How an adaptation in angiosperms to provide nutrition for its embryos has become such a major food source for humans

Let's see, the nutrition storage for the embryo would be:
the endosperm in seeds 
the cotyledon(s) in seeds may also be modified for storage (and may absorb the endosperm in doing so!) 

So: we eat seeds, which includes eating the cotyledon(s) and the endosperm. Our major food sources these days that are seeds include our grain crops, the seeds of legume crop plants (e.g. beans, peas), and "nuts."

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it

This dessert was once a barren place for glaciers therefore supporting her scientific find