1. Amphibians
1st tetrapods

2. Evolution of Amphibians
Copyright Cmassengale

3. Copyright Cmassengale
"Amphibian" comes from the Greek meaning "both life". Amphibians can live on water and on land.
Scientist infer that amphibians evolved from lobe-finned fishes called crossopterygians.
Copyright Cmassengale

4. Copyright Cmassengale
Biologist conclude that amphibians appeared during the late Devonian period, about 345 million years ago.
Copyright Cmassengale

5. Characteristics Ectothermic 3-chambered heart (Double circulation)
Smooth skin, lacks scales (Desiccation if dry)
Cutaneous respiration
Lungs (Positive pressure mouth breathing)
Excretes urea
Lack claws on toes

6. Copyright Cmassengale
Amphibians are cold-blooded, which means their blood temperature rises and falls with that of the surrounding environment •
Copyright Cmassengale

7. They use gills, lungs, skin, and mouth cavity in respiration.
Copyright Cmassengale

8. Copyright Cmassengale
They have moist, smooth, thin skin with no scales.Feet are webbed and the toes lack claws.
Copyright Cmassengale

9. Copyright Cmassengale
Amphibians have many prominent characteristics that are adaptations to a life spent both on land and in water: They change from an aquatic larval stage to a terrestrial adult form. This transformation is called metamorphosis
Copyright Cmassengale

10. Copyright Cmassengale
Metamorphosis
Newly hatched tadpoles live off yolk stored in their bodies. They gradually grow larger and develop three pairs of gills.
Tadpoles have a two-chambered heart. Tadpoles can also regenerate injured or lost body parts such as a leg or tail.
Legs grow from the body, and the tail disappears.
Copyright Cmassengale

11. Copyright Cmassengale
Metamorphosis
The mouth broadens, developing teeth and jaws. A saclike bladder in the throat divides into two sacs that become lungs. The heart develops a third chamber.
A hormone called thyroxin circulates throughout the bloodstream and stimulates metamorphosis.
The cells of the tad­pole are genetically programmed to respond to thyroxin at the appropriate stage of development.
Copyright Cmassengale

12. Copyright Cmassengale
Amphibians enter a state of dormancy or torpor when conditions are unfavorable. They often bury themselves in mud or leaves, emerging when conditions are better.
Copyright Cmassengale

13. Copyright Cmassengale
Larvae have two-chambered hearts; adults have three-chambered hearts and well-developed circulation.
Copyright Cmassengale

14. Amplexus

15. Copyright Cmassengale
Eggs lack multicellular membranes or shells. They are usually laid in water or in a moist environment and fertilized externally.
Copyright Cmassengale

17. Copyright Cmassengale
Toads and frogs have many similarities in the way they look. Some basic differences between them are: toads have dry, warty skin, while frogs have smooth, wet skin.
Copyright Cmassengale

18. Characteristics of a Reptile
Vertebrate animals
Lungs
Scaly skin
Amniotic egg
Characteristics of a Reptile
Vertebrate animals
Lungs
Scaly skin
Amniotic egg

19. Characteristics of Reptiles – Adaptations to life on land
More efficient lungs and a better circulatory system were developed for life away from water
Scaly skin provided protection against the elements and desiccation
The amniotic egg protected against desiccation

20. Reptile Lungs- Another Adaptation to Life on Land
A more efficient respiratory system
Reptiles use two efficient lungs (except snakes – they only have one long one that fits their bodies)

21. Reptile Lungs
Respiration is no longer through the skin, but only through internally protected and moistened lungs.
They have a much greater surface area for the exchange of gases.
They are inflated and deflated by the expansion & contraction of the rib cage.

22. Scaly Skin An adaptation to life out of water Waterproof Dry, leathery
Protective scales
Must be molted

23. Amniotic Egg – Reptiles and Birds
Compared to the development of seeds in plant evolution
Reptile eggs have leather shell
Has several membranes
Contains yolk rich in nutrients for embryo
Mammals have comparable modified membranes

24. Reptile Legs Short tetrapods for walking
Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.

25. Carnivores Some snakes have a diet of eggs exclusively.
They swallow the egg whole, pierce the shell with a specialized section of the vertebrate, suck out the insides and spit out the shell!

26. Reptilian Respiratory System
Reptilian lungs are better developed than amphibians
Muscular ribs help them expand the chest cavity as we do to draw in the air
Nostrils allow them to bring in air while their mouth is closed
Snakes only have one long, lung that fits in their bodies.
Snakes also have a tube that projects out of the mouth when the snake is swallowing so that it can breathe and swallow at the same time

27. Breathing Tube

28. Internal Transport Double-loop system
Most reptiles have a 3 ½ chambered heart (ventricle has a partial septum)
Crocodiles and Alligators have a 4 chambered heart like ours.

30. Excellent Sense of Smell - Snakes
Have pair of nostrils
Also have special organs (vomeronasal organs) on roof of mouth
Tongue picks up chemicals and brings them to the vomeronasal organs to “taste” the air

31. Jacobson’s Organ

32. Hearing
Most lizards have simple ears like an amphibian: external tympanum, single bone to transfer sound to inner ear . (we have an internal tympanum and 3 bones)
Snakes have no ears and are deaf – they “hear” the vibrations from the ground

33. Hearing - tortoises
Tortoises do not have a tympanum, but have a sound-conducting patch of skin on their head.
A “Red Ear Slider” turtle

34. Heat Sensors
Pit vipers are able to detect heat, to obtain a temperature image of their environment
Normal view Infrared view Combined view

35. Reptile Reproduction Most have internal fertilization
Penis delivers sperm into cloaca of female