Which of the following options is associated with the class of cold-blooded animals?

Correct — B. A chameleon is a lizard, and lizards belong to class Reptilia, which is ectothermic — cold-blooded. Its body temperature tracks the surroundings instead of being held steady from inside.

That is why a chameleon basks in the morning sun and moves to shade in the heat of the day: it regulates by behaviour, having no internal furnace to do the job.

The three other names are genera of birds and mammals, and both those classes are endothermic — warm-blooded.

Why the others are wrong

• (a)
  Pavo — Pavo is the peafowl genus, and Pavo cristatus is the Indian peafowl, India's national bird. Birds are warm-blooded, and feathers exist largely to hold that heat in.
• (c)
  Macropus — Macropus is the kangaroo genus of Australia. Kangaroos are marsupial mammals, and every mammal generates and maintains its own body temperature.
• (d)
  Psittacula — Psittacula is the parakeet genus — Psittacula krameri is the rose-ringed parakeet seen across India. Another bird, so warm-blooded again.

Ectotherms, the cold-blooded animals, take their heat from the environment. Fish, amphibians, reptiles and invertebrates work this way. They spend far less energy on temperature and so eat less, but they slow down in the cold and must bask, burrow or shelter to stay in range.

Endotherms, the warm-blooded animals, make heat from their own metabolism and hold a near-constant body temperature. Only birds and mammals do this, which is why they can stay active at night and in cold climates — and why they must eat so much more.

So the question reduces to a single sort: which of these four is not a bird or a mammal?

Key facts

• Reptiles, amphibians, fish and invertebrates are ectothermic, or cold-blooded.
• Only birds and mammals are endothermic, or warm-blooded.
• Chameleons are lizards, family Chamaeleonidae, within class Reptilia.
• Pavo is the peafowl genus, Macropus the kangaroo genus, Psittacula the parakeet genus.

Common traps

• Assuming an unfamiliar genus name must belong to something exotic and cold-blooded
• Taking 'cold-blooded' to mean the animal's blood is literally cold
• Reading the chameleon's colour change as pure camouflage, when it also signals mood and helps regulate heat

No directly related past PYQ was found.