Biology Chapter 17

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

2. 17-1 The Fossil Record I. Fossils and Ancient Life A. _______________ are scientists who study fossils. Paleontologists

3. B. The fossil record _________ evidence about the history of life on Earth. It also shows how different ________ ___________, including species, have changed over time. provides groups of organisms

5. 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

6. Feathers of the earliest birds, Archaeopteryx, are preserved in the Jurassic Solnhofen Limestone of Germany.

7. 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

8. 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.

9. 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:

10. 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

11. Relative Dating

12. 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. Genus: Archimedes Index fossil of the Mississipian Period

13. 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

14. 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

16. 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

17. Carbon-14

18. Radioactive Decay

19. 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.

20. 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 nonradioactive isotope in a specimen Imprecision and limitations of age data Difficulty of radioassay laboratory methods Compare/Contrast Table Section 17-1 Comparing Relative and Absolute Dating of Fossils Relative Dating Absolute Dating Can determine Is performed by Drawbacks Go to Section:

21. 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

22. 3 Precambrian and the present Paleozoic Era 1. Eras: There are __ eras between the ____________________________. a. ______________ b. ______________ (Age of Dinosaurs) c. ______________ (Age of Mammals) • Periods: Eras are subdivided into ________. Mesozoic Era Cenozoic Era periods

25. Continental Drift

26. Plate Boundaries

27. San Andreas Fault

28. 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

29. * 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.

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

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

32. 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

33. 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 filtering out Ozone layer forms in harmful UV rays shield

34. 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

35. Hallucigenia

37. 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

38. 410 mya..... the “______________” age of the fishes Cartilaginous Fishes: Sharks, Skates and Rays

40. Genus Bothriolepis It was a small benthic freshwater detrivore which lived in the Middle and Late Devonian (387-360 million years ago). Its box-like body was enclosed in armor plates, providing protection from predators.

42. Megalodon

43. It is the largest carnivorousfish known to have existed, and quite possibly the largest shark to have ever lived. It is believed that the average size of the megalodon was between 12 meters (39 ft) and 18 meters (59 ft).

44. Bony Fishes

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

46. Tiktaalik

47. Amphibian: Frog

48. 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

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

50. 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