Which of the following is an example of physiological variation in organisms?

Step 1: Analyze the question The question asks which option is an example of physiological variation. That means a difference in how the body functions, not in how it looks or is built.

Step 2: The concept Variation among organisms is classified in different ways:

• Morphological (structural) variation: differences in external form or structure, such as height, shape, color, and size.
• Physiological variation: differences in body functions or processes, such as blood pressure, heart rate, metabolic rate, blood group, and the ability to taste PTC.

Step 3: Check each option

• A. Blood pressure among individuals: blood pressure measures how the circulatory system functions. This is physiological. ✔
• B. Beak shape among finches: beak shape is a physical structure, so it is morphological. ✘
• C. Fur color in rabbits: color is an outward appearance, so it is morphological. ✘
• D. Leaf shape in plants: shape is structural, so it is morphological. ✘

Step 4: Answer Option A is the only one that describes a difference in how the body works rather than in how it looks.

Exam tip: Ask yourself, "Can I see it just by looking, or must I measure a body function?" If you can see it (shape, color, size), it is morphological. If it is a function such as blood pressure, pulse, or blood group, it is physiological.