BIOL 3427 1st Edition Lecture 14Outline of Current Lecture II. ProkaryotesIII. VirusesIV. FungiV. Symbiotic relationshipsCurrent LectureI. Gymnospermsa. Evolution of plantsi. Bryophytesii. Seedless, vascular plantsiii. Seed plants1. Gymnosperms2. Angiospermsb. Evolution of the seedi. Why are seeds advantageous?1. Protects embryo2. Stores foodii. All seeds heterosporousiii. Definition of seed1. Fertilized, mature ovule containing an embryo2. Ovulea. Nucellus/ megasporangium surrounded by 1 or 2 integuments with micropyle.b. Mature: contains a megagametophte composed of archegonia and nutritive tissuec. After fertilization, integuments develop into seed coatd. All seeds contain stored foodiv. Ovule evolution (7 events)1. Megaspore retained in megasporangium (nucellus)2. Number of megaspore mother cells reduced to one3. Only one of four megaspores survives4. Megasporophyte highly reduced, retained in megasporangium5. Embryo (young sporophyte) develops within megasporophyte6. Integument envelops megasporangium7. Apex of megasporangium modified to receive pollen grainsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Fossil recorda. Unclear exact order of events aboveb. Oldest seeds from late Devonian (365 mya)i. Gradually integuments fused until only opening left at apex (micropyle)c. Five phyla of seed plants with living representativesi. Seed plants typically possess megaphylls1. Coniferophyta2. Cyadophyta3. Ginkophytaa. Gymnospermsb. Naked seedsc. 840 speciesii. Modified into needles or scales in some groupsa. Gnetophya-gymnospermsb. Antherophyta-angiosperms “covered seed”, 300,000 speciesd. Progymnospermsi. Not gymnosperms1. Extinct group of seedless vascular plants2. Ancestors of seed plants were similar to progymnospermsii. Late Paleozoiciii. In between trimerophytes and seed plants1. Spores2. Bifacial vascular cambiuma. Secondary xylem similar to conifersb. Secondary phloem3. One group has eusteleIII. Extinct Gymnospermsa. Pteridospermales (seed ferns)b. Cordaitales (Cordaites)c. Bennettitales (cycadeoids)IV. Living Gymnospermsa. Ovules and seeds exposedV. Female Gametophytea. Produces several archegoniai. Results in polyembreyony; more than one embryo per ovuleVI. Fertilizationa. Water not requiredb. Pollinationi. Male gametophyte (pollen grain) transferred to female gametophyte via windii. Pollen tube formsc. No antheridia in seed plantsVII. Sperm differ among groupsa. Nonmotile in conifers and gnetophytesi. Pollen tube conveys sperm to eggb. Flagellated in cycads and Gingkoi. Pollen tube does not penetrate archegoniumii. Pollen tube absorbs nutrients for production of spermVIII. Phylum Coniferophytaa. Most numerous, most widespread, most ecologically important gymnospermsb. 70 genera, 630 speciesc. Late Carboniferous (300 mya)d. Leaves have many drought resistant characteristicsIX. Pines (Pinus)a. 100 speciesb. Dominate many areas of N. America and Eurasiac. Cultivated in Southern HemisphereX. Unique leaf arrangementa. Seedlings: needlelike leaves single, spirally arrangedb. In 1-2 years, leaves in bundles (fascicles of 1-8)XI. Leaves adapted for low soil moisturea. Thick cuticleb. Hypodermis: compactly arranged-thick walled cellsc. Sunken stomataXII. Xylema. Primarily tracheidsXIII. Phloema. Primarily sieve cellsXIV. Life cyclea. Two years to completeXV. Microsporangia and megasporangiuma. Borne on separate cones(stroboli) on same treeb. Usually male on lower branches and female on upperXVI. Microsporangiate conesa. Small (1-2 cm)b. Microsporocytes (microspore mother cells)c. Meiosis in early springi. Produce four haploid microsporesii. Each microspore becomes pollen grain (immature)iii. Male gametophyte: 2 prothalial cells, 1 generative cell, 1 tube cellXVII. Megasporangiate (ovulate) conesa. Much larger, more complex compound structureb. Seed-scale complex (modified branch system)i. Coniferious scale with two ovules on upper surfaceii. Subtending sterile tractc. Scales in spirald. Ovulei. Megasporocyte within nucellus undergoes meiosisii. Only one of four megaspores is functionale. Pollinationi. Occurs in spring1. Takes two years to completeii. Scales on ovulate code widely separatediii. Pollen grains land in pollination drops at the micropyleiv. Pollen grain grows pollen tune into nucellusv. Scales grow together to protect ovulesvi. Megaspore becomes megasporophyte1. Very slow development2. About 15 months after pollination, archegonia formedXVIII. Generative cell of pollen grain divides ~12 months after pollinationa. 1 sterile cellb. 1 spermatogeneous cell (which then divides into two sperm cells)c. When sperm produces, microgametophyte is