BIO 101 Lecture Notes - Lecture 5: Notochord, Shock Absorber, Agnatha
6 Aug 2016
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Document Summary
Chordates are considered because they have four anatomical structures. Notochord : stiff, flexible rod, runs (come back to) Dorsal (hollow) develops into central nervous system. Fossil records date back 500 million years ago. Vertebrae units of a serially arranged skeletal units that enclose the nerve cord (protects nerve cord) Hard bone or cartilage (ex: a mouse & shark only have cartilage) Gas exchange organs (ex: lungs, external gills) to release co2 and absorb o2. Live on the outside of host, can also be deposit feeders on. Hypothesis: jaws evolved from the gill arches. Up to 10 meters in length (30 ft) They developed jaws to hold prey and teeth to grip and tare. The anterior had an armor of bony plates. The importance of jaws evolving : open up a wide variety of foods. The cranium/skull (made of cartilage & more often bone) made of different bones. The spinal cord enters the skull in a very big opening.
