Chapter 19-Amphibians

Amphibian- “Double Life”

- Water and land

Amphibian Characteristics 1st true tetrapod vertebrates Bony skeletons with four limbs

– Exceptions: Caecilians (limbless) and Sirens (forelimbs only) Many w/webbed feet Thin moist skin; no scales Breathe w/ lungs lungs (Internal, bag-like organ that exchanges oxygen

and carbon dioxide with the air and blood)– Exception: Lungless salamanders– Larvae- gills

Cutaneous respirationCutaneous respiration- “Skin breathing”– Supplement oxygen intake w/ moist skin– Limited by body size

Double-Loop Circulation

Amphibian Characteristics

Partially divided heart: – Atrium separated into left and right sides by septumseptum,

ventricle is not– Right side sends oxygen-poor blood to lungs– Left side send oxygen-rich blood to organs

Double-loop circulationDouble-loop circulation:– Two large veins (pulmonary veins) return oxygen-rich

blood from lungs to heart– Blood pumped to tissues at higher pressure than fish– Systemic circulation- Blood flow to the body

Class Amphibia

Order Anura- Frogs and toads Order Urodela (Caudata) – Salamanders,

sirens, newts, waterdogs, mudpuppies Order Gymnophiona (Apoda)- Caecilians

Class Amphibia

Order Anura- Frogs and Toads Anura- without a tail Adult carnivores Skin with mucus and some with

poison glands Sticky tongue, hinged at the front,

attaches to prey– Vomerine teeth- two small nobs

help hold in prey Hind legs adapted for jumping Frogs are smooth w/ longer legs Toads are rough w/shorter legs

Most frogs depend on water for life cycle– Females lay eggs in water– Males fertilize them – Larvae are tadpolestadpoles

• Gills • Feed on algae• Incomplete

metamorphosis• Develop into adult

frogs• Rate depends on species

and food

Leopard Frog and Fowler’s Toad

Goliath Frog- Conraua goliath

- Largest frog in world- Found in Cameroon

Poison-Dart Frogs- Family Dendrobatidae

Frog Characteristics Tympanic membraneTympanic membrane- thin

membrane that detects vibration (eardrum)– Eustachian tubes- equalize

pressure on eardrums

Skin has mucus glands– Mucus is poisonous or foul

tasting in most

Nictitating membrane- transparent eyelid

Two teeth in roof of mouth Swallow food whole

CloacaCloaca- Chamber opening to outside of body– Serves as exit for wastes and

gametes

- Oviduct- carries eggs to cloaca- Vocal Sacs- Expandable membranes

that collect air after passing over vocal cords for louder croaking

Amplexus

Order Urodela (Caudata- with a tail) 369 species of salamanders, newts,

sirens, amphiuma, waterdogs, and mudpuppies

Elongated bodies w/long tails Smooth, moist skin; Require moisture External fertilization in water or

moist area– Internal fertilization- females

insert sperm packet into cloaca– Larvae gilled, carnivorous,

smaller version of adult– Some retain gills as adults

(neoteny- never lose larval characteristics)

Salamanders

Axolotl

Salamander that never loses its gills

Neoteny Found in N.

america

Other Urodela (Caudata)Newt

Amphiuma

Water dog

Mud puppy

Order Caudata- Sirens

Aquatic salamanders Have only front

extremities Maintain gills

throughout life Some can vocalize Most likely external

fertilization

Order Apoda- Caecilians

Apoda- without legs Tropical, burrowing

amphibians Small, bony scales

embedded in skin Legless Carnivorous Male deposits sperm directly

into female Females may have live

young or lay eggs