Chapter 30-1: The Chordates

Key characteristics:

-Dorsal, hollow nerve cord - nervous system
-Notochord (usually present only in embryo) - support
-Pharyngeal pouches -paired structures in throat; may develop into gills
-Tail - extends beyond anus

About 96% of all chordate species belong in one subphylum:

Subphylum Vertebrata- Vertebrates

---Animals with a backbone or vertebral column (endoskeleton)
----Have spinal cord - dorsal, hollow nerve cord
----Front end of spinal cord develops a brain

Nonvertebrate Chordates -- 2 subphyla of chordates without backbones:

Subphylum Urochordata

-Tunicates
-Filter-feeders in ocean, adults are sessile
-Only larval tunicates have chordate characteristics, having a notochord during early development

Subphylum Cephalochorodata

-Lancelets
-Small fishlike animals, that often live partly buried in the sand
-Adult lancelets have chordate characteristics
-Have definite head region

anatomy

Timeline of Vertebrate Evolution

Check out: The History of Life at Berkeley.edu

About When Age Animals
550 million years ago Ordovician Period

First vertebrates
jawless fishes

400 million years ago

Devonian Period

"Age of Fishes"

Acanthodians
jawed fishes
350 million years ago

Carboniferous Period (and Permian)

"Age of Amphibians"

Amphibians
240 million years ago

Triassic Period
Jurassic Period

"Age of Dinosaurs"

reptiles appeared

dinosaurs dominated the land for 150 million years - sauropods, theropods, etc..

60 million years ago

Tertiary Period

"Age of Mammals"

Dinosaurs extinct

Mammals appeard

340,000 years ago Quaternary period Humans appeard