The Vertebrates 1 Vertebrates Part 3 – Amphibians & Reptiles Tetrapods (four limbs) Hypotheses of tetrapod evolution  Lobe-finned fishes had an evolutionary advantage due to movement capability  further adaptations promoted by: ­Supply of food on land, and ­Absence of predators

2 Lobe-finned Fish vs. Amphibian

The Vertebrates 3 Diversity of Amphibians Amphibians today occur in three groups all in CLASS - Amphibia:  Salamanders and newts  Frogs and toads  Caecilians Most return to water for reproduction Most can absorb oxygen through their skin

The Vertebrates 4 Diversity of Amphibians  Salamanders and newts (not really a classification term) ­Terrestrial or aquatic ­Salamanders practice internal fertilization ­ ­Lack claws ­ ­Scale-free skin, either smooth or covered with tubercles ­ ­Tail flattened from side to side and often finned.

The Vertebrates 5 Diversity of Amphibians  Salamanders and newts

The Vertebrates 6 Diversity of Amphibians  Frogs and toads ­Tailless (always?) ­Most fertilization is external

The Vertebrates 7 Diversity of Amphibians  Caecilians ­Legless, sightless, worm-shaped ­Internal fertilization

8 Amphibians

The Vertebrates 9 Amphibian Features Usually tetrapods Lungs usually present in adults Metamorphosis Smooth and moist skin Three-chambered heart Ectothermic

10 Metamorphosis

11 Vertebrate Circulatory Pathways

The Vertebrates 12Reptiles Class Reptilia  Thought to have evolved from amphibian ancestors by the Permian period  Practice internal fertilization  Lay eggs protected by a leathery shell (amniotic egg)

13 Phylogenetic Tree of Reptiles

The Vertebrates 14 Anatomy and Physiology of Reptiles Reptiles have a thick, scaly skin that is keratinized and impermeable to water  Usually tetrapods  Lungs with expandable rib cage  Shelled amniotic egg  Dry, scaly skin  Ectothermic

15 Reptilian Diversity

16 Reptilian Anatomy