Frogs and Toads

Amphibians, metamorphosis, and permeable skin.

Frogs and toads are amphibians in the order Anura. The split between them is informal rather than taxonomic: “toad” usually names drier, warty, shorter-legged species, but the two groups are not separate branches.

Life cycle

Eggs are laid in water and hatch into gilled, herbivorous tadpoles. Metamorphosis grows limbs, replaces gills with lungs and reshapes the gut for a carnivorous diet.

Permeable skin

Amphibian skin exchanges water and gases directly, which makes these animals sensitive to pollutants and drying. That sensitivity is why they are treated as indicator species for habitat quality.