Ch. 17 Noteguide – The History of Life

17.1 The Fossil Record Are scientists who study fossils Life on Earth. It also shows how different groups of organisms have changed over time. Incomplete, because it takes precise combinations of conditions Extinct Precise combinations of conditions

How fossils form: Exposure to rain, heat, wind and cold breaks down existing rocks. Minerals replace all or part of the organisms body.

How scientists determine the age of a fossil: Relative dating Rock layers Index fossils

2. How Scientists determine the age of a fossil Radioactive dating Half-life Carbob-14 is taken in by living things and released slowly when they die. To determine when the organism lived. Carbon-14 Carbon-12

Geologic Time Scale Represent evolutionary time. Places Earth rock in order by relative age. Precambrian Time between Precambrian + 3 eras Paleozoic Mesozoic Cenozoic Eras that are subdivided

17.2 Earth’s Early History How did life on Earth Initially begin? Heat to melt the entire globe The most dense elements form the Earth’s core. The early Earth was much hotter with little oxygen.

How did life on Earth Initially begin 27. lots of dissolved iron 28. proteinoid microspheres 29.RNA 30. nucleotides 31. a series of experiments (miller and Urey) 32.microscopic fossils 33.oxygen gas 34. oxygen for respiration

35. proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms

36. refers to the large scale evolutionary changes that take place over long periods of time. 37. slow and steady 38. horseshoe crab 39. rapid evolution 40. hox genes