WATER BABIES

The image below is a photo of the exhibit panel. Following it is a transcript of the panel.

Photo of the panel from the exhibit.

Most adult amphibians live on land, but return to water to breed and lay eggs; a legacy of their aquatic ancestry.

Generally, young amphibians develop in the water. Tadpoles and other larvae undergo dramatic shape changes to become land-dwelling adults.

amphibians (am- FIB -ee-yuns): smooth-skinned vertebrates with aquatic larvae; frogs, salamanders, and caecilians

New features:

  • smooth, scaleless skin permits exchange of carbon dioxide and oxygen (skin-breathing)
  • mucous glands keep the skin moist and permeable for gas exchange
  • poison glands secrete toxins for defense
  • ribs are smaller, or absent
  • two-part teeth: crown attached to base of tooth by ligaments

When? at least 230 million years ago to present (although fossil evidence is lacking, modern amphibians are thought to have evolved before this date, from early lobefins.)

Jelly-like amphibian eggs must be protected from drying out. A variety of adaptations for keeping eggs moist permit some amphibians to lay them out of water.

Skin breathing restricts amphibians to moist or shady habitats, since gas exchange only occurs across a moist surface.

PICTURE CAPTIONS:

    Diagram showing common ancestry and evolution of caecilians, salamanders, and frogs from organisms with smooth skin with mucous glands and ribs reduced or absent. Evolution of salamanders and frogs is where loss of bony scales branches off.