Chapter 7 & 8

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Across
  1. 2. is a characteristic that can be passed from parent to off-spring through genes.
  2. 4. the remains or imprints of once living organism found in layers of rock
  3. 7. the species of hominids that include modern humans and their closest ancestors and that first appeared out 100,000 to 160,000 years ago.
  4. 8. began about 251 million years ago and lasted about 185.5 million years ago.
  5. 10. the time of the formation of earth 4.6 billion to 542 million years ago.
  6. 12. a calendar that scientists use to outline the history of life on earth
  7. 15. estimating the age of rocks and fossils.
  8. 16. a group of organisms that can mate with one another to produce fertile off-spring
  9. 19. the theory that explains how large pieces of the crust moves and change shape.
  10. 20. a historical sequence of life indicated by fossils found in layers of the Earth's crust.
  11. 21. the process by which organisms that are better adapted to their environment survive and reproduce more successfully than less adapt organisms do.
  12. 22. A characteristic that helps an organism survive and reproduce in its environment.
Down
  1. 1. began about 542 million years ago and ended about 251 million years ago.
  2. 3. began about 65 million years ago and continues today.
  3. 5. the formation of new species as a result of evolution.
  4. 6. a method that measures the age of fossils or rocks in years
  5. 9. the process in which humans select which plant or animal to reproduce based upon certain desired traits
  6. 11. includes only humans and their human like ancestors.
  7. 13. a species that has died out completely
  8. 14. the average time between one generation and the next.
  9. 17. the process in which populations gradually change over time
  10. 18. a group of mammals that include humans, apes, monkeys, and lemurs.