THE EVOLUTION OF FLIGHT

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Across
  1. 2. Important parts or characteristics of something.
  2. 5. To change and develop over a long period of time.
  3. 6. The ability to move through the air.
  4. 8. A change that helps a living thing survive or do something better.
  5. 10. Pulled to become longer or wider.
  6. 12. To fly high in the air without much effort.
Down
  1. 1. The ability or power to do something.
  2. 3. The soft covering on a bird's body and wings.
  3. 4. To move smoothly through the air without flapping wings.
  4. 6. To move wings up and down to fly.
  5. 7. Happening after something else; the last to appear.
  6. 9. How heavy a person, animal, or object is.
  7. 11. Happening first in time.