Lesson Number 3: The Fossil Record
1. Group Discussion – What is a paleontologist? What do they study? What
do we use this information for?
2. Objectives - Describe the process of permineralization and Explain the role
of isotopes in dating fossils
3. Perminearlization Fossils - Key concepts: Permineralization requires rapid
burial in an area with water. Over time, bones in the organism are replaced
with minerals. See page 361 in the book for an example.
4. Other Types of Fossils Include: a. Amber preserved (just like in Jurassic
Park), b. Trace fossils (foot prints, fossilized poop!), c. Ice-preserved
bodies (including mammoths and humans), d. Imprints of items that leave a
“cast” or “print” that fills in with sediment.
5. Human Fossil: There is a fossil of a man called “Tollund Man” whose body
was preserved in a bog in Scandinavia. Bogs are very acidic, which
prevented bacteria and fungus from being able to decompose his body. His
facial expression shows his brow was furrowed and there are many small
details still present, including facial hair and wrinkles. It is an amazing
example of a fossilized human from about 2,500 years ago!
6. Relative Dating (No, I don’t mean dating your cousin…). Relative dating is
one way scientists determine the age of a fossil or other substance. Relative
dating estimates when an organism lived by comparing the location of
fossils in layers of rock. Older organisms are in lower layers, younger
organisms are in top layers.
1. Radiometric Dating: Radiometric dating is a process that uses the half life
of an isotope to calculate the age of a material. Some common isotopes that
are used include: Carbon – 14: 5,730 years, Uranium – 238: 4,468,000,000
years Potassium – 40: 1,300,000,000 years, Uranium – 234: 80,000 years.
a. How old is the Earth?
b. Which element should we use to date the Earth?
7. Time to review what we have learned: How old is the Earth? Was early
Earth hot or cold? Would you want to live then? Why or why not? How are
permineralization fossils formed? What is a half life?