Why are there different ways of indicating gender for animals? For instance, by inflexion we get:
lion (male) & lioness (female)
where the female is distinguished from the male. Here the male is also known by the general (have I used this correctly?) term for this type of animal, i.e. lion.
But, in another instance, we have:
duck (female) & drake (male)
where the male is distinguished from the female by a distinct or different word and also from the general term for this type of fowl, i.e. duck.
Then, for kangaroos and rabbits, we have:
buck (male) & doe (female)
where neither are known by the general term, nor is there any inflexion; instead, distinct names are used.
Why do these different ways for indicating gender exist? Why is it that in some cases the male is differentiated from the female and vice-versa. And why in some cases are both female and male known by words so different from the general term used to describe them?