Which of these is an example of physiological variation?

Step 1: Analyze the question The question asks which option is an example of physiological variation.

Step 2: Explain the concept Variation is the differences among individuals of the same species. It is often grouped into:

• Morphological (structural) variation: differences in visible form or structure, e.g. height, weight, eye colour, fingerprints, skin colour.
• Physiological variation: differences in how the body functions or in its chemical makeup, e.g. blood group, ability to roll the tongue, taste ability (PTC tasting), sickle cell status, Rhesus factor, and the ability to resist disease.

Step 3: Go through the options

• A. Blood group: this is a biochemical, functional trait (the type of antigens on red blood cells). It is a classic example of physiological variation. ✔
• B. Eye colour: a visible structural feature, so morphological.
• C. Fingerprint: a structural pattern, so morphological.
• D. Height: measurable body structure, so morphological (continuous variation).
• E. Weight: a measurable physical characteristic, so morphological (continuous variation).

Step 4: Answer The correct answer is A. Blood group.

Step 5: Exam tip Ask yourself: "Can I see or measure it with a ruler or scale?" If yes, it is probably morphological. If it is about body chemistry or function, such as blood group, taste ability or genotype, it is physiological. Remember: blood group = body chemistry = physiological.