đ Whatâs Inside This CAT RC Practice Post?
đ Authentic CAT Reading Comprehension Passage: Practice with a real RC passage from a previous CAT exam.
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Detailed Questions with Step-by-Step Solutions: Each question is explained thoroughly for better understanding.
đ In-Depth Passage Analysis: Gain insights through line-by-line and paragraph-wise analysis, supplemented with a quick summary table for efficient revision.
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RC Passage
Direction for the questions 1 to 4: The passage below is accompanied by a set of four questions. Choose the best answer to each question.
But they donât 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 donât 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. . . . Itâs using the same properties that weâve seen in hologram stickers, or rainbows on puddles of oil. You move your head and you see a different colour.
The sticker isnât doing anything but reflecting light - itâs your movement thatâs changing the appearance of the colour. This property of holograms, oil and other such surfaces is called âiridescenceâ. . . . 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 bearâs 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.
RC Line-wise Explanation
Paragraph 1
Original: [Octopuses are] misfits in their own extended families . . . They belong to the Mollusca class Cephalopoda.
Explanation: Octopuses are unusual compared to other molluscs. They belong to the subgroup called Cephalopoda.
Original: But they donât look like their cousins at all. Other molluscs include sea snails, sea slugs, bivalves - most are shelled invertebrates with a dorsal foot.
Explanation: Unlike other molluscsâlike snails and clamsâwhich have shells and a body part called a dorsal foot, octopuses look completely different.
Original: 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.
Explanation: Cephalopods, such as octopuses, range widely in size and have many arms. Some even have relatively large brains compared to other animals without backbones.
Paragraph 2
Original: It makes sense for these molluscs to have added protection in the form of a higher cognition; they donât have a shell covering them, and pretty much everything feeds on cephalopods, including humans.
Explanation: Since cephalopods have no shell for protection and many predators, it makes sense they evolved with advanced intelligence.
Original: 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.
Explanation: How do they become nearly invisible? Cephalopods use multiple mechanismsâdifferently across speciesâto camouflage themselves.
Original: There are four main catalysts - chromatophores, iridophores, papillae and leucophores.
Explanation: They rely on four main skin features for camouflage: chromatophores, iridophores, papillae, and leucophores.
Paragraph 3
Original: [Chromatophores] are organs on their bodies that contain pigment sacs, which have red, yellow and brown pigment granules.
Explanation: Chromatophores are pigment-filled sacs that hold red, yellow, and brown color granules.
Original: 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.
Explanation: These sacs are surrounded by muscle fibers that radiate outwards and are connected to the brain via nerves.
Original: 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.
Explanation: To change color, the brain sends a signal to these muscles, which then pull open the pigment sacs, displaying their colors.
Original: 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).
Explanation: They use red, yellow, and brown because these are the only colors that sunlight reflects underwater at their typical depths.
Paragraph 4
Original: Well, what about other colours? Cue the iridophores.
Explanation: What about other visible colors? Thatâs where iridophores come in.
Original: Think of a second level of skin that has thin stacks of cells. These can reflect light back at different wavelengths.
Explanation: Iridophores are stacked skin cells that reflect light at various wavelengths, creating different colors.
Original: Itâs using the same properties that weâve seen in hologram stickers, or rainbows on puddles of oil. You move your head and you see a different colour.
Explanation: These cells work like holograms or oil slicksâmoving your viewpoint changes the color you see.
Original: The sticker isnât doing anything but reflecting light - itâs your movement thatâs changing the appearance of the colour. This property of holograms, oil and other such surfaces is called âiridescence.â
Explanation: The effect is called "iridescence"âitâs not the surface that changes, but the angle of viewing that changes the perceived color.
Paragraph 5
Original: Papillae are sections of the skin that can be deformed to make a texture bumpy.
Explanation: Papillae are skin structures that can change shape, making the surface look bumpy.
Original: Even humans possess them (goosebumps) but cannot use them in the manner that cephalopods can.
Explanation: Humans have papillae too (goosebumps), but we canât control them like cephalopods do.
Original: 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.
Explanation: Cephalopods use papillae to mimic their environmentâs textureâbecoming jagged on rocks or resembling coral formations.
Original: It actually matches the texture of the substrate it chooses.
Explanation: They can match the physical feel of whatever surface they are near.
Paragraph 6
Original: Finally, the leucophores: According to a paper, published in Nature, cuttlefish and octopuses possess an additional type of reflector cell called a leucophore.
Explanation: Lastly, leucophores are another reflective skin cell type found in cuttlefish and octopuses.
Original: They are cells that scatter full spectrum light so that they appear white in a similar way that a polar bearâs fur appears white.
Explanation: Leucophores reflect all wavelengths of light, making the skin appear whiteâsimilar to how polar bear fur looks white.
Original: 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.
Explanation: These cells can also reflect the color of the water around them, helping them blend in with their surroundings.
RC Paragraph Explanation
Paragraph 1 Summary
Octopuses belong to the Cephalopoda class of molluscs but look very different from their shelled cousins. They vary in size and possess unusually large brains for invertebrates.
Paragraph 2 Summary
Cephalopods, vulnerable due to their lack of shells, evolved multiple camouflage tools. These include chromatophores, iridophores, papillae, and leucophores, which differ across species.
Paragraph 3 Summary
Chromatophores are pigment-filled sacs controlled by the brain that enable cephalopods to display red, yellow, and brown colors, matching the light available in deep-sea environments.
Paragraph 4 Summary
Iridophores reflect light to create shimmering, angle-dependent colors using the same iridescent effect seen in oil puddles and holograms.
Paragraph 5 Summary
Papillae help cephalopods mimic textures, allowing them to physically resemble their surroundings, like rocks or coral, through skin deformation.
Paragraph 6 Summary
Leucophores reflect full-spectrum light, making octopuses and cuttlefish appear white or the color of their environment, aiding in their camouflage.
RC Quick Table Summary
| Paragraph Number | Main Idea |
|---|---|
| Paragraph 1 | Octopuses are intelligent, unique molluscs differing from their relatives. |
| Paragraph 2 | Cephalopods use four key skin mechanisms for camouflage. |
| Paragraph 3 | Chromatophores display red, yellow, and brown pigments using muscle control. |
| Paragraph 4 | Iridophores produce color shifts through light reflection and iridescence. |
| Paragraph 5 | Papillae allow cephalopods to mimic textures like rocks or coral. |
| Paragraph 6 | Leucophores reflect surrounding light, aiding in full-environment camouflage. |
RC Questions
Ques 1. Based on the passage, it can be inferred that camouflaging techniques in an octopus are most dissimilar to those in:
Ques 2. All of the following are reasons for octopuses being âmisfitsâ EXCEPT that they:
Ques 3. Which one of the following statements is not true about the camouflaging ability of Cephalopods?
Ques 4. Based on the passage, we can infer that all of the following statements, if true, would weaken the camouflaging adeptness of Cephalopods EXCEPT:
