CAT 2026 Slot 3 VARC Q19: Chameleon Camouflage

Passage 3

Chameleons are oddities within their own extended families. They belong to the class Reptilia and the order Squamata. But they don't resemble their cousins at all. Other squamates include geckos, skinks, iguanas — most are scaled reptiles with a sprawling gait. Chameleons are all crest and tongue, and can be as tiny as 2 centimetres and as large as 25 inches. Some of them have eyes that rotate independently, which is unusual for a reptile. . . .

It makes sense for these reptiles to have added protection in the form of a specialized skin; they don't have a venomous bite, and pretty much everything preys on chameleons, including birds and snakes. But how did chameleons manage to secure their own disappearing act? Chameleons fire from multiple cylinders to achieve this in varying degrees from species to species. There are four main catalysts — melanophores, guanophores, dermal ridges and erythrophores. . . .

[Melanophores] are organs on their bodies that contain pigment sacs, which have black 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 chameleon wants to change shade, the brain carries an electrical impulse through the nerve to the muscles that expand outwards, pulling open the sacs to display the shades on the skin. Why these two shades? Because these are the shades the light reflects at the altitudes they live in (the rest is absorbed before it reaches those heights). . . .

Well, what about other colours? Cue the guanophores. Think of a second layer of skin that has thin stacks of crystals. These can reflect light back at different wavelengths. . . . It's using the same properties that we've seen in soap bubbles, or rainbows on puddles of petrol. You move your head and you see a different colour. The bubble isn't doing anything but reflecting light — it's your movement that's changing the appearance of the colour. This property of bubbles, petrol and other such surfaces is called ‘iridescence’. . . .

Dermal ridges are sections of the skin that can be deformed to make a texture spiky. Even humans possess them (goosebumps) but cannot use them in the manner that chameleons can. For instance, the use of these cells is how a chameleon can wrap itself over a branch and appear rough or how a skink or anole can imitate the look of a bark surface by growing miniature bumps on its skin. It actually matches the texture of the substrate it chooses.

Finally, the erythrophores: According to a paper, published in Science, anoles and chameleons possess an additional type of pigment cell called an erythrophore. They are cells that scatter full spectrum light so that they appear red in a similar way that a flamingo's feathers appear pink. Erythrophores will also reflect any filtered light shown on them . . . If the forest appears green at a certain altitude, the anoles and chameleons can appear green; if the forest appears brown, they appear brown, and so on and so forth.

MCQ · +3 / −1 · medium

All of the following, if true, would weaken the camouflaging ability described in the passage EXCEPT:

Answer and solution

Correct answer: A

Solution

Answer: A — Melanophores are fewer in number than guanophores and erythrophores, but are still sufficiently numerous and fully functional to produce the required shade changes.

1. The question asks for the exception: the condition that does not weaken the mechanisms described.

2. B prevents useful wavelength reflection. C blocks reliable neural activation. D prevents the pigment sacs expanding. Each directly disrupts a described mechanism.

3. A says the cells remain sufficiently numerous and functional to make the required shade changes. A lower relative count by itself is not stated to be harmful.

4. Answer A. The words “sufficiently numerous” are essential to why this option does not weaken the ability.

Detailed reasoning and elimination check:
The EXCEPT answer must leave the described ability intact. A explicitly says the cells are sufficient and functional despite their relative number. The other alternatives disable a required physical or signalling mechanism, so they weaken the ability directly.

G Strategy shortcut

Spot: Identify the exact question task and the relevant passage claim.
Apply: For each option ask: which link breaks? B reflection, C signal, D muscle expansion; A expressly keeps enough functional cells.
Check: The EXCEPT answer must leave the described ability intact. A explicitly says the cells are sufficient and functional despite their relative number. The other alternatives disable a required physical or signalling mechanism, so they weaken the ability directly.

G Strategy: Spot: Identify the exact question task and the relevant passage claim. Apply: For each option ask: which link breaks? B reflection, C signal, D muscle expansion; A expressly keeps enough functional cells. Check: The EXCEPT answer must leave the described ability intact. A explicitly says the cells are sufficient and functional despite their relative number. The other alternatives disable a required physical or signalling mechanism, so they weaken the ability directly.

An expected paper by Cetking, not the actual CAT paper. CAT is conducted by the IIMs.