2Biblical ReferenceFrom one man he made all the nations, that they should inhabit the whole earth; and he marked out their appointed times in history and the boundaries of their lands.Acts 17:26
3Fossils Remains or traces of past life forms Most common in sedimentary rocks and in some accumulations of ashExtremely useful for determining relative ages of strata, but geologists also use them to determine environments of depositionProvide some evidence for organic evolutionThe word, fossil, comes from the Latin word, fossilis, which means “to obtain by digging”
4The Fossil Record Record of ancient life preserved as fossils in rocks Repository of prehistoric organisms that provides our only knowledge of such extinct animals as trilobites and dinosaursDemonstrates how species have evolved over time
5The Fossil RecordThe fossil record is made up of all the fossils ever discovered on Earth.The fossil record provides evidence that species have changed over time.Based on fossil evidence, scientists can recreate the physical appearance of species that are no longer alive on Earth.
6Fossil FormationAfter an animal dies, any soft tissues animals do not eat break down.Only the dead animal’s hard parts, such as bones, shells, and teeth, remain.Under rare conditions, these parts become fossils.Fossils form via two methods:MineralizationCarbonization
8Original Preservation Remains are considered Unaltered if:They retain their original composition and structure by freezing or mummification (usually in amber or tar)
9Altered Hard PartsSoft parts of remains decay while hard parts (shells, bones, etc.) become fossils.May become altered by:Mineral ReplacementUsually from Groundwater or Volcanic AshRecrystalizationDue to Changes in Pressure and Temperature over Time
11Molds and Casts Molds form Casts form Shell is buried. when buried remains dissolve and leave a cavityCasts formif minerals or sediments fill in the cavityShell is buried.Shell dissolves, leaving a cavity (Mold).Cavity fills with sediment, creating a Cast.
14Trace FossilsIndications of organic activity including tracks, trails, burrows, and nestsA coprolite is a type of trace fossil consisting of fossilized feces that may provide information about the size and diet of the animal that produced it
15Determining a Fossil’s Age Instead of dating fossils directly, scientists date the rocks the fossils are embedded inside.In relative-age dating, scientists determine the relative order in which rock layers were deposited.Relative-age dating helps scientists determine the relative order in which species have appeared on Earth over time.
16Absolute Age DatingScientists take advantage of radioactive decay, a natural clocklike process in rocks, to learn a rock’s absolute age, or its age in years.To measure the age of sedimentary rock layers, scientists calculate the ages of igneous layers above and below them.
17Absolute Age DatingIf the age of the igneous layers is known, it is possible to estimate the age of the sedimentary layers - and the fossils they contain - between them.
18Relative vs. Absolute Age Relative Time: This rock is older than that one.Absolute Time: This rock is 542 Million Years Old.
19The Geologic Time Scale The geologic time scale is a chart that divides Earth’s history into four different eons - the longest time units in the geologic time scale.Hadean EonArchaen EonProterozoic EonPhanerozoic Eon4.6 Billion years of Earth’s History has been reconstructed.
21Dividing Time 19th Century: Geologist began to organize a geologic columnOrdered succession of known strataBecause they did not have absolute age dating techniques yet, scientists create time boundaries based upon fossils or other evidence of relative ageOften a type of fossil disappeared from the rock record after a few layers.These were called index fossils.
22Index FossilsFossils that are easily recognized and widely distributed geographicallyRepresent species that lived for relatively short periods of timeGeologists can date a particular rock layer based on their presence.Trilobites are very common Index Fossils.
24ExtinctionsExtinction occurs when the last individual organism of a species dies.A mass extinction occurs when many species become extinct within a few million years or less.Extinctions can occur when environments change.
25Mass ExtinctionsThe fossil record contains evidence that five mass extinction events have occurred during the Phanerozoic eon.
26EvolutionThe fossil record contains evidence of the appearance of many new species over time.Biological evolution is the change over time in populations of related organisms.
27Evolution in HorsesThe fossil record is evidence that horses descended from organisms for which only fossils exist today.
28Pop QuizWhich refers to a chart that divides Earth’s history into different time units?A. fossil recordB. geologic time scaleC. relative-age datingD. trace fossil
29Pop QuizWhich is the preserved evidence of the activity of an organism?A. castB. fossil recordC. moldD. trace fossil
30Pop Quiz Which refers to the impression of an organism in a rock? A. castB. fossilC. moldD. trace fossil