 The Fossil Record – made up of all the fossils ever discovered on Earth  provides evidence that species have changed over time  Fossil – the remains or evidence of once-living organisms

 Mineralization  minerals in water replace the organism’s original material and harden into rock  Carbonization  extreme pressure drives off the organism’s liquids and gases leaving only the carbon outline

 Molds and Casts  Mold – impression of an organism in hardened mud or sand  Cast – a fossil copy of an organism in a rock created by sediment filling in the mold

 Trace Fossils  preserved evidence of the organism’s activity, like footprints  Original Material  original tissues of an organism, like insects in amber (tree sap)

 Relative-Age – scientists determine the relative order in which rock layers were deposited( Most Accurate when the rock layers are undisturbed.)  Absolute-Age (Radioactive Dating)– scientists use the ratio of unstable isotopes to stable isotopes to find the age of rocks; more precise  ex. carbon-14 dating

 a chart that divides Earth’s history into different time units

 Extinction – occurs when last individual organism of a species dies  Mass Extinction  when many species become extinct within a few million years or less  there have been 5 mass extinctions in the Phanerozoic eon  Causes of Extinction  Sudden change – like meteor impact or volcanic eruption  Gradual change – like tectonic plates or sea level changes

 the change over time in populations of related organisms