Weak Electric Systems in Fish

Weak Electric Systems in FishSome blind elephantnose fish produce weak electric signals that are used fordetecting objects in their surroundings a phenomenon called activeelectrolocation. These fish have specialized electric organs that dischargeeither in pulses or in a wave-like fashion, depending on the species. Althoughdischarges follow one another almost continuously throughout the life ofthe fish, their power level is much too low to be detected by humanhandlers but potent enough to create a stable electric field around thebody of the fish. When an object enters into this electric field, itcauses distortions in the current that are detected by electroreceptor organsdistributed over the fish's skin.Which of the sentences below best expresses the essential information in thehighlighted sentence in the passage? Incorrect choices change the meaning inimportant ways or leave out essential information.A.Throughout the life of the fish, its electric discharges vary in powerfrom undetectable to fairly potent.B.Nearly continuous discharges undetectable by humans create astable, low-level electric field around the body of the fish.C.Human handlers cannot feel the electric discharges because thedischarges are at such low power levels.D.The discharges are so weak that they would have to be fired almostcontinuously to create a detectable electric field.The word “distortions” in the passage is closest in meaning toA.decreasesB.signalsC.concentrationsD.irregularitiesA weak electric system may have several uses, including the exploration ofnovel environments. For example, blind elephantnose fish can easily find theonly opening that allows them to cross through a newly installed partition withintheir aquarium, even though they cannot see it with their eyes. Their electricsense must be implicated because when these individuals become electricallysilent (unable to use their electric system through denervation of their electricorgans), they can no longer find the opening.Paragraph 2 describes an experiment with elephantnose fish that wereelectrically silent and therefore unable toA.distinguish between new and familiar objects in their aquariumB.swim around the partition in their aquariumC.find their way through a hole in a barrierD.see with their eyesDuring the 1970s, biologists became interested in the role of the weak electricsystem not only as a means of electrolocation but also as a means of electricalcommunication between individual fish. Communication is possible becausethe rate and waveform of the electric discharges can vary between species,between sexes, between individuals, or even between situations in the sameindividual. Moreover, some fish can temporarily interrupt their normallycontinuous train of discharges, and these pauses can be full of meaning. Theeffective range of communication by electric signals can reach a little over 1meter depending on wat...