I think you do not understand the principles of evolution. Nature did not *do* anyting and even if it did so, it would not do something "so that". Evolution is a process of natural selection, you make it sound like some nature-goddess like Gaia thought "Oh, let's make onions in a way that predators have to cry when trying to eat them."

Living things are not designed, but Darwinian natural selection licenses a version of the design stance for them. We get a short cut to understanding the heart if we assume that it is 'designed' to pump blood. Karl von Frisch was led to investigate colour vision in bees (in the face of orthodox opinion that they were colour-blind) because he assumed that the bright colours of flowers were 'designed' to attract them. The quotation marks are designed to scare off mendacious creationists who might otherwise claim the great Austrian zoologist as one of their own. Needless to say, he was perfectly capable of translating the design stance into proper Darwinian terms.