DIRECTIONS for the question:The passage below is accompanied by a set of questions. Choose the best answer to each question.
[Octopuses are] misfits in their own extended families …….. They belong to the Mollusca class Cephalopoda. But they don’t look like their cousins at all. Other molluscs include sea snails, sea slugs, bivalves – most are shelled invertebrates with a dorsal foot. Cephalopods are all arms, and can be as tiny as 1 centimetre and as large at 30 feet. Some of them have brains the size of a walnut, which is large for an invertebrate……..
It makes sense for these molluscs to have added protection in the form of a higher cognition; they don’t have a shell covering them, and pretty much everything feeds on cephalopods, including humans. But how did cephalopods manage to secure their own invisibility cloak? Cephalopods fire from multiple cylinders to achieve this in varying degrees from species to species. There are four main catalysts – chromatophores, iridophores, papillae and leucophores……..
[Chromatophores] are organs on their bodies that contain pigment sacs, which have red, yellow and brown pigment granules. These sacs have a network of radial muscles, meaning muscles arranged in a circle radiating outwards. These are connected to the brain by a nerve. When the cephalopod wants to change colour, the brain carries an electrical impulse through the nerve to the muscles that expand outwards, pulling open the sacs to display the colours on the skin. Why these three colours? Because these are the colours the light reflects at the depths they live in (the rest is absorbed before it reaches those depths) ……..
Well, what about other colours? Cue the iridophores. Think of a second level of skin that has thin stacks of cells. These can reflect light back at different wavelengths……….. It’s using the same properties that we’ve seen in hologram stickers, or rainbows on puddles of oil. You move your head and you see a different colour. The sticker isn’t doing anything but reflecting light – it’s your movement that’s changing the appearance of the colour. This property of holograms, oil and other such surfaces is called “iridescence” ……..
Papillae are sections of the skin that can be deformed to make a texture bumpy. Even humans possess them (goosebumps) but cannot use them in the manner that cephalopods can. For instance, the use of these cells is how an octopus can wrap itself over a rock and appear jagged or how a squid or cuttlefish can imitate the look of a coral reef by growing miniature towers on its skin. It actually matches the texture of the substrate it chooses.
Finally, the leucophores: According to a paper, published in Nature, cuttlefish and octopuses possess an additional type of reflector cell called a leucophore. They are cells that scatter full spectrum light so that they appear white in a similar way that a polar bear’s fur appears white. Leucophores will also reflect any filtered light shown on them…….. If the water appears blue at a certain depth, the octopuses and cuttlefish can appear blue; if the water appears green, they appear green, and so on and so forth.
are consumed by humans and other animals.
The passage calls octopuses “misfits” in their extended families because they “don’t look like their cousins at all”. The features that set them apart from other molluscs are what count as reasons; anything that does not distinguish them from their relatives is not.
Higher intelligence: some cephalopods “have brains the size of a walnut, which is large for an invertebrate”, and the second paragraph speaks of their “higher cognition”. This sets them apart from other molluscs, so it is a reason.
Several arms: other molluscs have “a dorsal foot”, whereas “Cephalopods are all arms”. This is a clear point of difference, so it is a reason.
No outer shell: among other molluscs “most are shelled invertebrates”, while cephalopods “don’t have a shell covering them”. This too marks them out from their cousins.
Being eaten by humans and other animals: the passage notes that “pretty much everything feeds on cephalopods, including humans”, but only to explain why they need added protection. Being preyed upon is not something that distinguishes them from sea snails, slugs or bivalves, so it is not offered as a reason for their being misfits.
Hence, the answer is are consumed by humans and other animals.
Cephalopods can take on the colour of their predator.
Each statement must be checked against the four camouflage mechanisms the passage describes.
Changing colour is true: chromatophores contain pigment sacs that are pulled open by radial muscles “to display the colours on the skin”, and iridophores reflect light at different wavelengths.
Changing texture is true: papillae are skin sections “that can be deformed to make a texture bumpy”, letting an octopus look jagged over a rock or a squid imitate a coral reef.
Blending into the colour of the surroundings is true: leucophores reflect filtered light, so “if the water appears blue … they appear blue; if the water appears green, they appear green”.
Taking on the colour of a predator is nowhere supported. The colour changes are tied to the light at their depth and to the surrounding water or substrate, never to the appearance of a predator. This statement is therefore not true according to the passage.
Hence, the answer is Cephalopods can take on the colour of their predator.
sea snails
The octopus camouflages itself with chromatophores, iridophores, papillae and leucophores. The creature whose camouflage is least like this is the one that shares none of these mechanisms or analogies.
Cuttlefish: the passage says cuttlefish, like octopuses, possess leucophores and can imitate a coral reef using papillae. Their techniques are very similar.
Squids: a squid “can imitate the look of a coral reef by growing miniature towers on its skin”, the same papillae-based technique the octopus uses. Again, similar.
Polar bears: leucophores scatter full-spectrum light “in a similar way that a polar bear’s fur appears white”. The passage itself draws the parallel, so they are not the most dissimilar.
Sea snails: they are among the “other molluscs” that are “shelled invertebrates with a dorsal foot”. Their protection comes from a shell, and the passage says cephalopods “don’t look like their cousins at all”; none of the camouflage mechanisms is attributed to them. So the octopus’s techniques are most dissimilar to those of sea snails.
Hence, the answer is sea snails.
the number of chromatophores in Cephalopods is half the number of iridophores and leucophores.
A statement weakens the camouflaging adeptness if it interferes with a mechanism the passage describes. The one that does not touch any such mechanism is the exception.
Hydrostatic pressure hindering radial muscle movement: chromatophore sacs have “a network of radial muscles” that expand outwards to pull the sacs open. If these muscles cannot move easily, colour change suffers, so this weakens camouflage.
Water temperature hindering neural signals: the brain “carries an electrical impulse through the nerve to the muscles”. If signal transmission is impaired, the colour change cannot be triggered, so this weakens camouflage.
Light reflecting red, green and yellow at their depths: the pigments are red, yellow and brown “because these are the colours the light reflects at the depths they live in”. If the reflected colours included green rather than brown, the brown pigment would no longer match, so this weakens camouflage.
Chromatophores being half as many as iridophores and leucophores: the passage says nothing about how the number of each cell type affects camouflage; the mechanisms work together “in varying degrees from species to species”. A relative count implies no loss of function, so this does not weaken the camouflaging adeptness.
Hence, the answer is the number of chromatophores in Cephalopods is half the number of iridophores and leucophores.
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:
