Works cited:

http://www.slideshare.net/dindin04/respirat
ory-system-in-mammals

http://animals.pawnation.com/differen
ces-respiratory-systems-frogs-human
s-2684.html

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

http://sharks101.wordpress.com/circulator
y-and-respiratory-system/

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