Mammals

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Across
  1. 5. type of mammal carries their babies in a pouch
  2. 7. Destruction/The greatest cause of endangerment for mammals
  3. 9. is fertilized here
  4. 10. amount of bones that are in a mammal's middle ear
Down
  1. 1. Cord/Developing embryo is supported by this structure
  2. 2. of fertilization
  3. 3. amount of chambers a mammal's heart has
  4. 4. Dioxide/The purpose of the lungs is to remove this substance
  5. 6. time period that mammals started to appear in
  6. 8. most important structure of a mammal's respiratory system