The passage below is accompanied by a set of questions. Choose the best answer to each question. Time and again, whenever a population [of Mexican tetra fish] was swept into a cave and survived long enough for natural selection to have its way, the eyes disappeared. “But it’s not that everything has been lost in cavefish . . . Many enhancements have also happened.” . . . Studies have found that cave-dwelling fish can detect lower levels of amino acids than surface fish can. They also have more tastebuds and a higher density of sensitive cells alongside their bodies that let them sense water pressure and flow. . . . Killing the processes that support the formation of the eye is quite literally what happens. Just like non-cave-dwelling members of the species, all cavefish embryos start making eyes. But after a few hours, cells in the developing eye start dying, until the entire structure has disappeared. [Developmental biologist Misty] Riddle thinks this apparent inefficiency may be unavoidable. “The early development of the brain and the eye are completely intertwined—they happen together,” she says. That means the least disruptive way for eyelessness to evolve may be to start making an eye and then get rid of it. . . . It’s easy to see why cavefish would be at a disadvantage if they were to maintain expensive tissues they aren’t using. Since relatively little lives or grows in their caves, the fish are likely surviving on a meager diet of mostly bat feces and organic waste that washes in during the rainy season. Researchers keeping cavefish in labs have discovered that, genetically, the creatures are exquisitely adapted to absorbing and storing nutrients. . . . Fats can be toxic for tissues, [evolutionary physiologist Nicolas] Rohner explains, so they are stored in fat cells. “But when these cells get too big, they can burst, which is why we often see chronic inflammation in humans and other animals that have stored a lot of fat in their tissues.” Yet a 2020 study by Rohner, Krishnan and their colleagues revealed that even very well-fed cavefish had fewer signs of inflammation in their fat tissues than surface fish do. Even in their sparse cave conditions, wild cavefish can sometimes get very fat, says Riddle. This is presumably because, whenever food ends up in the cave, the fish eat as much of it as possible, since there may be nothing else for a long time to come. Intriguingly, Riddle says, their fat is usually bright yellow, because of high levels of carotenoids, the substance in the carrots that your grandmother used to tell you were good for your…eyes. “The first thing that came to our mind, of course, was that they were accumulating these because they don’t have eyes,” says Riddle. In this species, such ideas can be tested: Scientists can cross surface fish (with eyes) and cavefish (without eyes) and look at what their offspring are like. When that’s done, Riddle says, researchers see no link between eye presence or size and the accumulation of carotenoids. Some eyeless cavefish had fat that was practically white, indicating lower carotenoid levels. Instead, Riddle thinks these carotenoids may be another adaptation to suppress inflammation, which might be important in the wild, as cavefish are likely overeating whenever food arrives.
Which one of the following results for the cross between surface fish (with eyes) and cavefish (without eyes) would invalidate Riddle’s inference from the experiment?
Only eyeless offspring had yellow fat.
Riddle’s inference from the cross is that there is no link between having eyes and the build-up of carotenoids, which is what turns the fat yellow.
A result can only overturn that inference if it shows a clear link between eye status and yellow, carotenoid-rich fat.
If yellow fat appeared only in eyeless offspring, carotenoid storage would track eyelessness exactly, bringing back the idea that the fish store carotenoids because they lack eyes.
White fat in fish with eyes, yellow fat in fish with eyes, or white fat in eyeless fish all show a mixed pattern, which fits the finding of no link.
Hence, Only eyeless offspring had yellow fat.
Similar Questions
Zombie cells may contribute to age-related chronic inflammation: this finding could help scientists understand more about the aging process and why the immune system becomes less effective as we get older. Zombie or “senescent” cells are damaged cells that can no longer divide and grow like normal cells. Scientists think that these cells can contribute to chronic health problems when they accumulate in the body. In younger people, the immune system is more effective at clearing senescent cells from the body through a process called apoptosis, but as we age this process becomes less efficient. As a result, there is an accumulation of senescent cells in different organs in the body, either through increased production or reduced clearance by the immune system. The zombie cells continue to use energy though they do not divide, and often secrete chemicals that cause inflammation, which if persistent for longer periods of time can damage healthy cells leading to chronic diseases.
Identify the odd sentence out and key in the number of that sentence as your answer.
The last paragraph of the passage refers to “middle-class, white, professional men”. Which one of the following qualities best describes the connection among them?
Study the following sets of concepts and identify the set that is conceptually closest to the concerns and arguments of the passage.
According to the passage, who or what was an “alienist”?
“Conversely, when a defendant struck officials as unlike themselves, whether by dint of disease, gender, confession, or race, the precariousness of judgments about mental state was exposed.” Which one of the following best describes the use of the word “confession” in this sentence?
According to the incentive or moral hazard argument, which one of the designs below is most consistent with the claim that some inequality can raise growth?
Which one of the options below best summarises the passage?
The primary function of the three-part case for a positive income inequality–economic growth link in the first half of the passage is to show that:
The passage refers to "democratization". Choose the one option below that comes closest to the opposite of this process.
Important Questions from Non Grammar
- In formulating Principle VI (a), the ILC clarified the term "waging of a war of aggression" because:
- The author attributes the growing public frustration with the UN primarily to which pair of continuous failures?
- A primary point of divergence between the US Conservative position and the Secretary-General's Conservative position on security matters, according to the summary is:
- According to the critique's conclusion, the immediate, insurmountable barrier preventing the implementation of any reform, major or minor, is:
- The Secretary-General's 'Agenda for Peace' proposed a specific military capability intended to address the gap between traditional peace-keeping and full military action. This proposed unit was explicitly characterized by the summary as being:
