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

question 59

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.

---

Definitions:

Salt Uptake

The process by which plants, animals, and other organisms absorb salt (sodium chloride) and other ions from their environment.

Adventitia

The outermost layer of the wall of a blood vessel or other tubular structure, consisting of connective tissue.

Cortex

The outer layer of an organ or structure, such as the cerebral cortex of the brain or the cortex of a plant root or stem.

Medulla

The innermost part of an organ or structure, such as the medulla oblongata in the brain which controls vital body functions.