(a) Any part of a decedent's estate not effectively disposed of by will or otherwise passes by intestate succession to the decedent's heirs as prescribed in this code, except as modified by the decedent's will.
(b) A decedent by will may expressly exclude or limit the right of an individual or class to succeed to property of the decedent passing by intestate succession. If that individual or a member of that class survives the decedent, the share of the decedent's intestate estate to which that individual or class would have succeeded passes as if that individual or all members of that class had disclaimed their intestate shares.