Comparison of the avian 'unidirectional' respiratory system (a) where gases are exchanged between the lungs and the blood in the parabronchi, and the bidirectional respiratory system of mammals (b) where gas exchange occurs in small dead-end sacs called alveoli (From: West et al. 2007).s a result, air coming into a mammal's lungs is mixed with 'old' air (air that has been in the lungs for a while) & this 'mixed air' has less oxygen. So, in bird lungs, more oxygen is available to diffuse into the blood (avian respiratory system).
The Power of Sympathy or The Triumph of Nature (1789) is a cautionary novel by William Hill Brown (1765-1793). It is based on an actual case of seduction and incest in col â¦ onial America. It is considered by many to be the first American novel.
When to Write a Sympathy Card? A sympathy card is written when someone dear to your friend, colleague, relative, business acquaintance passes and you wish to inform them of your concern and compassion. Here are a few samples sympathy cards that help convey your compassion. Format of a Sympathy Card Opening Salutations. Dear Julie, Dear Julie and John, Dear Julie, John and Family,