Notes for March 15, 2006

Obj. sw:
1. Record “Early Earth’s Conditions.
2. Define fossils and give several examples
3. Describe two methods of dating fossils
4. Create a geologic time scale

Chapter 14 notes
Evolution

Evolution: change over time


Volcanoes(Image on p. 359): emerging molten rock from inner earth, pushing up through weaker points in mantle and crust.

Early Earth: Lots of volcanic activity
Volcanic activity spews
--Carbon dioxide
--Nitrous oxide
--Sulfur oxide
--Sulfuric acid
--Water vapor
--Ammonia gas
--Ash
--Lava
Elements of life: carbon, hydrogen, phosphorus, oxygen, sulfur, nitrogen

Fossil: evidence of life
--Evidence from long ago
--Bones
--See chart on p. 370
--Trace fossils
--Footprints, paths left by feet, tails
--Cast: replica of an organism
--Mold: hollow image formed around organism
--Petrified fossils
--Permineralization: minerals replace the organic material
--Rock forms where soft tissue once was
--Amber: tree sap that hardens
--Resin
--Smaller organisms trapped in amber
--Ice: traps larger organisms—mammoths, humans
--Tar: some fossils trapped in natural tar pits, forms around organism
What now?
Figuring out fossils
--Where did this come from?
--What is the organism?
--When was it alive?
How do you find out how old it is?
--Relative dating
--Layering
--Newer things nearer to the top of the soil
--Older things deeper in the ground
--Flashback Review: ROCK TYPES
--Igneous – molten rock
--Metamorphic – heat and pressure changes rock
--Sedimentary – compacted sediment
--Most fossils found in sedimentary rock. Too much heat and pressure in igneous and metamorphic rock Destroys organism rather than preserving it
--Radiometric Dating
--Using radioactive isotopes found in fossil and or rocks around it to measure the date
--Radioactive isotopes have nucleus that is coming apart
--Carbon 14 – unstable, nucleus comes apart of a steady rate
--Ie, “half of it will change in 10,000 years” This is the HALF-LIFE.
--Fairly accurate method for dating


Time periods
Pre-Cambrian
--oldest dated rock is4.6 billion years old
--first evidence of life
--prokaryotic cell


Homework for Thursday
Geologic Time Scale Activity
p. 274
Include
--Era
--Two or three facts
--Time frame (bya) (mya)
--picture