how did amphibians, such as frogs, trade their tails for legs?
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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UNIT QUESTIONS
1. How did the tetrapod leg evolve?
2. Why did early animals move from water to land?
3. How did amphibians transition from life in water to life on land?
4. What are the three major groups of modern amphibians
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By: Debra Cunningham
EARLY TETRAPODS AND MODERN AMPHIBIANS
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EARLY TETRAPODS Terrestrial vertebrates
adapted
Tetrapod leg evolved
Modern amphibians transitioned Caecilians Salamanders Frogs and toads
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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
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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
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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
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MODERN AMPHIBIANSwww.caf.wvu.edu/~rwhitmor/wman224/.../Modern
%20amphibians.pdf
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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
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CAECILIANS
• Elongated body, limbless
• Small scales on skin
• Many vertebrae (95-285)
• Small eyes (adults blind)
• Sensory tentacles on snout
• Pantropical
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SALAMANDERS
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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
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LIFE CYCLE OF A FROG
http://www.scienceclarified.com/Al-As/Amphibians.html
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CONCLUSION
Frogs traded their tails for legs
Modern amphibians evolved from lobe-finned fish
Modern amphibians transitioned from water to land
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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