Amphibians

• Amphibians e.g. Frogs


  • Probably first group to colonise land
  • All frogs start life as aquatic tadpoles (larval form), using gills for gas exchange
  • Metamorphose into the adult form, land animals with lungs for breathing air
• Frog lungs


  A pair of thin-walled sacs connected to the mouth through an opening, the glottis
• How frogs inflate their lungs

  1. Filling its mouth with air

  2. Closing its mouth

  3. Closing the internal openings to its nostrils

  4. Opening its glottis

  5. Raising the floor of its mouth, thus forcing air into the lungs
• Frogs breathe out with body contractions
• Lungs also help in water

  Filling the lungs with air gives a frog better buoyancy, making it float more easily
• Frog skin


  • When inactive the frogs moist skin is used as a respiratory surface
  • It must remain moist to do this, which is one reason that frogs, like other amphibians, live in moist places
  • It has tiny blood capillaries, under the outer skin layers
• African 'Hairy' frog


  • Has small lungs and during breeding seasons the males get hair like projections on their back legs
  • This is because of the high oxygen needs at this time