7.9 and megasheet - postzygotic mechanisms

what signifies a postzygotic mechanism?

zygote can possibly form, but will not be fertile

what are the postzygotic mechanisms?

hybrid lethality, hybrid sterility, hybrid breakdown

what is hybrid lethality?

zygote fails to develop and dies before maturity

what causes hybrid lethality and what can it lead to?

genetic incompatabilities between parents > development problems preventing survival

what is hybrid sterility?

zygote survives but is sterile and can't reproduce

what causes hybrid sterility and what can it lead to?

differences in chromosome number/structure > non-functional gametes

what is an example of hybrid sterility?

horse and donkey > mule (sterile)

What is hybrid breakdown?

first generation fertile, second generation sterile/reduced fitness

what is an example of hybrid breakdown

polar bear and brown bear > offspring: no adaptations for either parent's environment