Chordate Evolution (Chapter 30.1, and 33 )

1. Chordate Evolution (Chapter 30.1, and 33) Please set up your notebook for Cornell Notes

2. Phylum Chordata • Chordate  an animal that has 4 characteristics for at least part of it’s life cycle • Dorsal hollow nerve cord – hollow tube running on the dorsal side of the animal • Notochord  a rigid supporting rod running below the dorsal hollow nerve cord • Pharyngeal pouch  paired structures in the throat region • Tail that extends beyond the anus • Most chordates are vertebrates  animals with a backbone • Vertebrates have an endoskeleton that grows as the organism grows

4. Maintaining homeostasis • Ectotherm body temp controlled by the environment • Fish, amphibians, reptiles • Low metabolism • Endotherm  generate heat and maintain body temperature • Birds, Mammals • High metabolism

5. Form and Function • Feeding • Nonvertebrate chordates – tunicates and lancelets • Filter feeders • Vertebrates • Skull and teeth are adapted to a wide range of food • Have well developed digestive systems adapted for different eating habits

6. Respiration • Gills  tunicates, fish, amphibian larva • Lungs  adult amphibians, reptiles, birds, mammals • Alveoli  bubble-like structures in the lungs • Thin membranes so that oxygen and carbon dioxide can diffuse across

7. Circulation • Single loop  blood travels from heart, to gills, to body and back to heart • Double loop  oxygen poor blood to lungs, oxygen rich blood to heart and then to body • Hearts have chambers • Fish and larval amphibians – 2 chambers • Adult amphibians and most reptiles – 3 chambers • Crocodiles, birds, mammals – 4 chambers

8. Excretion • Nonvertebrate chordates and fish use gills to diffuse ammonia waste out of body • Other vertebrates use kidneys • Kidneys also help maintain homeostasis by maintaining balance of water and salt in body • Response • Nonvertebrate chordates have simple nervous systems with a mass of nerve cells forming brains • Vertebrates have more complex brains with regions that have specialized functions • Movement • Skeletal and muscular systems support body and make a wide range of motion possible

9. Reproduction • Almost all chordates reproduce sexually • External • Nonvertebrate chordates, fish, amphibians • Internal • Reptiles, birds, mammals • After fertilization • Oviparous  eggs develop outside of female body • Most fishes and amphibians, reptiles and all birds • Ovoviviparous  eggs develop inside of mothers body and are nourished from yolk inside the egg • Sharks • Viviparous  develop in mothers body and get nutrients directly from mother • Mammals

10. Nonvertebrate Chordates • Subphylum Urochordata tunicates (sea squirts) • Marine, filter feeder, adults are sessile • Use two siphons to draw in and expel water • Can live independently or in colonies • Triploblastic with a coelom • Have a heart and a circulatory system • Use cellulose as structural support

11. Subphylum Cephalochordata lancelets • Marine, filter feeder, live in sand with head region above sand • Fish like body with no head • Closed circulatory system but with no true heart • No respiratory system, diffuse gases through skin