<span>Polydactyly in its most common form, is an autosomal dominant mutation. Let's represent the mutation as P and the normal state as +. Thus, if both parents are heterozygous (P+), both would have the mutation (and thus have six fingered). They have 3/4 chances of having a child with the extra digit, 1/4 normal. </span>
Predation
It can be explained in that way or also called Predatory/prey relationships.
Parasitism is when one is benefited and the other harmed (ie leech and human)
Commensalism is when one is benefited and the other not affected (Tree frog and rainforest tree)
Mutualism is when both are benefited (Bee eats honey and Flower is pollinated).
It's an Agrarian society, hope this helps!