1. Warm-up 3/19/13 The Earth is an estimated 4.6 billion years old. 1. How did scientists come up with this estimate? 2. Describe an organism you would expect to be found on early Earth.

2. Geologic Time

3. Key Ideas How is the fossil record used to chronicle the history of life? How do paleontologists date fossils? What evidence was used to make the geologic time scale?

4. The Fossil Record The fossil record includes all fossil remains of living things on Earth. With fossils you can determine: When an organism lived on Earth Where an organism lived on Earth How organisms are related to each other Although our examination of the fossil record will never be complete, it presents strong evidence for evolution.

5. Fossil Formation Most fossils are found in sedimentary rock. Fossils form when organisms are rapidly buried in fine sediments that are deposited by water, wind, or volcanic eruptions. Great environments for fossil formation: Wet lowlands Slow-moving streams Lakes Shallow seas Areas near volcanoes that spew ash BUT... many species are found in areas where fossils do not form.

6. Analyzing Fossils Earth’s surface changes constantly. Rocks are eroding and laid down as sediment. This sediment forms layers of sedimentary rock called strata. BUT how do we know the age of the strata??

7. What are their ages?

8. ???????????????? We don’t know their absolute age!! Relative age- The age of an event or object (person) in relation to other events or objects (people) In other words, you put things in order oldest to youngest… …Or youngest to oldest

9. Law of Superposition According to the law of superposition, older strata are covered by younger strata. So, what can we learn about time from this picture???

10. Law of Superposition We know that.........according to the law of superposition, older strata are covered by younger strata. However, geologic events such as earthquakes can affect how strata are arranged. In order to analyze fossil evidence, paleontologists use both relative and absolute dating methods to date fossils.

11. What’s the oldest layer?

12. Relative vs. Absolute Dating Relative Age is determined by relative dating- A method used to estimate the ages of fossils found within strata... but can’t tell you the age of the fossil! Absolute Age is determined by radiometric dating- A method used to estimate the age in years of an object by measuring certain radioactive isotopes that the object contains.

13. Absolute Age An isotope is a form of an element whose atomic mass differs from that of other atoms of the same element. Radioactive isotopes are unstable isotopes that break down and give off energy in the form of charged particles, or radiation. When the radioactive isotope, called a “parent,” decays, it produces new daughter isotopes that are smaller and more stable. We can measure the number of each “parent” and “daughter” isotope to determine the age!..... but how??

14. But how.... Each radioactive isotope has a specific half-life. Half-life- The time required for half of the parent radioisotope to decay into the daughter isotope. By comparing the amounts of certain radioisotopes and their daughter isotopes, scientists can calculate how many half-lives have passed since a material formed.

15. Example Carbon-14 has a half-life of 5,730 years. If you found a fossil with a composition of 1/2 parent isotope and 1/2 daughter isotope, how old would it be? 5,730 years old!! If you found a fossil with a composition of 3/4 parent isotope and 1/4 daughter isotope, how old would it be? 5,730/2 = 2,865 years old!

16. Warm-up 3/20/13 1. Draw the diagram!! 2. Which layer is the oldest? Which layer is the youngest? Youngest layer = A… but what about E? Oldest layer = C

17. Today’s Activity Relative and absolute dating worksheet 20 minutes independent work-time 10 minutes group work 20 minutes of presentations!

18. Warm-up 3/21/13 Math review- Metric Scale Conversions!!! 1. 1 m = ____________ cm 2. 1 cm = __________ mm Complete the following scale: 1 m = 1,000,000,000 years 3. 1 cm = ____________ years 4. 1 mm = ____________ years

19. A timeline of your education If we made a timeline of your education, where would you fall?? What would we use as the scale? Grade level K123456789101112 K  Where would you fall on the timeline of the Earth’s history?? 4.6 billion years agoPresent day

20. Warm-up 3/22/13 1. How many years does 1 mm represent on your timeline? 1,000,000 YEARS!! 2. How long ago did the earliest known animals exist? 1.2 billion years ago

21. 21 Warm-up 3/25/13 1.What evidence was used to create the geologic time scale?  Fossil evidence 2. Is relative or absolute dating the most utilized technique for dating fossils?  BOTH! Without the combination of both we would not have been able to build the geologic time scale.

22. Geologic Time Scale 22

23. Fossils and Geologic Time The geologic time scale organizes geologic and evolutionary events. It is based on evidence in the fossil record and has been shaped by mass extinctions.

24. Geologic Time Scale Divisions of the Geologic Time Scale Precambrian Era Paleozoic Era Mesozoic Era Cenozoic Era

25. How do extinctions shape Geologic Time? When large numbers of species become extinct, the event is called a mass extinction. Mass extinctions have been used to mark the divisions of geologic time. Evidence indicates that worldwide geologic and weather changes are common factors that contribute to mass extinctions. Mass extinctions may have contributed to overall biodiversity on Earth. After a mass extinction, opportunities open for new life- forms to emerge.

26. The Precambrian Era  4.6 billion years ago – 542 million years ago  ~88% of the earth’s history

27. EVOLUTIONARY DEVELOPMENTS  Formation of the Earth’s crust from molten rock  First appearance of life=prokaryotes(bacteria)  Evolution of photosynthesis (cyanobacteria)  Origin of oxygenated atmosphere

28. EVOLUTIONARY DEVELOPMENTS  first eukaryotes  first multi-cellular organisms

29. EVOLUTIONARY DEVELOPMENTS  750 mya- a widespread glaciation event played a critical role in the extinction of many early unicellular eukaryotes  Geologists compared the Earth to a giant snowball during this time

30. DOMINATE ORGANISMS  Prokaryotes  Simple Eukaryotes  Multicellular organisms (Edicaran Biota) Fossils found in South Australia Cyanobacteria and stromatolites

31. Pictures of Precambrian Era Life and Fossils

32. The Paleozoic Era  542 million years ago - 251 million years ago

33. EVOLUTIONARY DEVELOPMENTS  Cambrian explosion (of life)!  Primitive fishes appear  Ordovician EXTINCTION

34. EVOLUTIONARY DEVELOPMENTS  Plants colonize land  Insects and amphibians appear  Devonian EXTINCTION

35. EVOLUTIONARY DEVELOPMENTS  Seed plants dominate land  Reptiles become dominate

36. DOMINATE ORGANISMS  Plants  Fungi  Arthropods  Vertebrates

37. Pictures of Paleozoic life and fossils

38. The Mesozoic Era  251 million years ago – 65.5 million years ago

39. EVOLUTIONARY DEVELOPMENTS  Dinosaurs appear  Mammals appear  Birds appear

40. EVOLUTIONARY DEVELOPMENTS  Conifer forests dominate land  Phytoplankton are abundant in fossil record  Flowering plants appear

41. EVOLUTIONARY DEVELOPMENTS  MASS EXTINCTION! - Hypothesized that the extinction occurred abruptly when a 10 km meteorite hit the Earth.

42. DOMINATE ORGANISMS  Reptiles  Dinosaurs  Conifer trees  Flowering Plants

43. Mesozoic Era pictures and fossils

44. Warm-up 3/26/13 1. What years did the Precambrian Era span? 4.6 billion years ago – 542 million years ago 2. What percentage of Earth’s history does the Precambrian Era account for? 88% 44

45. The Cenozoic Era  65.5 million years ago – Present day

46. EVOLUTIONARY DEVELOPMENTS  Mammals diversify (age of the mammals)  Forests dominate land  Grasslands appear

47. EVOLUTIONARY DEVELOPMENTS  Mammal diversity peaks  Human-like primates appear  Modern humans appear

48. DOMINATE ORGANISMS  Wooly Mammoth  Primates  Early Humans

49. Cenozoic Era pictures and fossils

51. 51

52. Pictures of Precambrian Era Life and Fossils

53. Pictures of Paleozoic life and fossils

54. Mesozoic Era pictures and fossils

55. Cenozoic Era pictures and fossils