Grouping Species Using DNA

Question 1

Which explanation correctly uses shared derived characteristics to demonstrate that modern birds (Aves) are a subgroup of theropod dinosaurs?

Accepted Answer

Birds share several unique derived features with theropod dinosaurs—such as a furcula (wishbone), a three‑digit hand with an inverted wrist, and feathers—indicating they belong within the dinosaur clade.

Answer

Because birds and dinosaurs both lived in the distant past, the similarity in their overall appearance means they are placed in the same group.

Answer

Birds have wings while dinosaurs never had wings, so birds must be a completely separate lineage from dinosaurs.

Answer

Since feathers appear in some dinosaurs and in birds, the trait must have evolved independently in each group, placing birds outside the dinosaur lineage.

Question 2

Which of the following statements most accurately uses shared derived traits to explain why a sparrow is placed inside the dinosaur clade?

Accepted Answer

Sparrows and theropod dinosaurs both have hollow bones, a furcula (wishbone), and three‑fingered hands, which are derived characters that unite them as members of the same clade.

Answer

Sparrows and dinosaurs both lay eggs, so they belong to the same group because egg‑laying is a unique feature of dinosaurs.

Answer

Sparrows can fly while most dinosaurs could not, showing that the ability to fly links them together evolutionarily.

Answer

Sparrows and some dinosaurs both have beaks, which means the beak evolved once and places sparrows inside the dinosaur group.

Question 3

Which brief explanation correctly uses shared derived traits to justify placing the modern ostrich within the theropod dinosaur branch?

Accepted Answer

Because ostriches and theropod dinosaurs share feathers, a furcula (wishbone), hollow limb bones, and a three‑digit hand—synapomorphies that indicate common ancestry.

Answer

Because both ostriches and dinosaurs lay eggs, a trait that links them together.

Answer

Because ostriches have long legs like some dinosaurs, a similarity that arose independently for speed.

Answer

Because ostriches are warm‑blooded, a characteristic found in many animal groups.

Try three questions

Which explanation correctly uses shared derived characteristics to demonstrate that modern birds (Aves) are a subgroup of theropod dinosaurs?

Which of the following statements most accurately uses shared derived traits to explain why a sparrow is placed inside the dinosaur clade?

Which brief explanation correctly uses shared derived traits to justify placing the modern ostrich within the theropod dinosaur branch?

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