Phylum Chordata 1 Chordates Characterized by a notochord

Phylum Chordata 1

Chordates • Characterized by – a notochord, – a hollow dorsal nerve cord, and – pharyngeal (throat) slits • Some chordates posses these characteristics as adults; others as only embryos; but all have them at some stage of life 2

Organization • 3 Sub-phyla – Subphylum Urochordata • Tunicates – small marine chordates – filter feeders • notochord and dorsal nerve cord present in the tadpole-shaped larvae only 3

Organization • Subphylum Chephalochordata – Lancelets – small fishlike creatures – Live in sandy bottoms of shallow tropical oceans – Adult lancelets have a definite head – Filter feeders 4

Organization • Subphylum Vertebrata – Fish, Amphibians, etc. – Notochord replaced by the vertebrae (backbone) – Two pairs of appendages – Closed circulatory system with a ventral heart – Vetebral column surrounds and protects the dorsal nerve cord 5

Subphylum Vertebrata • Advantages to having vertebrae: – Provides body with structure and support while allowing flexibility. – Provides attachment sites for muscles – Protects the nerve cord 6

Vertebrates • Seven classes – Fish • Agnatha • Chondrichthyes • Osteichthyes – Amphibia – Reptilia – Aves – Mammalia 7

Fish • Class Agnatha – Jawless fish • • Long eel-like body Circular mouth 2 -chambered heart No scales No paired fins No bones Have notochords as adults Ectothermic 8

Vertebrates • Class Chondrichthyes – Cartilagenous fish • • Ex. Sharks, skates, etc. Jaw 2 -chambered heart Tough, small scales Paired fins Cartilagenous endoskeleton Ectothermic 9

Evolutionary Advances • Jaws – Made it possible to • Eat larger organisms, and • Defend themselves by “biting” • Paired fins – pectoral (anterior) and pelvic (posterior) 10

Vertebrates • Class Osteichthyes – Bony fish • • • Ex. Tuna, salmon, etc. Jaw 2 -chambered heart Scales Paired fins Bony endoskeleton Gills Swim bladder Ectothermic 11

Evolutionary Advances • Important adaptations of bony fishes – Swim bladder • regulates buoyancy – Lateral line system • assesses rate of movement through water as pressure waves against the lateral line – Operculum (Gill cover) • flexing the operculum permits bony fish to pump water over their gills 12

Amphibians • Amphi = both; bio = life • Larvae are fish-like and aquatic. • Adults are terrestrial. – Require moist environment • Smallest group of living vertebrates. • Have moist slimy skin that contains many glands • No scales and claws. • Webbed feet. • Ectothermic 13

Evolutionary Advances • Movement onto land – Lungs • Made it possible to breathe on land – Limbs with stronger bones • Support body weight – 3 -chambered heart 14

Class Reptilia • • Dry skin covered with scales. Lungs 3 chambered heart Toes and claws • Ectothermic • Lay AMNIOTIC eggs 15

Evolutionary Advances • Movement onto land – Dry skin – Scales – Respiratory muscles – Amniotic egg • Allows for dry 16

Class Aves • Dry skin covered with feathers. – Scales on feet. • • Wings Lungs 4 chambered heart Bipedal – Toes and claws • Endothermic • Lay AMNIOTIC eggs 17

Evolutionary Advances • Wings and Feathers – Flight • Porous Bones – Reduces weight • Very efficient Respiratory system • Endothermic – Active in all climate 18

Feathers • Three types of feathers: – Contour • Large feathers that cover the body and wings • Flight feathers – Down • Grow underneath and between the contour feathers • Insulate the bird – Powder • Important for water birds for waterproofing. • Preening is when birds groom their 19

Class Mammalia • Diverse group of organisms • Size varies from tiny bumblebee bat to large blue whales • Endothermic – Excellent temperature regulation • Most are viviparous 20

Evolutionary Advances • Dry skin covered with fur. • Mammary glands • Subcutaneous fat for insulation. • Diaphragm • Sweat glands • Specialized teeth – – Incisors Canines Premolars Molars 21