DOL 52 53 AMPHIBIANS Biology ~ Advanced Studies 6. Closed circulation, 3 heart chambers 7. Sexual reproduction a. frogs & toads external fertilization b. salamanders & caecilians internal fert. 8. Metamorphosize a. change body form as they mature 9. The dominant terrestrial life form in the Carboniferous Period a. about 350 million years ago b. a.k.a. Age of Amphibians III. Class Amphibia A. General characteristics 1. frogs, toads, salamanders, newts, caecilians 2. bilateral symmetry 3. larvae = aquatic herbivores with gills & tails 4. adults = terrestrial carnivores with lungs & legs a. some aquatic adults keep gills 5. moist, mucousy skin lacking scales a. aids respiration B. Frog Anatomy & Physiology 1. Digestion a. feeding styles change 1) larvae = filter-feeders 2) older tadpoles = herbivores 3) adults = carnivores b. sticky, elastic tongues help capture prey c. have maxillary & vomerine teeth on upper jaw & palate to grip prey 1) not present in toads d. cloaca is present in intestinal tract 1) at end of large intestine 2) for waste removal, gamete release
FROG DIGESTIVE ADAPTATIONS Cloaca Elastic tongue Vomerine teeth Maxillary teeth 3. Circulation a. 2 atria, 1 ventricle b. closed, double-loop system 1) path between heart & lungs 2) path between heart & body 2. Respiration a. larvae use gills b. tadpoles transform gills into lungs c. adults develop lungs 1) nostrils take in air 2) moist skin & mouth lining bring in some d. vocal sacs & vocal cords produce sounds 1) for mating, territory, weather change, danger/pain 4. Movement a. larvae swim, propelled by tail b. tadpoles grow legs, tail aids for a time c. adults legs provide locomotion, grasping 1) hind legs more muscular to climb, jump 2) front legs adapted to grip d. feet may have separate toes or webbing to aid swimming
5. Response 1. well-developed nervous system, senses 2. eyes work independently a. on top of head for near 360o-vision b. cover w/nictitating membrane to see underwater, prevent drying out on land c. aid swallowing push down in mouth 3. tympanic membranes on sides of head behind eyes aid hearing a. sense vibrations, sounds 6. Reproduction and development a. occurs in water b. external fertilization stimulated by physical contact known as amplexus 1) male mounts female & both shed gametes from cloaca into water 2) females shed 200+ soft, jelly-like eggs c. fertilized eggs develop on own in water, are buried on land or are carried by parent until hatching FROG SENSES FROG REPRODUCTION Well-developed brain Large eyes w/ nictitating membranes Tympanic membrane for hearing Amplexus stimulates gamete release External fertilization After hatching, metamorphosis occurs over several weeks
d. during metamorphosis, key changes occur 1) eggs hatch, larvae grow & filter feed 2) tadpoles develop a) have fish-like tails, external gills, eat plants b) gills become internal, lungs start forming c) back legs form first, then front legs 3) froglets develop a) mouths widen, eat insects b) tails are reabsorbed c) grow in size 4) adults move onto land a) fully developed lungs, legs C. Amphibian Orders 1. Order Urodela a. salamanders & newts b. long bodies, 4 equal-sized limbs, tails throughout life c. prefer moist habitats d. internal fertilization e. ex: mudpuppies, barred tiger salamander, rough skinned newt
2. Order Anura a. frogs & toads b. squatty bodies, front & back legs different sizes, lack tails as adults c. ex: bull frog, Goliath frog (largest), P. amauensis (smallest), European green toad 12.5 inch body, 7+ pounds! Frogs 7.7 mm body Toads Slimy, more colorful skin Thicker, rougher, browner skin Longer, more powerful hind legs for jumping Live in or near water Shorter, less powerful hind legs for walking, hopping Live on land, only reproduce in water Lay eggs in clusters Lay eggs in chains Narrow body, waist Stout, flatter body Teeth on upper jaw & palate No teeth Higher, more bulging round eyes Eyes lower, more oval More predators Fewer predators toxins in skin FROG VS. TOADS FROG & TOADS
3. Order Apoda a. caecilians b. snake-like bodies, lack legs c. burrow in moist soil or live in water d. many have fish-like scales on skin e. internal fertilization f. ex: South American caecilian, yellow striped caecilian CAECILIANS!