 Fossils are preserved remains or traces of living things  Most fossils form when living things die and are buried by sediments. The sediments slowly hardens into rock and preserves the shapes of the organisms.

 Fossils found in rock includes molds and casts, petrified fossils, carbon films and trace fossils.  Other fossils form when the remains of organisms are preserved in substances such as tar, amber or ice

 Most common fossils  Mold is forms when the organism is buried in a sediment, then water may deposit minerals and sediment into a mold, forming a cast.  A cast is a solid copy of the shape of an organism

 Petrified means “turned into stone.”  They are fossils in which minerals replace all of an organism, or a part. For example a dinosaur bone

 An extremely thin coating of carbon on rock  When sediments bury an organism, some gases escape from the sediment and leave carbon behind, which eventually a thin layer of carbon remains

 Provide evidence of the activities of ancient organisms  A print is buried by sediment, which slowly becomes a solid rock

 Scientists that study fossils are called paleontologists.  The fossil record provides evidence about the history of life and past environments on Earth.  Shows how different groups of organisms have changed over time

 The fossils found in an area tell whether the are was a shallow bay, an ocean bottom or a freshwater swamp  Also shows the past climate of the region

 Fossil records reveal changes in organism  Fossils show how life on Earth has evolved.  Evolution is the change in living things over time

 Is a record of the geologic events and the evolution of life forms.

 Precambrian Time:  Beginning of geologic time  Covers 88% of Earth’s history and ended 542 years ago.  Eras:  3 eras divide the time between the Precambrian time and present day. They are the Paleozoic Ear, Mesozoic Era, and the Cenozoic Era  Periods:  Eras are divided in subgroups called periods.

 The Cambrian Period is when many organisms evolved that had hard parts, such as shells and outer skeletons.  At this time, all animals lived in the sea and many were invertebrates

 After the Cambrian Period, we go through the Ordovician Period, which the first vertebrates evolved  Then during the Silurian Period, plants became more abundant but only in damp areas low in the ground  Then during the Devonian Period, plants were able to grow in drier areas

 The Devonian period is also called the Age of Fishes because every main group of fish were present in the oceans at this time  The Devonian period is also when animals began to spread widely on land  Amphibians and reptiles began to develop during this period.  At the end of the Permian Period, most species of life on Earth died out  90% of all ocean species died out  70% of all species on land died out  How do you think this all happened?

 Remember that during this Era, there were three periods.  Triassic Period  The first dinosaurs appeared during this period  Mammals first appeared during this period.  A mammal is a vertebrate that can control body temp. and feed milk to its young

 Jurassic Period  Dinosaurs became more common on land  Cretaceous Period  Reptiles, including dinosaurs, became more widespread  Birds started replacing flying reptiles  Flowering plants first evolved

 Toward the end of the Cretaceous period, (65 million years ago), another mass extinction occurred.  Scientist believe that an asteroid from space hit Earth.  Once it hit, huge amounts of dust and water vapor were thrown in the atmosphere  The dust and heavy clouds blocked the sunlight for many years, which made plants die and animals that ate plants died because they had no food.

 Mammals evolved to live in many different environments- on land, water and even in the air  During this era, climates started changing