l>Seed-Bearing tree Seed-Bearing PlantsSeeds appeared about 360 million years ago. Seeds ferns and also gymnosperms (e.g. Pine tree trees) were dominant at first. Angiosperms (flowering plants) developed later.Seed-bearing plants have three differentiating characteristics:They produce microspores which offer rise come pollen grains which serve as carriers of the sperm to the eggs.They develop megaspores which build within the ovules which will eventually produce seedswhen the sperm fertilizes the egg.They have water-conserving traits, including thick cuticles ~ above the pipeline (particularly in the Gymnosperms).Pollen grains room sperm-bearing masculine gametophytes that construct from microspores. They allow transfer the sperm to egg without water. They have the right to drift on air currents, or be brought by pollinatorsOvules space female reproductive structures that become seeds. Castle consist the a female gametophyte with an egg cell, plus nutrient-rich tissue, and a coat of cell layers that will kind a seeds coat.Gymnosperms Gymnosperms are called plants through "naked seeds". This way the seeds don"t form inside one ovary (as they perform in the angiosperms). Over there are 4 groups, the Conifers , the Cycads, the Ginkgos, and the Gnetophytes.
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Conifers are the finest known v the largest number of living species. They room woody trees or shrubs. Most are evergreen and produce needlelike leaves. Most create woody cones and also they bear seed on exposed cone scales. jaw trees produce two kinds of spores in 2 kinds that cones. Male cones create sporangia which yield microspores that construct into pollen seed (male gametophyte). Male cones are not woody and also typically much smaller than female cones. You will miss them top top a pine tree, unless you look at closely. Female cones are the typical woody pine tree cones and produce ovules the yield megaspores (female gametophyte). Pollination is the come of a pollen serial on the female reproductive parts, after i beg your pardon a pollen pipe grows towards the egg. Fertilization, i beg your pardon is delayed for approximately a year, results in a zygote that creates into one embryo in ~ the conifer seed.This computer animation (Audio - Important) defines the jaw life cycle. Conifers overcame during the Mesozoic. However, they reproduce more slowly 보다 angiosperms and also are in ~ a vain disadvantage in many habitats. They still overcome in the far North, in ~ higherelevations, and also in specific parts that the southerly Hemisphere.Ginkgos are represented today by just one hardy species, Ginkgo biloba, that is indigenous to China, and also that has actually survived native the times of dinosaurs. The tree mirrors remarkable resistance to insects, disease, and air pollutants. That is a deciduous tree through fan-shaped leaves. Trees are male or female. Mrs trees produce seeds extended with a fleshy, foul-smelling coat. There are several Ginkgo tree on campus. Friend can uncover one top top the north side of Haring hall (or the southern side that Storer Hall). Cycads are palmlike trees that flourished throughout the Mesozoic era. Only about 185 varieties still exist, largely confined to the tropics and subtropics. They bear enormous cone-shaped strobili that create either pollen (transferred by air currents or insects) or ovules. The pollen-bearing and also seed-bearing cap are found on different plants.Gnetophytes are the many unusual gymnosperms. Castle live in tropical and desert areas. Ephedra (joint fir, Mormon tea) is the ideal known the the three surviving genera. That is a natural source forthe chemical ephedrine. Welwitschia has actually two long, prominent leaves. Gnetum has actually leaves the look similar to those that angiosperms. Tree domestication began about 11,000 year ago, about 3,000 species have been offered as food. Currently, about 200 tree are significant crops. Over there are plenty of uses because that plants in addition to food:Lumber, paper, and also fuel indigenous conifersFurniture native hardwoodsRope indigenous agave, hempThatched roofing indigenous grasses, palmsNatural insecticidesDrugs native foxglove, periwinkleTobacco plants are Nicotiana sp.


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Cannabis sativa is the source of marijuanaCoca leaves are supplied to create cocaineToxic tree alkaloids, such together henbane and belladona, have actually been supplied as poisons and as medicine.This computer animation (Audio - Important) evaluate the evolution of plants. REVIEW: GymnospermsAnswerwere the very first plants no to have swimming sperm and also were thus freed indigenous the need for water come reproduce. REVIEW: Microspores tires intoAnswerpollen grains. REVIEW: The conifers, such together pines and junipers, are examples of theAnswergymnosperms. REVIEW: i beg your pardon of the following statements is no true?a.Monocots and also dicots are two class of angiosperms.b.Bryophytes room nonvascular plants.c.Lycophytes and angiosperms space both vascular plants.d.Gymnosperms are the simplest vascular plants.Answerd REVIEW: Which walk NOT use to gymnosperms and also angiosperms?a.vascular tissuesb.diploid dominancec.single spore typed.all that the aboveAnswerc REVIEW: A seeds is _____ .Answera mature ovule PREVIOUS following LECTURE 25 INDEX main INDEX