Read it through once

But it is in cultivated lands and in open, rather dry and arid country that one finds the most interesting weapons in the fights between plant and animal. It is in such places that some of the most beautiful and useful creatures have their home. The horse, ass, camel, goat, and sheep probably belong to those wonderful lands which border the great deserts of Africa and Asia. These animals have been obliged to travel far and fast, and to perfect their bodily strength in order to pick up a living.