What is the Difference Between Reptiles and Amphibians?

            Do you know the difference between a lizard and a salamander?  People often confuse them.  Although they both have long thin bodies one is a reptile and the other is an amphibian.
            Herpetology is the science of reptiles and amphibians.  Though they are both grouped together in this science, amphibians and reptiles are two distinctly different and unique classes of vertebrates.  Their body coverings are the most obvious difference between amphibians and reptiles.  Most amphibians are adapted for moist conditions.  Their skin is often smooth and slimy.  Amphibians lay jelly-like eggs in water.  The legless tadpoles that hatch live in water have gills and a tail fin.  Tadpoles later go through great changes to become adults with legs and lungs.
            Reptiles, on the other hand, are better adapted for dry land.  Their dry and scaly skin, better lungs and clawed toes are the most obvious physical characteristics of reptiles.  Eggs covered with a shell are laid on land.  The hatchlings look like small versions of the adults.
            Amphibians were the first group of animals to move from water onto land.  Their ancestors were lobe-finned fishes that could stumble about on their bony fins and absorb air in a pocket in their throats.  Between 370 and 350, during the Devonian period of Earth’s history, amphibians evolved and adapted to the swampy conditions that existed on land at that time.  For almost the next 70 million years or so the amphibians were the only vertebrates dominating life on land.
            Reptile evolution began around 280 million years ago as the land became drier.  Unlike their amphibian ancestors, reptile’s scaly skin didn’t lose water and their shelled eggs meant that reptiles didn’t have to return to the water to reproduce.  Many different groups of reptiles evolved at first, but most became extinct at the end of the Permian Era when a mass extinction wiped out 90% of the life on Earth.

Activity: Identifying the major groups of reptiles and amphibians

Reptiles include:

• Turtles, tortoises and terrapins are the reptile order with shells.  Tortoises have the toughest shells and are thoroughly adapted to land.  The more aquatic species are known as turtles or terrapins. There are about 240 species of turtles and tortoises living in the world today.
• Snakes and Lizards are closely related.  Snakes have developed a number of specialized features for living without legs including a jaw that can spread wide open for swallowing food larger than the head.  Lizards can’t open their mouths as wide but with clawed feet and strong jaws they can rip food apart.  There are over 3700 species of lizards and about 2400 species of snakes.
• Crocodilians include crocodiles, alligators, caimans and the gavial.  They also have some of the most advanced features including a four chambered heart and care for their eggs and young.  Only 23 species are alive today in tropical environments.
• The tuatara is an order unto itself.  The only surviving species of this ancient reptilian order is found only in New Zealand.

Amphibians include:

• Frogs and Toads are the tailless amphibians.  Frogs tend to stay near water and have slimy moist skin, whereas the toads have drier skin and wander far from water.  Their “warts” are really glands that produce distasteful chemicals that keep many predators away. There are about 5,250 species of frogs and toads in the world.
• Salamanders have long thin bodies and long tails like lizards, but their slimy skin and lack of claws identifies them as amphibians.  Newts are salamanders that live in water even after they have become adults.  The most common local salamander is the red-backed salamander.  Don’t hold these in your hands too long.  They absorb all their oxygen through their skin unlike other salamanders which do have lungs.  There are about 500 types of salamanders.
• Caecilians are burrowing amphibians found in the tropics.  These legless amphibians are generally under a foot in length although some grow to over a yard long.  About 160 species of caecilians exist at present.