Amphibians Copyright Cmassengale. Evolution of Amphibians Copyright Cmassengale.
17.3 amphibians
Transcript of 17.3 amphibians
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17.3 AmphibiansPage 353
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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
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Amphibian Examples
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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
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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
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Frogs & ToadsNo tailsSpend lives in & around water
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Frog ReproductionHundreds of eggs laidMale fertilizes outside bodyEggs hatch tadpoles in several weeksMost toads similarSome species – no tadpoles
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TadpolesThey have gills, fins, tails, streamlined bodyUndergoes great changes
(METAMORPHOSIS)Once complete, adult is land-dwelling
vertebrate
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Salamanders & NewtsAmphibians with tailsSmooth, moist skinSome live in dry habitats, some moist, some
water