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

Phylum ChordataChordate 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 animalNotochord a rigid supporting rod running below the dorsal hollow nerve cordPharyngeal pouch paired structures in the throat regionTail that extends beyond the anus

Most chordates are vertebrates animals with a backbone

Vertebrates have an endoskeleton that grows as the organism grows

Maintaining homeostasisEctotherm body temp controlled by the environment

Fish, amphibians, reptilesLow metabolism

Endotherm generate heat and maintain body temperature

Birds, MammalsHigh metabolism

Form and FunctionFeeding

Nonvertebrate chordates – tunicates and lancelets

Filter feedersVertebrates

Skull and teeth are adapted to a wide range of foodHave well developed digestive systems adapted for different eating habits

RespirationGills tunicates, fish, amphibian larvaLungs adult amphibians, reptiles, birds, mammals

Alveoli bubble-like structures in the lings

Thin membranes so that oxygen and carbon dioxide can diffuse across

CirculationSingle loop blood travels from heart, to gills, to body and back to heartDouble loop oxygen poor blood to lungs, oxygen rich blood to heart and then to bodyHearts have chambers

Fish and larval amphibians – 2 chambersAdult amphibians and most reptiles – 3 chambersCrocodiles, birds, mammals – 4 chambers

ExcretionNonvertebrate chordates and fish use gills to diffuse ammonia waste out of bodyOther vertebrates use kidneys

Kidneys also help maintain homeostasis by maintaining balance of water and salt in body

ResponseNonvertebrate chordates have simple nervous systems with a mass of nerve cells forming brainsVertebrates have more complex brains with regions that have specialized functions

MovementSkeletal and muscular systems support body and make a wide range of motion possible

ReproductionAlmost all chordates reproduce sexually

ExternalNonvertebrate chordates, fish, amphibians

InternalReptiles, birds, mammals

After fertilizationOviparous 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

SharksViviparous develop in mothers body and get nutrients directly from mother

Mammals

Nonvertebrate ChordatesSubphylum Urochordata tunicates (sea squirts)

Marine, filter feeder, adults are sessileSubphylum Cephalochordata lancelets

Marine, filter feeder, live in sand with head region above sandClosed circulatory system but no true heart

Subphylum Cephalochordata lanceletsMarine, filter feeder, live in sand with head region above sand