BIOL359 Chapter Notes - Chapter 18: Burgess Shale, Cambrian Explosion, Molecular Clock
26 Apr 2013
School
Department
Course
Professor
Document Summary
First animal appeared in the fossil record 565 million years ago. Cambrian period: first appearance of most of the animals today large & complex , represent <1% of earth"s. Chapter 18 the cambrian explosion and beyond history: there"s total of 5 episodes of cataclysmic extinction, phanerozoic: interval between the start of cambrian & the present. How organic remains fossilize: fossil: any trace left by an organism that lived in the past, 4 category distinguished by the method of formation. Compression fossils: when organic material is buried in water/wind-borne sediment before it decomposes. Casts & molds: when remains decay after being buried in sediments, preserve information about external & internal surfaces. Casts: when new material infiltrates the space, fills it, and hardens into rock. Permineralized fossils: when structures are buried in sediments & dissolved minerals precipitate in the cells, preserves details about internal structures.
