Works cited:

https://media.goboard.io/respiratory-system
-in-mammals

https://media.goboard.io/differences-re
spiratory-systems-frogs-humans-2684.
html

http://www.brown.edu/Departments/Engineerin
g/Courses/En123/MuscleExp/Frog%2520Respiratio
n.htm

https://media.goboard.io/circulatory-and-
respiratory-system

http://wiki.hicksvilleschools.org/gro
ups/hsbiology/wiki/80571/Respirator
y_System.html