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Amphibians. “Two Lives”. Chapter 16 p. 311 - 323. “ Amphibia ” means having two lives: they can live on land but are never completely free of water.
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Amphibians “Two Lives” Chapter 16 p. 311 - 323
“Amphibia” means having two lives: they can live on land but are never completely free of water. Fossil and genetic evidence reveal that they evolved from the fishes – development of lungs and leg-like fins were probably an adaptation for survival. Selective advantages to the first amphibians: 1. avoid aquatic predators 2. exploit more diverse habitats 3. exploit an untapped food source (insects, worms …..)
Major difficulties adapting to land: 1. gravity & body support (no water to buoy them up) 2. desiccation (drying out) – modify gas exchange organ & stay in moist habitat 3. rapid & large temperature shifts in air (water has a much higher heat capacity)
Characteristics of Amphibians: A. skin is smooth, thin and usually moist B. feet, if present, usually webbed C. toes soft & lack claws D. immature forms “tadpoles” vegetarian; adults carnivorous E. heart 2-chambered in immature forms 3-chambered as adults F. respiration by gills, lungs, and skin G. eggs laid in water; fertilized externally as soon as laid H. metamorphosis from aquatic larval stage to adult stage
Integument (Frogs and Toads) • Integument thin and moist • Chromatophores • Glands • Mucous (protective, watery) • Serous (poison; larger glands)
Orders of Amphibians: Apoda– legless, tropical (caecilians) Caudata– tailed amphibians (salamanders & newts) Anura– tailless (as adults) (frogs & toads)
Life Cycle See p. 323!! Amplexus of Common Toads
Tympanic Membrane - Used as an eardrum
Nictitating Membrane - Covers eyes to keep them moist and protect them
Panamanian Golden Frog (sexual dimorpism)
Poison Arrow Frogs (Amazon)
Illinois Amphibians Tiger Salamander Small mouth Salamander
American Toad Spring Peeper