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Reaching a cautious hand
out to pet the snake, Jesse said,
“Well, Simba’s skin is dry, thick,
and scaly. Those frogs look
damp. And from what I know
about frogs, they do need to
stay moist.”
“That’s exactly right!” said
Mia. “The skin of the amphib-
ians is thin and has to be moist. These animals have adapted to different environments. Also,
reptile skin is made of scales, while amphibian skin is smooth. That’s because the reptiles molt,
or shed their skin as they grow. The scales make that process easier. Amphibians don’t molt, so
their skin can grow as their body grows.
Also, water is important to the life cycle of an amphibian, like the frogs here. Amphibians lay
their eggs in water and spend the early part of their lives in water. Adults live on land, but will
return to the water to lay their eggs.
“But reptiles don’t do that. They lay their eggs on land. Their eggs have a thick shell that lets
oxygen into the egg. The egg has fluids and a yolk to keep the embryo cushioned, safe, and fed
while in the egg. These eggs don’t need to be in the water because the egg is designed to con-
serve water.”
“That sounds a little bit like a chicken
egg,” Gabriella realized.
“Yes, it does. But instead of sitting on
their eggs, like a hen does, to keep them
warm, a reptile will usually cover their
eggs in sand and wait for the sun to
warm them.”
“That’s right! One time we were
on the beach and saw turtles laying
eggs in the sand.”
amphibian
a cold-blooded organism who
lives in the water during its early life and
then on land as an adult
reptile
a cold-blooded animal that lays
eggs on land and has dry, scaly skin
Words to Understand
These frogs began
life as tadpoles,
animals that are
adapted to live in
water.