Which type of plants represents approximately 80 percent of all known green plants and has seeds protected by an ovary wall?

The correct answer is Angiosperms, which are indeed the most abundant group of plants, representing about 80 percent of all known green plants. Angiosperms are characterized by having seeds that are enclosed within an ovary wall, which typically develops into a fruit. This unique feature distinguishes them from other plant groups. The presence of flowers in angiosperms also plays a crucial role in their reproductive success, attracting pollinators and facilitating the process of fertilization.

In contrast, ferns do not produce seeds; they reproduce via spores, making them a separate category of vascular plants. Gymnosperms, while they produce seeds, do so without an ovary wall, as their seeds are often found exposed on cones. Algae, being a diverse group of primarily aquatic organisms, can be unicellular or multicellular and do not possess the vascular system or reproductive structures characteristic of higher plants, further distinguishing them from angiosperms. These differences highlight why angiosperms are the predominant type of green plants within the plant kingdom.