The third line of defence against pathogenic invasion is the adaptive immune response, which has two key qualities: It is specific (it can differentiate between specific microorganisms and respond accordingly) It is adaptive (it can produce a heightened response upon re-exposure - in other words, it has memory)
Not all of those offspring are likely to live to adulthood, whereas the parent penguin can pay attention to the one chick it has so it is more likely to live to adulthood
