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Amphibians : The First Terrestrial Vertebrates

Amphibians : The First Terrestrial Vertebrates. Infraphylum : Vertebrata C lass Amphibia. Amphibia - means “ double life ” Live their lives in the water and on land Tetrapods : 4 muscular limbs & feet Have toes & fingers (digits). History of Amphibians.

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Amphibians : The First Terrestrial Vertebrates

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  1. Amphibians: The First Terrestrial Vertebrates

  2. Infraphylum: VertebrataClass Amphibia • Amphibia- means “double life” • Live their lives in the water and on land • Tetrapods: • 4 muscular limbs & feet • Have toes & fingers (digits)

  3. History of Amphibians • Oldest fossils discovered in Greenland in 1932 • 400 myofossil- Ichthyostegalia • Differences from fish: • Loss of some cranial bones • Loss of opercular bones • Reduction of notochord • More rigid vertebral column • 4 muscular limbs • Loss of fins/rays • Presence of vertebrae that fuse the vertebral column and the pelvis

  4. Presence of Amphibians • All continents except Antarctica • Absent from many oceanic islands • 6,000 modern species

  5. Amphibian Characteristics • Adults are carnivores • Circulatory system: • 2 chambered heart (atrium & ventricle) • Gas exchange: breathe through skin and/or with lungs • Ectothermic- body temperature depends on external heat sources • Nictitating membrane- transparent lower moveable eyelid • Vocalization- species specific • Males call to females for mating

  6. Class: AmphibiaOrder: Caudata • Salamanders • Mostly found in the N. Hemisphere • All have…. • Tail throughout life • Both pairs of legs • Terrestrial salamanders • Live in the moist, forest-floor litter • Aquatic larvae • Sometimes live in caves

  7. Class: AmphibiaOrder: Caudata • Reproduction: • Most fertilize internally • Males deposit sperm on a substrate and females pick up the sperm with their cloaca • Young salamanders look like miniature adults (called newts) • Have gills & tail fin • May be paedomorphic- undergo metamorphosis while retaining larval characteristics

  8. Class: AmphibiaOrder: Gymnophiona • Caecilians • 160 species • Confined in tropical regions • Worm like burrowers • Feed on worms & other invertebrates in the soil • “Segments” are folds in the skin

  9. Infraphylum: VertebrataOrder: Anura • Frogs & Toads • Live in moist environments or dry deserts • Adults… • Lack tails • Caudal vertebrae fuse into a rodlike structure (urostyle) • Long, muscular hind limbs • End in webbed feet

  10. Infraphylum: VertebrataOrder: Anura • Fertilize externally • Eggs & larvae are aquatic • Larvae (tadpoles) • Well-developed tail • Lack limbs until near adulthood • Herbivores • Undergo metamorphosis to turn into an adult

  11. Frogs VS. Toads Frogs Smooth skin Aquatic habitats Toads Dry & warty skin More terrestrial

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