Although Having Evolved Independently, the Tracheal Tubes of Mammals and Insects

Multiple Choice

Although having evolved independently, the tracheal tubes of mammals and insects are both supported by rigid tissues. The trachea of a mammal is supported by cartilage, and the tracheae of an insect are supported by chitin. What selective pressure most likely led to the convergent evolution of these respiratory structures?

A) Both mammals and insects have similar oxygen needs.
B) When air is the respiratory medium, there is a greater risk that the tracheal tubes will collapse.
C) Insects and mammals both keep their internal temperature constant.
D) A decrease in environmental carbon dioxide made structural support necessary.