areas with no remnants of an older community. It occurs
on bare rock surfaces where no soil exists. The first species to live in an area of primary
succession are called pioneer species.
Secondary succession occurs when a disturbance changes a community without
completely destroying it.
Climax Communities A climax community is a mature, relatively stable ecosystem.
Secondary succession in healthy ecosystems following natural disturbances often
reproduces the original climax community.
Ecosystems may or may not recover from extensive human-caused disturbances.
Primary and Secondary Succession
1. What is ecological succession?
2. What is primary succession?
3.
When a disturbance changes a community without removing the soil, what type of
succession follows?
4. Describe the process of succession in an ecosystem.
5. Why does secondary succession typically proceed faster than primary succession?
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6. Use the Venn diagram to compare the two types of ecological succession.
Primary
succession
Both
Secondary
succession
7. The panels show changes taking place in an ecosystem after a volcano erupts and covers
an area with rock and ash. Number each panel in the order that changes occur. Then,
under each panel, write a description of the changes taking place.
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Climax Communities
For Questions 8–10, complete each statement by writing the correct word or words.
8. After a natural disaster occurs in a healthy ecosystem, secondary succession will cause
the ecosystem to return to its original
.
9. The clearing of a rain forest is the example of a(n)
enough to prevent the original climax community from reforming.
10. During primary succession,
determining which pioneer species arrives in an area first.
drastic
plays a large role in
11. What are the two kinds of disturbances that change ecosystems? Give an example of
each.
Apply the Big idea
12. Many biotic and abiotic factors determine how quickly ecological succession can cause a
climax community to develop in an area. Complete the graphic organizer by adding two
factors that contribute to the development of a climax community.
No major
disturbances
occurring
Development
of a Climax
Community
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4.4 Biomes
Lesson Objectives
Describe and compare the characteristics of the major land biomes.
Identify the areas that are not classified into a major biome.
Lesson Summary
The Major Biomes A biome is a group of terrestrial regional climate communities that
covers a large area and is characterized by soil type, climate, and plant and animal life.
In tropical rain forests, the tops of tall trees form a covering called the canopy. Shorter
trees and vines form another layer called the understory. It is hot and wet all year.
Tropical dry forests are found in areas with alternating wet and dry seasons. The trees in
these forests may be deciduous, meaning they shed their leaves during a particular
season.
In a tropical grassland, grassy areas are spotted with isolated trees.
Deserts have less than 25 centimeters of precipitation annually.
Temperate grasslands have warm summers, cold winters, and deep soil.
Temperate woodlands and shrublands are large areas of grasses and wildflowers such as
poppies interspersed with trees or shrubs.
Temperate forests are made up of deciduous and evergreen coniferous trees. Coniferous
trees produce seed-bearing cones and most have waxy needles. Temperate forests have
soils rich in humus, which forms from decaying leaves and makes soil fertile.
Northwestern coniferous forests have mild temperatures with cool, dry summers and
abundant precipitation in fall, winter, and spring.
Boreal forests, or taiga, are dense forests of coniferous evergreens.
Tundra is characterized by permafrost, a layer of permanently frozen subsoil.
Other Land Areas Some areas, such as mountains and polar ice caps, do not fall neatly
into the major biomes.
The Major Biomes
For Questions 1–4, complete each statement by writing the correct word or words.
1. The side of a mountain range that faces the wind often receives more
than the downwind side of the same range.
2. A(n)
is a group of terrestrial communities that covers a large area and
is characterized by certain soil and
conditions and particular types of
plants and animals.
3. Organisms within each biome can be characterized by
to live and reproduce successfully in the environment.
that enable them
4. In a tropical rain forest, the layer formed by the leafy tops of tall trees is called the
and the layer of shorter trees and vines is called the
.
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5. THINK VISUALLY In the box below, draw and label a diagram showing how a
coastal mountain range can affect a region’s climate.
Use the graph to answer Questions 6–9.
6. Complete the climate diagram by adding labels to the bottom and both sides of the graph
to show what the variables are.
7. Describe what a climate diagram summarizes.
8. Explain what the line plot on a climate diagram shows.
9. Explain what the vertical bars on a climate diagram show.
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10. Complete the table about some of Earth’s major biomes.
Some Major Biomes
Biome
Climate and Soil
Plants and Animals
warm year-round with wet and
dry seasons; rich soil
plants: tall, deciduous trees; succulents
animals: undergo estivation or migration
Tropical rain
forest
cold, dark winters and short,
soggy summers; permafrost
plants: ground-hugging plants
animals: birds and mammals that can
tolerate the harsh conditions
Temperate
grassland
low precipitation with variable
temperatures
plants: short growth cycles, cacti
animals: adaptations to quickly lose body
heat and regulate body temperature
Boreal forest
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Other Land Areas
11. What is the main cause for variation of abiotic and biotic conditions on a mountain?
12. Describe the conditions you would most likely find on a mountain in the Rocky
Mountains as you moved from the base to the mountain’s summit.
13. Which producers can be found in the polar ice regions?
14. Which animals can be found in the northern polar region?
Apply the Big idea
15. How are the plants and animals found in a biome related to the biome’s climate? Give at
least two examples to support your answer.
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4.5 Aquatic Ecosystems
Lesson Objectives
Discuss the factors that affect aquatic ecosystems.
Identify the major categories of freshwater ecosystems.
Describe the importance of estuaries.
Describe and compare the distinct ocean zones that make up marine ecosystems.
Lesson Summary
Conditions Underwater Aquatic ecosystems are determined mainly by the depth,
flow, temperature, and amount of dissolved nutrients of the water.
The photic zone is the sunlit upper layer of water where photosynthesis can occur.
The aphotic zone is the dark lower layer where photosynthesis cannot occur.
The benthic zone is found on the bottoms of lakes, streams, and oceans. The organisms
that live on the floor of a body of water are called benthos.
Freshwater Ecosystems Freshwater ecosystems include flowing-water ecosystems,
standing-water ecosystems, and freshwater wetlands. Plankton are common. They form the
base of many aquatic food webs.
Estuaries Estuaries are wetlands formed where rivers meet the sea. They contain a
mixture of fresh and salt water. Most of the food produced in estuaries enters food webs as
tiny pieces of organic matter, or detritus.
Marine Ecosystems Marine ecosystems are found in the ocean.
The intertidal zone is the shallowest and closest to land. It is exposed to the rise and fall
of tides each day.
The coastal ocean is the relatively shallow border of water that surrounds the continents.
The open ocean begins at the continental shelf and extends outward. The open ocean can
be divided into the photic zone and the aphotic zone.
Conditions Underwater
1.
What are the four main factors that affect aquatic ecosystems?
2.
What does the depth of the water determine?
3.
What distinguishes the photic zone from the aphotic zone in an aquatic ecosystem?
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Freshwater Ecosystems
For Questions 4–10, complete each statement by writing the correct word or words.
4. The three main categories of freshwater ecosystems are
and .
5.
,
,
Flowing-water ecosystems originate from underground water sources in
.
6. Circulating water in lakes and ponds distributes
and throughout the system.
,
,
7.
and
.
Plankton is a general term that includes both
8. An ecosystem in which water either covers the soil or is present at or near the surface of
the soil is called a(n)
.
9.
Freshwater wetlands purify water by
pollutants.
10. The three types of freshwater wetlands are
and .
,
,
Estuaries
Write the letter of the correct answer on the line at the left.
11. Estuaries form where
A. a lake evaporates.
B. a river meets the sea.
C. a river becomes dammed.
D. a wetland becomes filled in.
12. The salinity of estuary water is
A. equal to the salinity of river water.
B. less than the salinity of river water.
C. less than the salinity of ocean water.
D. greater than the salinity of ocean water.
13. Shallow estuaries allow
A. freshwater wetlands to merge with the estuary.
B. large marine mammals to hibernate in the estuary.
C. sunlight to reach the benthos to power photosynthesis.
D. salt to sink to the bottom of the estuary.
14. Temperate estuaries characterized by salt-tolerant grasses above the low-tide
line and seagrasses below water are called
A. bogs.
C. mangrove swamps.
B. salt marshes.
D. freshwater wetlands.
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Marine Ecosystems
15. Complete the diagram by adding labels for each marine zone. Then shade in the aphotic
zone.
16. Complete the table about the type of organisms living in each ocean zone.
Marine Life by Ocean Zone
Zone
Life Forms
kelp forests, coral reefs
barnacles, seaweed, starfish
large marine mammals such as whales, chemosynthetic bacteria
Apply the Big idea
17. Which type of marine ecosystem do you think supports the least life? Explain your
answer.
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6.3 Biodiversity
Lesson Objectives
Define biodiversity and explain its value.
Identify current threats to biodiversity.
Describe how biodiversity can be preserved.
Lesson Summary
The Value of Biodiversity The sum of all the genetic diversity among all the
organisms in the biosphere is called biodiversity. There are three general types of
biodiversity:
Ecosystem diversity is the variety of habitats, communities, and ecological processes in
the biosphere.
Species diversity is the number of different species in an area or in the biosphere.
Genetic diversity is the total of all genetic information carried in living things.
Biodiversity benefits humans through its contributions to medicine and agriculture and
through the provision of ecological goods and services.
Threats to Biodiversity Human activities threaten biodiversity.
Development splits ecosystems into pieces, resulting in habitat fragmentation. The
smaller the pieces of a habitat, the less likely that species in the habitat can survive.
Other threats to biodiversity include hunting, introduced species, pollution, and climate
change.
Conserving Biodiversity Conservation efforts are focused on three things:
Protecting single species is the focus of groups such as the Association of Zoos and
Aquariums (AZA), which oversees species survival plans (SSPs).
Protecting habitats and ecosystems is the main thrust of global efforts. Biologists are
particularly concerned about ecological hot spots, which are places where significant
numbers of habitats and species are in immediate danger of extinction.
Considering local interests is part of developing plans to replace harmful activities with
ones that conserve environments and biodiversity.
The Value of Biodiversity
1. What is biodiversity?
2. Why is biodiversity one of Earth’s greatest natural resources?
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3. Complete the table to define the types of biodiversity.
Diversity in the Biosphere
Type of Diversity
Definition
Ecosystem diversity
Species diversity
Genetic diversity
Threats to Biodiversity
For Questions 4–8, write True if the statement is true. If the statement is false,
change the underlined word or words to make the statement true.
4. The current rate of species loss is 10 times the typical rate of
extinction.
5. The smaller a habitat “island,” the larger the number of species that
can live there.
6. Habitat fragmentation increases the impact of hunting on endangered
species.
7. Endangered species can become invasive and threaten biodiversity.
8. The increased concentration of carbon dioxide in air is making
oceans more acidic and putting stress on coral reefs.
9.
10.
What are five ways that human activity reduces biodiversity?
Identify three reasons why endangered species are hunted.
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How can introduced species lead to economic losses?
12. How does climate change threaten biodiversity?
Conserving Biodiversity
13. What is the main purpose of biodiversity conservation today?
14. Why have ecologists identified ecological hot spots?
15. What are some of the challenges that conservationists face?
16. What are some strategies that encourage conservation? Provide an example of one of
these strategies.
Apply the Big idea
17. Why is preserving entire ecosystems a better idea than protecting single species from
extinction?
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6.4 Meeting Ecological Challenges
Lesson Objectives
Explain the concept of ecological footprint.
Identify the role of ecology in a sustainable future
Lesson Summary
Ecological Footprints The ecological footprint of an individual or a population is the
amount of land and water needed to provide resources, absorb wastes, and render the wastes
harmless.
Ecology in Action Three case studies illustrate the three steps of ecology in action: (1)
recognize a change in the environment, (2) determine the cause of that change, and (3) change
behavior to have a positive impact.
Case Study 1: Atmospheric Ozone This gas blocks ultraviolet (UV) radiation.
 Ozone gas blocks ultraviolet (UV) rediation.
 The ozone layer is an area of relatively high concentration of ozone in the atmosphere,
between 20 and 50 kilometers above Earth’s surface. In the 1970s, a hole in the layer
was observed.
 Regulations reduced CFC use, and the hole may be slowly disappearing.
Case Study 2: North Atlantic Fisheries
 Commercial fish catches have declined in recent years.
 The cause is overfishing.
 Regulations closed some fishing grounds to allow fish stocks to replenish. In the mean
time, aquaculture, or fish farming, also can provide food for people.
Case Study 3: Climate Change
 Global warming, the rise in the biosphere’s average temperature, and climate change, a
shift in Earth’s overall weather patterns, has occurred.
 Physical evidence includes rising sea levels due to melting ice. Biological evidence
includes temperature-related behavior changes in organisms.
 Using less fossil fuel will reduce greenhouse gases in the atmosphere.
Ecological Footprints
For Questions 1–2, refer to the Visual Analogy that shows examples of factors that
contribute to a population’s ecological footprint.
1.
VISUAL ANALOGY Why do you think
ecologists use the term footprint to describe the
total resources a population uses and its wastes that
must be absorbed?
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2. Explain this statement: The average American has an ecological footprint more than four
times larger than the global average.
Ecology in Action
3. List three factors that will affect the future of the biosphere.
4.
Complete the table to summarize how the basic principles of ecology can lead to positive
impacts on the environment.
Examples of Ecology in Action
Environmental Change
Cause
Behavior Change Needed
Hole in the ozone layer
Declining numbers of fish in the
oceans
Global warming and climate
change
Case Study 1: Atmospheric Ozone
For Questions 5–7, complete each statement by writing the correct word or words.
5. The ozone layer is a high concentration of ozone at about
Earth’s surface.
above
6. The ozone layer is important to humans because it protects against exposure to
from the sun.
7. UV radiation causes
,damages eyes, and reduces resistance to disease.
Case Study 2: North Atlantic Fisheries
For Questions 8–10, complete each statement by writing the correct word or words.
8. Technologies that have led to large increases in the mass of ocean fish caught include
large boats and high-tech
equipment.
9.
caused the decline in fish catches since 1997.
10. An alternative to commercial fishing is
,which produces large amounts
of food with minimal environmental damage if properly managed.
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Case Study 3: Climate Change
Use the graph to answer Questions 11–12.
11. How does the change in global temperature between 1850 and 2000 compare with the
change that occurred between 1850 and 1880?
12. List three factors that may have contributed to the trend shown in the graph.
13. Suggest three possible effects of global warming on the future of the biosphere.
Apply the Big idea
14. Explain why populations with the largest ecological footprints change the biosphere the
most.
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