Taken from: The World Book Encyclopedia
World Book, Inc. 1995
Frog is a
small, tailless animal with bulging eyes. Almost all frogs also have
long back legs.
The strong hind legs enable a frog to leap distances
far greater than the length of its body.
Frogs live on every
continent except Antarctica. But tropical regions have the greatest
of species. Frogs are classified as amphibians. Most
amphibians, including most frogs, spend
part of their life as a water
animal and part as a land animal.
Frogs are related to
toads but differ from them in several ways.
The first frogs
appeared on earth about 180 million years ago. About 3,800 species of
toads have developed from these early ancestors. Some
species spend their entire life in or near
water. Others live mainly
on land and come to the water only to mate. Still other species
enter the water, not even to mate. Many kinds are climbers
that dwell in trees. Other are burrowers
that live underground.
Throughout history, frogs have been the source of
superstitions. One old myth says that frogs fall
from the sky
during a rain. Actually, many species that liver underground leave
their burrows during
or after a rain at the start of the mating
season. Because people seldom see these frogs the rest
of the year,
they imagine the animals fell from the sky with the rain.
Frogs, like all other amphibians, are cold-blooded----that is, their
body temperature tends to be the
same as the temperature of the
surrounding air or water. Frogs that live in regions with cold
hibernate. Some species hibernate in burrows. Others spend
the winter buried in mud at the bottom of
a pond or stream, breathing
through their skin. During hibernation, a frog lives off materials
in its body tissues.
Frogs benefit us in many
ways. They eat large numbers of insects, which might otherwise become
pests. Frogs also provide us with food. The meaty hind legs
of larger frogs are considered a
delicacy in many countries. In the
United States, people mainly eat the legs of bullfrogs, green frogs,
and leopard frogs. Frogs also are used widely in the laboratory.
Medical researchers use frogs to test
new drugs, and students dissect
frogs to learn about anatomy.
Human beings are, in fact,
the frog's worst enemy. People obtain most of the frogs used for food
and in the
laboratory from the wild. Furthermore, people destroy the
homes and breeding places of frogs by replacing
natural areas with
cities and farms. They also pollute and so poison the waters in which