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Photosynthesis occurs in the green leaves of
plants. How is photosynthesis important in the
flow of carbon through an ecosystem?

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Textbook Table of Contents

Ten

C H A P T E R

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Photosynthesis

Chapter Outline

CHAPTER OUTLINE
Photosynthetic organisms are autotrophs.
What is light?
Pigments absorb light, which drives photosynthesis.
Photosynthesis requires both photochemical and
biochemical reactions to produce sugars.
Chloroplasts are the site of photosynthesis in plants.
The light reactions of photosynthesis produce ATP.
The light reactions of photosynthesis also
produce NADPH.
Perspective 10.1 The Evolution of the Light Reactions
The biochemical reactions convert CO2 to
carbohydrates.
Rubisco is not perfect and fuels carbon loss via
photorespiration.
Perspective 10.2 The Evolution of Photosynthesis:
Why Aren’t Plants Black?
Perspective 10.3 How Did Such a Wasteful Process as
Photorespiration Evolve?
C4 photosynthesis employs two CO2 fixation steps and
probably evolved during times of low CO2 levels in
the atmosphere.
Perspective 10.4 Why Don’t C4 Plants Dominate the
Landscape?

Crassulacean acid metabolism (CAM) is the
third main type of photosynthesis known and
probably evolved in arid ecosystems.
What environmental factors affect the rates of
photosynthesis?
What happens to the products of the Calvin cycle?
Perspective 10.5 Atmospheric CO2 and Photosynthesis

Learning Online
LEARNING ONLINE

The Online Learning Center at www.mhhe.com/botany provides
practice quizzes and key term flashcards to help you study for upcoming exams and assignments. Do you know how the release of oxygen in ancient atmospheres was important to the evolution of plants and animals? Visit http:/

/photoscience.la.asu.edu/photosyn
in chapter 10 of the OLC to learn more about photosynthesis and the formation of carbohydrates.

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C H A P T E R

T E N

Photosynthesis is a light-driven series of chemical reactions that convert the energy-poor compound, carbon dioxide (CO2), to energy-rich sugars. In plants, photosynthesis also splits water and releases oxygen (O2). Over time, the oxygen released by photosynthesis has

dramatically changed the earth’s atmosphere and enabled the evolution of aerobic respiration in animals and other organisms. Today, as in the past, virtually all life
depends on photosynthesis, which can be summarized
with the following general equation:
CO2 ϩ H2O

light
chlorophyll

sugars ϩ O2

Photosynthesis has real meaning for you other
than just directly providing your fruits, vegetables, and

grains and the oxygen in the air you breathe. In fact, today you have probably used many processed products of photosynthesis, such as cotton fiber for shirts or pants, wood to form a pencil or toothpick, and plastic or paper

to make a soft drink cup. If you drove an automobile today, it most likely ran on gasoline, which is really just a modern product formed by processing the products of
ancient photosynthesis that became gas, oil, and coal
long ago. The next time you drive into a filling station,
ask for a tank of ancient photosynthesis and see what
kind of response you receive.
How does photosynthesis work in plants? Look at
a leaf of a green plant. Is it carrying on photosynthesis
now? This chapter will provide the information necessary to begin to answer these questions. As you study the process of photosynthesis, keep in mind its importance
in ecology and in the evolution of life on earth today.

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Photosynthetic Organisms
Are Autotrophs.

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Before the evolution of photosynthesis, virtually all organisms used organic compounds (those with carbon-tocarbon bonds; see chapter 3) as sources of energy in the planet’s “primeval broth”. Those one-celled organisms

were heterotrophs—that is,...
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