amphibians

Amphibians

Amphibia

• Comes from the Greek amphi “both” and bios “life”

• Appeared during the Devonian period

Adaptations

• Four limbs• Lungs instead of gills• Both internal & external nares (nostrils)• Three chambered heart (two atria & one

ventricle)

• Skin with keratin (protein) to prevent water loss

• Most with smooth, moist skin to take in dissolved oxygen

• Some with oral glands to moisten food they eat

• Ectothermic - body temperature changes with environment

• Show dormancy or torpor (state of inactivity during unfavorable environmental conditions)

• Hibernate in winter and aestivate in summer• Males with vocal sacs to croak • Digested system adapted to swallow prey whole • Well developed muscular system

Anura

• Frogs • Toads

Characteristics

• Both terrestrial & freshwater species • Tadpole with tail, gills, & two-chambered

heart • Adults without a tail, four limbs, & lungs • Frog skin smooth & moist for cutaneous

respiration, while toads is rough & warty (poison glands)

• Long hind limbs for jumping

• Aquatic larva called tadpole goes through metamorphosis to adult

• Metamorphosis controlled by hormone called thyroxine

Reproduction

• External fertilization with amplexus (male clasps back of female as sperm & eggs deposited into water)

• Eggs coated with sticky, jelly like material so they attach to objects in water & do not float away

• Eggs hatch into tadpoles in about 12 days

Tad pole life cycle

Caudata

• Newts and Salamanders

Characteristics

• Have elongated bodies with a tail & four limbs • Smooth, moist skin for cutaneous respiration • Size from a few centimeters long to 1.5

meters • Nocturnal when live in drier areas • Newts are aquatic species

• Lay eggs in water or damp soil • Some bear live young • May or may not go through tadpole stage

(some hatch & look like small adult)

• All newts are salamanders but not all salamanders are newts

Apoda

• caecilians

• Tropical, burrowing, worm like amphibians • Legless • Small eyes & often blind • Eat worms & other invertebrates • Average length 30 centimeters, but can grow

up to 1.3 meters • internal fertilization • Female bear live young