Amphibians & ReptilesDonald Winslow, 7 April 2008

Readings from Hickman, et al., 2008

Ch 25 544-559 (amphibians); Ch 26: 563-582 (reptiles)

Colonization of land by tetrapods

Early tetrapods colonized land in Devonian Period, radiated during CarboniferousDouble circulation, pulmonary & systemic circuitsFins became legs—humerus, radius, ulnaIchthyostega

Coelacanth Lungfish Ichthyostega AmniotaAnura Apoda Caudata

Class Amphibia

Can use land, but usually tied to water for reproductionWebbed feet, forelimb usually with 4 digitsSkin smooth & moist with many glands, chromatophores, no scalesRespiration by skin, gills, and/or lungs, 3-chambered heart (2 atria)Ectothermal, paired mesonephric kidneys, urea main nitrogenous wasteSeparate sexes, usually oviparous, mesolecithal eggs laid in waterMetamorphosisOrder Apoda (caecilians)

No legs, tropical forests, internal fertilization, egg-guardingOrder Caudata or Urodela (salamanders)

Internal fertilization, female picks up spermatophoreAquatic species metamorphic, gills as larvae & lungs as adults Terrestrial species develop directly; plethontids breathe thru skinPaedomorphic species (mudpuppy, axolotl) retain gills as adults American newts: aquatic larvae, terrestrial efts, aquatic adultsParental care

Order Anura (frogs & toads)

Order Anura (frogs & toads)

VocalizationExternal fertilization during amplexusEgg, tadpole stages, adult

Family RanidaeBullfrog, leopard frog, etc.

Family HylidaeTreefrogs

Family BufonidaeToads

Factors affecting amphibian declines

DroughtsWetland lossesPollutantsIntroduced predators & competitors

Bullfrog, African clawed frogOzone depletionDiseases—chytridiomycosis

Amniotes

Enclosing the pondAnapsids

Turtles secondarily anapsidDiapsids

LepidosaursSnakes, lizards, amphisbaenasTuataras

ArchosaursCrocodilians, dinosaurs, birds

Synapsids—Mammals

Class Reptilia (paraphyletic taxon)

Shelled, amniotic eggExtra-embryonic membranes

Amnion, chorion, allantoisMost species entirely terrestrialDry, scaly skin, chromatophoresPowerful jaws, ectothermicInternal fertilization, separate sexesAdaptations to conserve waterHigher blood pressure than amphibiansNo gills, respiration usually by lungsMain nitrogenous waste is uric acid

Class Reptilia

Order Testudines (turtles)Superorder Lepidosauria

Order SquamataOrder Sphenodonta

Superorder ArchosauriaOrder Crocodilia