Amphibians

Life on land presented new challenges to the emerging amphibians. Water availability was not reliable. Air temperatures were variable, and air itself was not the strong supporting medium that water was, but it was a richer source of oxygen. New habitats, including vast arrays of plants, necessitated keener sensory input. Fortunately, climate shifts in the Carboniferous provided an abundance of insects as food for the amphibians.

This animation (No Audio) describes the structure of early amphibians.

Existing amphibians share several common characteristics:

• All have bony endoskeletons and usually four legs.
• All require water at some stage in the life cycle. Most shed their eggs into water, which is also home to a free-swimming larval stage.
• Depending on their habitat, amphibians can respire by use of gills, lungs, skin, and pharyngeal lining. Lungs are less efficient than those of other vertebrates.
• Skin serves as a respiratory organ. The skin is usually thin and sometimes supplied with glands that produce toxins.

• Frogs and toads
• Salamanders
• Caecilians

These animals possess long hindlimbs capable of responding to powerful muscles. Their success on land is due in part to the excellent prey-grasping capability of the tongue attached at the front of the mouth.

The frog tutorial reviews the interesting life cycle of a frog.

This animation (Audio - Important) describes the life cycle of a frog.

Salamanders

When salamanders walk, the body bends from side to side, much like a fish moving through water. Adults may retain larval features including gills and tail. Some larvae may become sexually mature but do not reach a true adult stage.

Caecilians

These unusual creatures live burrowed in the forest floor where they hunt for invertebrate prey. They have no limbs but do have small scales embedded in the skin.

REVIEW: Amphibians are completely dependent on an aquatic environment for
Answer reproduction.