The Following Questions Refer to the Evolutionary Tree in the Figure

question 31

Multiple Choice

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

-Which of the five species, labeled V-Z, is the common ancestor of the fewest number of species?

• A) V
• B) W
• C) Y
• D) Z

---

Definitions:

Unconditioned Response

An automatic, natural reaction to a stimulus that occurs without previous conditioning or learning.

Conditioned Response

An acquired reaction to a stimulus that initially had no specific response but has been paired with an unconditioned stimulus through the process of conditioning.

Classical Conditioning

The process of learning that happens when an ambient stimulus is paired with a stimulus that occurs naturally, causing a learned behavior.

Operant Conditioning

A means of learning in which the magnitude of an action is shaped by reinforcements or consequences.