Traditionally, Zoologists Have Placed Birds in Their Own Class, Aves

question 40

Multiple Choice

Traditionally, zoologists have placed birds in their own class, Aves. More recently, molecular evidence has shown that birds are more closely related to reptiles than their anatomy reveals. Genetically, birds are more closely related to crocodiles than crocodiles are to turtles. Thus, bird anatomy has become highly modified as they have adapted to flight, without their genes having undergone nearly as much change.
-Traditional zoologists have long agreed that birds evolved from dinosaurs. What keeps such zoologists from agreeing that birds, like dinosaurs, should be considered reptiles?

• A) There is not yet enough evidence to be sure.
• B) Stubbornness, insofar as they are unwilling to change their thinking when new data warrants it.
• C) They deny the validity of genetic molecular data.
• D) They differ in what they consider to be important traits for assigning organisms to the class Reptilia.

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Definitions:

Posterior Tibial Artery

A major artery of the lower leg, supplying blood to the posterior compartment of the leg and plantar surface of the foot.

Thoracic Aorta

The portion of the aorta passing through the chest, from which arise the branches that supply oxygenated blood to the chest cage and organs within the thorax.

Abdominal Aorta

The main artery that runs down the abdomen and supplies blood to the organs and tissues of the abdomen.

Aortic Arch

The portion of the main artery that bends between the ascending and descending aorta, distributing blood to the head, neck, and arms.