1. Biology Chapter 17 Evolution: The History of Life More than ______ of all species that have ever lived on Earth have become extinct. 99.9%

2. 17-1 The Fossil Record I. Fossils and Ancient Life A. _______________ are scientists who study fossils. B. The fossil record _________ evidence about the history of life on Earth. It also shows how different __________ _____________, including species, have changed over time. Paleontologists provides groups of organisms

3. II. How Fossils Form A. For a fossil to form, either the _________ ___________ or some trace of its presence must be preserved. 1. A precise _________________ must be present to form a fossil. 2. The fossil record provides ____________ ____________ about the history of life. remains of the organism set of conditions incomplete information

4. B. Most fossils are formed in ___________ _______. 1. Sedimentary rock forms from the _________________________________ 2. These particles are carried by _________ ___________ into lakes or seas, where they eventually settle to the bottom. sedimentary rock. erosion of rock into sand, silt, and clay. streams and rivers

5. 3.As layers of sediment build up over time, ________________________________ _______ and become buried. 4. If conditions are right, the ________ may be kept intact and free from decay. 5.The sediment gradually _____________ _______ dead organisms may also sink to the bottom remains compresses into rock.

6. Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied. Section 17-1 Figure 17-2 Formation of a Fossil Go to Section:

7. III. Interpreting Fossil Evidence A. Paleontologists determine the ________ _______ using two techniques: 1. Relative Dating a. The age of the fossil is determined by ______________________ with that of fossils in other layers of rock. b. Rock layers __________________ are generally ________ than those below it. age of fossils comparing its placement nearer to the surface younger

8. Relative Dating

9. c. Does not determine the ___________ of the rocks or the fossils. d. Index fossils are used to ____________ ___________________. These fossils must be easily recognized and must have existed for a short period of time. actual age compare the relative age of fossils

10. 2. Radioactive Dating a. Based on the ___________________ ___________________. b. Radioactive elements decay, ________ ______, at a steady rate which is measured in a unit called half-life. c. Half-life: the length of time required for __________________________ in a sample to decay. radioactive decay of elements in the rocks or break down half of the radioactive atoms

11. d. Different radioactive elements have different half-lives and therefore provide ______________ that “tick” at ______________. Example: Carbon-14:half-life of about ______ ________ Potassium-40 : half-life of about ______ ___________ natural clocks different rates 5,730 years 1.26 billion years

12. e. Carbon-14 is _________ by living things while ______________. After an organism dies, the __________ in its body begins to decay to form _________ ___, which escapes into the air. f.Carbon-14 has a relatively ____________, it is useful only for dating fossils younger than about ____________. taken up they are alive Carbon-14 nitrogen- 14 short half-life 60,000 years

13. Carbon-14

14. Radioactive Decay

15. B. Most fossils are __________. Paleontologists must reconstruct an extinct species from a few fossil bits--- remains of bone, a shell, leaves, or pollen. not intact

16. Relative Dating Can determine Is performed by Drawbacks Absolute Dating Comparing Relative and Absolute Dating of Fossils Section 17-1 Compare/Contrast Table Go to Section: Imprecision and limitations of age data Difficulty of radioassay laboratory methods Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen Age of fossil with respect to another rock or fossil (that is, older or younger) Age of a fossil in years

17. IV. Geologic Time Scale A. Scientists first developed the _________ _____________ by studying rock layers and index fossils worldwide. As geologists studied the fossil record, they found _______ ________ in the fossil animals and plants _________________________. These times were used to mark the segments. geologic time scale major changes at specific layers in the rock

18. 1. Eras: There are __ eras between the ___________________________. a. ______________ b. ______________ (Age of Dinosaurs) c. ______________ (Age of Mammals) 2. Periods: Eras are subdivided into ______. 3 Precambrian and the present Paleozoic Era Mesozoic Era Cenozoic Era periods

21. Continental Drift

22. Plate Boundaries

23. San Andreas Fault

24. 17-2 Earth’s Early History and 17-3 Evolution of Multicellular Life 4.6 bya....*___________________ *many sources of energy: volcanic activity, lightening, meteorites *______________ in atmosphere: water vapor (H20), nitrogen (N2), and carbon dioxide (CO2), with only small amounts of hydrogen (H2) and carbon monoxide. The primitive atmosphere had little, if any, free _______. no life forms present poisonous gases oxygen

25. * intense UV (ultraviolet radiation) from sun * In the presence of so much available energy, the primitive gases may have reacted with one another and produced small organic compounds, such as nucleotides and amino acids.

26. 3.5 bya…*geological disturbances have calmed *____________________________ _____________ (much like the bacteria of today and well adapted) bacteria evolve and inhabit most environments

27. 2.2 bya....*____________________ and form mats in shallow seas. ________ ___________ to produce oxygen (0 2 ) via ______________ cyanobacteria evolve First organisms photosynthesis

28. 1 bya....*algae and other water-borne photosynthetic organisms abound in the seas * __________________ in the seas with many ______________________ like sponges, jellyfish and worms. Green AlgaeRed AlgaeBrown Algae animal life abounds multicellular organisms

29. A SPECIAL NOTE ON THE EVOLUTION OF OUR ATMOSPHERE: 1.__________________ begins in the seas 2.____________________________ (electrical storms split atmospheric water molecules releasing a single oxygen) 3._______________________________ - (here single oxygen and regular oxygen unite to form O 3 or ozone) 4.___________________ stratosphere - ________ _____ most of the ________________. Life on land can now thrive under this protective ______ which begins 12-15 miles above the earth’s surface. Oxygen saturation Oxygen moves into atmosphere Oxygen reaches upper atmosphere Ozone layer forms in filtering out harmful UV rays shield

30. Paleozoic Era 550 mya.... “____________________” - the Cambrian Period records _____________ _______ of life in evolution’s history. Nearly all of the animal groups known today as well as a strange collection of animals that cannot be assigned to any living group of today appeared in a period of about 10 million years. This evidence is not based upon fossils. the Cambrian Explosion an unmatched burst

31. 550 mya.... “the Cambrian Explosion” Scientists are ________________________ ________________ of evolution found in the genes drawn from the living species of 16 animal groups. This has allowed scientists to estimate when all animals last shared a common ancestor with other forms of life. Although controversial, this evidence without the fossil “backup” is widely accepted by many scientists in the field today. If this finding holds up, the animal kingdom had __________________ ___________to develop than the fossils reveal. basing this new finding upon molecular evidence hundreds of millions of years longer

32. 410 mya.....the “______________” Cartilaginous Fishes: Sharks, Skates and Rays age of the fishes

33. Bony Fishes

34. 360 mya...... ________________________ climb onto the land. first land-based amphibians

35. Amphibian: Frog

36. 300 mya......______________________-- the earth is now a large vegetated landmass with open plains, swamps and primitive trees. ____________ flourished in a tropical climate. Invertebrates flourished in the ocean. From these forests and swamps, of the so called “_____________” period, came the organic materials that ultimately formed our___________________. primitive reptiles appear Large insects Carboniferous fossil fuels of today

37. Coal Forest “Carboniferous Period” (300 mya)

38. 240 mya..._______________________ __________________________________ over a 100,000 year period. This was possibly due to a meteor impact. This occurred at the end of the_____________. a period of mass extinctions where perhaps 95% of all life perished Paleozoic Era

39. Mesozoic Era: Began 245 mya Lasted 180 million years

40. Reptiles: Lay eggs on land Bull Snake

41. 205 mya.....beginning of the domination of ___________ for 120 mya 138 mya.....____________________ occur on land and the beginnings of tropical rain forests in some areas. The flowering plants spread and ultimately dominated the landscape through a period of 65 million years. dinosaurs first flowering plants

42. 65 mya..... Meteorite activity is one explanation for this extinction. This occurred at the end of the_______________. an era of mass extinction that ended the dinosaurs as well as 75% of all plant and animal life. Mesozoic Era

44. Cenozoic Era: Mammals spread out and began to dominate the landscape.

45. Mammal: Chimpanzee

46. 100,000-200,00 years ago....... __________________ Homo sapiens date to about this time. Homo sapiens means “_________ __________” and modern humans are classified in this species. the earliest fossils of intelligent human

47. that are can undergo inunder formin Species Unrelated Related Inter- relationshiops Similar environments Intense environmental pressure Small populations Different environments Coevolution Convergent evolution Extinction Punctuated equilibrium Adaptive radiation Go to Section: 17-4 overview