Transcript plant unit
PLANT DIVISIONS Invasion of land • Stomata • Cuticle • Lignin: bonds to cell wall cellulose to add strength and waterproofing • Vascular tissue: xylem and phloem • Roots: absorb nutrients and water vs. rhizoids of moss and holdfasts of algae that don’t. • Seeds: dormancy • Fruit: spreading seeds • Flowers: cross pollination Cuticle – A waxy cuticle covers parts exposed to air to prevent dessication. Openings in the cuticle (stomata) allow for gas exchange and are controlled by the guard cells. Guard cells Vascular tissue – Most division (all except bryophytes) have vascular tissue of xylem (water and minerals) and phloem (nutrients). – Picture shows vascular tissue in a leaf in a bundle known as a vein. These are the lines you can see in the leaf. Carbon dioxide • Plants lowered the levels of carbon dioxide from 25X current levels to current levels over a period of 100 million years as they adapted to and spread on land. Cuticle, Dermal tissue, ground tissue, and vascular tissue Flagellated sperm vs. pollen • The more primitive plants have flagellated sperm that allow them to swim to the egg. This means that the mosses, ferns, and other primitive plants require water to have fertilization. Fern sperm Types of pollen Plant Divisions • Divisions is used instead of phyla Evolution of plants from green algae • A certain group of green algae known as the charophytes have the following in common with plants. – Chloroplasts of both have thylakoids stacked as grana and chlorophyll b and carotene to act as accessory pigments for chlorophyll a. – The % of cellulose in both is around 25% – Similar mitosis and cytokinesis mechanisms – Similar sperm structure for sperm – DNA evidence backs this up. – Body of some charophytes is haploid, but fertilized egg is retained in the organism and grows and then does meiosis: clue to how alternation of generations started. Plants • NOTE: We use the term Divisions instead of the term Phyla when referring to plants. • Characteristics of plant kingdom members – Alternation of generations with the diploid sporophyte generation dominant except in bryophytes Plant Divisions: Bryophyta • MOSSES • Dominant gametophtye generation (green) • Also includes liverworts and hornworts • Need sperm to fertilize egg • NO vascular tissue limits height of the plant and therefore have no true roots, stems, or leaves. • haploid spores are made by meiosis in the sporangium of the sporophyte. Moss sporophyte Other Bryophytes Hornwort Liverworts • Homospory: one type of spore • Heterospory: female and male spore. Gametophytes • Antheridium • Male gametophyte • Makes sperm Archegonium Female gametophyte makes egg Pterophyta: Ferns • Homosporous: create one spore that is bisexual. • Vascular tissue but no seeds: allows them to get taller, but limits them to shady moist areas for reproduction. • Fronds: big “leaf like” arrangement • Fiddlehead: emerging sporophyte • Sporangium make spores on underside of fronds when reproducing. Ferns • Fiddlehead • Sporangia on underside of frond • Fronds • Bisexual gametophyte Gymnosperms (naked seeds) have no flowers: gingko, cycad, and conifers Coniferophyta • • • • • • Redwoods, firs, pines, yews, cypresses Naked seeds: not enclosed in fruits Wind pollination (NEEDS A LOT) Seeds, vascular tissue No flowers Often needles thick with cuticle and small in size to limit transpiration. Seed cones vs. pollen cones Seed cones seeds Pollen cones Oldest and largest • Redwoods (400 feet tall) bristlecone pine (4600 years old) Anthophyta • Flowering plants • Flower will develop into fruit that is used for seed dispersal via wind, water, or animal. • Pollination can be by wind, bird, bat, insect. • Most advanced (recent) • Gametophyte is reduced and within the flower. • Most diverse: grasses to trees Monocot (one cotyledon) vs. Dicot (two cotyledons): the subdivisions of anthophyta/angiosperms Monocots •Often grasses and the relatives of grasses Dicots • Trees, garden plants Vascular bundles location Monocot: scattered Dicot: ring around the outside #2: veination in the leaves • Parallel veins • Monocot Netlike veins Dicot #3: number of seed parts #4:Flower parts • Monocot • Petals: in multiples of 3 Dicot Petals: 4 or 5 Review Questions • • • • • • • • Which is haploid, spore or gamete? Which is made by mitosis, spore or gamete? Where is the vascular tissue of a monocot? Are ferns homosporous or heterosporous? Do bryophytes have roots? Do ferns have pollen? Do gymnosperms have seeds? Where are fern sporangia found? Flower structure: reproduction organ of some plants Parts: functions • Female (carpel/pistil) – Stigma is sticky “top” that collects pollen – Style is connection between stigma and ovary. – Ovary is where eggs are made in the ovules • Male (stamen) – Anther makes the pollen – Filament holds anther away from female part to allow for wind/insect to carry pollen away • Petals (collectively called corona): attracts pollinators • Sepals (collectively called calyx); protects the bud before blooming Monoecious (one house) plant: has both male and female on one plant • Name the parts • Dioecious: Two houses/ male and female plant • Complete: one flower had both female and male while incomplete has only one Prefixes for plants • • • • • • Mega and Arche are female Micro and Anther are male Microgametophyte = pollen (becomes sperm) Megagametophyte = makes eggs Atheridium: anthers make male gametes Archegonium: place where eggs are made Double Fertilization • Generative nucleus becomes two “sperm” through mitosis. First sperm fertilizes egg in the ovule and second sperm fertilizes polar nuclei to become triploid endosperm. Endosperm will become “food” for seed. Seed and Fruit • Seed, Develops from the ovules within the ovaries: Covering (seed coat), food (endosperm), embryo – Allows for dormancy until conditions are right – Germination triggers massive cell division and cellular respiration • Fruit: The ripened ovary becomes the fruit after fertilization leading to making of the seeds: seed dispersal is the goal • Vegetable: part of a plant you eat: not a biological term Fruit: Seed dispersal Review • The helicopters of a maple tree are what part of the plant? • What is made by the archegonium? • What part of the flower “catches the pollen? • What is one gymnosperm other than coniferophyta? • What part of a flower becomes the fruit? • What part of the flower becomes the seed? • What are the two products of double fertilization? More review • • • • • • How do pine trees get pollen to the female? How do apple trees get pollen to the female? What division of plants includes the tallest trees? What is the food of a seed called? What is the purpose of the endosperm? What group of green algae are the closest relatives to plants? • What does the cuticle prevent? • What division of plant has no flowers, but does have seeds? • What is true of plants that are heterosporous?