Julie Bunker, age 12, of Grand Rapids,Minnesota, for her question:
How do lizards differ from salamanders?
Zoologists tell us that lizards are reptiles and salamanders are amphibians. Both tribes are cold blooded creatures that have lived on earth through hundreds of millions of years. At a quick glance, a salamander looks very much like a smallish lizard. But actually, their squat little bodies are very different and so are their life stories.
A lizard has a scaly skin, strong enough to shed the rain and protect him from drying out in the sunshine. He is a warmth loving reptile. The salamander has a soft skin, moist with clammy mucus. It can absorb dissolved oxygen from water and from moisture in the damp air. But it cannot protect its owner from dry air and bright sunshine. He must live in moist shady surroundings, preferably near a stream or pond. He is called an amphibian because life is shared with water and dry land. Chances are, the lizard has claws on his tiny toes. The salamander's toes may be tipped with soft little pads, but he has no claws.
The lizards` 6,000 or so reptilian relatives include all the snakes and crocodiles; the turtles and tortoises plus the nine foot long Komodo dragon who weighs up to 300 pounds. The salamander's 3,000 or so amphibian relatives include all the frogs and toads, a variety of dainty little newts plus some lazy mud puppies and hellbenders.
Just a touch of your finger can tell you which is which, for the lizard’s scaly skin is dry and the bumpy looking skin of the salamander is moist and clammy. But the really insurmountable difference lies in the way they live. And their different family life styles are related to the long stories of their family trees.
Way back in Devonian days, some 350 million years ago, a few fishy creatures flopped onto the dry land. Most of them perished. But a few managed to gulp down oxygen from the air and survive out of the water. They were amphibian ancestors, the very first backboned animals who left the ancient seas for life on the dry land.
However, only the, adult amphibians performed this bold miracle. They returned to the water to lay their eggs. Their hatchlings lived through a fishy stage, with only gills to take oxygen from the water. When they graduated to the adult stage, the gills were traded for air breathing lungs. The salamanders and other amphibians still lay je111f1ed eggs in water or moisture and go through a fishy childhood.
The first reptiles arrived on land several million years latex. And they laid eggs with tough shells, able to survive out of water. Their young ones hatched with air breathing lungs, ready to live all their lives on the dry land.
In time, the successful reptile clan produced the remarkable dinosaurs that dominated all life on the land. Most reptiles still lay eggs, though a few give birth to live young. All the amphibians still lay soft jellified eggs like those of their ancestors. And the eggs, plus the first fishy stage of life, must be spent where gills can take oxygen from moisture.