SWBAT create a fossil timeline for species to track the visible changes. Bellringer: In your notebooks, write down everything you know about fossils. Notes are in yellow

How are fossils made? Something dies It is covered in sand or mud That sand or mud is covered by more sand or mud and compresses it and turns to stone The parts of the body filled with air or water are replaced with minerals and become hard

The Fossil Record Fossils are the remains of organisms preserved in Earth Fossils can be any record that remains of an organism. Examples: bones, teeth, imprints of footprints or skin, shells. The fossil record helps scientists to determine when species lived and died during Earth’s history Two ways to determine a fossil’s age: Relative Dating and Absolute Dating

Relative Dating: Fossil Layers The Law of Superposition: Sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top. In other words, if one fossil is on top of another, the top one will be the newest. Index fossil: shorthand way to identify a geologic age.

Absolute Dating Radioactive dating is the Sometimes called numerical dating Gives rocks an actual date, or date range, in number of years. This is different than relative dating, which only puts geological events in time order. How does this work? Radioactive dating is the use of half-lives to determine the age of a sample.

RADIOACTIVE DATING Scientists use radioactive decay to assign an age to rocks. A half-life is the length of time required for half of the radioactive atoms in a sample to decay. Sometimes that’s billions of years.

Relative Dating Older Younger Which organism in this picture is older, the clams or the trilobites? How do you know?

SWBAT create a fossil timeline for species to track the visible changes. Activity: Timeline done in 20 minutes Check with teacher before gluing! Analysis: Due on Monday