Frogs have a complex life cycle that begins with eggs and progresses through tadpole and young frog stages. Male frogs fertilize eggs externally as the female lays them over 10 minutes. The eggs develop protective jelly coats and hatch into tadpoles that breathe with gills and feed on yolk. Tadpoles then undergo metamorphosis where their tails shorten and lungs form, allowing them to live on land as young frogs. Most frogs reach sexual maturity at 3 years old to complete the cycle by reproducing new eggs.