natural selection

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Across
  1. 4. death
  2. 8. lizards
  3. 9. If an environment changes
  4. 12. genetically determined
Down
  1. 1. Continuous or discontinuous variation
  2. 2. a kind or sort
  3. 3. down syndrome
  4. 5. invisible
  5. 6. group of linked ideas to explain something
  6. 7. theory of evolution by natural selection
  7. 10. giraffe
  8. 11. the theory behind giraffes neck