Certain populations worldwide are much more lactose intolerant than others. Why might this be the case?

Lactose persistence, and therefore lactose tolerance, is inherited as a dominant trait. Lactose intolerance is the result of  having two identical alleles of a particular gene or genes. for the recessive lactase allele that is poorly expressed after early childhood.

You basically can get it from your parents.

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls