Amphibians 16.2

History 350 million years ago there were no vertebrates living on land. Fish lived wherever there was water Land had many resources and little predators Vertebrates developed legs for walking and lungs for breathing outside of water. Amphibians-animals that live in water and have lungs and legs. Evolved from ancestors of lungfish

Characteristics of Amphibians Lung- saclike organ that takes oxygen from the air and delivers it to the blood Amphibian- means “double life”-they spend part of their life in water and part on land The egg doesn’t have a shell so the embryo develops in a wet environment and when they have developed into adults they move to land. -They are extotherms (cold blooded)

Skin Thin, smooth, and moist Absorb water through skin (don’t drink it) Breath through absorption of oxygen through skin into blood vessels Some are bright colors and may be poisonous

Double Life The change from immature form to an adult is called metamorphosis tadpole- immature frog or toad that must live in water and gets oxygen through gills CRAZY FACT Adult Darwin’s frogs lay eggs on moist ground and when the embryo begins to move they hold it in their mouth until its developed. Out comes a tiny frog

Joke Break

Fertilized Eggs Newly hatched tadpole feeds on yolk stored in its body and uses gills to breath Tadpole begins to feed and grow legs Tail disappears and lungs become functional Adult frog

3 Groups of Amphibians 1.Caecilians 2.Salamanders 3.Frogs and Toads

Caecilians Over 160 species Tropical areas of Asia, Africa and South America Look like worms or snakes with no legs Have thin, moist skin of amphibians

Salamanders 500 known species Under stones or logs in the woods of North America Most like ancient amphibians (4 legs and long tail) Few centimeters to 1.5 meters long Most lose their gills and grow lungs

Frogs and Toads 90% of all amphibians Everywhere but cold regions Strong legs good hearing and vocal cords Tongue attached to front of mouth to be flipped out to catch insects Use vocal sac that surrounds their vocal cords to make noise louder

Ecological Indicators Unhealthy amphibians can be and early sign of changes in an ecosystem Death or deformities Extremely sensitive to change (chemical or temperature) Skin absorbs chemicals in water or air – Golden toad began to disappear from Costa Rica