All the answers here are about evolution and variation. The number (in brackets) tells you how many letters the word has.

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Across
  1. 3. When a species that is more adapted for the environment will be more likely to survive and breed. All by chance (7,9)
  2. 5. A group of living things that share common traits and can interbreed (7)
  3. 8. Where a living thing lives. Includes their climate and what else lives there (11)
  4. 9. Another word for trait (14)
  5. 12. The insect that varies between black or white - black in the cities, white in the forests (8,4)
  6. 13. First name Charles, the person who came up with the theory of evolution (6)
  7. 14. On The ______ Of Species, a book all about evolution (6)
  8. 15. When humans breed a living thing to benefit them. Think dogs! (13)
Down
  1. 1. When all of a species dies out (10)
  2. 2. The bird that Charles noticed was different on each of the Galapagos Islands (5)
  3. 4. The process of species all gradually changing over time (9)
  4. 6. When two groups of the same species vary too much and become two different species (10)
  5. 7. Survival of the _______, where the living things most suited to an environment survive (7)
  6. 10. _______ engineering, when humans modify the genes of a living thing to immediately change its traits (7)
  7. 11. When different living things will start to change because of a different environment (9)