Exploring Evolution: Fossils and Geologic Time Scale

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 remains of the organism 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. set of conditions incomplete information

4. sedimentary rock. 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. erosion of rock into sand, silt, and clay. streams and rivers

5. dead organisms may also sink to the bottom • 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. • The sediment gradually _____________ _______ remains compresses into rock.

6. Figure 17-2 Formation of a Fossil Section 17-1 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. Go to Section:

7. III. Interpreting Fossil Evidence age of fossils 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. comparing its placement nearer to the surface younger

8. Relative Dating

9. actual age compare the relative age of fossils 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.

10. radioactive decay of elements in the rocks 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. or break down half of the radioactive atoms

11. natural clocks 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 ______ ___________ different rates 5,730 years 1.26 billion years

12. taken up they are alive Carbon-14 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. • Carbon-14 has a relatively ____________, it is useful only for dating fossils younger than about ____________. nitrogen- 14 short half-life 60,000 years

13. Carbon-14

14. Radioactive Decay

15. not intact B. Most fossils are __________. Paleontologists must reconstruct an extinct species from a few fossil bits--- remains of bone, a shell, leaves, or pollen. http://www.colorado.edu/physics/2000/isotopes/radioactive_decay3.html

16. Compare/Contrast Table Section 17-1 Comparing Relative and Absolute Dating of Fossils Relative Dating Absolute Dating Can determine Is performed by Drawbacks Age of fossil with respect to another rock or fossil (that is, older or younger) Age of a fossil in years 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 non-radioactive isotope in a specimen Imprecision and limitations of age data Difficulty of radio-assay laboratory methods Go to Section:

17. IV. Geologic Time Scale 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. major changes at specific layers in the rock

18. 3 Precambrian and the present Paleozoic Era 1. Eras: There are __ eras between the ___________________________. a. ______________ b. ______________ (Age of Dinosaurs) c. ______________ (Age of Mammals) 2. Periods: Eras are subdivided into ______. 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. bacteria evolve and inhabit most environments 3.5 bya… *geological disturbances have calmed *____________________________ _____________ (much like the bacteria of today and well adapted)

27. cyanobacteria evolve First organisms 2.2 bya.... *____________________ and form mats in shallow seas. ________ ___________ to produce oxygen (02) via ______________ photosynthesis

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

29. A SPECIAL NOTE ON THE EVOLUTION OF OUR ATMOSPHERE: Oxygen saturation • __________________ begins in the seas • ____________________________ (electrical storms split atmospheric water molecules releasing a single oxygen) • _______________________________ - (here single oxygen and regular oxygen unite to form O3 or ozone) • ___________________ stratosphere - ________ _____ most of the ________________. Life on land can now thrive under this protective ______ which begins 12-15 miles above the earth’s surface. 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. basing this new finding upon molecular evidence 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. hundreds of millions of years longer

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

33. Bony Fishes

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

35. Amphibian: Frog

36. primitive reptiles appear • 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___________________. Large insects Carboniferous fossil fuels of today

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

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

39. Mesozoic Era: Began 245 myaLasted 180 million years

40. Reptiles: Lay eggs on land Bull Snake

41. dinosaurs first flowering plants • 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.

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

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

45. Mammal: Chimpanzee

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

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

48. Study guide 17-1 1. Paleontologists 2. It is information about past life that is based on fossils. 3. It provides evidence about the history of life on Earth and how different groups of organisms, including species, have changed over time. 4. Extinct 5. False 6. B, D 7. Sediments settle to the bottom of lakes and seas ad bury dead organisms. The weight of upper layers of sediment compresses lower layers into rock and turns the dead organisms into fossils. 8. a) Relative dating b) Radioactive dating 9. A, B, D 10. False 11. True 12. Half-life 13. Radioactive dating 14. They measure the amount of remaining radioactive isotopes it contains. The smaller the amount, the older the sample. 15. False 16. Cenozoic, Mesozoic, Precambrian time, Tertiary, Jurassic, Carboniferous, Silurian, Cambrian 17. C 18. A, B 19. Eras and periods 20. Mesozoic Era 21. Cenozoic Era

49. Study guide 17-2 1. a) Hydrogen Cyanide b) Carbon Dioxide c) Carbon Monoxide d) Nitrogen e) Hydrogen Sulfide f) Water 2. False 3. Spark simulating lightning storms 4. A, B 5. They are tiny bubbles, formed of large organic molecules, that have some characteristics of living cells. 6. False 7. Experiments show that small sequences of RNA could have formed and replicated on their own in the conditions present on early Earth. 8. DNA is a more stable information-storing molecule than RNA. 9. Microfossils 10. A 11. They produced oxygen, which first removed iron from the oceans and then accumulated in the atmosphere. 12. True 13. True 14. The first step was the evolution of internal cell membranes. 15. It proposes that eukaryotic cells arose from living communities formed by several organisms. 16. A,C,D 17. Sexual reproduction shuffles and reshuffles genes in each generation. This increase in genetic variation greatly increases the chances of evolutionary change due to natural selection. 18. False

50. Study Guide 17-3 • True • A,B,C • The animals were al soft-bodied • Cambrian • False • A,B,D • B • C • A • Devonian • Vast swampy forests of giant ferns and other plants that grew during that time formed thick deposits of sediment that changed into coal over million of years. • Mass extinction • False • Triassic, Jurassic, Cretaceous • Reptiles • Triassic • True • True • Reptiles • Their seeds are enclosed in a fruit, which protects the seed and aids in dispersing it to new locations. • More than half of all plant and animals groups were wiped out, including all of the dinosaurs. • True • Mammals • They were generally warm and mild. • First it cooled, causing a series of ice ages. The, it began to warm again. • False