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 erasPrecambrianPaleozoicMesozoicCenozoicepisodes of mass extinction separates eras
3 At 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
4 The 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
5 Analyzing the fossil record Life was incredible diverseSize, structure, functionEpisodes of mass extinctionEpisodes of evolutionary explosions
6 Covered with mud, sand- no decay Fossil FormationOrganism diesCovered with mud, sand- no decayCompression over time = sedimentary rock and fossilWhere might fossils be forming today?
7 Formation of fossilsCasts- minerals fill inMold- leaves an empty spaceAmber-preserved or frozenTrace or carbon imprint
8 Determining the age of a fossil: 2 ways Relative datingAbsolute dating
9 Relative datingFossils in deepest layer are oldest
10 2. Absolute datingMore accurate than relative datingUses radioactive decay of isotopesIsotopes are radioactive natural variations of elements
11 Examples 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?
13 Carbon 14 is used for fossils < 50,000 years old Potassium-40 for older specimens