17.3 amphibians
TRANSCRIPT
17.3 AmphibiansPage 353
Movement Onto LandAmphibians evolved from lobe-finned fish,
now extinctAs they evolved, fins got stronger & more
supportiveUsed for swimming & crawling
Fossil records suggest these fins evolved into two pairs of legs
Amphibian Examples
Amphibian CharacteristicsGills & simple lungs evolved into lungs able
to exchange gases with atmosphereBegan using skin for respirationAlthough adapted to land life, still need water
Reproduction
Amphibian ReproductionDepend on water
Eggs don’t have waterproof shellEggs laid in water and externally fertilized by
maleMany amphibians develop into a fish-like
larval stage (tadpole)
Red-Eyed Tree Frogs
Red-Footed Tortoise
Frogs & ToadsNo tailsSpend lives in & around water
Frog ReproductionHundreds of eggs laidMale fertilizes outside bodyEggs hatch tadpoles in several weeksMost toads similarSome species – no tadpoles
TadpolesThey have gills, fins, tails, streamlined bodyUndergoes great changes
(METAMORPHOSIS)Once complete, adult is land-dwelling
vertebrate
Salamanders & NewtsAmphibians with tailsSmooth, moist skinSome live in dry habitats, some moist, some
water