Unit of Selection in Family Selection

Correct Answer: Family Mean

From the notes: In family selection, the unit of selection is the family mean — animals are selected or culled as a whole family based on the average performance of the entire family group (collateral relatives/sibs).

Units of Selection for Each Method

• Individual selection: Own phenotypic value
• Pedigree selection: Ancestors' performance records
• Progeny testing: Mean performance of progeny (daughters)
• Family selection (incl. sib selection): Family mean ✔

Why Family Mean?

When heritability is low, individual performance is a poor predictor. Averaging across the whole family reduces environmental noise and provides a more reliable estimate of the genetic merit of all family members.