Irene must've had real political clout, to get an environmental variance.

The Environmental variance is much more straightforward.

The variance will include terms for genetic variance (since they did not all get the same genotype) and environmental variance.

An evolutionarily successful species is likely to populate its habitat fully and individuals are likely to be forced into peripheral regions where they face a greater environmental variance.

In an experiment with sires and progeny per sire, we can calculate the following ANOVA, using as the genetic variance and as the environmental variance:

General natural pedigree are analyzed using a mixed effects model in which components of variance (e.g. additive genetic variance, maternal effects, environmental variance) can be estimated from a pedigreed population of individuals of any structure (Slate, 2005.

These known differences in genetic similarity, together with a testable assumption of equal environments for identical and fraternal twins creates the basis for the twin design for exploring the effects of genetic and environmental variance on a phenotype.