LIFESCI 1 Lecture Notes - Lecture 8: Pyrite, Cosmic Ray, Lead
Document Summary
Instructor: tonya kane: provide evidence for phylogenetic hypotheses. Organisms that branch early in phylogenies appear early in geologic record. Also enables us to calibrate phylogenies in terms of time. Provides our only record of extinct species. Places evolutionary events in the context of earth"s dynamic environmental history. Mass extinctions (about 6x in the past) = large environmental disturbances that sharply decreased earth"s biological diversity: fossils = remains of once living organisms, preserved through time in sedimentary rocks. Requires burial; w/o burial, remains of organisms are eventually recycled by biological and physical processes, and no fossil forms. Marine fossil record is more complete than land; marine habitats = more likely to be buried where sediments accumulate and become rock. Incompleteness of fossil record: due to biological factors as well, depending on body type, can be over/under- represented in the fossil record.
