Reptiles and Amphibians: What's the Difference?

Two groups that look similar but live very differently

A lizard basking on a wall and a frog hiding in a pond might both seem like small, scaly, cold creatures. But reptiles and amphibians belong to two different classes of vertebrates, and the differences are bigger than they first appear. Understanding them tells you a lot about how animals conquered the land.

Both groups are vertebrates (they have backbones) and both are ectothermic, sometimes called "cold-blooded". But their skin, eggs, breathing and life cycles set them apart. To see how they fit alongside mammals and birds, you can explore animal groups: mammals, birds and reptiles.

Reptiles: built for dry land

Reptiles include lizards, snakes, turtles, tortoises, crocodiles and alligators.

• Skin: dry and covered in tough scales made of keratin (the same material as your fingernails). This skin is waterproof, so it locks moisture inside the body. That is the secret to living in deserts and other dry places.
• Eggs: most reptiles lay eggs with a leathery or hard shell. The shell holds water inside, so the eggs can be laid on land without drying out. The baby develops fully inside the egg.
• Young: reptiles hatch as miniature adults — a baby snake looks like a small snake. There is no tadpole stage.
• Breathing: reptiles breathe with lungs their whole lives.

Why does this matter? The waterproof skin and shelled egg were huge evolutionary steps. They freed reptiles from needing water to reproduce, which let their ancestors spread across dry land that amphibians could never fully colonise.

Amphibians: caught between water and land

Amphibians include frogs, toads, newts and salamanders. The word amphibian means "double life", because most live partly in water and partly on land.

• Skin: moist, smooth and thin. Amphibians can absorb oxygen straight through their skin, especially in water, so it must stay damp. This thin skin also makes them very sensitive to pollution.
• Eggs: soft and covered in jelly, with no waterproof shell. They must be laid in water or damp places, or they dry out and die.
• Young: amphibians go through metamorphosis. A frog hatches as a tadpole with a tail and gills, living underwater, then slowly grows legs, loses its tail and develops lungs to become a land-going adult. You can see this in detail in our lesson on the life cycle of a frog.
• Breathing: through gills as larvae, then through lungs and skin as adults.

Why does this matter? Because amphibians depend on water for their eggs and damp skin for breathing, they are tied to wet habitats. This makes them excellent "indicator species" — when amphibians vanish from an area, it often warns scientists that the water is polluted.

Side-by-side comparison

Feature	Reptiles	Amphibians
Skin	Dry, scaly, waterproof	Moist, smooth, thin
Eggs	Shelled, laid on land	Jelly, laid in water
Young	Mini adults	Larva → metamorphosis
Breathing	Lungs only	Gills, then lungs + skin
Body temperature	Ectothermic	Ectothermic
Examples	Snake, lizard, turtle	Frog, newt, salamander

Watch out for tricky cases

Some animals are easy to mix up. A newt looks a bit like a lizard, but it is an amphibian — it has moist skin and lays eggs in water. A slow worm looks like a snake but is actually a legless lizard (a reptile). The reliable test is always the skin: dry and scaly means reptile; moist and smooth means amphibian.

Observe and investigate

1. Spring pond watch: in spring, visit a pond (with an adult) and look for frogspawn — clumps of jelly-covered eggs. Over a few weeks, watch tadpoles hatch and slowly change shape. This is metamorphosis happening before your eyes.
2. Skin test: look at clear photos of a gecko and a salamander. Notice the gecko's dry scales versus the salamander's shiny, wet-looking skin. Predict which can survive in a dry place.
3. Basking behaviour: on a sunny day, see if you can spot a lizard sitting still on a warm rock or wall. It is warming its ectothermic body using the sun. Note the time of day — reptiles are most active when it is warm.

Knowing these differences, you will never confuse a frog with a lizard again — and you will understand why each one lives where it does.