Alternation of generations Seed Plants The life cycle typically found in plants Gymnosperms & Angiosperms in which the spore producing generation alternates with the gamete producing generation. By Diana Wheat Plants have 2 forms …… . Heterospory: The Rule The different forms Among Seed Plants Gametophyte : The multicellular, Seed plants evolved from plants that had haploid stage in the life cycle of megasporangia plants. – Which produce megaspores that give rise to: female gametophytes Sporophyte : The diploid form of a Seed plants evolved from plants that had plant that produces , haploid, asexual microsporangia spores through the process of meiosis spores through the process of meiosis – Which produce microspores that give rise to: – reduction division. male gametophytes Land Plants ’ Adaptations Pollen Seed plants release pollen grains which Seeds and pollen allowed allow fertilization to gymnosperms and angiosperms occur even in the (flowering plants) to survive and thrive absence of available in drier habitats. water. ……… ..Allowed wider range of dispersion Transported via: Wind or Animals Two major categories of Ovules and Production of seed plants Eggs will become seeds. An ovule consists of I.Gymnosperms – Cone bearing plants A megasporangium, megaspore, and protective integuments! Conifers, Cycads, Ginko, Integument Gnetophytes Spore wall Megasporangium (2 n) II.Angiosperms – Flowering plants Megaspore ( n) Unfertilized ovule. a Most plants we know that have fleshy megasporangium is surrounded by a flowers e.g. tulips, roses, & grasses protective layer of tissue called an integument . (Angiosperms have two integuments.) Seed Bearing Strobili – Essentially the same as Gymnosperm Diversity Welwitschia cones. Gymnosperm Life Cycle Onto Angiosperms Anatomy of a Flower The Participants Male Female Pollen : Male gametophyte of Produces Pollen Produces Ovules , seed plants. Stamen: Pistil: Anther Anther Stigma Ovule : Female gametophyte of Filament Style seed plants. Ovary Double Fertilization Fertilization in Angiosperms Double fertilization results from the discharge of two sperm from the pollen tube into the embryo sac One sperm the egg The other combines with the polar nuclei in ovule food -storing …………………………… .endosperm. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Angiosperm Life Cycle The Products Seed – From the ovule Seed Coat – From the Ovule Wall Fruit – From the Ovary Agents of Dispersal.