You should now be able toDescribe two plant adaptations that
save water in hot, dry climatesDetail how photosynthesis could help
moderate globing warmingDiscuss the importance of the Earths
protective ozone layerCopyright 2009 Pearson Education, Inc.
Photosynthesis nourishes almost the entire living world directly
or indirectly. Almost all plants are autotrophs, meaning that they
sustain themselves without eating anything derived from other
living beings. Plants produce oxygen, a by-product of
photosynthesis, that is used in respiration.The solar energy used
in photosynthesis traveled 150 million kilometers from the sun to
Earth to be converted into chemical energy.You may want to
reintroduce the terms producers and consumers within the context of
this chapter.The importance of greenhouse gases that lead to global
warming will be discussed later in this chapter.Although
photosynthesis occurs on a microscopic level, when carried out
repeatedly in plants around the world, it is responsible for an
enormous amount of product.A very interesting class of autotrophs
are the autotrophic bacteria that use carbon dioxide to synthesize
organic molecules without solar energy.
Teaching Tips1. When introducing the diverse ways that plants
impact our lives, consider challenging your students to come up
with a list of products made from plants that they come across on a
regular basis. The collective lists from your students can be
surprisingly long and might help to build up your catalog of
examples.2. The evolution of chloroplasts from photosynthetic
prokaryotes living inside of eukaryotic cells is briefly noted in a
reference to Module 4.16. If your students have not already read
Chapter 4, consider discussing the evidence that suggests this
endosymbiotic origin.3. Some students might think that the term
producers applies to the production of oxygen by plants. In turn,
they might think that consumers are organisms that use oxygen
(which would include all aerobic organisms). Extra care may be
needed to clarify the definitions of these frequently used
terms.
There are about half a million chloroplasts per square
millimeter of leaf surface.Chloroplast membranes are similar to
mitochondrial membranes in that both are important in
energy-harvesting duties of the cell.
Teaching Tips1. When introducing the diverse ways that plants
impact our lives, consider challenging your students to come up
with a list of products made from plants that they come across on a
regular basis. The collective lists from your students can be
surprisingly long and might help to build up your catalog of
examples.2. The evolution of chloroplasts from photosynthetic
prokaryotes living inside of eukaryotic cells is briefly noted in a
reference to Module 4.16. If your students have not already read
Chapter 4, consider discussing the evidence that suggests this
endosymbiotic origin.3. Some students might think that the term
producers applies to the production of oxygen by plants. In turn,
they might think that consumers are organisms that use oxygen
(which would include all aerobic organisms). Extra care may be
needed to clarify the definitions of these frequently used
terms.
Figure 7.2 The location and structure of chloroplasts.Figure 7.2
The location and structure of chloroplasts.Figure 7.2 The location
and structure of chloroplasts.C. B. van Niel of Stanford University
hypothesized that plants split water into hydrogen and oxygen. His
hypothesis was confirmed 20 years later.A significant result of
photosynthesis is the extraction of hydrogen from water and its
incorporation into sugar. Oxygen is a waste product of
photosynthesis.The chloroplast is the site where water is split
into hydrogen and oxygen.
Student Misconceptions and Concerns1. Students may not connect
the growth in plant mass to the fixation of carbon during the
Calvin cycle. It can be difficult for many students to appreciate
that molecules in air can contribute significantly to the mass of
plants.
Teaching Tips1. Many students do not realize that glucose is not
the direct product of photosynthesis. The authors note that
although glucose is shown as a product of photosynthesis, a
three-carbon sugar is directly produced (G3P). A plant can use G3P
to make many types of organic molecules, including glucose.
Figure 7.3A Oxygen bubbles on the leaves of an aquatic
plant.Figure 7.3B Experiments tracking the oxygen atoms in
photosynthesis.Figure 7.3C Fates of all the atoms in
photosynthesis.The simple sugar produced in photosynthesis is
glucose, using a number of energy-releasing redox reactions.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.
Figure 7.4A Photosynthesis (uses light energy).In respiration,
mitochondria harness chemical energy to synthesize ATP.In
photosynthesis, the energy boost is provided by light and occurs in
chloroplasts. Eventually, ATP is synthesized.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.
Figure 7.4B Cellular respiration (releases chemical energy).
The sugar produced in photosynthesis is stored for later use or
as raw material for biosynthesis of new plant material.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.
The two metabolic stages are the light reactions and the Calvin
cycle.
Student Misconceptions and Concerns1. Students may understand
the overall chemical relationships between photosynthesis and
cellular respiration, but many struggle to understand the use of
carbon dioxide in the Calvin cycle. Photosynthesis is much more
than gas exchange.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.2. Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure demonstrates where water and
sunlight are used in the thylakoid membranes to generate oxygen,
ATP, and NADPH. The second step, in the stroma, reveals the use of
carbon dioxide, ATP, and NADPH to generate carbohydrates.
Catabolic processes like cellular respiration generally use NAD+
as the initial hydrogen acceptor, while anabolic reactions, such as
photosynthesis, use NADP+.Sugar is not produced in the light
reactions; it is not produced until the Calvin cycle, the second
stage of photosynthesis.
Student Misconceptions and Concerns1. Students may understand
the overall chemical relationships between photosynthesis and
cellular respiration, but many struggle to understand the use of
carbon dioxide in the Calvin cycle. Photosynthesis is much more
than gas exchange.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.2. Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure demonstrates where water and
sunlight are used in the thylakoid membranes to generate oxygen,
ATP, and NADPH. The second step, in the stroma, reveals the use of
carbon dioxide, ATP, and NADPH to generate carbohydrates.
The Calvin cycle was named for the Nobel laureate, Melvin
Calvin, who traced the path of carbon in the cycle.
Student Misconceptions and Concerns1. Students may understand
the overall chemical relationships between photosynthesis and
cellular respiration, but many struggle to understand the use of
carbon dioxide in the Calvin cycle. Photosynthesis is much more
than gas exchange.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.2. Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure demonstrates where water and
sunlight are used in the thylakoid membranes to generate oxygen,
ATP, and NADPH. The second step, in the stroma, reveals the use of
carbon dioxide, ATP, and NADPH to generate carbohydrates.
The Calvin cycle occurs during daytime in most plants when the
light reactions are powering the cycles sugar assembly line.
For the BioFlix Animation Photosynthesis, go to Animation and
Video Files.For the Discovery Video Trees, go to Animation and
Video Files.
Student Misconceptions and Concerns1. Students may understand
the overall chemical relationships between photosynthesis and
cellular respiration, but many struggle to understand the use of
carbon dioxide in the Calvin cycle. Photosynthesis is much more
than gas exchange.
Teaching Tips1. In our world, energy is frequently converted to
a usable form in one place and used in another. For example,
electricity is generated by power plants, transferred to our homes,
and used to run computers, create light, and help us prepare foods.
Consider relating this common energy transfer to the two-stage
process of photosynthesis.2. Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure demonstrates where water and
sunlight are used in the thylakoid membranes to generate oxygen,
ATP, and NADPH. The second step, in the stroma, reveals the use of
carbon dioxide, ATP, and NADPH to generate carbohydrates.
Figure 7.5 An overview of the two stages of photosynthesis that
take place in a chloroplast.Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure reminds students where water
and sunlight are used in the thylakoid membranes to generate
oxygen, ATP, and NADPH. The second step, in the stroma, reveals the
use of carbon dioxide, ATP, and NADPH to generate carbohydrates.
Figure 7.5 An overview of the two stages of photosynthesis that
take place in a chloroplast.Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure reminds students where water
and sunlight are used in the thylakoid membranes to generate
oxygen, ATP, and NADPH. The second step, in the stroma, reveals the
use of carbon dioxide, ATP, and NADPH to generate carbohydrates.
Figure 7.5 An overview of the two stages of photosynthesis that
take place in a chloroplast.Figure 7.5 is an important visual
organizer that notes the key structures and functions of the two
stages of photosynthesis. This figure reminds students where water
and sunlight are used in the thylakoid membranes to generate
oxygen, ATP, and NADPH. The second step, in the stroma, reveals the
use of carbon dioxide, ATP, and NADPH to generate carbohydrates.
Student Misconceptions and Concerns1. The authors note that
electromagnetic energy travels through space in waves that are like
ripples made by a pebble dropped in a pond. This wave imagery is
helpful, but can confuse students when energy is also thought of as
discrete packets called photons. The dual nature of light, which
exhibits the properties of both waves and particles, may need to be
discussed further, if students are to do more than just accept the
definitions. 2. The authors note that sunlight is a type of
radiation. Many students think of radiation as a result of
radioactive decay, a serious threat to health. The diverse types of
radiation and the varying energy associated with each might need to
be explained. 3. Even at the college level, students struggle to
understand why we perceive certain colors. The authors discuss the
specific absorption and reflection of certain wavelengths of light,
noting which colors are absorbed and which are reflected (and thus
available for our eyes to detect). Consider spending time to make
sure that your students understand how photosynthetic pigments
absorb and reflect certain wavelengths.
Teaching Tips1. Consider bringing a prism to class and
demonstrating the spectrum of light. Depending on what you have
available, it can be a dramatic reinforcement.
Shorter wavelengths such as gamma rays and X-rays contain much
more energy than the longer wavelengths, such as radio waves.
Student Misconceptions and Concerns1. The authors note that
electromagnetic energy travels through space in waves that are like
ripples made by a pebble dropped in a pond. This wave imagery is
helpful, but can confuse students when energy is also thought of as
discrete packets called photons. The dual nature of light, which
exhibits the properties of both waves and particles, may need to be
discussed further, if students are to do more than just accept the
definitions. 2. The authors note that sunlight is a type of
radiation. Many students think of radiation as a result of
radioactive decay, a serious threat to health. The diverse types of
radiation and the varying energy associated with each might need to
be explained. 3. Even at the college level, students struggle to
understand why we perceive certain colors. The authors discuss the
specific absorption and reflection of certain wavelengths of light,
noting which colors are absorbed and which are reflected (and thus
available for our eyes to detect). Consider spending time to make
sure that your students understand how photosynthetic pigments
absorb and reflect certain wavelengths.
Teaching Tips1. Consider bringing a prism to class and
demonstrating the spectrum of light. Depending on what you have
available, it can be a dramatic reinforcement.
Figure 7.6A The electromagnetic spectrum and the wavelengths of
visible light. (A wavelength of 650 nm is illustrated.)Each type of
pigment absorbs certain wavelengths of light because it is able to
absorb the specific amount of energy in those photons.
Student Misconceptions and Concerns1. The authors note that
electromagnetic energy travels through space in waves that are like
ripples made by a pebble dropped in a pond. This wave imagery is
helpful, but can confuse students when energy is also thought of as
discrete packets called photons. The dual nature of light, which
exhibits the properties of both waves and particles, may need to be
discussed further, if students are to do more than just accept the
definitions. 2. The authors note that sunlight is a type of
radiation. Many students think of radiation as a result of
radioactive decay, a serious threat to health. The diverse types of
radiation and the varying energy associated with each might need to
be explained. 3. Even at the college level, students struggle to
understand why we perceive certain colors. The authors discuss the
specific absorption and reflection of certain wavelengths of light,
noting which colors are absorbed and which are reflected (and thus
available for our eyes to detect). Consider spending time to make
sure that your students understand how photosynthetic pigments
absorb and reflect certain wavelengths.
Teaching Tips1. Consider bringing a prism to class and
demonstrating the spectrum of light. Depending on what you have
available, it can be a dramatic reinforcement.
Figure 7.6B The interaction of light with a chloroplast.The
colors of fall foliage in certain parts of the world are due partly
to the yellow-orange hues of longer lasting carotenoids that show
through once the green chlorophyll breaks down.
Student Misconceptions and Concerns1. The authors note that
electromagnetic energy travels through space in waves that are like
ripples made by a pebble dropped in a pond. This wave imagery is
helpful, but can confuse students when energy is also thought of as
discrete packets called photons. The dual nature of light, which
exhibits the properties of both waves and particles, may need to be
discussed further, if students are to do more than just accept the
definitions. 2. The authors note that sunlight is a type of
radiation. Many students think of radiation as a result of
radioactive decay, a serious threat to health. The diverse types of
radiation and the varying energy associated with each might need to
be explained. 3. Even at the college level, students struggle to
understand why we perceive certain colors. The authors discuss the
specific absorption and reflection of certain wavelengths of light,
noting which colors are absorbed and which are reflected (and thus
available for our eyes to detect). Consider spending time to make
sure that your students understand how photosynthetic pigments
absorb and reflect certain wavelengths.
Teaching Tips1. Consider bringing a prism to class and
demonstrating the spectrum of light. Depending on what you have
available, it can be a dramatic reinforcement.
Student Misconceptions and Concerns1. Even at the college level,
students struggle to understand why we perceive certain colors. The
authors discuss the specific absorption and reflection of certain
wavelengths of light, noting which colors are absorbed and which
are reflected (and thus available for our eyes to detect). Consider
spending time to make sure that your students understand how
photosynthetic pigments absorb and reflect certain wavelengths.
Teaching Tips1. The authors discuss a phenomenon that most
students have noticed: dark surfaces heat up faster in the sun than
do lighter-colored surfaces. This is an opportunity to demonstrate
to your students the various depths of scientific explanations and
help them appreciate their own educational progress. In elementary
school, they might have learned that the sun heats darker surfaces
faster than lighter surfaces. In high school, they may have learned
about light energy and the fact that dark surfaces absorb more of
this energy than lighter surfaces. Now, in college, they are
learning that at the atomic level, darker surfaces absorb the
energy of more photons, exciting more electrons, which then fall
back to a lower state, releasing more heat.
Figure 7.7A A solution of chlorophyll glowing red when
illuminated (left); a diagram of an isolated, light-excited
chlorophyll molecule that releases a photon of red light
(right).Figure 7.7A A solution of chlorophyll glowing red when
illuminated.Figure 7.7A Light-excited chlorophyll molecule that
releases a photon of red light.Because of their functions, you can
think of photosystems as light-gathering antennae.
Student Misconceptions and Concerns1. Even at the college level,
students struggle to understand why we perceive certain colors. The
authors discuss the specific absorption and reflection of certain
wavelengths of light, noting which colors are absorbed and which
are reflected (and thus available for our eyes to detect). Consider
spending time to make sure that your students understand how
photosynthetic pigments absorb and reflect certain wavelengths.
Teaching Tips1. The authors discuss a phenomenon that most
students have noticed: dark surfaces heat up faster in the sun than
do lighter-colored surfaces. This is an opportunity to demonstrate
to your students the various depths of scientific explanations and
help them appreciate their own educational progress. In elementary
school, they might have learned that the sun heats darker surfaces
faster than lighter surfaces. In high school, they may have learned
about light energy and the fact that dark surfaces absorb more of
this energy than lighter surfaces. Now, in college, they are
learning that at the atomic level, darker surfaces absorb the
energy of more photons, exciting more electrons, which then fall
back to a lower state, releasing more heat.
Student Misconceptions and Concerns1. Even at the college level,
students struggle to understand why we perceive certain colors. The
authors discuss the specific absorption and reflection of certain
wavelengths of light, noting which colors are absorbed and which
are reflected (and thus available for our eyes to detect). Consider
spending time to make sure that your students understand how
photosynthetic pigments absorb and reflect certain wavelengths.
Teaching Tips1. The authors discuss a phenomenon that most
students have noticed: dark surfaces heat up faster in the sun than
do lighter-colored surfaces. This is an opportunity to demonstrate
to your students the various depths of scientific explanations and
help them appreciate their own educational progress. In elementary
school, they might have learned that the sun heats darker surfaces
faster than lighter surfaces. In high school, they may have learned
about light energy and the fact that dark surfaces absorb more of
this energy than lighter surfaces. Now, in college, they are
learning that at the atomic level, darker surfaces absorb the
energy of more photons, exciting more electrons, which then fall
back to a lower state, releasing more heat.
The photosystems were named in order of their discovery, not in
order of their function.
Student Misconceptions and Concerns1. Even at the college level,
students struggle to understand why we perceive certain colors. The
authors discuss the specific absorption and reflection of certain
wavelengths of light, noting which colors are absorbed and which
are reflected (and thus available for our eyes to detect). Consider
spending time to make sure that your students understand how
photosynthetic pigments absorb and reflect certain wavelengths.
Teaching Tips1. The authors discuss a phenomenon that most
students have noticed: dark surfaces heat up faster in the sun than
do lighter-colored surfaces. This is an opportunity to demonstrate
to your students the various depths of scientific explanations and
help them appreciate their own educational progress. In elementary
school, they might have learned that the sun heats darker surfaces
faster than lighter surfaces. In high school, they may have learned
about light energy and the fact that dark surfaces absorb more of
this energy than lighter surfaces. Now, in college, they are
learning that at the atomic level, darker surfaces absorb the
energy of more photons, exciting more electrons, which then fall
back to a lower state, releasing more heat.
Figure 7.7B Light-excited chlorophyll embedded in a photosystem:
Its electron is transferred to a primary electron acceptor before
it returns to ground state.Teaching Tips1. The authors develop a
mechanical analogy for the energy levels and movement of electrons
in the light reaction. Figure 7.8B equates the height of an
electron with its energy state. Thus, electrons captured at high
levels carry more energy than electrons in lower positions.
Although this figure can be very effective, students might need to
be carefully led through the analogy to understand precisely what
is represented.
Figure 7.8B A mechanical analogy of the light reactions.Although
Figure 7.8B can be very effective, students might need to be
carefully led through the analogy to understand precisely what is
represented. Teaching Tips1. The authors develop a mechanical
analogy for the energy levels and movement of electrons in the
light reaction. Figure 7.8B equates the height of an electron with
its energy state. Thus, electrons captured at high levels carry
more energy than electrons in lower positions. Although this figure
can be very effective, students might need to be carefully led
through the analogy to understand precisely what is
represented.
Figure 7.8A Electron flow in the light reactions of
photosynthesis: Both photosystems and the electron transport chain
that connects them are located in the thylakoid membrane. The
energy from light drives electrons from water to NADPH.The gradient
is produced as the electron transport chain passes electrons down
the chain.
Teaching Tips1. Module 7.9 notes the similarities between
oxidative phosphorylation in mitochondria and photophosphorylation
in chloroplasts. If your students have not already read or
discussed chemiosmosis in mitochondria, consider assigning Modules
6.6 and 6.10 to show the similarities of these processes. (As noted
in Module 7.2, the thylakoid space is analogous to the
intermembrane space of mitochondria.)
Students should realize that electrons flowing between the two
photosystems do not end up at a low energy level in water as they
do in respiration; instead they are stored at a high state of
potential energy in NADPH.
Teaching Tips1. Module 7.9 notes the similarities between
oxidative phosphorylation in mitochondria and photophosphorylation
in chloroplasts. If your students have not already read or
discussed chemiosmosis in mitochondria, consider assigning Modules
6.6 and 6.10 to show the similarities of these processes. (As noted
in Module 7.2, the thylakoid space is analogous to the
intermembrane space of mitochondria.)
Figure 7.9 The production of ATP by chemiosmosis in
photosynthesis: The small diagram on the upper left illustrates the
location of the components of the light reactions in a thylakoid
membrane. Numerous copies of these components are present in each
thylakoid.Figure 7.9 The production of ATP by chemiosmosis in
photosynthesis.The Calvin cycle is called a cycle because the
starting material is regenerated as the process occurs.
Student Misconceptions and Concerns1. As noted in Module 7.5,
the terms light reactions and dark reactions can lead students to
conclude that each set of reactions occurs at a different time of
the day. However, the Calvin cycle in most plants occurs during
daylight, when NADPH and ATP from the light reactions are readily
available.
Teaching Tips1. Glucose is not the direct product of the Calvin
cycle, as might be expected from the general equation for
photosynthesis. Instead, G3P, as noted in the text, is the main
product. Clarify the diverse uses of G3P in the production of many
important plant molecules for students.
Figure 7.10A An overview of the Calvin cycle.To synthesize one
G3P molecule, the Calvin cycle consumes nine ATP and six NADPH
molecules, which were provided by the light reactions.
Student Misconceptions and Concerns1. As noted in Module 7.5,
the terms light reactions and dark reactions can lead students to
conclude that each set of reactions occurs at a different time of
the day. However, the Calvin cycle in most plants occurs during
daylight, when NADPH and ATP from the light reactions are readily
available.
Teaching Tips1. Glucose is not the direct product of the Calvin
cycle, as might be expected from the general equation for
photosynthesis. Instead, G3P, as noted in the text, is the main
product. Clarify the diverse uses of G3P in the production of many
important plant molecules for students.
Figure 7.10B Details of the Calvin cycle, which takes place in
the stroma of a chloroplast.Figure 7.10B Details of the Calvin
cycle, which takes place in the stroma of a chloroplast.Figure
7.10B Details of the Calvin cycle, which takes place in the stroma
of a chloroplast.Figure 7.10B Details of the Calvin cycle, which
takes place in the stroma of a chloroplast.Although
photosynthesizers produce sugar for self-consumption, their sugar
is a source for virtually all other organisms on Earth.
Student Misconceptions and Concerns1. Some students do not
realize that plant cells also have mitochondria. Instead, they
assume that the chloroplasts are sufficient for the plant cells
needs. As noted in the text, nearly 50% of the carbohydrates
produced by plant cells are used for cellular respiration
(involving mitochondria).
Teaching Tips1. Challenge students to explain how the energy in
beef is ultimately derived from the sun.2. The authors note that
G3P is also used to produce cellulose, the most abundant compound
on Earth. Each year, plants produce about 100 billion tons of
cellulose!
Figure 7.11 A summary of the chemical processes of
photosynthesis.Botanists believe photorespiration is an
evolutionary relic, left from times when there was little oxygen in
the atmosphere.
Teaching Tips1. If you can find examples of C3, C4, and CAM
plants, consider bringing them to class. Referring to living plants
helps students understand these abstract concepts. Nice photographs
can serve as a fine substitute.2. Relate the properties of C3 and
C4 plants to the regions of the country where each is grown.
Students might generally understand that crops have specific
requirements, but may not specifically relate these physiological
differences to their geographic sites of production or specific
evolutionary histories.
Teaching Tips1. If you can find examples of C3, C4, and CAM
plants, consider bringing them to class. Referring to living plants
helps students understand these abstract concepts. Nice photographs
can serve as a fine substitute.2. Relate the properties of C3 and
C4 plants to the regions of the country where each is grown.
Students might generally understand that crops have specific
requirements, but may not specifically relate these physiological
differences to their geographic sites of production or specific
evolutionary histories.
For the BLAST Animation Photosynthesis: Light-Independent
Reactions, go to Animation and Video Files.
Teaching Tips1. If you can find examples of C3, C4, and CAM
plants, consider bringing them to class. Referring to living plants
helps students understand these abstract concepts. Nice photographs
can serve as a fine substitute.2. Relate the properties of C3 and
C4 plants to the regions of the country where each is grown.
Students might generally understand that crops have specific
requirements, but may not specifically relate these physiological
differences to their geographic sites of production or specific
evolutionary histories.
Figure 7.12 Comparison of photosynthesis in C4 and CAM plants:
In both pathways, CO2 is first incorporated into a four-carbon
compound, which then provides CO2 to the Calvin cycle.Student
Misconceptions and Concerns1. Students may confuse global warming
with the breakdown of the ozone layer. Be prepared to explain both
phenomena and the impact of human activities.2. Students often do
not fully understand how the burning of fossil fuels contributes to
global warming. They might wonder, How does the burning of fossil
fuels differ from the burning of ethanol produced from crops?
Students might not realize that the carbon in fossil fuels was
removed from the atmosphere hundreds of millions of years ago,
while the carbon in crops was removed much more recently, when the
crops were grown.
Teaching Tips1. Some students might better relate the greenhouse
effect to what happens inside their closed car on a sunny day. The
glass in our automobiles functions just like the glass of a
greenhouse, trapping heat inside our car. This can be an advantage
during the winter but is usually not welcome on a hot summer
day!
Student Misconceptions and Concerns1. Students may confuse
global warming with the breakdown of the ozone layer. Be prepared
to explain both phenomena and the impact of human activities.2.
Students often do not fully understand how the burning of fossil
fuels contributes to global warming. They might wonder, How does
the burning of fossil fuels differ from the burning of ethanol
produced from crops? Students might not realize that the carbon in
fossil fuels was removed from the atmosphere hundreds of millions
of years ago, while the carbon in crops was removed much more
recently, when the crops were grown.
Teaching Tips1. Some students might better relate the greenhouse
effect to what happens inside their closed car on a sunny day. The
glass in our automobiles functions just like the glass of a
greenhouse, trapping heat inside our car. This can be an advantage
during the winter but is usually not welcome on a hot summer
day!
Student Misconceptions and Concerns1. Students may confuse
global warming with the breakdown of the ozone layer. Be prepared
to explain both phenomena and the impact of human activities.2.
Students often do not fully understand how the burning of fossil
fuels contributes to global warming. They might wonder, How does
the burning of fossil fuels differ from the burning of ethanol
produced from crops? Students might not realize that the carbon in
fossil fuels was removed from the atmosphere hundreds of millions
of years ago, while the carbon in crops was removed much more
recently, when the crops were grown.
Teaching Tips1. Some students might better relate the greenhouse
effect to what happens inside their closed car on a sunny day. The
glass in our automobiles functions just like the glass of a
greenhouse, trapping heat inside our car. This can be an advantage
during the winter but is usually not welcome on a hot summer
day!
Figure 7.13A Plants growing in a greenhouse.Figure 7.13B CO2 in
the atmosphere and global warming.
Student Misconceptions and Concerns1. Students may confuse
global warming with the breakdown of the ozone layer. Be prepared
to explain both phenomena and the impact of human activities.
Teaching Tips1. Consider an analogy between the ozone layer and
sunscreen applied to the skin. The thinning of the ozone layer is
like putting on less and less sunscreen. In both situations, more
harmful UV light penetrates the layers and causes damage.2.
Frustration can overwhelm concerned students alarmed by the many
problems addressed in this chapter. One way to address this is to
provide meaningful ways for students to respond to this information
(for example, changes in personal choices and voting). The Earth
Day Network, www.earthday.net, is just one of many Internet sites
devoted to positive action.
Figure 7.14A Mario Molina.Figure 7.14B The ozone hole in the
Southern Hemisphere, spring 2006.