Presentation on theme: "Evolution- Change in life forms over time Why do things change? How do they change?"— Presentation transcript:
Evolution- Change in life forms over time Why do things change? How do they change?
Estimated age of earth-4.6 Billion years 4 geologic eras 1.Precambrian 2.Paleozoic 3.Mesozoic 4.Cenozoic episodes of mass extinction separates eras
At the beginning Hot, lots of volcanic activity, no free oxygen, but lots of water vapor. 3.9 Billion years ago, oceans formed 3.5 BYA first fossil evidence of life- photosynthetic bacteria
The history of earth is written in the rocks. Fossil: evidence of existence preserved in rock Structure indicates function Oldest fossils found are 3.5 billion years old and are microscopic photosynthetic bacteria
Analyzing the fossil record Life was incredible diverse –Size, structure, function Episodes of mass extinction Episodes of evolutionary explosions
Fossil Formation Organism dies Covered with mud, sand- no decay Compression over time = sedimentary rock and fossil Where might fossils be forming today?
Formation of fossils Casts- minerals fill in Mold- leaves an empty space Amber-preserved or frozen Trace or carbon imprint
Determining the age of a fossil: 2 ways 1.Relative dating 2.Absolute dating
1.Relative dating Fossils in deepest layer are oldest
2. Absolute dating More accurate than relative dating Uses radioactive decay of isotopes Isotopes are radioactive natural variations of elements
Examples of IsotopesT1/2 in years C-14 decays to N years Uranium 235 to Lead million Potassium 40 to Argon billion Half life is the time it takes for half (50%) of the isotope to change into new form.
Parent compound is C14 Daughter compound is N14 T1/2 is 5730 years Start with 12.5g of C14 and g of N14. How old is your fossil?
Carbon 14 is used for fossils < 50,000 years old Potassium-40 for older specimens