Due to its system of nine air sacs connected to the lungs, the respiratory system of birds is arguably the most effective respiratory system of all air-breathers. upon inhalation, air first flows into posterior air sacs, then into the lungs, and then into anterior air sacs on the way to being exhaled. thus, there is one-way flow of air through the lungs, along thousands of tubules called parabronchi. if archaeopteryx had air sacs, then which of its features would have had the opposite effect on enabling archaeopteryx to fly long distances from that provided by air sacs?

Why was the sample heated in step 5? describe the chemical principles involved in the reasoning behind this step?

Cladistics is a way of classifying organisms by examining the characteristics of their ancestors and descendants and depicting the relationships in a cladogram. which of the following best describes a challenge in classifying organisms this way? a. there are millions of species on earth, and a cladogram is not a practical means for classifying all of them. b. it is impossible to tell which organisms are most closely related to each other using a cladogram. c. cladograms are detail-oriented and do not provide a useful understanding of evolutionary relationships. d. there is a limited number of ways to organize the information, so most cladograms end up looking very similar.

Which feature would you expect to find in a population in which sexual selection depends on male competition?