1. Amphibians
The double life

2. Origin and Evolution of Amphibians
Lobe – finned fish
Bone structure within their fins allowed for them to function as “legs”
Modified pouches in digestive tract evolved into lungs of the lungfish and swim bladder of modern fish
Amphibians also share skull and vertebral column

3. Lobed – finned fish: Coelocanth

5. Oldest amphibian fossils were dated to 360 m.y.a
Between 359 – 299 m.y.a amphibians split into two main evolutionary lines
Modern amphibians
Ancestors of reptiles

6. Classification Domain: Eukarya Kingdom: Animalia Phylum: Chordata
Subphylum: Vertebrata
Class: Amphibia, 4500 species
Order Anura, largest order contains the frogs and toads
Order Caudata, contains salamanders
Order Gymnophiona, contains caecilians

7. Order Anura
Frogs and toads (squat bodies, shorter legs, skin not as smooth as frog)
Found in a variety of moist habitats
Adults are carnivorous
Reproduction
Amplexus
Metamorphosis

8. Life Cycle Fertilization takes place
Eggs hatch, tadpole lives off yolk stored in its body
Tadpole grows larger, three gills develop
Mouth opens, begins to feed on algae
Tadpole grows slowing changing from an aquatic larva into an adult
May vary depending on species

9. Metamorphosis Process of change from an egg to larva to adult
Triggered by the hormone thyroxine that is produced by the thyroid gland

10. Order Caudata Salamanders, newts, mudpuppies
Elongated tails, and smooth, moist skin
Lay eggs in water or moist places
Both young and adult are carnivorous
Hatchlings are small versions of parent except young have gills

11. Order Gymnophiona Caecilians Legless amphibians
Live in tropical areas, burrow in the soil, also aquatic
Lay eggs or young are born alive

13. Characteristics of Amphibians
Five key characteristics; legs, lungs, double – loop circulation, 3 - chambered heart, cutaneous respiration
Live in moist habitats
Mostly external fertilization

14. Movement Skeleton Strong endoskeleton
Vertebrae of the spine is interlocked to form a rigid structure
Limbs support body
Forelimbs attach to the pectoral girdle (shoulder)
Hind limbs attach to the pelvic girdle
Transfers body weight to the limbs
Frogs, lower limbs are fused into a single bone
Forelimb (radio – ulna) and hind limb (tibiofibula)

16. Response Sense Organs Lateral line as larvae Sight, sound, smell
Nictitating membrane
Transparent membrane that covers eyes
Tympanic membrane
Eardrum

17. Respiration Gills, most loose as adults
Skin serves two important functions – respiration and protection
Cutaneous respiration
Diffusion
Mucous glands
Pulmonary respiration

18. Pulmonary Respiration
Pump air into lungs in a process called positive – pressure breathing
Frog breathes by changing the volume and pressure of air in its mouth while either opening or closing its nostrils

20. Circulation Three chambered heart and double – looped circulation
Increase pressure and speed of delivery for oxygen rich blood to organs
Divided into two separate loops

21. Two separate loops Pulmonary circulation Systemic circulation
Carries deoxygenated blood from the heart to the lungs and back to the heart
Systemic circulation
Carries oxygenated blood from the heart to the body and back to the heart

22. Three chambered heart Right and Left Atrium (septum divides)
Ventricle (spongy surface and contraction)
Deoxygenated blood enters from the body, right atrium
Oxygenated blood enters from the lungs, left atrium
Contraction of the atria forces blood into a single ventricle
Ventricle contracts pushes all of the blood into the conus arteriosus, which directs the blood to the lungs or the body