The following are example of morphological variation except

Analyze the question: We are asked which option is NOT an example of morphological variation. Morphological variation refers to differences in the physical, visible form or structure of organisms of the same species.

Concept: Variation in a population can be classified into two types:

• Morphological (continuous or discontinuous) variation: Differences in external or structural features, such as height, size, weight, skin color, and fingerprint patterns.
• Physiological variation: Differences in how the body functions, such as blood group, ability to taste PTC (phenylthiocarbamide), ability to roll the tongue, and resistance to disease.

Solution, checking each option:

• A. Size: a visible, measurable physical feature, so it is morphological.
• B. Ability to taste PTC: this is a functional or chemical-sensing ability controlled by a gene. You cannot tell by looking at someone whether they can taste PTC, so it is physiological, not morphological.
• C. Color: a visible physical feature (skin, eye, or hair color), so it is morphological.
• D. Fingerprint: a structural pattern of ridges on the skin, so it is morphological.

Answer: B. Ability to taste PTC is physiological variation, so it is the exception.

Exam tip: Ask yourself, "Can I see it or measure it on the body's outside?" If yes, it is morphological. If it involves how the body works, such as tasting, blood group, or tongue-rolling, it is physiological. Remember: PTC = Physiological, Taste, Chemical.