Amphibians

AmphibiansTwo LivesChapter 16 p. 311 - 323Amphibia 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 predators2.exploit more diverse habitats3.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 moistB.feet, if present, usually webbedC.toes soft & lack clawsD.immature forms tadpoles vegetarian; adults carnivorousE.heart 2-chambered in immature forms 3-chambered as adultsF.respiration by gills, lungs, and skinG.eggs laid in water; fertilized externally as soon as laidH.metamorphosis from aquatic larval stage to adult stageIntegument (Frogs and Toads)

Integument thin and moistChromatophoresGlandsMucous (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 CycleAmplexus of Common ToadsSee p. 323!!

Lobed-finned fish

Caecilians

Axolotl Permanent Larva

Salamanders with egg mass

Tympanic Membrane- Used as an eardrum

Nictitating Membrane- Covers eyes to keep them moist and protect them

Vocal sac

Panamanian Golden Frog(sexual dimorpism)

Cane Toad

Pac man Frogs

Goliath Frog

Poison Arrow Frogs(Amazon)Illinois Amphibians

Tiger Salamander

Small mouth Salamander

American Toad

Spring Peeper

Gray Tree Frog

Leopard Frog

Bullfrog

Practice Quiz: