Glowing in the Dark Ocean
Written by Studio AM.
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Sunlight reaches only the upper layers of the ocean. Below about a thousand meters lies a realm of permanent darkness, crushing pressure, and frigid cold. Yet this seemingly empty zone teems with life, and much of it makes its own light. The ability of an organism to produce light through a chemical reaction is called bioluminescence, and it is widespread among animals in deep ocean waters.
Animals there use their glow for many purposes. Some anglerfish dangle a luminous lure to draw curious prey within reach of their jaws. Certain squid release a cloud of glowing fluid to confuse a predator, much as a shallow-water octopus releases ink. Others flash patterns to find a mate in the vast blackness. Because the open water offers few solid hiding places, light has become both a weapon and a language.
A sudden burst can startle an attacker, while a steady glow can betray the swimmer that produces it, so each animal must balance the risk of being seen against the benefit of being noticed. The color and timing of light can help animals recognize signals, although a display may also be detected by other species.
Studying these creatures is difficult, since the delicate animals often die when hauled up through warmer, lower-pressure water, so researchers increasingly send cameras and robotic vehicles down to observe them where they live. Such observations document behaviors that may be lost in a laboratory and sometimes reveal previously undescribed species. Much of the deep ocean remains unexplored.
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Questions
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Question 1 of 4
As used in the passage, 'bioluminescence' is
The answer is B: an organism producing light by a chemical reaction
The text defines it as 'the ability of an organism to produce light through a chemical reaction.'
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Question 2 of 4
How does an anglerfish use its light, according to the passage?
The answer is B: To dangle a lure that attracts prey
The text says anglerfish 'dangle a luminous lure to draw curious prey within reach of their jaws.'
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Question 3 of 4
The central idea of this passage is that
The answer is B: many deep-sea animals make and use light to survive
The passage describes how bioluminescence is widespread in the deep sea and serves many survival purposes.
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Question 4 of 4
Based on the passage, why might a deep-sea animal sometimes keep its light dark?
The answer is A: Its glow could give away its position to a predator
The text notes that "a steady glow can betray the swimmer that produces it," so each animal must weigh the risk of being seen against the benefit of being noticed.
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