Coloration of the eye is ______ variation

Analyze the question: The question asks what type of variation eye colour is. Variation means the differences between individuals of the same species. We need to decide which category eye colour belongs to.

Explain the concept: Variation can be classified in different ways:

• Morphological variation: differences in the physical form or structure of organisms, such as height, skin colour, eye colour, hair colour, and body shape. These can be seen and measured.
• Physiological variation: differences in how the body functions, such as blood group, Rhesus factor, tolerance to drugs, or the ability to taste PTC.
• Adaptive variation: differences that help an organism survive in its environment.
• Recessive: this describes an allele or trait expression in genetics. It is not a type of variation.

Step-by-step solution:

1. Eye colour is something you can see, as a structural feature of the iris (the pigment in it).
2. It is an external physical trait, not a function of the body's chemistry or processes.
3. Physiological is therefore ruled out, since it covers functions such as blood group.
4. Recessive is not a category of variation at all.
5. Adaptive is not the best fit, since eye colour is generally not classified as an adaptation to the environment in this context.
6. Visible physical features fall under morphological variation.

Answer: B. morphological

Exam tip: Remember "Morphology = Mirror". If you can see it when you look in the mirror (height, eye colour, skin colour), it is morphological. If you need a test to find it (blood group, enzyme activity), it is physiological.