Plants Unit Notes Week 1-3
Plants Unit Notes Week 1-3 BSC2011
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This 10 page Class Notes was uploaded by Jessica Brown on Tuesday September 13, 2016. The Class Notes belongs to BSC2011 at University of Florida taught by Douglas,Norman A Gerlach,Nicole Palmer,Todd in Fall 2016. Since its upload, it has received 4 views. For similar materials see biology 2 in Biology at University of Florida.
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Date Created: 09/13/16
Biology 2 - BSC 2011 Section: 0575 Plants: Norman Douglas Lecture 1 - 8/22/16 Print Syllabus Due by Friday @ 11:55pm: Done 8/22/16 1. Get into Launchpad after 5pm today 2. Sign up for TopHat 3. Pre-Test Lecture 2 - 8/24/16 Throwback to Phylogeny: Chapter 16 Tree of life- all life on earth star a common ancestor (root) Ribosomes and protein makers made of RNA Phylogeny- the evolutionary history of these relationships Phylogenetic tree- a diagrammatic reconstruction of that history Tree is a hypothesis, based on evidence, for what the true tree is likely to be Lineage- series of ancestor and descendant pop., shown as a line drawn on a time axis single species, as new generations form over time it forms a lineage dot at the start and over time turns into a line when single lineage divides into two (speciation), it is depicted as a split and splits are the node and forks out (sister species) Interpreting a phylogeny A and B are more closely related and are called a clade A and B and C form a clade A and C cannot form a clade How to build a phylogenic tree B C A 1. Observe and compare characteristics Morphology (physical) Molecular sequences (DNA or internal) Homologous: shared by 2 or more species and inherited from a common ancestor Can be any heritable traits, including DNA sequences, protein structures, anatomical structures, and behavior patterns. Homology is evidence of common ancestry. Bat and Bird wing is not homologous, but the genes and bone structure is homologous Lecture 3 - 8/26/16 - Each character in a phylogenetic analysis evolves from ancestral to derived. • Shared or derived - Taxon: any group of species that we designate with a name - Clade: group that consists of all the evolutionary descendants of a common ancestor. (monophyletic) Takeaways - All life is related by a phylogeny. - Use evidence to make make hypotheses about the relationships, sometimes change with new evidence. Phylogenetic Tree of Life - 3 Main Domains: Bacteria, Archaea, Eukaryotes What is a Plant? - Photosynthesis is an important feature. CO2 + H2O = glucose + O2. Need Sunlight and puts energy from sun into sugar molecule. - Origin of Photosynthesis • You can look at old rocks and they contain these thin layers of cyanobacteria (blue green algae), prokaryotes but also photosynthetic, can “ﬁx” nitrogen gas from the atmosphere. • Oxygenic photosynthesis drastically inﬂuenced the course of evolutionary history on earth. Oxygen rich atmosphere favored organisms that could utilize O2 • Set stage for the rise and diversiﬁcation of eukaryotes • Endosymbiotic Events in the Evolution of Chloroplast - Cell with mitochondrion gets a photosynthetic cell and engulfs it making it a cell with both mitochondrion and chloroplast. Both bacteria beneﬁt. - Primary endosymbiosis produced the ﬁrst photosynthetic eukaryotes - Primary endosymbiosis: a cyanobacteria was engulfed. Chloroplast has 2 membranes. - This event gave rise to chloroplast of red and green algae and land plants. - Some clades have chloroplasts derived from a primary endosymbiont! (green and red alga) Green Plants - Plantae: that clade with chloroplasts derived from primary endosymbiosis. Red Algae - these plants vary from single-celled to elaborately branched multicellular organisms - They have cellulose cell walls. - They only have chlorophyll - Chloroplasts with chlorophyll a and b - Store carbohydrates as starch Lecture 4 - 8/29/16 Life Cycle of Green Algae - In Chara and Coleochaete the vegetative bodies are haploid and fusion of egg and sperm produces a diploid cell, the zygote, which immediately undergoes meiosis, resulting in 4 haploid spores. • Synapomorphies on the Streptophytes include: retention of the egg in the parental organism, apical growth, oogamy (production of egg and sperm), plasmodesmata. • Isogamy vs. oogamy: small pos and neg cells. vs. gender of egg and sperm cell. - Plasmodesmata: channels between cells (little holes in the cell wall. - Parenchyma: the basic tissue type in the steptophytes with cells linked by plasmodesmata. Key Adaptations Permitted Plants to Colonize Land: - Adapt to dry, high light (xeric) conditions - Develop transport systems for water and nutrients - Develop structural support - Find new ways to disperse gametes and progeny - Waxy Cuticle: impermeable layer to keep moist on the inside. - Stomata: gates that open and close to control the concentration of CO2 and Oxygen. Downfall is that you also evaporate water because there is no cuticle. - Pigments: Protects against UV radiation. Light is absorbed or dissipated (in form of heat or pass it off to another process or reﬂect it) by accessory pigments. - Reproduction: spores with a thick sporopollenin (amazing polymer) wall protects spores against drying out and decay. Pollen takes on all sorts of shapes and some are speciﬁc to certain plants, they do not decay even at bottom of lakes. Early Spore Fossils date back to -470MYA - Mycorrhizae: associated with the fungi that provide nutrients to plants. - Plants are not very good at decomposing inorganic or organic materials, they rely on fungi and bacteria. Mycorrhizae: mutually beneﬁcial association with fungi - Mycorrhizae: Fungi associated with underground parts (roots). - Ectomycorrhizal (EM): fungi wrap themselves around the plant, increasing surface area for water and mineral absorption. - Vesicular-arbuscular mycorrhizal (VA): fungi grow into root cell and exchange water and nutrients. Land plants have alternation of generations: - Includes a multicellular diploid stage and a multicellular haploid. • Gametes are produced by mitosis, spores and produced by meiosis. • Spores develop into multicellular haploid organisms. - Diploid zygote develops by mitosis and cytokinesis into a multicellular embryo, which eventually grows into a mature diploid plant. • This multicellular diploid plant is called the sporophyte, that forms spore-producing sporangia (singular: sporangium) • Cells in sporangia produce haploid spores by meiosis. Lecture 5 - 8/31/16 - Alternation of Generations • This life cycle is a synapomorphy of the land Plant clade… especially th presence of a Sporophyte (multicellular diploid organism) - Meiosis creates spore and then undergoes mitosis to form Gametophyte. undergo mitosis to create gametes. • Gametophytes and gametes are genetically identical - Bryophytes • Gametophyte (haploid) is the dominant life form. • Sporophyte is dependent on the gametophyte for nutrition at some or all stages of development and usually remains attached. • Gametes are produced int he antheridium and archegonium. The sperm must swim or be splashed by water to reach the egg. - Have no true roots, stems, or leaves. - Obtain and move water around in a relatively undirected fashion via osmosis. - Have no strong support tissue plant body. - Have signaling proteins that are involved in desiccation tolerance… Why? - Have swimming sperm (2 ﬂagella) - Key Adaptations • Gametangia (singular: gametangium) are organs that enclose gametes and prevent them from drying out: “Archegonium” (Female) “Antheridium” (Male) • Embryos, young plants contained within protective structure. - Liverworts (-9000 extant species) • Green, ﬂat leaf-like gametophytes. • Growth occurs at growing points at the apex of plant. • Sporophyte remains attached to the larger gametophyte. • Most liverworts can reproduce asexually and sexually. No internal water conduction • • No true stomata (don’t need it) • Liverwort sporophytes - sporophyte has a stalk and capsule (the sporangium) (site of meiosis) - Sporophyte is attached to the gametophyte and physiologically dependent on it - Stalk elongates rapidly by cell elongations throughout its length - Mosses (-15000 extant species) • Erect, leafy gametophytes • Have stomata • Have cells called hydroids, which die and leave a channel through which water can move. • Sporophyte attached to gametophyte, dependent sporophyte unbranched, producing a single capsule. Peristome teeth aid dispersal • - Peristome Teeth line the apex of the capsule (sporangium) • These structures are hygroscopic, i.e. they change shape with humidity, and they allow gradual spore dispersal. • Flex in response to changes in humidity • The dung mosses have specialized capsules for ﬂy dispersed spores • Sphagnum (Peatmoss) • Sporophyte capsule pops off Large ecological and economic importance • - Uses: fertilizer, ﬁre starter, peat ﬁre is what is used to make scot whiskey - Hornworts (-100 extant species) • Sporophytes look like small horns • Cells contain only one chloroplast • Sporophyte grows from a basal region capable of indeﬁnite cell division. • Have a symbiotic relationships with cyanobacteria that live in interval cavities and ﬁx nitrogen - Branching sporophyte • specialized organs: roots, stems, and leaves - make sugars by photosynthesis - Support the plant to elevate the leaves and maximize photosynthesis - Absorbs water and nutrients - Tracheophytes • The evolution of - vascular tissue and organs to move water and sugars - reproductive mechanisms to minimize dependence on water - diverse partnerships with land animals Lecture 6 - 9/7/16 - Vascular Tissue (Tracheophytes): Specialized system of “pipes” for: Conducting water and minerals from the roots up the plant (xylem) • - in center of stem, water conduction and strengthening rod - Tracheids: long xylem cells, full of holes called pits, empty and dead at maturity, water moves freely between tracheas in continuous ﬂow. • evolved ﬁrst before ﬂowering plan vessels. • very thick-walled and strengthened by lignin - lignin: complex polymer • Conducting sugars from the leaves to the lower part of the plant (phloem) • Major clade of Land Plant • Sieve Cell (in early-diverging vascular plants, ferns) - in ﬂowering plants, evolved into sieve tube elements, with companion cells. • Phloem: layer around the xylem - phloem is mostly sucrose in solution - ﬂow rate can be very high - different sieve tubes conduct in different directions - movement of phloem sap requires living cells • Sieve cells are just long phloem cells, living at maturity, that have perforated ends in the cell wall. - sieve cells have no organelles and depend upon companion cells for metabolism - Solutes are Transported in the Phloem by Pressure Flow • sucrose is actively (uses energy) transported into companion cells then it enters sieve tubes (low to high) from source cell (leaf) • water moves into the sieve tube from the xylem through osmosis (no energy) raises pressure in tube • high pressure differences drives the phloem sap along the sieve tube to sink cell (fruit) • sucrose is unloaded into sink cells • water moves back to xylem by osmosis (no energy) - Ancient Forest • earliest fossil of vascular plants date to early devonian period -400mya • major diversiﬁcation does not happen until Carboniferous, between 360 and 300 mya (high O2) • Once lineages with vascular tissue diversify, forests became possible. • vascular tissue enables plants to get large - solves problem of hydrating leaves and feeding roots “Coal Forests” of large trees • Original deposition of many of the major coal deposits in the Carboniferous • • Climate change connection • Fern, Horsetails, and lycophytes have a long fossil record, dom in carboniferous (300-350mya) - Lycophytes: club mosses (1200 species) • independent sporophyte and gametophyte generations - true dichotomous branching roots - have leaﬂike structures (microphylls), arranged spiral on the stem - Dichotomous branching - Sporangia (spore forming structures) in many species in club-like clusters called strobili. - not true leaves, evolved microphylls: small leaves with a single midvein some lycophyte spores are extremely ﬂammable!!! in air - • Most vascular plants are heterophorous: • a megaspore develops into a female gametophyte (megagametophyte) that produces only eggs • microspores develop into a male gametophytes (microgametophytes) that produce only sperm - Homospory • found in bryophytes, some lycophytes, most ferns - Heterospory • found in some lycophytes, some ferns, and seed plants Lecture 7 - 9-12-16 - Functions of Stomata • Open: - CO2 free to enter - O2 free to leave - water evaporates and leaves the leaf tissue • Closed - CO2 can be depleted by PS - O2 can accumulate, inhibiting photosynthesis - H2O is trapped within leaf • How it works: open when the guard cells are turgid (full), and close when they become ﬂaccid (empty) - Wilted plans have lost too much water making the cells “ﬂoppy”. The cells have lost turgor pressure. - When each cell is ﬁrm the cells have regained turgor pressure and are turgid. • A proton pump responds to light to change the osmotic potential of guard cells so they swell and open in the light. • Stomata are the key to water transport via the xylem - During day, stomata open to allow CO2, to enter. - At night, stomata close to conserve water (may also close in daytime in water loss is too great). - Tall trees need to water their leaves! how is it possible for a tree to raise -100gal/day on average to great height? • • 1 ton of water every 2 days. - Cohesion: Bonds between like substances i.e. hydrogen bonding in liquid water. “surface tension” - Adhesion: Bonds between unlike materials, i.e. hydrogen bonding between liquid water and glass tube (or cellulose ﬁber!) - Capillary Action: • Adhesion: attraction between water and glass, ﬁber, ect. causes a meniscus to form raising the edge of the water surface. • Cohesion: all water molecules in column and on surface cling to each other. - Pulls liquid along surface, and liquid in tube follows. - Effective to raise water a few inches or so in xylem cells, but stronger in cells walls. - The whole process is controlled by evaporation (plant does not need to “pump” or expend ATP. - Apical Meristem: the point where plants grow in shoot and root - Wood • secondary xylem • produced by secondary growth • different from primary growth i.e. elongation of the growing tip of a plant by the apical meristem • secondary growth increases the diameter of a plant • Wood and bark growth - Vascular cambium produces secondary xylem (wood) and secondary phloem (inner bark) - Cork cambium produces waxy-walled protective cells; some become the outer bark Lecture 8 - 9/14/16 - Gymnosperms: seed plants that do not form ﬂowers or fruits • Ovules and seeds are not protected by ovary or fruit tissue. (some species have “berries”, which are modiﬁed cones) • Have only tracheas as the water-conducting and support cells with the xylem. • Four Groups: - Cycads: tropical, earliest diverging clade. • -300 species • Palm-like appearance, few branches, soft wood • Usually tropical/subtropical • Dioecious (seperate male and female plants), females with special seed- bearing leaves, or both sexes with strobili • Sperm with ﬂagella • Nostoc in roots (Nitrogen-ﬁxation) - Ginkgos: common in Mesozoic, today only one species: Ginkgo biloba Fossil record >200 mya • 1extant species, Gingko biloba • • Motile sperm (like cycads) • Fan-shaped leaves • Dioecious (seperate male and female ind) and deciduous • Cultivated in China for centuries • Plants may live >1000 years • Females smell like vomit so in most places they plant the males - Gnetophytes: some characteristics similar to angiosperms; Ephedra, Welwitschia • Welwitschia: probably oldest plant on earth! has only 2 leaves that grow continuously - Conifers: cone-bearing plants, common, but dominate forests at high latitudes and high altitudes. -700 species • • Cones: contain the reproductive structure - Megastrobilus: female cone, seeds protected by woody scales (familiar woody cone) - Microstrobilus: male pollen-bearing cone (usually herbaceous, not woody) • No motile gametes • well-branches trees with simple leaves (usually needle like or scale-like • Resins (protective chemicals) • Wind pollinates, and seeds dispersed by wind, birds, mammals • Female and Male Cones: - Megastrobili: female (seed-bearing) • woody scales are modiﬁcations of branches. • For each scale there is 2 helicopter like seeds in pines - Microstrobili: male (pollen-bearing) • Contains microsporangium which contain microspores • Microgametophyte = pollen grain - pollen mother cell (2n) > meiosis 1 > meiosis 2 = tetrad of 4 (n) pollen cells > secretion of walls = separate pollen grains - Florida • has always had large expanses of pine - dominated plant communities • “longleaf pine” Pinus palustris Longleaf pine communities have the highest local plant species diversity in North • America. Up to 52 species. - Flowering Plants - Angiosperm • Angiosperms: reproductive organs in ﬂowers; seeds enclosed in fruits. • Synapomorphies of the Angiosperms - Vessels in xylem • Vessels and tracheids occur in ﬂowering plants. - Net venation in leaves - Flowers - Fruits - Ovules and seeds enclosed in a carpel - Germination of pollen on a stigma - Double fertilization - Nutritive tissue called the endosperm • Angiosperm Reproduction - Flowers: modiﬁes stems, with ﬂower parts being modiﬁed leaves. • Petals (inner leaves in ﬂower, collectively called the corolla) and sepals (outer leaves in ﬂower, collectively called the calyx) can be important in attracting pollinators. • Inﬂorescence: a group of ﬂowers • All ﬂower parts are modiﬁed leaves. • Ovules and seeds are enclosed in a modiﬁes leaf called a carpel • The pistil is one or more fused carpels containing the ovaries (organs that make the eggs) • Carpels: have evolved from leaves with sporangia on the margins. fused and became more buried in receptacle tissue. • Stamens bear the male microsporangia. (anthers) • Pollen lands on stigma and grows through a style to the ovary Lecture 9 - 9/16/16 - Angiosperm Reproduction • Perfect: (hermaphroditic) ﬂowers have both megasporangia and microsporangia in same ﬂower. • Imperfect: (unisex) 2 ﬂower types male and or female on each plant Monoecious: male and female ﬂowers occur on the same plant. • • Dioecious: male and female ﬂowers produced on different plants. - Development of Seed Plant Gametophytes • Heterospory- 2 kinds of sporangia produce 2 kinds of spores which lead to 2 kinds of gametophytes. - Female gametophyte: • Megasporangium - megaspores - Megagametophyte (ovule) - Archegonia = Egg - Male gametophyte: • Microsporangium - Microspores - Microgametophyte (pollen grain) - Antheridia = sperm - in the microsporangium diploid cells called microspore mother cells undergo meiosis to make microspores. - Microspores grow to 2-3 cell microgametophyte, aka pollen grain - Pollination • Self-incompatibility: pollen from the same individual is prevented from fertilizing the ovule - Seeds and woody secondary growth are synapomorphies of the seed plants. - Development of gymnosperm megagametophytes • The megasporangium is surrounded by an integument, a protective layer of sporophyte tissue. • A diploid cell, the “megaspore mother cell” undergoes meiosis to make 4 megaspores. 3 disintegrate • The remaining spore develops into the megagametophyte (ovule), which then makes the archegonium and the egg. - After Pollination • Gymnosperm seed - Seed coat (derived from the integument) - Diploid parental tissue. - Megagametophyte provides nutrients (starchy). Haploid - Embryo (embryonic sporophyte) Diploid - Angiosperm Megagametophyte development • 4 haploid megaspores formed by meiosis; 3 disintegrate • Remaining megaspore undergoes 3 rounds of mitosis without cytokinesis = 1 cell with 8 nuclei • Cell walls form to make a 7 celled megagametophyte with 8 nuclei • One cell is the egg cell; large central cell contains 2 polar nuclei. Angiosperm ovules have 2 integuments • • Double Fertilization - 2 sperm cells arrive in one pollen grain: • One sperm combines with egg to form diploid zygote. • The other sperm combines with the 2 polar nuclei of the megagametophyte to form a triploid cell. • Triploid cell develops into the endosperm, which nourishes the embryo during its early development. • Seed Maturation - Zygote (2n) develops into an embryo with one or 2 cotyledons (seed leaves). • Cotyledons can absorb and digest the endosperm (3n) or enlarge and become photosynthetic when the seed germinates.
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