Transcript Chapter 4: Photosynthesis, Cellular Respiration and Global Warming

Chapter 4
Life in the Greenhouse
Photosynthesis, Cellular Respiration, and
Global Warming
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Chapter 4 Section 1
The Greenhouse Effect
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4.1 The Greenhouse Effect
 Effects of global warming
 Rise in sea levels
 Global melting of glaciers
 Loss of habitat for temperature-sensitive
species
 More severe storms
 Most scientists agree that global warming
is occurring and human activities are part
of the reason.
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4.1 The Greenhouse Effect
Greenhouse Effect
Sun rays
Less heat escapes.
 Sunlight warms the
surface of the Earth.
 Most of the warmth
Heat is trapped.
radiates into space.
 Some is absorbed by
gases in the atmosphere,
Earth
making the Earth
warmer.
Greenhouse Gases
 Increased amounts of
CO2, methane, water,
“greenhouse gases”
result in higher
ozone, nitrous oxide
temperatures.
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Figure 4.1
4.1 The Greenhouse Effect
Difference between heat and temperature
 Heat is the total amount of energy in a
substance.
 Temperature measures the intensity of
heat – how rapidly molecules are moving.
 Earth’s water plays a major role in
moderating temperatures.
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4.1 The Greenhouse Effect
Sun
Water’s effect on Temperature
 Water has a high capacity to
absorb and release heat, due
to hydrogen bonding between
molecules.
Heat
(a) Water molecules
Hydrogen
bonds
(b) Heat absorbed
Hydrogen
bonds
break
 Therefore, water helps stabilize
earth’s temperature
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(c) Heat released; water cools
Hydrogen
bonds
reform
Figure 4.2
End Chapter 4 Section 1
The Greenhouse Effect
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Chapter 4 Section 2
The Flow of Carbon
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4.2 The Flow of Carbon
The Carbon Cycle
 Carbon cycles between living organisms,
the atmosphere, bodies of water, and the
soil.
Carbon
dioxide
(CO2)
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Oxygen (O2)
Figure 4.3
4.2 The Flow of Carbon
CO2 concentration (parts per million)
CO2 is increasing in the atmosphere
 Measurements of carbon dioxide from
Antarctic ice cores shows that it has been
increasing in the atmosphere over the past
50 years.
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Average concentration of CO2
is steadily increasing.
CO2 fluctuates yearly
because photosynthesis is
suppressed in the winter.
Year
Figure 4.5
4.2 The Flow of Carbon
CO2 is increasing in the atmosphere
CO2 concentration
Temperature
Years before present
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CO2 concentration (parts per million)
Ice core temperature (degrees C)
 Data from ice cores show present levels of
carbon dioxide are the highest in the last 400,000
years.
 Temperature and amount of carbon dioxide are
correlated
Figure 4.7
4.2 The Flow of Carbon
What will be the effects of increasing CO2?
 Predictions are based on computer models
 Negative feedbacks negate change
 Higher temperatures produce more clouds,
reducing energy input
 Positive feedbacks enhance change
 Melting ice reduces reflectiveness of the Earth
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End Chapter 4 Section 2
The Flow of Carbon
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Chapter 4 Section 3
Cellular Respiration
Part A – ATP as cellular energy source
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4.3 Cellular Respiration
Cellular Respiration
 Cellular respiration converts energy from
food into energy stored in ATP.
 ATP consists of adenine, a sugar, and 3
phosphate groups.
Nitrogenous base
(adenine)
Sugar
Three negatively
(ribose) charged phosphates
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Figure 4.9
4.3 Cellular Respiration
Phosphorylation
 When a phosphate group is transferred
from ATP to another molecule
(phosphorylation), energy is transferred
and ADP is produced.
+
+
ADP
ATP
Enzyme
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Phosphorylated (energized)
enzyme
Figure 4.11
4.3 Cellular Respiration
 The energy from ATP can power different
kinds of work in the cell.
(a) Mechanical work
(b) Transport work
(c) Chemical work
Low concentration of solute
ADP + P
Chlamydomonas
ATP
ATP
ADP + P
ADP + P
ATP
Enzyme
Flagella
Substrates
Product
High concentration of solute
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Figure 4.12
4.3 Cellular Respiration
 As ATP is used in the cell it must be
replenished by cellular respiration.
 Food energy adds phosphates to ADP
molecules to make ATP.
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4.3 Cellular Respiration
Energy in Molecular Bonds
 Fire releases energy by breaking molecular
bonds
 It requires oxygen – it is aerobic.
Glucose+oxygen ->carbon dioxide+water+energy
C6H12O6 + 6 O2-> 6 CO2 + 6 H2O + energy
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4.3 Cellular Respiration
 Cellular respiration releases the energy of
molecular bonds slowly,
 so that the energy can be captured to make high
energy ATP molecules
 The process uses oxygen – it is aerobic.
Glucose+oxygen ->carbon dioxide+water+energy
C6H12O6 + 6 O2-> 6 CO2 + 6 H2O + energy
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Chapter 4 Section 3
Cellular Respiration
END Part A – ATP as cellular energy source
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Chapter 4 Section 3
Cellular Respiration
Part B – Converting Glucose to ATP
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4.3 Cellular Respiration
How Glucose is converted to ATP
 Many of the reactions in cellular repiration occur
in the mitochondria.
Glucose+oxygen ->carbon dioxide+water+energy
C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy
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4.3 Cellular Respiration
Cellular Respiration occurs in three steps.
1. Glycolysis
2. Kreb’s Citric Acid Cycle
3. Electron Transport Chain & ATP synthesis
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4.3 Cellular Respiration
Step 1: Glycolysis
 6-carbon glucose molecule is broken down
into two 3-carbon pyruvic acid molecules.
 Takes place in the cytosol
 Anaerobic: does not require oxygen
 Produces 2 ATP molecules
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4.3 Cellular Respiration
Step 1: Glycolysis
 Following glycolysis, pyruvic acid is
decarboxylated to become a 2-carbon
molecule
 These 2 carbon molecules enter the
mitochondria
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4.3 Cellular Respiration –
Step 2: Citric Acid Cycle
 Mitochondria have an inner and outer
membrane, with an intermembrane
space between them.
 Matrix: semifluid medium inside the
mitochondrion
(a) Cross section of a mitochondrion
(b) Mitochondrial features
Outer
membrane
Inner
membrane
Matrix
Intermembrane
space
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Figure 4.18
4.3 Cellular Respiration
Step 2: Citric Acid Cycle
 Citric acid cycle: series of chemical
reactions catalyzed by 8 different enzymes
in the mitochondrial matrix
 The result is the generation of 2 ATP,
NADH and release of carbon dioxide.
3-Carbon pyruvic acid
CO2 released
Citric acid
cycle
2-Carbon molecule
Oxaloacetate
Matrix
NADH
Citric acid cycle
enzymes
2 ATP
Mitochondrion
CO2 released
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Figure 4.19
4.3 Cellular Respiration
Step 2: Citric Acid Cycle
 Electrons removed during the citric acid
cycle are carried by electron carriers.
 Nicotinamide adenine dinucleotide
(NAD+) and (NADH)
1 proton added
2 electrons added
Electron
Proton
NAD+
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+
2 H atoms
(2 protons
and 2 electrons)
NADH
+
H+
(1 positively
charged proton)
Figure 4.20
4.3 Cellular Respiration
Step 2: Citric Acid Cycle
NAD+ & NADH
 Like a taxi, NAD+
picks up electrons,
becoming NADH.
 NADH brings the
electrons to the
electron transport
chain, turning back
into NAD+
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Electron transport
chain
NAD+
Citric
acid
cycle
NADH
Mitochondrion
Figure 4.21
4.3 Cellular Respiration
Step 3: Electron Transport and ATP Synthesis
 Electron transport chain acts like a
conveyor belt, moving electrons through a
series of proteins.
 At the end of the chain, the electrons combine
with oxygen & H+ to produce water.
Cytosol
Outer mitochondrial
membrane
H+
H+
H+ 2
Electron transport
chain proteins
2
H+
Inner
mitochondrial
membrane
Intermembrane
space
ADP + P
26
NADH
1/2 O2 + 2H+
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ATP
H2O
Figure 4.22
4.3 Cellular Respiration
Step 3: Electron Transport and ATP Synthesis
 Each time an electron is passed to another
protein, H+ ions are pumped into the
intermembrane space.
 The concentration of H+ ions increases within
the intermembrane space.
Cytosol
Outer mitochondrial
membrane
H+
H+
2
H+
Electron transport
chain proteins
H+
2
Inner
mitochondrial
membrane
Intermembrane
space
ADP + P
26
NADH
1/2 O2 + 2H+
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ATP
H2O
Figure 4.22
4.3 Cellular Respiration –
Step 3: Electron Transport and ATP Synthesis
 H+ ions are charged, and can’t simply diffuse
back across the membrane.
 So they pass through protein channels called
ATP synthase, generating 26 ATPs as they
do.
Cytosol
Outer mitochondrial
membrane
H+
H+
H+
2
Electron transport
chain proteins
2
H+
Inner
mitochondrial
membrane
Intermembrane
space
ADP + P
26
NADH
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1/2 O2 + 2H+
ATP
H2O
4.3 Cellular Respiration –
Step 3: End result of Electron Transport
 The 2 pyruvic acids produced by glycolysis
are converted into carbon dioxide and water.
Summary of ATP from Cellular Respiration
 36 total ATP are generated by cell
respiration
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4.3 Cellular Respiration Summary
Glycolysis Summary
•Glucose input
•2 ATP & 2 Pyruvic acids & NADH output
Krebs Citric Acid Cycle Summary
•2 ATP, 6 CO2 , and NADH produced
Electron Transport Summary
•6 O2 input
•32 ATP & 6 H2O produced
Overall Summary
C6H12O6 + 6 O2->6 CO2 + 6 H2O+ 36 ATP(energy)
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4.3 Cellular Respiration
Cellular Respiration
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Chapter 4 Section 3
Cellular Respiration
Part C – Converting Other Nutrients to ATP
And Anaerobic Respiration
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4.3 Cellular Respiration
Metabolism of Other Nutrients
 Proteins and fats can also provide energy
when carbohydrates are unavailable.
 They are broken down and their subunits
feed into the carbohydrate breakdown
pathway just described.
Fats
Fatty acids
Glycerol
Carbohydrates
Glucose
Glycolysis
NH3
Proteins
Pyruvic
acid
2-carbon
fragment
ATP
Amino acids
Cytosol
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Mitochondrion
Figure 4.23
4.3 Cellular Respiration - Metabolism Without
Oxygen: Anaerobic Respiration and
Fermentation
(a) Human muscle
 Cells can generate
energy without oxygen
through anaerobic
respiration.
 Muscle cells can
produce lactic acid to
regenerate NAD+
through fermentation.
Regeneration
NAD+
Glucose
NADH
2 pyruvate
Glycolysis
2 ADP
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NADH
NAD+
2 lactate
Fermentation
2
ATP
Figure 4.24a
4.3 Cellular Respiration - Metabolism Without
Oxygen: Anaerobic Respiration and
Fermentation
(b) Yeast
 Bacteria in yogurt also
use fermentation to
make lactic acid.
 Yeast cells use
fermentation to convert
glucose to ethanol.
Regeneration
NAD+
Glucose
NADH
2 pyruvate
Glycolysis
2 ADP
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NADH
NAD+
2 ethanol + 2CO2
Fermentation
2
ATP
Figure 4.24b
4.3 Cellular Respiration
PLAY
Animation—Glucose Metabolism
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Chapter 4 Section 3
Cellular Respiration
END Part C – Converting Other Nutrients to ATP
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Chapter 4 Section 4
Photosynthesis
Part A – Chloroplasts, The Light Reaction
& Calvin Cycle
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4.4 Photosynthesis - Overview
 Photosynthesis accomplishes the opposite of
aerobic cellular respiration.
 Carbon dioxide is combined with water, using
light energy to produce glucose and oxygen.
carbon dioxide+ water+energy ->Glucose+oxygen
6 CO2 + 6 H2O + energy -> C6H12O6 + 6 O2
 Photosynthesis is done by plants and some
bacteria, but not by animals or fungi.
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4.4 Photosynthesis
Photosynthesis
 Occurs in organelles
called chloroplasts.
 Stroma: thick fluid
inside chloroplasts.
(b)
Envelope
Outer
membrane
Inner
membrane
Stroma
Thylakoids
Granum
•Thylakoids: disk-like membrane structures that give
the chloroplast more surface area.
•Surface of thylakoid is covered with chlorophyll pigment
molecules
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Figure 4.29b
4.4 Photosynthesis - The Light Reactions
Two Steps of Photosynthesis:
1. Light reactions



Photo step
Occurs in thylakoids
Produce ATP, NADPH, and Oxygen
2. Calvin Cycle



Synthesis step
Occurs in stroma of chloroplast
Use ATP and NADPH to make Sugar & O2
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4.4 Photosynthesis - The Light Reactions
Light reactions (thylakoids):
 light energy is absorbed by chlorophyll
and excites chlorophyll electrons.
 Electrons move down an electron transport
chain, producing ATP
Outer
chloroplast
membrane
Inner
chloroplast
membrane
CO2
NADP++ H++ 2e–
Light
energy
1 Light
energy
Stroma
NADPH
Stroma
ATP
3 Electron
transport
chain
Calvin
cycle
Chlorophyll
Sugar
H+
Chloroplast
H2O
H+
H+
2 Water is split
Thylakoid
Stroma
O2
Thylakoid membrane
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ATP
synthase
4.4 Photosynthesis - The Light Reactions
 Water is split to give off:
 Electrons to replace those lost by chlorophyll
 H+ is released to thylakoid interior
 O2 releases as waste product
Outer
chloroplast
membrane
Inner
chloroplast
membrane
CO2
NADP++
Light
energy
1 Light
energy
Stroma
H+ +
2e–
NADPH
Stroma
ATP
3 Electron
transport
chain
Calvin
cycle
Chlorophyll
Sugar
H+
Chloroplast
H2O
H+
H+
ATP
synthase
2 Water is split
Thylakoid
Stroma
O2
Thylakoid membrane
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Figure 4.30
4.4 Photosynthesis - The Light Reactions
 NADP+ captures electrons to become NADPH.
 NADPH ferries electrons to the stroma for the
Calvin cycle.
Outer
chloroplast
membrane
Inner
chloroplast
membrane
CO2
NADP++
Light
energy
1 Light
energy
Stroma
H+ +
2e–
NADPH
Stroma
ATP
3 Electron
transport
chain
Calvin
cycle
Chlorophyll
Sugar
H+
Chloroplast
H2O
H+
H+
ATP
synthase
2 Water is split
Thylakoid
Stroma
O2
Thylakoid membrane
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Figure 4.30
4.4 Photosynthesis - Calvin Cycle
Calvin Cycle
 Takes place
independently of
presence of light
 Occurs in the stroma
Light
energy
Light reactions
occur in the
thylakoids.
H2O
Thylakoids
CO2
Stroma
NADP+
ADP + P
ATP
NADPH
Chloroplast
Calvin
cycle
Sugars
The Calvin cycle
occurs in the stroma
of the chloroplast.
O2
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Figure 4.31
4.4 Photosynthesis
Calvin Cycle
 Hydrogen atoms
removed from
NADPH
 Combined with
carbon dioxide to
produce
carbohydrates
Light
energy
Light reactions
occur in the
thylakoids.
H2O
Thylakoids
CO2
Stroma
NADP+
ADP + P
ATP
NADPH
Chloroplast
Calvin
cycle
Sugars
The Calvin cycle
occurs in the stroma
of the chloroplast.
O2
CO2 + 2 H+ + energy -> CH2O + O or
6 CO2 + 12 H+ energy -> C6H12O6 + 3O2
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Figure 4.31
4.4 Photosynthesis
Photosynthesis
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Chapter 4 Section 4
Photosynthesis
END Part A – Chloroplasts, The Light
Reaction & Calvin Cycle
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Chapter 4 Section 4
Photosynthesis
Part B – C3, C4, and CAM Plants
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4.4 Photosynthesis - C3, C4, and CAM Plants
Leaf Structure
 Guard cells regulate stomata openings
 Transpiration = movement of water out of a
plant through stomata
 Stomata open: plenty of carbon dioxide, but
loss of water
 Stomata closed: conserves water, but limits
photosynthesis
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4.4 Photosynthesis
PLAY
Animation—Leaves: The Site of Photosynthesis
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4.4 Photosynthesis - C3, C4, and CAM Plants
C3 Plants
 Most plants are C3 plants
 (Calvin cycle makes 3 carbon sugar G3P)
 Close stomata to conserve water when hot
 Can cause photorespiration to occur
 Calvin cycle uses O2 instead of CO2
 Creates toxic glycolate instead of G3P
 must be removed
Use ATP and release carbon dioxide in
the breakdown of toxic glycolate.
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4.4 Photosynthesis - C3, C4, and CAM Plants
C4 plants avoid photorespiration
 An additional enzyme allows them to make
sugars even though stomata are almost
closed
 Examples: corn and sugar cane
 But there is a cost
 C3 plants need 3 ATP to make sugar,
 C4 plants need 5 ATP
 And enzymes in C4 are more cold sensitive
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4.4 Photosynthesis - C3, C4, and CAM Plants
CAM Plants (crassulacean acid metabolism)
 CAM plants open their stomata only at
night.
 Carbon from CO2 is stored as an acid
 During the day, acid is broken down to
carbon dioxide for use in photosynthesis
 But, growth is limited as only small amount
of CO2 is stored at night for photosynthesis
during the day
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4.4 Photosynthesis - C3, C4, and CAM Plants
C3 versus C4 versus CAM plants
 C3 plants
 C3 plants need 3 ATP to make sugar
 Good in cool, shady environments
 C4 plants
 C4 plants need 5 ATP to make sugar
 enzymes in C4 are more cold sensitive
 Good in hot, sunny environments
 CAM plants
 Can live in very hot, very dry environments
 But growth is limited
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Chapter 4 Section 4
Photosynthesis
END Part B – C3, C4, and CAM Plants
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Chapter 4 Section 4 Part C and
Section 5
Plants, fossil fuels and greenhouse gases
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4.4 Photosynthesis & Fossil Fuels
Photosynthesis & Fossil Fuels
Oil (AKA hydrocarbons) is composed of long chains of
carbon & hydrogen
Fossil fuels come from plant matter that with pressure,
heat, time converted plants simple sugars into oil
The high carbon fossil fuels are the result of 100 million
years of photosynthesis that converted CO2 into energy rich
molecules.
As we burn oil & natural gas, we are releasing 100 million
years of accumulated photosynthetic CO2 into the
atmosphere
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4.4 Photosynthesis –
Global Warming and Photosynthesis
 Carbon dioxide is currently being released
faster than photosynthesis can remove it
 Deforestation: clearing of forests for
farming and human settlements
 25% of carbon dioxide added to the
atmosphere comes from cutting and burning
forests in the tropics.
 Grasslands and crops remove 30-60% less
CO2 per acre than forests
 Replanting helps: young trees have faster
net photosynthetic rates than older trees.
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4.5 Decreasing the Effects of Global Warming
 Biggest sources of carbon dioxide emissions:
 Industry
 Transportation
 Commercial, residential, agricultural
 Each of us can work to reduce our own
contribution (“carbon footprint”) to worldwide
emissions.
 Calculate your carbon footprint at:
www.nature.org/initiatives/climatechange/calculator/
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4.5 Decreasing the Effects of Global Warming
Polar Bears and Global Warming
•Polar bears live on
arctic ice flows
hunting seals for
food
•As the ice flows
melt, polar bears are
drowning as they
swim between now
distance ice
www.nwf.org/Global-Warming/Effects-on-Wildlife-and-Habitat/Polar-Bears.aspx
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END of Chapter 4
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