Read the following information carefully and answer the given questions.…
2021
Read the following information carefully and answer the given questions.
Bioluminescence, emission of light by an organism or by a laboratory biochemical system derived from an organism. It could be the ghostly glow of bacteria on decaying meat or fish, the shimmering radiance of protozoans in tropical seas, or the flickering signals of fireflies. The phenomenon occurs sporadically in a wide range of protists and animals, from bacteria and fungi to insects, marine invertebrates, and fish, but it is not known to exist naturally in true plants or in amphibians, reptiles, birds, or mammals. Bioluminescence results from a chemical reaction (chemiluminescence) in which the conversion of chemical energy to radiant energy is direct and virtually 100 percent efficient; i.e., very little heat is given off in the process. For that reason, the emission is called cold light or luminescence. The functional role of bioluminescence in lower organisms such as bacteria, dinoflagellates, and fungi is difficult to discern. Partly because the glow of luminous bacteria is extinguished when oxygen is removed, it has been suggested that the bioluminescent reaction was originally used to remove oxygen toxic to primitive types of bacteria that developed when oxygen was absent or very rare in Earth’s atmosphere. The metabolic reaction that combines the oxygen with a reducing substance (luciferin) liberates sufficient energy to excite a molecule in the organism to emit visible radiation. Most of those luminous primitive organisms subsequently developed systems of using oxygen, but they have retained the luminescent capability as parts of related metabolic pathways or for some survival value that luminescence may confer on the organism.
Why the functional role of bioluminescence in lower organisms is difficult to recognize?
- A.
When oxygen is removed the bacteria is 17unable to survive.
- B.
The glow of bacteria blows out as soon as the oxygen is removed.
- C.
Bacteria couldn’t find the sufficient energy in the absence of oxygen.
- D.
Their luminescent capability wears off in the presence of oxygen.
Attempted by 32 students.
Show answer & explanation
Correct answer: B
Answer: The glow of bacteria is extinguished as soon as the oxygen is removed.
Explanation: The passage states that the glow of luminous bacteria is extinguished when oxygen is removed. Because bioluminescence depends on oxygen, it can be hard to observe under different conditions, making the functional role in lower organisms difficult to discern. The passage also offers a hypothesis that the reaction may originally have helped remove toxic oxygen in primitive bacteria, so luminescence may now be a retained metabolic byproduct rather than an obvious adaptive trait.
Because luminescence stops without oxygen, researchers cannot observe its effects in oxygen-free conditions, hindering identification of its functional role.
Hypothesis from the passage: the bioluminescent reaction may have been used to remove oxygen that was toxic to early bacteria; luminescence may therefore be a retained part of metabolic pathways rather than a clearly separable function.
Why other suggested reasons are incorrect:
"When oxygen is removed the bacteria is unable to survive." — The passage does not claim bacterial death; it refers specifically to the loss of visible glow.
"Bacteria couldn’t find sufficient energy in the absence of oxygen." — The passage describes the bioluminescent chemical reaction using oxygen to liberate energy for light, but it does not state that bacteria as a whole cannot obtain enough energy without oxygen; this is not the reason given for difficulty in recognizing function.
"Their luminescent capability wears off in the presence of oxygen." — This contradicts the passage, which says luminescence is extinguished when oxygen is removed.