Biology reading for 3/2/15 Pages 172-175The greening of EarthThere are more than 290,000 known plant species on EarthPhotosynthetic protists are aquatic plants that distinguish themselves from algaeLand plant roots stabilize the soilLand plants evolved from green algaeCharophytes: green algae that has the closest relations to land plantsMorphological and molecular evidencePlants are multicellular, eukaryotic, photosynthetic, autotrophs like brown, red, and certain greenalgae.Call walls are made by celluloseChloroplasts with chlorophylls a and b are presentTraits that charophytes share with land plants: rings of cellulose-synthesizing proteins, structure of flagellated sperm, formation of a phragmoplastRings of cellulose-synthesizing proteins: located in the plasma membrane. Synthesize the cellulose microfibrils. Noncharophyte algae have linear seats of proteinsStructure of flagellated sperm: closely resembles charophyte spermFormation of a phragmoplast: A group of phragmoplast forms between the daughter nuclei of adividing cell. A cell plate then develops in the middle of the phragmoplast across the midline of the dividing cellAdaptations enabling the move to landSporopollenin: a layer of a durable polymer that prevents exposed zygotes from dying out. Located in charophytes.A similar chemical reaction is found in land plants located in the sporopollenia walls that incase plant spores.Derived traits of plantsFive traits that are found in land plants, but not in charophyte algae: altenation of generations, multicellular dependent embryos, walled spores produced in sporangia, multicellulargametangia, apical meristemsAlternation of GenerationsLife cycles of plants alternate between two organisms: gametophytes and sporophytesAlternation of generations: A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte characteristic of plants and some algaeGametophyte: multicellular haploid. Produces by mitosis of haploid gamotes that fuse during fertilization forming diploid zygotesSporophyte: Multicellular diploid that is produced by mitotic division of the zygote. It is a sporeproducing plant.Spores: produced during meiosis in a mature sporophyte. They are reproductive cells that can develop into a new haploid organism without fusing with another cell.The steps of alternation of generations1. A gametophyte produces haploid gametes by mitosis →(haploid) 2. Two gametes (one from another plant) unite (fertilization) and form a diploid zygote →(haploid) 3. The zygote develops into a multicellular diploid sporophyte →(diploid) 4. The sporophyte produces unicellular haploid spores by meiosis→(diploid) 5. The spores develop into multicellular haploid gametophytes (Haploid) → Step 1Multicellular, dependent embryosEmbryophytes: the multicellular dependent embryo of land plantsPlant embryos develop from zygotes that are retained within the tissues of the female parent (gametophyte) Placental transfer cells enhance nutrient transfer to embryoWalled spores produced in sporangiaSporangia: multicellular organs that produce sporesSporocytes: spore mother cellsSporocytes undergo meiosis and generate haploid sporesKey adaptations of land plants are sporopollenin-enriched walls produced by multicellular sporangiaMulticellular gametangiaGametangia: Multicellular organs that contain the production of gametesArchegonia: Female gametangia/ a pear shaped organ that produces a single nonmotile egg retained within the bulboas part of the organAntheridia: The male gametangia, Produce sperm and relase them into the environmentApical meristemsPhotosynthetic organisms find essential resources in light, CO2, water, and mineral resourcesApical meristems: localized regions of cell division at the tips of the roots and shootsQuizlet link: