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Frogs

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Submitted By RoseRune
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Imagine traveling back through time millions of years to the age of the dinosaurs. Pterodactyls glide above a soggy marsh. Nearby, a colossal 80-ton Brachiosaurus munches on a tree. On the ground at its feet, something strangely familiar hops by: a frog.

Ichthyostega, prehistoric predecessor to the modern frog, lived 370 million years ago during the Devonian Period. Sometimes referred to as "the first four-legged fish," skeletal remains of this earliest-known amphibian were first discovered in East Greenland.
Surprised? Few people realize just how ancient frogs are. For 190 million years, the ancestors of modern frogs have roamed (if not ruled) the earth, looking much the same as they do today. The secret to their success is their amazing adaptability.

As amphibians, frogs have one webbed foot in each of two worlds. The advantages of this double life are clear to see: Are land predators giving you trouble? Dive into the water. Not enough to eat in the pond? Hop out and see what they're serving on shore.

Frogs have evolved to live in an astounding variety of climates. They can be found just about anywhere there's fresh water, from the desert to the Arctic, on all continents except Antarctica. Though they thrive in warm, moist tropical climates, frogs also live in deserts and high on 15,000 foot mountain slopes. The Australian water-holding frog is a desert dweller that can wait up to seven years for rain. It burrows underground and surrounds itself in a transparent cocoon made of its own shed skin.

Frozen Wood Frog Like all amphibians, frogs are cold-blooded, meaning that their body temperatures change with the temperature of their surroundings. When temperatures drop, some frogs dig burrows underground or in the mud at the bottom of ponds. They hibernate in these burrows until spring, perfectly still and scarcely breathing. Wood frogs can live north of the Arctic Circle, surviving for weeks in a frozen limbo state. This frog uses glucose in its blood as a kind of antifreeze that concentrates in its vital organs, protecting them from damage while the rest of the body freezes solid.…...

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