Pairing Continuous (Spectrum Traits) and Discontinuous (Categorical Traits) Variation

Steps:

• Continuous variation involves polygenic traits with environmental influence, forming a gradual range (e.g., intelligence).
• Discontinuous variation involves single-gene traits with distinct, non-overlapping categories (e.g., blood groups).
• Review options: Seek one trait of each type without both being the same.
• Option C fits: intelligence (continuous range via IQ scores), blood groups (discrete A, B, AB, O types).

Why C is correct:

• Intelligence follows polygenic inheritance, producing continuous variation across a spectrum; blood groups follow Mendel's law via alleles at one locus, yielding discontinuous categories.

Why the others are wrong:

• A: Skin colour is continuous (polygenic shades), blood groups discontinuous, but skin colour overlaps with intelligence as continuous without distinct example pairing.
• B: Height is continuous (range of values), but free/attached ear lobes are discontinuous; ear lobes show incomplete penetrance, blurring categories.
• D: Intelligence is continuous, but hair colour is also continuous (polygenic shades from black to blonde).

Final answer: C