Which of the following classes includes the family of turtles?

Correct — B. Turtles are reptiles, placed in the order Testudines, and they carry the class marks of Reptilia: dry skin with horny scales or scutes, lungs from birth, and a shelled egg laid on land.

Even sea turtles come ashore to lay, because a shelled amniotic egg cannot develop under water. That single habit separates them from amphibians more sharply than the shell does.

Reptilia is option (b).

Why the others are wrong

• (a)
  Aves — Aves is the birds — feathers, a beak, forelimbs modified into wings. A turtle has none of those three, so it cannot sit in this class.
• (c)
  Chondrichthyes — Chondrichthyes is the cartilaginous fishes, sharks and rays, which breathe through gills. A turtle breathes air with lungs.
• (d)
  Amphibia — Amphibia covers frogs, toads and salamanders, with moist permeable skin and eggs laid in water. A turtle's skin is dry and its eggs are shelled.

Vertebrate classes are separated by a short list of hard characters: skin covering, respiratory organ, heart chambers, egg type, and whether body temperature is regulated internally.

Reptilia — dry scaly skin, lungs, shelled eggs on land, ectothermic.
Amphibia — moist skin, a larval gill stage, eggs in water.
Aves — feathers, beak, endothermic, hard-shelled eggs.
Chondrichthyes — cartilage skeleton, gills, mostly marine.

Turtles, tortoises, snakes, lizards and crocodiles all sit inside Reptilia.

Key facts

• Turtles belong to the class Reptilia, order Testudines.
• Reptiles have dry skin with epidermal scales and lay shelled eggs on land.
• Sea turtles return to land to lay their eggs.
• Chondrichthyes are the cartilaginous fishes, such as sharks and rays.

Common traps

• Filing turtles with amphibians because they live in and around water.
• Taking the word family as a taxonomic rank and hunting for a family name.

No directly related past PYQ was found.