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