Is a frog a reptile or an amphibian? How about a snake or a salamander?
Reptiles and amphibians share some similarities, so which species belong to which class of animals can be confusing. Reptiles include snakes, turtles and lizards. Amphibians include toads, frogs and salamanders.
One difference between reptiles and amphibians is how they use water. Amphibians need water in their habitat, because they spend at least part of their life cycle in water. In addition, most amphibians lay their eggs in water. Reptiles do not have to spend part of their lives in water. However, many reptiles live near water and spend time in water.
Take frogs. Frogs are amphibians. They spend time on land, but in their larval stage, as tadpoles, they live in water. Snakes, on the other hand, are reptiles. Some snakes, like the northern water snake, live in water, but not all snakes do. In fact, many snake species live in desert climates.
The skin of these animals is also different in reptiles compared to amphibians. Reptiles have scaly skin that allows them to survive in hot, dry climates. Amphibians have thin, delicate skin that they can breathe through.
Because the skin of an amphibian is porous, they are very sensitive to toxins and other pollutants, especially in water. The presence of amphibians in an area is a sign of good water quality. Reptiles can protect themselves from pollutants because toxins can't penetrate their scales. The differences in their skin is also why reptiles can live in salt water, but amphibians cannot.
Both reptiles and amphibians hatch from eggs, although the eggs are quite different. Reptile eggs are coated with a leathery or brittle coating. The animals that hatch from them are miniature versions of the full-sized animals. A baby snake looks like a smaller version of an adult snake. Amphibian eggs are transparent and jelly-like. The animals that hatch from them still must go through metamorphosis. For instance, a tadpole develops into a frog.
Despite all the differences, reptiles and amphibians do have a few things in common. Both reptiles and amphibians can be found on every continent in the world except Antarctica. In addition, all the animals in the two classes are vertebrates, meaning they have backbones. They are also all ectothermic, which means their body temperature is determined by their environment rather than regulated by their bodies as it is in humans and other mammals. Another term for ectothermic is cold-blooded. Humans and mammals are endothermic, or warm-blooded.
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