Chordata- vertebrates Animal phylogeny based on sequencing of SSU-rRNA Phylum Chordata Distinguishing Features 1. Pharyngeal gill slits 2. Dorsal hollow nerve cord 3. Notochord 4. Muscular postanal tail 3 Chordate Subphyla: Urochordata - tunicates (invert.) Cephalochordata - lancelets (invert.) Vertebrata - fishes, amphibians, reptiles, birds and mammals Chordate Characteristics 1
Subphylum Vertebrata: in search of a diagnostic feature 3 chordate characteristics Segmentation Cephalization Vertebrae Cranium Endoskeleton *NEURAL CREST MATERIAL* Seven Extant Classes of Vertebrates Agnatha - jawless fishes Chondrichthyes - cartilagenous fishes Osteichthyes - bony fishes Amphibia - amphibians Reptilia - reptiles Aves - birds Mammalia - mammals Fish Classification of Fish Cl. Agnatha and Cl. Placoderma Agnathans - Ancestral vertebrates: 470-500 mya extinct by 370 mya Modern representatives: cartilage skeleton, smooth skin, retain notochord Lampreys and Hagfish Cl. Placoderma: (410-350 mya) Two important innovations: jaws and fins Hagfish Notochord; slime!; cartilaginous skeleton; poor eyes; slime (I know, but its worth mentioning twice ) 2
Figure 34.12a Ray-finned fishes (class Actinopterygii): yellow perch Class Chondrichthyes: sharks, skates and rays Bouyancy control Cartilagenous skeleton Adaptations of sharks, skates and rays Ventilation Feeding Sensory Osmoregulation Reproduction Class Chondrichthyes Cartilaginous Fish Jaws; scales; spiral valve in intestine; pared gills Subclass Elasmobrachii- Sharks, skates, rays Subclass Holocephali- Chimaeras Class Ostiechthyes: bony fishes General features Evolution in freshwater: lungs Divergence of bony ancestor into 2 groups Ray finned fishes lobe finned fishes and lungfish Counter-current gas exchange 7 Basic Requirements of Animal Life 1. Gas exchange 2. Nutrition 3. Distribution and transport 4. Disposal of cellular wastes 5. Internal water and salt balance 6. Reproduction and development 7. Support and movement 3
Vertebrate Invasion Onto Land Demands of terrestrial life: How to move on land? How to exchange gases? How to prevent desiccation? How to reproduce and develop? A coelocanth (Latimeria), the only extant lobe-finned genus Amphibians: the first tetrapods 3 Orders Urodela - salamanders and newts Anura - frogs and toads Apoda - caecilians (legless amphibs) General Features Locomotion Feeding Gas exchange Osmoregulation Circulation Reproduction and development Metamorphosis Hearing and voice 4
Figure 34.18 Dual life of a frog (Rana temporaria) Modern Reptiles: Adaptations Desiccation resistant covering Respiratory changes Reproductive advances: amniotic egg extraembryonic membranes Amniotic Egg Tiny intermolecular forces - van der Waals forces - are produced by literally billions of tiny hair-like structures, or spatulae, on each gecko toe. unbalanced electrical charges around molecules attract one another 5
Geckro Birds and Mammals Temperature and metabolic rate Poikilotherms: reptiles Homeotherms: mammals and birds Ectothermy Endothermy Why cold-blooded and warm-blooded doesn t cut it Ancient Birds: Archaeopteryx Reptile-like characteristics Reptilian jaw Claws Tail Solid bones Bird-like characteristics Feathers - modified scales Posture Large avian eye Archaeopteryx sp. Archaeopteryx, a Jurassic bird-reptile 6
Avian Characteristics 1. Endothermic Homeotherms 2. Feathers 3. Hollow bones 4. Skeletal fusion 5. Loss of tail 6. Beak 7. Gizzard 8. Digestive and urinary changes 9. Respiratory changes 10. Circulatory changes 11. Reproductive changes 12. Parental care Form fits function: the avian wind and feather A bald eagle in flight Mammalian Characteristics 1. Endothermic Homeotherms 2. Hair or fur covering 3. Mammary glands 4. Single boned jaw 5. Heterodont dentition 6. Rearrangement of pectoral and pelvic girdles 7. Circulatory changes 8. Respiratory changes 9. Reproductive Adaptations 7
Australian monotremes and marsupials: echidna (top left), marsupial mouse (lower left), sugar glider (right) Mammalian Reproductive Strategies: Monotremes: Echidna and Duck-billed platypus Marsupials: premature delivery Placental Mammals: internal development Reuse of extraembryonic membranes Placenta Evolutionary convergence of marsupial and eutherian (placental) mammals Move from trees onto ground Concomitant morphological changes 8
Hominid Evolution Lucy ~ 3.5 mya 7 Basic Requirements of Animal Life 1. Gas exchange 2. Nutrition 3. Distribution and transport 4. Disposal of cellular wastes 5. Internal water and salt balance 6. Reproduction and development 7. Support and movement 9