1. Section 1 Origin and Evolution of Amphibians
Chapter 40 Amphibians
Section 1
Origin and Evolution of Amphibians

2. Amphibians Greek word meaning “double” and “life”
Many amphibians spend part of their life in water and part on land

3. Adaptation to Land Most likely evolved from lobe-finned fishes
Pre-adaptations- adaptations in an ancestral group that allow a shift to new functions which are later favored by natural selection

4. Adaptation to Land
Lobe-finned fish ancestral amphibians- appendages to walk
Had modified pouches in their digestive tract that evolved into lungs
Had nostrils to help aid in breathing on land

5. Characteristics of Early Amphibians
Amphibians and lobe-finned fishes share many similarities: skull & vertebral column
Sarcopterygian- extinct lobe-finned fish that is thought to be closely related to amphibians

6. Sarcopterygian

7. Diversification of Amphibians
4,500 species belonging to three orders
Anura- frogs and toads
Caudata- salamanders
Gymnophiona- caecilians- legless tropical amphibians

9. Modern Amphibians
Most change from aquatic larval stage to a terrestrial adult form- metamorphosis
Most have moist, thin skin with no scales
Feet, if present, lack claws and often are webbed

10. Modern Amphibians Most use gills, lungs, and skin respiration
Eggs lack multi-cellular membranes or shells. They are usually laid in water or in moist places and are usually fertilized externally

11. Order Anura Frogs & toads
World-wide, except in polar climates and a few oceanic islands
Either spend part of or entire live in water
Toad- rough, bumpy skin
Frog- smooth, moist skin

12. Order Anura Body adapted for jumping (long muscular legs)
Adult anurans are carnivores
Have a sticky tongue to help capture food
Return to water to reproduce
Tadpoles- fertilized eggs hatch into swimming, tailed larva

13. Poison Dart Frog

14. Gray Tree Frog

15. Bull Frog

16. Leopard Frog

17. Cane Toad

18. American Toad

19. Order Caudata
Salamanders- elongated bodies, long tails, and moist skin
Smallest are only a few centimeters long, largest are over 4.5 feet
Aquatic and terrestrial species
Carnivores

20. Order Caudata Most live in North America and Central America
Some are lungless and breathe through their skin
Some reproduce in water, while others lay eggs on land

21. Order Caudata Water reproduction- larval stage
Land reproduction- no larval stage
Internal fertilization
Some terrestrial species stay with eggs until hatched

22. Spring Salamander

23. Dusky Salamander

24. Red-Spotted Newt

25. Spotted Salamander

26. Order Gymnophiona Caecilian- legless amphibian- resembles snakes
Found in tropical areas of Asia, Africa, and South America
12 inches to 4.5 feet
Often are blind because their eyes are found under skin and bone

27. Order Gymnophiona Rarely seen- little is known
Some burrow and some are aquatic
Have teeth- eat worms and other invertebrates

28. Order Gymnophiona Internal fertilization
Some species lay eggs & some are born live
Young use their jaws and teeth to scrape secretions “uterine milk” from the walls of the female’s reproduction tract

29. Sagalla Caecilian

30. Purple Caecilian

31. REVIEW!!!
Name some characteristics that are common to modern amphibians.
Compare and contrast the three living orders of amphibians.