Which statement best describes the effect of environment on trait variation when heritability is moderate to low?

Which statement best describes the effect of environment on trait variation when heritability is moderate to low?

• A. Genetic factors are the sole contributor to variation.
• B. The trait has no variation.
• C. Heritability cannot be measured precisely.
• D. Most of the observed variation is due to environmental factors.

Answer: (D)

When heritability is moderate to low, most of the observed differences among individuals come from environmental and non-genetic factors rather than genetic differences. Heritability is the fraction of total phenotypic variance that is due to genetic variance within a given population and environment. If that fraction is not large, environmental influences like nutrition, management, climate, or measurement conditions drive the variation you see. So the statement that most of the observed variation is due to environmental factors correctly reflects the meaning of low to moderate heritability. The other ideas fall short because they imply genetics dominates, no variation exists, or misstate what heritability can or cannot tell you.

When heritability is moderate to low, most of the observed differences among individuals come from environmental and non-genetic factors rather than genetic differences. Heritability is the fraction of total phenotypic variance that is due to genetic variance within a given population and environment. If that fraction is not large, environmental influences like nutrition, management, climate, or measurement conditions drive the variation you see. So the statement that most of the observed variation is due to environmental factors correctly reflects the meaning of low to moderate heritability. The other ideas fall short because they imply genetics dominates, no variation exists, or misstate what heritability can or cannot tell you.