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Evolution- Change in life forms over time

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Presentation on theme: "Evolution- Change in life forms over time"— Presentation transcript:

1 Evolution- Change in life forms over time
Why do things change? How do they change?

2 Estimated age of earth-4.6 Billion years
4 geologic eras Precambrian Paleozoic Mesozoic Cenozoic episodes of mass extinction separates eras

3 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

4 The history of earth is written in the rocks.
Fossil: evidence of existence preserved in rock Structure indicates function 2 questions – how are fossils formed and how to we determine their age Oldest fossils found are 3.5 billion years old and are microscopic photosynthetic bacteria

5 Analyzing the fossil record
Life was incredible diverse Size, structure, function Episodes of mass extinction Episodes of evolutionary explosions

6 Covered with mud, sand- no decay
Fossil Formation Organism dies Covered with mud, sand- no decay Compression over time = sedimentary rock and fossil Where might fossils be forming today?

7 Formation of fossils Casts- minerals fill in Mold- leaves an empty space Amber-preserved or frozen Trace or carbon imprint

8 Determining the age of a fossil: 2 ways
Relative dating Absolute dating

9 Relative dating Fossils in deepest layer are oldest

10 2. Absolute dating More accurate than relative dating Uses radioactive decay of isotopes Isotopes are radioactive natural variations of elements

11 Examples of Isotopes T1/2 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.

12 “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?

13 Carbon 14 is used for fossils < 50,000 years old
Potassium-40 for older specimens

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