science crossword puzzle

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Across
  1. 3. occurs when a few individuals start, or found, a new population.
  2. 4. occurs when a population suddenly gets much smaller.
  3. 5. occurs when there are differences in fitness among members of a population.
  4. 6. occurs when individuals move into or out of a population.
Down
  1. 1. creates new genetic variation in a gene pool.
  2. 2. is a random change in allele frequencies that occurs in a small population.