Existing, Endangered, Extinct

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Across
  1. 3. harmful substances added to the environment
  2. 4. bees and butterflies belong in this animal group
  3. 6. the basis of food chains and webs
  4. 8. animals that have no natural predators
  5. 11. a major cause of endangerment of species
  6. 13. any animal that feed its young with milk
Down
  1. 1. cold-blooded animal group
  2. 2. process plants change sunlight into energy
  3. 5. greenhouse effect gas
  4. 7. any animal with no backbone
  5. 9. endangered animal native of China
  6. 10. extinct mammal
  7. 12. human activity that destroys habitats