electronic systems
a. thet paint and wield
b. a reality
c. have made robots
d. many factories now have made robots
e. and
put them in right order
pleasssssss help me
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HomeHealth & MedicineAnatomy & Physiology
Photosynthesis
biology
WRITTEN BY
Hans Lambers See All Contributors
Head of the School of Plant Biology, University of Western Australia, Crawley, Western Australia.
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ARTICLE CONTENTS
overview of photosynthesis
overview of photosynthesis
The location, importance, and mechanisms of photosynthesis. Study the roles of chloroplasts, chlorophyll, grana, thylakoid membranes, and stroma in photosynthesis.
Encyclopædia Britannica, Inc.
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Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.
photosynthesis
photosynthesis
Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.
Encyclopædia Britannica, Inc.
Photosynthesis
QUICK FACTS
KEY PEOPLE
Joseph Priestley
Melvin Calvin
Jan Ingenhousz
Jean Senebier
Robert Huber
Johann Deisenhofer
Nicolas-Théodore de Saussure
Hartmut Michel
Robert Hill
RELATED TOPICS
Plant
Life
Chloroplast
Blue-green algae
Elysia chlorotica
Chlorophyll
Photolysis
Phototroph
Chlorophyll a
Living things
It would be impossible to overestimate the importance of photosynthesis in the maintenance of life on Earth. If photosynthesis ceased, there would soon be little food or other organic matter on Earth. Most organisms would disappear, and in time Earth’s atmosphere would become nearly devoid of gaseous oxygen. The only organisms able to exist under such conditions would be the chemosynthetic bacteria, which can utilize the chemical energy of certain inorganic compounds and thus are not dependent on the conversion of light energy.
TOP QUESTIONS
Why is photosynthesis important?
What is the basic formula for photosynthesis?
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Energy produced by photosynthesis carried out by plants millions of years ago is responsible for the fossil fuels (i.e., coal, oil, and gas) that power industrial society. In past ages, green plants and small organisms that fed on plants increased faster than they were consumed, and their remains were deposited in Earth’s crust by sedimentation and other geological processes. There, protected from oxidation, these organic remains were slowly converted to fossil fuels. These fuels not only provide much of the energy used in factories, homes, and transportation but also serve as the raw material for plastics and other synthetic products. Unfortunately, modern civilization is using up in a few centuries the excess of photosynthetic production accumulated over millions of years. Consequently, the carbon dioxide that has been removed from the air to make carbohydrates in photosynthesis over millions of years is being returned at an incredibly rapid rate. The carbon dioxide concentration in Earth’s atmosphere is rising the fastest it ever has in Earth’s history, and this phenomenon is expected to have major implications on Earth’s climate.
Requirements for food, materials, and energy in a world where human population is rapidly growing have created a need to increase both the amount of photosynthesis and the efficiency of converting photosynthetic output into products useful to people. One response to those needs—the so-called Green Revolution, begun in the mid-20th century—achieved enormous improvements in agricultural yield through the use of chemical fertilizers, pest and plant-disease control, plant breeding, and mechanized tilling, harvesting, and crop processing. This effort limited severe famines to a few areas of the world despite rapid population growth, but it did not eliminate widespread malnutrition. Moreover, beginning in the early 1990s, the rate at which yields of major crops increased began to decline. This was especially true for rice in Asia. Rising costs associated with sustaining high rates of agricultural production, which required ever-increasing inputs of fertilizers and pesticides and constant development of new plant varieties, also became problematic for farmers in many countries.
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A second agricultural revolution, based on plant genetic engineering, was forecast to lead to increases in plant productivity and thereby partially alleviate malnutrition. Since the 1970s, molecular biologists have possessed the means to alter a plant’s genetic material (deoxyribonucleic acid, or DNA) with the aim of achieving improvements in disease and drought resistance, product yield and quality, frost hardiness, and other desirable properties. However, such traits are inherently complex, and the process of making changes to crop plants through genetic