Chapter 30: Plant Diversity 2: The Evolution of Seed PlantsConcept 30.1: Seeds and pollen grains are key adaptations for life on land• characteristic common to all seed plans• seeds• reduced and dependent gametophytes• heterospory-produce 2 types of spores, megaspores-female, microspores-male• ovules-structures that house the female gametophytes• pollen-structures that house male gametophytes and gets dispersedGametophyte/Sporophyte relationships• gametophytes of seed plants develop within the walls of spores retained within tissues of the parentsporophyte• no longer dependent on water for fertilization•• non vascular and seedless non vascular- rely on water at some point so the sperm can swim out andfertilize the eggsOvules and Production of Eggs• an ovule consists of megasporangium, megaspore, and protective integuments•• megaspore develops into the female gametophytePollen and Production of sperm• microspores develop into pollen grains• contains male gametophyte• pollen can be dispersed by air or animals, eliminates the need for water in fertilization• don't need water because pollen grains can be dispersed by the winds or by animalsif a pollen grain germinates....• it gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovule• figure 30.3b (in above picture)A seed• once fertilization takes place, the whole ovule becomes the seed• includes sporophyte embryo, food supply, protective coat• food source gets transferred to the embryo which is the new sporophyte stage• figure 30.3c(in above picture)Which does not apply to gymnosperms or angiosperms?• single spore type• seed bearing vascular plants will have vascular tissue, the dominant stage is the sporophyte stage with is diploid and they do have cuticles with stomata, they also have heterospory so they produce 2types of sporesIn seed bearing plants, microspores develop into ____?• pollen grains• seed happens after fertilization occurs and it produces a new embryo. the whole structure of the ovule becomes the seedConcept 30.2: Gymnosperms bear "naked" seeds, typically on conesGymnosperms include...• phylum cycadophyta• sago palms• phylum gingkophyta• only 1 species within this phylum• tolerant to adverse conditions (tolerate high levels of pollution)• phylum gnetophyta• found in desert regions• reproductive stages, they produce cones• phylum coniferophyta• includes: pines, firs, junipers, sequoiasA closer look at the lifecycle of the gymnosperm• key features of the gymnosperm life cycle include:• dominance of the sporophyte generation• the role of pollen in transferring sperm to ovules• no water required because they are dispersed by the wind• the development of seeds from fertilized ovulesPine Life Cycle•• alternation of generations• sporophyte stage- pine tree is the mature sporophyte• microsporangia have microsporocytes• megasporangium has megasporocytes which undergoes meiosis to form 4 megaspores, 1 develops into the female gametophyte, the other 3 disintegrate • in pines, the female gametophyte contains archegonia, each of which contain an egg• in pines, a megaspore repeatedly grows and divides, giving rise to a female gametophye. the female gametopye is the site in which egg-bearing gametophytes develop• in pines, an embryo is an immature sporophyte. the diploid embryo will develop into a seedling and then into a mature pine tree• in pines, pollen grains get to the ovule via the micropyle• the gametophye tissue that surrounds the pine embryo functions as a haploid food reserve. the tissue is a source of nourishment for the embryo• in the pine, diploid microsporangia form haploid microspores by meiosisHow many generations are represented in the seed of a gymnosperm• three• seed coat is derived from parent sporophtye, the food reserve is the gametophyte, and the embryo is the new sporophyteGymnosperms include_____?• cycads, conifers, ginkgo biloba, and gnetopytes• gymnosperms do not include flowering plants or plants with fruitsConcept 30.3: The reproductive adaptations of angiosperms include flowers and fruits• angiosperms means covered seeds and the things that cover those seeds are fruits• derived traits are the reproductive structures called flowers and fruits• they are the most widespread and diverse of all plants• 250,000 species• 90% of all extent plant species, so they are the dominant plant todayAngiosperm Diversity• some groups found within this clade include amborella trichopoda, water lilies, star anise, and southern magnolias• most recent common ancestor of all living angiosperms is at 150 million years ago• all come from 2 groups:• monocots -include pine trees, etc• embryo has 1 seed leaf• vascular tissue in ...-parallel• vascular bundles throughout the stem• eudicots- include• 2 seed leaves• vascular tissue-•Flowers• specialized for sexual reproduction... a structure used for reproduction• specialized shot with modified leaves• sepals:enclose the flower• protect the flower when it is not in bloom• petals: brightly colored, attract pollinators• stamens: produce pollen• consists of the filament and the anther• carpels: produce ovules• consists of the sigma, the style, and the ovary(which holds the ovules)•Fruits• a mature ovary• ovary matures after fertilization of ovules• can be carried by wind, water, or animals, enhancing dispersal.The angiosperm life cycle• double fertilization (a derived feature, it is unique to angiosperms(flowering plants)) occurs when a pollen tube discharges 2 sperm into the male gametophyte within an ovule• the first sperm fertilizes the egg• the second sperm combines with 2 nuclei in the center cell of the female gametophyte and initiates development of the endosperm• endosperm nourishes the developing embryo•• within the ovary of a flower are the ovules, the ovules have megasporangium which contain the megasporocytes which undergo meiosis to create 4 megaspores, 3 of the megaspores separate and get reabsorbed and one survives and develops into the female gametophyte. The femalegametophyte is made up of 3 antipodal cells, 2 polar nuclei, an egg cell, and 2 synergids. the pollen tube then deposits 2 sperm nuclei into the ovule where we have the female gametophyte. 1 sperm nucleus fuses with the egg cell and the other fuses with the two polar nuclei. We end up with a
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