Amphibians   All Materials Cmassengale  

Amphibian Evolution:

bullet Arose from lobe-fined ancestor called Crossopterygians
bullet Land plants & insects provided new food source
bullet Had primitive lungs & short, limb like fins for short periods on land
bullet Appeared during late Devonian
bullet Icthyostega early amphibian with 4 limbs, lungs, & a tail for swimming

Adaptations:

bullet Four limbs with claws on digits (toes)
bullet Lungs instead of gills
bullet Both internal & external nares (nostrils)
bullet Three chambered heart (two atria & one ventricle)
bullet Double loop blood circulation to lungs & rest of body cells

bullet Skin with keratin (protein) to prevent water loss
bullet Necks to more easily see & feed
bullet Most with smooth, moist skin to take in dissolved oxygen
bullet Some with oral glands to moisten food they eat
bullet Webbed toes without claws
bullet Ectothermic - body temperature changes with environment
bullet Show dormancy or torpor (state of inactivity during unfavorable environmental conditions)
bullet Hibernate in winter and aestivate in summer
bullet Aquatic larva called tadpole goes through metamorphosis to adult
bullet Metamorphosis controlled by hormone called thyroxine

American Toad Tadpole photograph
Tadpole

bullet External fertilization with amplexus (male clasps back of female as sperm & eggs deposited into water)
bullet Eggs coated with sticky, jelly like material so they attach to objects in water & do not float away
bullet

Eggs hatch into tadpoles in about 12 days


Eggs

Classification:

Anuran Characteristics:


Frog


Toad

Urodela Characteristics:

Spotted salamander photograph
Spotted Salamander

red-spotted newt photograph
Red Spotted Newt

Apodan Characteristics:


Caecilian

Trachystoma Characteristics:


Mud Eel or Siren

External Frog Anatomy:

Internal Frog Anatomy:
Skeletal System

Digestive System

Circulatory System

Respiratory System

Excretory System

Nervous System

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