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How does a fossil form? Living things die and are buried by sediment. The sediment hardens into rock preserving the shape of the organism.

How do mold and a cast fossils form? A mold fossil forms when the hard part of the organism is buried in sediment. (Ex: a bone or a shell) Cast fossils: Groundwater contains dissolved minerals and sediment. The water seeps into an empty mold and deposits the minerals and sediment into a cast fossil. It forms a solid copy of the shape.

Types of fossils Mold Fossil Cast Fossil

Petrified fossils and trace fossils Petrified means it turned into stone. Ground water deposits the minerals which in turn replaces all or part of the organism. Trace fossils: provide evidence of the animals activities. Ex: a footprint.

How are carbon films formed?

Preserved remains BBC - Science & Nature - Making fossils Animals that were trapped in tar. The tar preserved bones from decaying Animals that were frozen. These animals had hair and skin preserved.

Preserved remains

How do paleontologists determine changes over time? Paleontologists collect fossils to determine the characteristics of past life forms. Information that paleontologists gather about past lives is called the fossil record. The fossil record provides evidence about organisms changing over time, history of life, and the past environments. Ex: coal found in Antarctica.

Is there an order of fossils? Fossils occur in a particular order. Older rocks have simple organisms. Younger rocks have more complex organisms. Evolution gradually changes things over time. Ex: Gal. lizards. Extinction: no longer exists. Ex: Chinese freshwater dolphin

Can you make a fossil? BBC - Science & Nature - Burying bodies

Venn Diagram Activity In your notes complete the following: Create Venn Diagrams comparing the following types of fossils. Mold Fossils vs. Cast Fossils Petrified Fossils vs. Trace Fossils Carbon Films vs. Preserved Remains You may use your notes to complete the Venn Diagrams.

Extinction Evolution

Geological Evolution

Relative Age of Rocks The relative age of rocks would be the age compared to the age of other rocks. Law of superposition: In a horizontal sedimentary rock layer, the oldest layer is at the bottom. Thus the higher layers are younger.

How do paleontologists determine relative age? Oldest layer on the bottom and newest layer at the surface. This is true if the following situations don’t occur.

1. Extrusion: magma beneath the surface flows onto the surface 1. Extrusion: magma beneath the surface flows onto the surface. Exits the ground

2. Intrusion: Magma pushes bodies of rock 2. Intrusion: Magma pushes bodies of rock. Magma cool, hardens, into the mass of igneous rock. Which is always younger.

3. Faults: break in the Earth’s crust 3. Faults: break in the Earth’s crust. Forces inside the Earth causes movement of rock. Fault is always younger than the rock it cuts through.

What are gaps in the geologic record? Unconformity: gaps in the geological records. Some rock layers are lost due to erosion. Index fossils: help geologist match layers of rocks and tell the relative age. They represent an organism that existed briefly and was widely distributed. Ex: Ammonite fossils.

What are the types of unconformities? Angular Unconformities: Rock layers are tilted. Tilted rock layers are eroded. New sediment deposited on top. Disconformities: Gaps missing in parallel rock layers. Nonconformities: Sedimentary rock deposited on top of an eroded layer.

Name that Unconformity What type of unconformities do you see in this picture? Angular and Noncomformity

What type of unconformity is shown in this picture? Angular and Nonconformity

What type of unconformity is being shown here? Disconformity and Nonconformity

What type of unconformity is being shown here? Nonconformity and Disconformity

Absolute Age of Rocks Absolute Age: Is the age, in years, of a rock or other objects. How do scientist find absolute age? Radiometric Dating: The process of calculating the ratio of parent isotope to daughter isotope in a mineral.

What is Radiometric Dating? Radiometric dating determines the absolute age of rocks. Half life: The time is takes for half of the atoms in the isotope to decay. *Paper demo on half-life. Potassium-40: used to date rocks because it has a long half life. (Used to date rocks) Carbon 14: used to date organisms up to 75,000 years old. (Used to date bones, wood, and charcoal)

Calculate Absolute Age The half-life of potassium-40 is 1.3 billion years. An igneous rock is found 25% potassium-40 and 75% daughter product. Calculate the absolute age of this rock. 1 half-life = 50% parent material left- 50% daughter 2 half-life = 25% parent material left- 75% daughter 3 half-life = 12.5% parent material left- 87.5% daughter 4 half-life = 6.25 % parent material left- 93.75 % daughter

Can all Rocks be Radiometrically Dated? No, sedimentary rocks can’t be dated this way because they are made of too many parent rocks. Radiometrically Dated Rock: Igneous Rocks Metamorphic Rocks

Geologic Time scale The geologic time scale was developed by scientist studying rock layers and index fossils world wide. Precambrian time was 88% of the Earth’s history, 544 million years ago.

How is the Geological Time Scale Divided? The Geological Time Scale is divided by time periods: longest to shortest. Eon- Longest time period. Era- Next longest, marked by major changes in fossils present. Period- Next longest, characterized by the type of life that existed. Epochs- A division of a period.

What are the major events in Paleozoic Era? A variety of organism evolved The first vertebrate evolved => Jawless fish Land plants, insects and spiders, appeared Lungfish first vertebrate to crawl onto land. Reptiles, winged insects, forests. Mass Extinction: Affected both plants and animals. Scientist hypothesize => Pangaea. Pangaea: the Earth’s continents moved together to form one large land mass.

Paleozoic Era Jawless fish Pangaea

What are the major events in the Mesozoic Era? Known as the Age of Reptiles 225 million years ago first dinosaur Mammals first appeared: Morganucodon Birds first appeared: Achaeopteryx Mass Extinction: Scientist hypothesize that objects from space struck the Earth.

What were the major events in the Cenozoic Era? Mammals evolved to live in the water, land, and in the air. Earth’s climate cooled due to a series of ice ages. Modern humans evolved 100,000 years ago. 12,000 to 15,000 humans migrated around the world except Antarctica.