| Cephalochordata (Lancelets) |
Non-vertebrates |
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Small, fish-like, notochord persists throughout life |
Branchiostoma (Amphioxus or Lancelet) |
Simple body structure, no true vertebrae, marine habitat |
| Urochordata (Tunicates) |
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Marine, free-swimming larvae, sessile adults, tunic-like outer covering |
Ascidia (Sea Squirt),Salpa,Doliolum
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Marine habitat, filter-feeding, undergo metamorphosis from larvae to adult form |
| Vertebrata |
Agnatha (Jawless) |
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Cyclostomata |
6-15 pair gill slits, cartilaginous skeleton, round mouth with sucker-like structure |
Petromyzon (Lamprey), Myxine (Hagfish) |
No jaws, parasitic or scavengers, mostly marine, lack scales |
Gnathostomata (Jawed) |
| Pisces (Fishes) |
Chondrichthyes (Cartilaginous fishes) |
Cartilage skeleton, paired fins, no swim bladder |
Selachimorpha (Sharks), Raja (Skates) |
Teeth replaceable, spiral valve in the intestine, live birth in some species |
| Osteichthyes (Bony fishes) |
Bony skeleton, paired fins, swim bladder for buoyancy |
Salmo (Salmon), Carassius (Goldfish) |
Operculum covering gills, lateral line system, external fertilization in most |
| Gnathostomata (Tetrapoda) |
Amphibia (Amphibians) |
Cold-blooded, moist skin, eggs without shells, amphibious lifestyle |
Rana (Frog), Ambystoma (Salamander) |
Undergo metamorphosis (e.g., tadpole to adult frog), can respire through skin and lungs |
| Reptilia (Reptiles) |
Cold-blooded, dry scaly skin, lay eggs with leathery shells |
Crotalus (Rattlesnake), Agama (Lizard) |
Body covered with scales, internal fertilization, some are viviparous |
| Aves (Birds) |
Warm-blooded, feathers, beak, hard-shelled eggs, endothermic |
Aquila (Eagle), Psittacula (Parrot) |
Wings for flight, hollow bones, high metabolic rate |
| Mammalia (Mammals) |
Warm-blooded, hair/fur, live young (mostly), mammary glands |
Homo (Human), Elephas (Elephant) |
Live birth (except monotremes), endothermic, specialized teeth and lungs |