Chapter 15
Evolution
Evidence & Theory
15-1 The Fossil Record
Nature of Fossils
• Fossil– Trace of long dead organism
• Where Found– Sedimentary rock
• How Created– Dust, sand, mud deposited by wind/water
over dead organisms• Develop From
– Shell, bone, teeth, stem
Types of Fossils
• Mold– Imprint on rock such as limestone– Shape of organism
• Cast– Mold filled with hard minerals
• Amber– Fossilized tree sap
Robert Hooke
• In 1668– Concluded fossils are remains of once living
plants and animals– What else did he do? Remember way back
when…
– Hmmm?
Distribution of Fossils• Age
– Relative• Steno 1670 Law of Superposition• Determined by fossils position in strata/rock• Oldest fossils = deepest youngest = surface
– Absolute• Radioactive dating• Radioactive isotopes
– Carbon-14; Carbon-12– Ratio of decay of carbon-14 to
stable carbon-12
Succession of Forms
• Extinct– Species no longer exists
• Mass Extinction– Period in which large number of species
disappear• Biogeography
– Study of geographical distribution of fossils & living organisms
– Ex of biogeography
Geological History of Earth
• Table 15-1
• Era Period Epoch
• Interactive geologic time