E&S-U3-C2-Ch. 9-Vocabulary Crossword

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Across
  1. 2. the current geologic era, which began 65.5 million years ago; also called the Age of Mammals
  2. 4. an ordered arrangement of rock layers that's based on the relative ages of the rocks & in which the oldest rocks are at the bottom
  3. 7. an episode during which large numbers of species become extinct
  4. 9. a subdivision of geologic time that's longer than an age but shorter than a period
  5. 10. a unit of geologic time that's longer than an epoch but shorter than an era
Down
  1. 1. the geologic era that followed Precambrian time & that lasted from 542 million to 251 million years ago
  2. 3. the interval of time in the geologic time scale from Earth's formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million years ago
  3. 5. a unit of geologic time that includes 2 or more periods
  4. 6. the geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles
  5. 8. a heritable change in the characteristics within a population from 1 generation to the next; the development of new types of organisms from preexisting types of organisms over time