Presentation on theme: "Evolution- Change in life forms over time"— Presentation transcript:
1Evolution- Change in life forms over time Why do things change?How do they change?
2Estimated age of earth-4.6 Billion years 4 geologic erasPrecambrianPaleozoicMesozoicCenozoicepisodes of mass extinction separates eras
3At the beginningHot, lots of volcanic activity, no free oxygen, but lots of water vapor.3.9 Billion years ago, oceans formed3.5 BYA first fossil evidence of life- photosynthetic bacteria
4The history of earth is written in the rocks. Fossil: evidence of existence preserved in rockStructure indicates function2 questions – how are fossils formed and how to we determine their ageOldest fossils found are 3.5 billion years old and are microscopic photosynthetic bacteria
5Analyzing the fossil record Life was incredible diverseSize, structure, functionEpisodes of mass extinctionEpisodes of evolutionary explosions
6Covered with mud, sand- no decay Fossil FormationOrganism diesCovered with mud, sand- no decayCompression over time = sedimentary rock and fossilWhere might fossils be forming today?
7Formation of fossilsCasts- minerals fill inMold- leaves an empty spaceAmber-preserved or frozenTrace or carbon imprint
8Determining the age of a fossil: 2 ways Relative datingAbsolute dating
9Relative datingFossils in deepest layer are oldest
102. Absolute datingMore accurate than relative datingUses radioactive decay of isotopesIsotopes are radioactive natural variations of elements
11Examples of Isotopes T1/2 in years C-14 decays to N yearsUranium 235 to Lead millionPotassium 40 to Argon billionHalf 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 N14T1/2 is 5730 yearsStart with 12.5g of C14 and g of N14. How old is your fossil?
13Carbon 14 is used for fossils < 50,000 years old Potassium-40 for older specimens