Objectives: 1. To understand metamorphosis in amphibians.
2. To know the characteristics of the classes amphibia & reptilla.
3. To learn the unique features of the orders gymnophiona (caecilians), caudata (salamanders), and anura (frogs).
4. To know the characteristics of the deciduous and coniferous forest biomes. I. Class Amphibia ~4200 species (Caecilians, salamanders, & frogs) A. Characteristics 1. Amphibians developed the four-limbed (tetrapod) body plan, although the limbs are primitive often with webbed feet tied to aquatic environments.
2. Skin is smooth & moist, with glands for poison, moisture, and pigments.
3. Ectothermic or cold-blooded meaning their body temperature fluctuates with the environment.
b. The aquatic juvenile (tadpole) has a limbless body with a tail adapted to an aquatic life.
c. Gradually the tail is absorbed; lungs and legs develop in a process called metamorphosis to produce the terrestrial adult. B. Order Gymnophiona ~160 species (Caecilians) 1. Caecilians have elongate, limbless bodies adapted to a burrowing existence.
2. Live in tropical rainforests.
3. Eat primarily worms and underground invertebrates.
4. Feature internal fertilization and some species guard the eggs in burrows. C. Order Caudata ~360 species (Newts, salamanders) 1. Found in the northern temperate regions.
2. Small, under 15cm, with reduced limbs or limbless for burrowing, while the larger aquatic species can reach 1.5 meters in length.
3. Carnivorous as both larvae and adults eating worms, arthropods, and mollusks.
4. They range from totally aquatic forms like the Hellbender to leaf litter burrowers like the Tiger salamander. D. Order Anura ~3450 species (Frogs, Toads) 1. Anurans have a characteristically shortened body adapted for jumping and swimming.
2. Rely on their lungs more than salamanders to take in oxygen, but release carbon dioxide through their skin.
3. Carnivorous, feeding on invertebrates, which they catch with a protruding sticky tongue.
4. Frogs tend to be more aquatic (Bullfrogs) or arboreal (Tree frogs), while toads are more terrestrial.
II. Forests A. Deciduous Forest 1. The deciduous forests of the eastern U.S. and central Europe are dominated by broad leaf trees like oak, maple, and beech. 2. Deciduous trees go through seasonal shedding of leaves and dormancy in winter. 3. Animals such as bears and groundhogs respond by hibernating while many birds migrate. 4. The removal of most large carnivores such as wolves and mountain lions has led to an overabundance of herbivores like deer. B. Coniferous Forest 1. Coniferous forests form a continuous belt of vegetation in the northern regions of North America and Eurasia. 2. Evergreens such as pine, fir, and spruce dominate. 3. These trees are important for building materials, particularly in the southern United States. 4. Conifer adaptations such as a conical shape and flexible limbs let them deal with the heavy snows and cold temperatures. III. Alabama Amphibian Connection A. Red Hills Salamander is an endangered species, exclusive to Alabama, which feeds nocturnally on spiders and insects. B. Two-toed Amphiuma is a large (~3 feet) aquatic salamander; with greatly reduced limbs it looks eel-like. C. Gray Tree Frog is a common species found high in the treetops, descending only to chorus & breed. D. Fowler’s Toad is a nocturnal toad, commonly seen catching insects beneath artificial lights. E. Pig Frog is the most aquatic of the “Bullfrogs” feeding mainly on crayfish it is sought for its edible legs by humans.