Evidence of Change

 What are fossils?  What is the fossil record?  How do they form?  Types of fossils  What do they tell us?  Determining their age

Shall Sally Sell Sea Shells on the Sea Shell Shore?  Few people know the entire tongue-twister.  The author of the rhyme wants Sally to be stopped. Sally sells seashells by the seashore. She sells seashells on the seashell shore. The seashells she sells are seashore shells, Of that I'm sure. She sells seashells by the seashore. She hopes she will sell all her seashells soon. If neither he sells seashells Nor she sells seashells, Who shall sell seashells? Shall seashells be sold?

“Sally” was really Mary Anning   15 months old she was hit by lightening that killed 3 other girls  Mary’s father taught her to find “curiosities” nearby ocean cliffs  Mary’s father died when she was 11.  She grew up poor, and had little education.

Mary became a great paleontologist.  Her first major discovery was an Ichthyosaur  She also found a Plesiosaurus and the first Pterodactyl.

Mary Was Just One of Many.  “Curiosities” were being found by scientists all around the world.  Traditionalists believed the Earth was young (4000 – 6000 years) and the “curiosities” were the remains of recent creatures alive today.  Scientists argued the curiosities were the remains of once living creatures, and proof that the Earth was old (millions of years), and that life had changed (evolved).

Fossil = remains of past life  To be a fossil the creature must be extinct, and from the time of the last ice age or older (12,000-15,000 years old)  Fossils commonly form when the remains of a creature are quickly buried and preserved; then later exposed by erosion.  Fossils can also be preserved in amber or ice, or by tar. Fossil Formation

The Data is in the Strata  Modern day science accepts the idea that the layers of the Earth show the past.  Different layers have different kinds of fossils.  That means life on Earth has changed (evolved).  The pattern of fossils changing can be found around the world.  The same fossils in different places mean the rocks are the same age.

 Any preserved evidence of an organism  Evidence can be the preserved remains of plants or animals that lived a long time ago  Or any other preserved indications of their existence  Imprints  Molds & casts

 Most fossils form when organisms that die become buried in sediments  Some remains that become buried in sediments actually change to rock  Minerals dissolved in the water soak into the buried remains. Gradually, the minerals replace the remains, changing them into rock. Fossils that form this way are called petrified or replacement fossils  Sometimes shells or other hard parts buried by sediments gradually dissolve and form an empty space  The hollow space in the sediment that is in the shape of the organism is called a mold  When the space becomes filled in with hardened minerals, a cast, or copy of the shape of the organism is formed

 Sometimes organisms are preserved in substances other than sediments  Organisms such as the mammoth have been perfectly preserved in ice  Insects like the mosquito have been preserved in the sap of trees called amber

 Trace  Molds and Casts  Replacement  Petrified or Permineralized  Amber  Freezing or Mummification

Trace fossils are indications that an organism existed, not the actual organism. They include footprints, nests, tooth marks, worm burrows, root traces, etc.

 Molds  A mold forms when something is pressed into soft mud and removed by decomposition or pulled out, leaving an impression of the object.  Casts  A cast is a 3-D representation of an object from the past. It is created when a mold fills up with sediment that hardens.

The organism is preserved but its original skeletal material or pores are filled with or replaced with mineral crystals

Assignment: Read pages 197 – 200 in your text, complete study guide handout and concept map on fossils (Due Friday: 10/31/2014)

ated elated The Fossilization Process

 Fossils can act like pieces in a jigsaw puzzle, helping scientists piece together information about Earth’s past.  They provide a history book of past life forms (with many missing pages)  Lets us know of extinct life forms that once lived on earth (99% of all life forms on earth are now extinct)  Shows us that there have been transitional species and evolution of species  The millions of fossils that scientists have collected are called the fossil record

 Relative Dating  Determine the relative age of rocks and fossils by comparing them with other layers  The Law of Superposition  Relative dating is based on the law of superposition  A sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not disturbed  It is not a coincidence that older fossils of more primitive life forms are found at deeper and deeper layers

Index Fossils  Species go extinct and others appear and sometimes they overlap for a brief time.  Index fossils = fossils or combinations that indicate a specific time.

Match the layers, 0 is oldest, 7 is youngest.  Same fossils means the same layer.  Some layers or evidence may be missing. 0

Use the fossils to put the layers in order from youngest to oldest. AA  B H II  JE KK  CL  FD GG