Apple seeds are dispersed in the wild via zoochory, or when they are carried by animals. Animals eat the fruit and carry the seeds away in their digestive tracts. When the seed passes in the animal's stool, the seed sprouts and propagates a new apple tree.
Cultivated apple trees are propagated asexually via grafting. Farmers do this to keep apple varieties consistent within an orchard. Because each apple seed contains a unique combination of DNA, no two seeds from the same tree or even within the same apple produce identical trees. Different sizes of rootstock used in a graft produce different sizes of apple trees, which all produce fruit at different rates.