Vertebrate animals

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Across
  1. 2. The egg develops inside the mother's body
  2. 4. Cannot regulate their body temperature
  3. 9. Animals that feed on other animals
  4. 12. Group to which snakes belong
  5. 13. Group to which frogs and toads belong
  6. 15. Fish with skeletons made of cartilage, like sharks
  7. 16. Structure used by mammals, birds, and reptiles to breathe
  8. 17. They have smooth, moist skin with glands
  9. 19. Animals whose embryos develop in the mother's uterus
  10. 21. Maintain a constant internal temperature
  11. 23. Mammals that lay eggs
  12. 25. Process amphibians undergo to transform from tadpole to adult
  13. 26. They have a beak, two legs, and two wings
  14. 27. The embryo develops inside a pouch in the mother's body
Down
  1. 1. Animals that lay eggs
  2. 3. They are called this because they have a backbone
  3. 5. Group of reptiles that includes iguanas
  4. 6. Group of reptiles to which turtles belong
  5. 7. Animals with fins, scales, and gills
  6. 8. Type of fish that have a skeleton made of bones
  7. 10. Mammals with a placenta
  8. 11. Group to which newts belong
  9. 14. Animals that have lips and bodies covered with hair
  10. 18. Variety of living beings on Earth
  11. 20. Streamlined body shape of fish
  12. 22. Glands that secrete milk in mammals
  13. 24. Bony cover that protects the gills in bony fish