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Difficulty: EasyContinuous and Discontinuous Variation

In human populations, physical and physiological traits are inherited through different genetic mechanisms. Which of the following characteristics displays continuous variation?

  1. Body massAnswer
  2. B
    ABO blood group
  3. C
    Tongue rolling ability
  4. D
    Ability to taste phenylthiocarbamide (PTC)

Answer

Body mass
Body mass exhibits continuous variation because it varies quantitatively across a smooth spectrum with intermediate phenotypes, influenced by polygenic inheritance and environmental factors such as diet and lifestyle.

Step-by-Step Solution

1
Distinguish between continuous and discontinuous variation.
Continuous variation features a continuous range of phenotypes between two extremes, whereas discontinuous variation presents distinct, non-overlapping categories.
Phenotypic distribution depends on whether traits form a spectrum or clear-cut groups.
2
Evaluate each given human trait.
Body mass forms a smooth continuous curve due to polygenic control and environmental interaction. Blood group, tongue rolling, and PTC tasting fall into distinct categories.
Polygenic traits influenced by environmental factors exhibit continuous variation.

Key Concept

Continuous variation features quantitative differences forming a unbroken spectrum of phenotypes, typically mediated by polygenic inheritance and environmental effects.
Estimated Time:45s
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Topics

Continuous and Discontinuous Variation

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