Angiosperms rely on diverse animals to disperse their

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Angiosperms rely on diverse animals to disperse their pollen Part of the life cycle that moves around What is a seed? Seed coat is a protective covering that is genetically identical to maternal plant Food tissue (may not be present when seed matures) Embryo has genes from father and mother o Diploid like seed coat but not genetically identical Gymnosperms bear “naked” seeds, typically on cones Naked seeds are not enclosed in tissue that will develop into a fruit/that pollen has to grow through The gymnosperms consist of four Divisions: Cycadophyta (cycads) o Don’t grow fruit Gingkophyta (one living species: Ginkgo biloba) o Ginkgos are male and female. Females produce the bad smelling scent Gnetophyta (three genera: Gnetum, ephedra, Welwitschia) o Welwitschia grow only in desert in Namibia, have huge underground structure, leaves keep growing forever (never fall off) o Ephedra have male and female individuals Coniferophyta (conifers such as pine, fir, and redwood) Gymnosperms dominated the Mesozoic Era 250-65 mya including Jurassic
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Oldest living organism is a bristlecone pine (4800 years old) Ponderosa pine has male cones and female cones Life cycle of a pine Two kinds of cones: pollen and ovulate one that produces seed Microsporangia produce male gametes within which you will find microsporocytes Ovules are immature seeds o Within ovule is megasporocyte which is within the megasporangium Four products of meiosis: three die, one lives Female sporocyte contains multiple archegonium o No artheridium Pollen lands on opening of ovule and discharges the sperm that opens on the egg Fertilization produces the embryo Development of the male gametophyte in gymnosperms Pollen from gymnosperms have wing-like structures that help them get transported in the wind Microspores (n) -> conifer pollen 4 cells (n) o 2 are not functional
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o 1 tube cell -> pollen tube o 1 generative-> 2 sperm (1 functional, 1 not functional) Development of the female gametophyte in gymnosperms multiple egg cells in what could be a single seed o sometimes you plant a gymnosperm seed and get two plants o selective abortion Before fertilization, a pollen tube is produced; the 2 sperm travel down the tube, 1 sperm is not functional, 1 fertilizes an egg; more than one pollen grain may land on the opening to the ovule (micropyle) and more than one egg may be fertilized, each by the one sperm from a different pollen grain Megagametophyte: more than one embryo may develop if more than one egg is fertilized, but usually only one matures; the megagametophyre remains as food, but the archegonia are no longer visible Pollination Movement of pollen to an ovule Wind-dispersed pollen of all kinds end up in lake sediments and yield clues about past vegetation You can use lake sediments to reconstruct vegetation history of the site Old pollen can be at the bottom of the lake
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  • Fall '08
  • FevziDaldal
  • Vacuole, Xylem, vascular tissue

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