Membranous coverings of the egg contents formed by interlaced protein fibres; permeable to gases and water vapour but impermeable to colloidal proteins; two membranes—outer and inner.
An area that allows birds to scratch.
All traits except the gonads by which males and females differ externally and in...
The choice of individuals within a population to achieve a defined breeding obje...
The base population within which selection is carried out.
A measured trait or condition used as the basis for selection.
The difference between the mean of a selected group and the mean of the original...