The life cycle of a frog includes which stages?

The life cycle of a frog includes which stages?

• A. Egg stage; tadpole stage (with gills); juvenile stage
• B. Egg stage; larval stage (with gills); adult stage
• C. Egg stage; tadpole stage; adult stage
• D. Egg stage; tadpole stage (with gills); adult stage (with lungs)

Answer: (D)

Frogs undergo metamorphosis, moving from an egg laid in water to a larval stage called a tadpole, and finally to an air-breathing adult. The tadpole is aquatic, with gills, a tail, and no legs. Through metamorphosis, it develops legs, its tail shortens or is absorbed, and lungs form, producing the adult frog that breathes air. So the life cycle goes: egg stage → tadpole stage (with gills) → adult stage (with lungs). This sequence is what makes sense biologically, since the adult differs from the larva in structure and respiration.