Also, in a population with no variance for a trait, for example if everyone has blue eyes, the heritability for that trait in that population will be undefined because there is no variation to inherit.
(everyone; has; blue eyes) (the heritability for that trait in that population; will be; undefined; because there is no variation; L:in a population with no variance for a trait)
everyone the heritability for that trait in that population
has will be
blue eyes
undefined because there is no variation L:in a population with no variance for a trait