Amphibian Basics

Amphibian Basics

Amphibian Basics

Amphibians

  • Amphi = double, bios = life

  • Aquatic stage and terrestrial stage

  • First vertebrates on land

  • Paved the way for the evolution of all terrestrial vertebrates

  • about 5000 species, mostly frogs

  • <1cm to >m

  • Moist skin—susceptible to environmental factors—indicator species

What makes an amphibian an amphibian?

  • Smooth, moist, glandular skin

  • No claws, scales, feathers or fur

  • Breathe through lungs, skin, or gills

  • Mostly tetrapods, bony skeleton

  • 3-chambered heart with double circulation

  • Tympanum to hear and olfactory epithelium to smell

  • Ectothermic

  • Webbed feet

Amphibian classification

  • Kingdom = Animalia

  • Phylum = Chordata

  • Subphylum = Vertebrata

  • Class = Amphibia

  • Only one extant subclass—Lissamphibia

  • Three extant orders

    • Anura—frogs and toads

    • Caudata—salamanders and newts

    • Gymnophiona—caecilians

Amphibian Evolution

  • Sarcopterygian ancestor—lobe-finned, lung fish or Coelocanth

  • Three current amphibian groups diverged about 100 MYA

    • Anura

    • Caudata

    • Caecilia

  • Homologous structures

Amphibian Orders

  • Caudata—salamanders

    • “bearing a tail”

    • 400 spp

    • 4 limbs and a tail

    • Mucus and poison glands

  • Anura—frogs and toads

    • 4500 spp+

    • 4 limbs of unequal size

    • widespread

    • males vocalize

  • Gymnophiona—Caecilians

    • “Without legs”

    • underground diggers

    • 150 spp

    • Tropics and subtropics

    • Eyes may be covered