Light from a living plant or animal is called bioluminescence, or cold light, to distinguish it from
incandescence or heat-generating light. Life forms could not produce incandescent light without being
burned. Their light is produced in chemicals combining in such a way that little or no measurable hcat is
produced, and the life forms generating it are unharmed. Although bioluminescence is a relatively
complicated process, it can be reduced to simple terms. Living light occurs when luciferin and oxygen
combine in the presence of luciferase. In a few cases, fireflies the most common, an additional compound
called ATP is required.
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The earliest recorded experiments with bioluminescence in the late 1800s are attributed to Raphael
Dubois, who extracted a luminous fluid from a clam, observing that it continued to glow in the test tube
for several minutes. He named the substance luciferin, which means "the bearer of life". In further
research, Dubois discovered that several chemicals were required for bioluminescence to occur. In his
notes, it was recorded that a second important substance, which he called luciferase, was always present.
In later study of small, luminous sea creatures, Newton Harley concluded that luciferin was composed of
carbon, hydrogen, and oxygen, which are the building blocks of all living cells. He also proved that there
are a variety of luciferin and luciferase, specific to the plants and animals that produce thcm.
Much remains unknown, but many scientists who are studying bioluminescence now believe that the
origin of the phenomenon may be traced to a time when there was no oxygen in the Earth's atmosphere.
When oxygen was gradually introduced to the atmosphere, it was actually poisonous to life forms, plants
and animals produced light to use up the oxygen in a gradual but necessary adaptation. It is speculated
that millions of years ago, all life may have produced light to survive. As the millennia passed, life forms
on Earth became tolerant of, and finally dependent on oxygen, and the adaptation that produced
bioluminescence was no longer necessary, but some primitive plants and animals continued to use the
light for new functions such as mating or attracting prey.
Question 30: Which of the following is the main topic of the passage?
A. Cold light B. Luciferase
C. Primitive plants and animals D. Earth's atmosphere
Question 31: The word “it” refers to___________
A. a plant B. an animal C. bioluminescence D. incandescence
Question 32: Where in the passage does the author explain how living light occurs?
A. Line 3-4 B. Line 5-6 C. Line 8-10 D. Line 10-12
Question 33: Bioluminescence is described as all of the following EXCEPT___________
A. a complex chemicals process
B. an adaptation of early plants and animals to the environment
C. a form of cold light
D. a poisonous substance
Question 34: The paragraph following the passage most probably discuss___________
A. incandescence in prehistoric plants and animals
B. incandescence in modern plants and animals
C. bioluminescence in prehistoric plants and animals
D. bioluminescence in modern plants and animals
