What is the fundamental reproductive unit that the cones of gymnosperms, flowers of angiosperms, and the reproductive fronds of ferns all share in common?

Answerin 1991 as an open source software;

Hmm this is a hard heterotroph's can't produce its own food. a human can produce it's own food because people kill animals and eat them like squirrel, deer, oak trees need rain which they don't produce the rain, bee's need flowers and pollen and nectar but they don't produce it either, rabbit's don't produce either, because they either steal carrots from your garden and eat leaves.so, the best answer that i would pick is a. humanshope my answer has you and sorry if it doesn't : ) : (