Answer:
The name angiosperm is derived from the Greek words angeion, which means urn/vase, and sperma, meaning seed and gives us clues to the main feature of this group. In the flower, the eggs are protected within a structure called the ovary, which will develop in the fruit, carrier of the seeds.
Flowers are, therefore, the structures responsible for the reproduction of angiosperms, being their exclusive characteristic. In moss and ferns, reproduction is ensured by very simple structures - the sporangia, responsible for spore production. The sporangia are grouped in leaves (sporophylls) that can be more or less modified concerning the leaf pattern of the plant. The unicellular spores are easily carried by the wind, can travel long distances and, when favorable, germinate, giving rise to a new individual (gametophyte). In mosses, the gametophyte consists of a spiral arrangement around the kaolin and the sporophyte consists of an elongated stem (arrow) and a capsule into which the spores are produced.
The most important step in the evolution of gymnosperms is that the embryo is protected by a wrap (integument) and, together with the nourishing tissue, form what we call a seed. The seed replaces spore as a unit of propagation in gymnosperms and angiosperms, conferring great advantages to these groups.
