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How did amphibians, such as frogs, trade their tails for legs?

How did amphibians, such as frogs, trade their tails for legs?. Unit Questions. 1. How did the tetrapod leg evolve? 2. Why did early animals move from water to land? How did amphibians transition from life in water to life on land? What are the three major groups of modern amphibians.

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How did amphibians, such as frogs, trade their tails for legs?

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  1. How did amphibians, such as frogs, trade their tails for legs?

  2. Unit Questions 1. How did the tetrapod leg evolve? 2. Why did early animals move from water to land? • How did amphibians transition from life in water to life on land? • What are the three major groups of modern amphibians

  3. Early Tetrapods and Modern Amphibians By: Debra Cunningham

  4. Early Tetrapods • Terrestrial vertebrates adapted • Tetrapod leg evolved • Modern amphibians transitioned • Caecilians • Salamanders • Frogs and toads

  5. Origin of Terrestrial Vertebrates • The Devonian period • 400 million years ago • time of mild temperatures • alternating droughts and floods • Lungs and limbs evolved for terrestrial life • Unstable freshwater environment • Pools and streams evaporated • Foul water resulted • Lobe-finned and lungfish evolved into modern amphibians

  6. Evolution of Tetrapod Leg • Lobe-finned fish fins • Paddle-like fins • Paired muscular fins • Anterior fin - humerus • Forearm bones - radius and ulnar • Bony elements - wrist bones

  7. Lobe-finned Fishwww.abdn.ac.uk/.../coelacanth/coelacanth.jpg

  8. Adaptations for Life on Land Sensory Development Skeletal Structure • Special sense priority shift • Foreshortening skull • Lengthened snout • Advanced ear structure (tympanic membranes) • Olfactory epithelium to detect airborne odors • Skeletal strengthening • Stronger backbone • Strengthened shoulder and hip girdle; tetrapod leg • Protective rib cage • Muscles to support body in air and elevate head

  9. www.estrellamountain.edu/.../comparison.gif

  10. Modern Amphibianswww.caf.wvu.edu/~rwhitmor/wman224/.../Modern%20amphibians.pdf

  11. Amphibian Breeding Habits ▪ Caecilians: • Internal fertilization • Deposit eggs in moist soil ▪ Salamanders: • Internal fertilization • Lay eggs in stringy masses, clusters in water ▪ Frogs and Toads: • External fertilization • Lay eggs in masses anchored to vegetation

  12. Caecilians • Elongated body, limbless • Small scales on skin • Many vertebrae (95-285) • Small eyes (adults blind) • Sensory tentacles on snout • Pantropical

  13. Salamanders • Typically small • Limbs set at right angles to body • Forelimbs & hindlimbs are equal in size • Vertebrae (10-60) • Breathe through skin • Ectothermic; predominantly holarctic

  14. Frogs and Toads •Typical tetrapod pattern of bones and muscles • Shortened body-only nine (9) trunk vertebrae • Three main joints in each limb • Light-weight skull with flattened profile • Tail and gills resorbed • Ectothermic

  15. Life Cycle of a Frog • http://www.scienceclarified.com/Al-As/Amphibians.html

  16. Conclusion • Frogs traded their tails for legs • Modern amphibians evolved from lobe-finned fish • Modern amphibians transitioned from water to land

  17. References Hickman, Jr. C.P., Roberts, L.S., & Larson, A. (2001). Integrated Principles of Zoology, ed 11. McGraw-Hill: Boston, 538-558. Color illustrations and pictures from: • http://www.scienceclarified.com/Al-As/Amphibians.html • www.abdn.ac.uk/.../coelacanth/index.html • www.caf.wvu.edu/~rwhitmor/wman224/.../Modern%20amphibians.pdf • www.estrellamountain.edu/.../comparison.gif

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