This chapter explain why pollen grains were an important adaptation for successful reproduction on land; list the four phyla of gymnosperms; describe the life history of a pine; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation;. | Chapter 30 Plant Diversity II: The Evolution of Seed Plants Overview: Feeding the World Seeds changed the course of plant evolution Enabling their bearers to become the dominant producers in most terrestrial ecosystems Figure Concept : The reduced gametophytes of seed plants are protected in ovules and pollen grains In addition to seeds, the following are common to all seed plants Reduced gametophytes Heterospory Ovules Pollen Advantages of Reduced Gametophytes The gametophytes of seed plants Develop within the walls of spores retained within tissues of the parent sporophyte Gametophyte/sporophyte relationships Figure –c Sporophyte dependent on gametophyte (mosses and other bryophytes). (a) Large sporophyte and small, independent gametophyte (ferns and other seedless vascular plants). (b) Microscopic female gametophytes (n) in ovulate cones (dependent) Sporophyte (2n), the flowering plant (independent) Microscopic male gametophytes (n) inside these parts of flowers (dependent) Microscopic male gametophytes (n) in pollen cones (dependent) Sporophyte (2n) (independent) Microscopic female gametophytes (n) inside these parts of flowers (dependent) Reduced gametophyte dependent on sporophyte (seed plants: gymnosperms and angiosperms). (c) Gametophyte (n) Gametophyte (n) Sporophyte (2n) Sporophyte (2n) Heterospory: The Rule Among Seed Plants Seed plants evolved from plants that had megasporangia Which produce megaspores that give rise to female gametophytes Seed plants evolved from plants that had microsporangia Which produce microspores that give rise to male gametophytes Ovules and Production of Eggs An ovule consists of A megasporangium, megaspore, and protective integuments Figure (a) Unfertilized ovule. In this sectional view through the ovule of a pine (a gymnosperm), a fleshy megasporangium is surrounded by a protective layer of tissue called an integument. (Angiosperms have two integuments.) Integument Spore wall Megasporangium (2n) Megaspore | Chapter 30 Plant Diversity II: The Evolution of Seed Plants Overview: Feeding the World Seeds changed the course of plant evolution Enabling their bearers to become the dominant producers in most terrestrial ecosystems Figure Concept : The reduced gametophytes of seed plants are protected in ovules and pollen grains In addition to seeds, the following are common to all seed plants Reduced gametophytes Heterospory Ovules Pollen Advantages of Reduced Gametophytes The gametophytes of seed plants Develop within the walls of spores retained within tissues of the parent sporophyte Gametophyte/sporophyte relationships Figure –c Sporophyte dependent on gametophyte (mosses and other bryophytes). (a) Large sporophyte and small, independent gametophyte (ferns and other seedless vascular plants). (b) Microscopic female gametophytes (n) in ovulate cones (dependent) Sporophyte (2n), the flowering plant (independent) Microscopic male gametophytes (n) inside these parts of flowers .
