BIO 201 (LECTURE) Organismic Biology - Angiosperms, Bryophytes, Evolution of Vascular Plants, Gymnosperms, and Seed Evolution
BIO 201 (LECTURE) Organismic Biology - Angiosperms, Bryophytes, Evolution of Vascular Plants, Gymnosperms, and Seed Evolution BIO201
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This 185 page Bundle was uploaded by Ericah Notetaker on Thursday March 31, 2016. The Bundle belongs to BIO201 at Kansas State University taught by Dr. Bruce A. Synder in Fall 2015. Since its upload, it has received 45 views. For similar materials see Organismic Biology in Biology at Kansas State University.
Reviews for BIO 201 (LECTURE) Organismic Biology - Angiosperms, Bryophytes, Evolution of Vascular Plants, Gymnosperms, and Seed Evolution
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Straws! The evolution of the plant vasculature: Ferns BidlackChapter 21 Objectives • Symbiosis – Mycorrhizalfungi • What do xylem and phloem do? – Which are alive and/or dead? • Which species to pseudo -vasculature appear in ? • Which species do the true vasculature (xylem and phloem) appear in? • Does xylem transport water or salt/nutrients better? • Seedless vascular pants (Ferns and allies) – Life cycles of 4 key phyla – Compare life cycles to Bryophytes and to Gymnosperms and Angiosperms (upcoming lectures) – Air dispersal of Equisetum spores – Homosporous and heterosporuslife cycle species in the ferns compared to those in other phyla – Fern vs. Fern ally life cycle simila nd differences. A quick aside: More symbiosis in biology • Mycorrhizalfungi • Fungi in symbiosis with plant rhizoids or roots • Many (>90%) plants have some sort of a fungal symbiont • Like a second set of roots for plants • Plant donates sugar, fungi donate minerals Traversing into E bryophyta Simple character evolution in plants Flowers Seed production Vascular tissue Movement onto land Algae Vascular and seed plants • Bryophytes - the non-vascular plants • Vascular plants – Seedless vascular plants (today) • Ferns • Club mosses • Horsetails • Whiskferns – Seed plants (in due time) • Gymnosperms (non -flowering seed plants) • Angiosperms (flowering seed plants) Vascular tissues have two functions • 1) Conduct commodities – Conduct water • Capillary forces • Cohesion and evapotranspirational suction/tension (negative pressure) – Conduct photosynthates • Cytoplasmic transport in sieve cells Vascular tissues have two functions • 2) Support body – Evolution of a lignified support str-e ur stronger than cellulosic structures • These characteristics are essential for the diversification in the terrestrial environment. Why? Moving stuff within plants Xylem - two types 1) Tracheids- primitive Ferns Gymnosperms (Conifers) Vessels Populussp. Tracheids inussp. 2) Vessel elements-advanced Flowering plants Xylem • Tracheidsand vessel elements are elongated cells with thick secondary walls • Dead at maturity- basically just tubes. Or, are they? • Tracheids ; water flows through pits • Vessel elements; water flows through sieve plates. • Compare flow rates - evolutionary advantage for flowering plants? – More info in Stern and in future lectures Vessel element function Although the cells are deadat maturity they function chemically. Xylem fluidK Clconcentration rapidly and reversibly alters vessel conductivity. Are vessel elements inert pipes or physiologically active KCl-regulated hydrogels? Much like stomata… Keep this in mind for later... Phloem - again, two types Sieve cells and sieve tube members: long, tapered, continuous tubes with overlapping ends Sieve tube members Companion cell which regulates carbohydrate flow Sclerenchyma for support Phloem • Both sieve cells and sieve tube members alive at maturity but lack nuclei and vacuoles • Cytoplasmic transport through continuous cytoplasm of adjacent cells - active transport Evolution of vascular tissue • Seedless vascular plants have what many bryophytes don’t – True conducting tissues (not jusltptoids, hydroids) – True functional stomata (no -functional in mosses, hornworts) – Cuticle (in some mosses and liverworts) – Lignin biosynthesis- lignin strengthened the secondary cell walls Within seedless vascular plants Carnivorous Droserahas trichomes • Emergence of roots, bryophytes had rhizomes • Megaphyllous leaves (branched system of veins) - compare with microphyll (single unbranched vein) • Trichomes (epidermal extensions - cotton seed, Drosera, Pinguicula ) Four phyla 1) Phylum Psilophyta- whisk ferns 2) Phylum Lycophyta- club mosses 3) Phylum Equisetopyta - horsetails Psilotum- a 4) Phylum Polypodiophyta - ferns whiskfern Equisetum - a horsetail clubmossu- a Pteridium-a fern Generalized life cycle Fig. 21.17 in stern -fern as an example Phylum Psilotophyta – The Whisk Ferns • Greek psilos = naked – No organs so naked ferns • Structure and form: – Sporophytes: • Dichotomously forking stems – Above ground stems arise from rhizomes beneath surface of ground. • Have neither leaves nor roots • Enations along stems. – Enations - Tiny, green, superficially leaflike, flaps of tissuesynthetic • Roots, aided by mycorrhizal fungi, scattered along rhizomes. 1) Phylum Psilophyta - whisk ferns • No roots (rhizoids), no Psilotumsp. leaves (enations and photosynthetic stems), dichotomous branching Enations and sporangia. 1) Phylum Psilophyta - whisk ferns • Many characteristics fern -like (shoots can be interpreted as fronds (well-divided leaf) Psilotum • DNA data supports fern - similarit-chromosomal rearrangement in the chloroplast genome Phylum Psilotophyta – The Whisk Ferns 2) Phylum Lycophyta - club mosses • AKA, Ground pines • Sporophyte tissues differentiated to leaves (microphyll), stems, and roots • Usually sporophylls (spore- bearing, nonphotosynthetic leaves) packed into a strobilus – cone • Evolution of true root hairs along rhizomes 2) Phylum Lycophyta - club mosses • Sporophylls (non- photosynthetic) usually packed into a strobilus that produces the spores on the 2n sporophyte • Heterosporyemerges within the Lycophyta– Club mosses - like horsetails - produce their sporeslike on- • Compare Lycopodiumand strobili Selaginella 2) Phylum Lycophyta - spike mosses • Heterosporous(Selaginella) and homosporous (Lycopodium ) species • Selaginella produces heteromorphic micro- and megaspores - compare seed plants (the spores develop into pollen and embryo sac - micro- and megagametophytes ) • Highly branched sporophytes • Appear “leafy” compared to club mosses Phylum Lycophyta: Lycopodium Reproduction Homosporous in red Phylum Lycophyta: Selaginellareproduction: Heterosporous in red 3) Phylum Equisetophyta - horsetails • Equisetumonly living genus • No true leaves (microphyll); stem is the photosynthetic organ • Sporangia on terminal strobili. Form either on the vegetative or separate, non-green, fertile shoots Microphyll -leaves with unbranched veins Megaphyll -true leaves with branching veins Equisetum palustre 3) Phylum Equisetophyta • Equisetum reproduction: – Asexual by fragmentation of rhizomes – Sexual reproduction: • Strobili at tips of stems with sporangia connected to sporangiophores. • Spores green with 4 ribbon- like elaters attached. – Aid in spore dispersal • Gametophytes lobed, green, cushionlike, up to 8 mm in diameter. Spores with Phylum Equisetophyta • Stem anatomy: – Hollow central cavity from break down of pith – Two cylinders of smaller canals outside pith. – Carinal canals conduct water with xylem and phloem to outside. – Vallecular canals outside carinal canals contain air. v Silica deposits on walls of stem epidermal cells. 3) Phylum Equisetophyta: Equisetum reproduction: 4) Phylum Polypodiophyta – The • Structure and form: Ferns – Vary in size from tiny floating forms less than 1 cm to giant tropical tree ferns up to 25 m tall • Fern leaves are megaphylls - Referred to as fronds. – Typically divided into smaller segments • Require external water for reproduction 4) Phylum Polypodiophyta- ferns • Fern leaves usually fertile; but form no strobili. • Instead, on lower leaf surfaces have clusters of sporangia called sori (read more about the ingenious catapulting of spores; p. 402 and Fig. 21.20) Aspleniumsori on the underside of Phylum Polypodiophyta– The Ferns Emergence of Flowers– Angiosperms Origin of flowers • Let’s look at the character evolution in the seed plants Bisporangiate strobili? Double fertilization? Loss of flagellated sperm Seed? Origin of angiosperms • Timing: late Cretaceous (c. 125mya), or… Location: Most likely in the cool, dry uplands. • Emergence of angiosperms is thought to precede or coincide with mass extinction of the dinosaurs and vast numbers of gymnosperms, including the cycadeoids What lead to the dominance of angiosperms? • Dinosaurs in the Mesozoic era (2-66mya, includes Triassic, Jurassic and Cretaceous periods) - contemporary to then dominating gymnosperms and early angiosperms • Disappearance of dinosaurs and a vast diversity of gymnosperms coincide at the end of Cretaceous period (c. 125 mya). Dinosaur Mass Extinction Dinosaurs Permian-Triassic Extinction Olson’s Extinction Fern Allies Ferns and Seed Plants What lead to the dominance of angiosperms? • Two possible explanations – Dinosaurs • The large herbivores in Jurassic mysteriously were replaced by resulted in difficulty of completing gymnosperm life cycle; faster reproducing angiosperms replaced gymnosperms – Insect pollination • Greater accuracy in pollen delivery, greater energy conservation A quick aside: Cycadeoids • Cycadeoids are an extinct group of seed plants • Became extinct at the end of the Cretaceous (about the same time as dinosaur extinction) Fossil Cycad cone with • Have protected reproduction –bisporangiate surrounding leaves • Almost flower-like Origin of angiosperms • Closer look at the cladogram with extinct and extant taxa – Most gymnosperms had male-and female sporangia in different cones – Cycadeoids (extinct) bisporangiate – Welwitschia had an abortive ovule in the microsporangialcones (bisporangiate ?) and double fertilization – Angiosperms have male and female structures in one flower and + the double fertilization Origin of angiosperms • Two conflicting hypotheses: shared Gnetophyte ancestry or shared Cycadeoid and Gnetophyte ancestry • Former includes extant taxa, latter may have extinct ones • Angiosperm ancestry not well-resolved Koonwarra angiosperm 120mya Origin of angiosperms • Let’s take a look at the competing hypotheses – The former assumes that the last divergence gave rise to angiosperms and gnetophytes Caytonia 200mya – The alternative hypothesis suggests that angiosperm divergence preceded cycadeoid-gnetophyte lineage – Timing becomes more interesting... Cladogram of seed plants • Angiosperms preceding cycadeoids, would also explain what Charles Darwin considered as an abominable mystery: the sudden and extremely abundant appearance of angiosperms • Bottom line - Angiosperm ancestors may have been around already 200mya, not 100 mya Origin of angiosperms • What was the common ancestor like? • 125 my old fossils have minuscule flowers – Bisporangiateand double fertilized • Archaefructus liaoningensis – of flowering plants!earliest known genera Origin of angiosperms – Red parts are microsporangia- bearing, yellowish brown megasporangia-bearing Origin of angiosperms • The recent molecular evidence within angiosperms may cast a different light on the ancestry issues • Ceratophyllumpossibly resembles the earliest flowering plants – Aquatic plant; the dogma stated that angiosperms emerged in cool, drier upland environments Origin of angiosperms • If Ceratophyllumresembles the most simple, i.e., ancestral type of angiosperms, then the ancestral flower may have been: – Monoecious – Simple and single-chambered carpel – The bisporangiate strobilus of the cycadeoids from a monoeciou“ sseed- fern” origin THIS WILL NOT BE ON TEST 2 Embryogenesis Flowers to fruits and seeds BidlackChapter 8 Today ’s Objectives: embryogenesis • Quick review of angiosperm fertilization with a bit more detail – Details of the embryo sac and fertilization event • Finally, the development of the young sporophyte and the differences between di - and monocotyledons. Introduction • Annual plants- Cycle completed in single season. – Cycle = from seed germination to mature plant producing seeds • Biennial plants- Cycle completed in two growing seasons. • Perennial plants- Cycle takes several to many growing seasons or plant produces flowers on new growth, while other plant parts persist indefinitely. Differences Between Dicots and Monocots v Two major classes of flowering plants: • Magnoliopsida(dicots) and Liliopsida (monocots) Dicots Monocots Two cotyledons One cotyledon Flower parts in multiples of four or five Flower parts in multiples of three Leaves with distinct network of veins Leaves with parallel primary veins Vascular cambium and cork Vascular cambium and cork cambium cambium present absent Vascular bundles of stem in ring Vascular bundles of stem scattered Pollen grains with three aperturesPollen grains with one aperture Embryo development Sequence of events: After fertilization, the zygote lies underneath the endosperm. The endosperm (3n) divides to produce mass of endosperm tissue surrounding the embryo. Zygote divides to form two distinct parts - embryo and its suspensor. Embryo development Sequence of events: Suspensor anchors the embryo and transfers nutrients. Embryo will differentiate to cotyledons, epicotyl, hypocotyl and radicle; it will also have the necessary apical meristems Embryo development Sequence of events: The endosperm is food for the developing embryo and cotyledons in dicots. The cotyledons are the source of nutrition for the seedling. In monocots cotyledon rarely stores food - it transfers food from the endosperm to the embryo. At the end, a mature seed with an embryo inside. Fruits • Fruit - Matured ovary and its accessory parts – Contains seeds – All fruits develop from flower ovaries and accordingly are found exclusively in flowering plants. Tomato fruit Fruits vFruit Regions – Exocarp - Skin – Endocarp - Inner boundary around seed(s) – Mesocarp - Tissue between exocarp and endocarp Peach fruit – Three regions collectively called pericarp. Fruits • Variability of fruits – Can consist of only ovary and seeds – Can include adjacent flower parts – May be fleshy or dry at maturity – May split or not split – May be derived from a one or more ovaries Fruits vFleshy Fruits - Mesocarp at least partly fleshy at maturity. vSimple fleshy fruits develop from flower with single pistil. • Drupe - Simple fleshy fruit with single seed enclosed by hard, stony endocarp (pit) Drupes: peaches, almonds, olives Fruits • Simple fleshy fruits – Berry • From compound ovary, with more than one seed, and with fleshy pericarp • True berry - With thin skin and relatively soft pericarp – Tomatoes, grapes, peppers, blueberries, bananas • Pepo - Relatively thick rind – Pumpkins, cucumbers Grape berries Fruits • Berry – Hesperidium - Leathery skin containing oils o Citrus • Pome - Flesh comes from enlarged floral tube or receptacle that grows up around ovary. – Endocarp papery or leathery – Apples, pears - Core and a little of adjacent tissue is from ovary; remainder is fromfloral tube and Apple pomes receptacle Fruits • Dry Fruits - Mesocarp dry at maturity – Dehisicent or indehiscent • Dehiscent fruits - Split at Maturity • Follicle - Splits along one side – peonypur, milkweed, • Legume - Splits along two sides – Legume family: peas, beans, lentils, peanuts Milkweed follicle Fruits • Dehiscent fruits – Siliques and silicles - Split along two sides, but seeds on central partition, which is exposedwhen two halves separate. – Silique - More than three times longer than wide – Silicle - Less than three times longer than wide – Mustard family: broccoli, cabbage Silicle Silique Fruits • Dehiscent fruits – Capsules - Consist of at least two carpels, and split in a variety of ways • Irises, poppies, violets, snapdragons Capsules Fruits • Dry Fruits • Indehiscent Fruits - Do Not Split at Maturity • Single seed united with pericarp – Achene - Base of seed attached to pericarp. o Sunflower seed, buttercup, buckwheat Inside of sunflower – Nut - Similar to achene, but larger, achene with harder and thicker pericarp, and a cluster of bracts at base o Acorns, hazelnuts, hickory nuts Acorn Fruits • Indehiscent Fruits – Grain (Caryopsis) - Pericarp tightly united with seed • Grasses: corn, wheat, rice, oats, barley • Samara - Pericarp extends Corn section as wings for dispersal. – Maples, ashes, elms • Schizocarp - Twin fruit that breaks into one-seeded segments called Samaras mericarps Schizocarp of mericarps – Parsley family: carrots, anise, dill Fruits • Aggregate Fruits – Derived from single flower with several to many pistils • Individual pistils mature as clusteredunit on singlereceptacle. o Raspberries, blackberries, Blackberry aggregate fruits strawberries v Multiple Fruits • Derived from several to many individual flowers in single inflorescence – Mulberries, Osage orange, pineapples,figs Osage orange multiple fruit Fruit and Seed Dispersal • Dispersal by Wind – Fruits: Samaras, plumes or hairs on fruit – Seeds: Small and lightweight, or with wings Fruit and Seed Dispersal • Dispersal by Animals – Seeds pass through digestive tract. – Fruits and seeds adhere to fur or feathers. – Oils attract ants. • Elaiosomes on bleeding SeeElaiosome is white.arts. hearts used as food by ants. v Water Dispersal • Some fruits contain trapped air for floatation. Seeds • Structure – Ovules develop into seeds. • Cotyledons - Food storage organs that function as “seed leaves” • Embryo = cotyledons and plantlet • Plumule - Embryo shoot – Epicotyl -Stem above cotyledon attachment – Hypocotyl - Stem below cotyledon attachment – Radicle - Tip of embryo that develops into root Bean seed Seeds v Epigeous germination – Hypocotyl lengthens, bends and becomes hook-shaped. – Top of hook emerges from ground, pulling cotyledons above ground. Epigeous germination v Hypogeous germination • Hypocotyl remains short and cotyledons do not emerge above surface. Germination Prerequisites: To break dormancy, stimuli needed. Water-imbibition through the seed coat and, voilá(!), the seed coat bursts open. Alternatively, water may rinse the inhibitory substances off the seed surface (desert plants) Temperature - optimal or need for stratification Light -may inhibit or stimulate germination Scarification - chemical or physical breaking or weakening of the seed coat. Germination Sequence of events: Radicle emerges from the seed first. This first root will acquire the water/nutrients. Depending on which part grows fastest, cotyledons may emerge with the extending hypocotyl or remain in soil. Germination Sequence of events: Although the cotyledons may be green, they usually lack stomata and are nonphotosynthetic, i.e., they are merely a source of stored energy. In grasses, coleoptile and coleorhiza protect the emerging leaves and radicle. Longevity • Seed viability varies, depending on species and storage conditions. – Viability extended: • At low temperatures • When kept dry • Vivipary - No period of dormancy; embryo continues to grow while fruit is still on parent. Vivipary in red mangrove Dormancy William Beal buried seeds of common plants in cheap Usual after fertilization and early one-pint glass bottles. He harvested the seed at 5 yr embryo development, the embryo intervals. Now the interval is ceases to grow. 20 yr. Experiment continues until 2100. How long can seed stay dormant? William Beal at the U Michigan started an experiment 1879. Seeds are still viable; tested spring of 2001. Test plant V:e rbascum blattaria- moth mullein Test plant M: lva neglecta - mallow weed Conquering Land: Bryophytes BidlackChapter 20 Objectives • Finish algae • Bryophytes – What is needed to colonize land – Life cycles of key Bryophtesand alternation of generations – DistinguisingChloroplylls – Shared and diverging features between algae and Bryophtes ? Stramenopila Alveolata Chlorophyta Phylum Stramenopila/Heterokonta • Brown algae (Phaeophyceae) – Relatively large; none unicellular or colonial – Most marine; majority in cold, shallow water – Many have a thallus differentiated into a holdfast, a stipe, and blades. • Blades may have gas-filled bladders. – Chlorophylls a and c, fucoxanthin – Food reserve = laminarin – Algin in cell walls. Nereocystis, a kelp Phylum Stramenopila/Heterokonta v Brown algae (Phaeophyceae) • Fucus - Common rockweed • Sexual reproduction: – Receptacles at tips of branches contain spherical chambers called conceptacles with gametangia inside. » Oogonium produces 8 eggs. » Antheridium produces 64 sperm. – Eggs and sperm released into water. Traversing into E bryophyta Simple character evolution in plants Flowers Seed production Vascular tissue Movement onto land Algae Bryophytes are A. Evolutionary progenitors of plants B. Evolved due to secondary endosymbiosis C. Evolved many convergent characters to plants D. Evolutionary progenitors of algae E. The first group with true vascular tissue Bryophytes are A. Evolutionary progenitors of plants B. Evolved due to secondary endosymbiosis C. Evolved many convergent characters to plants D. Evolutionary progenitors of algae E. The first group with true vascular tissue Colonizing Land – Required Traits What are the biological mechanisms? • Resist drying out • Source of nutrition? • Resist intensity sunligh ->t cannot swim deeper when sunlight is too bright • Plants can no longer soak up ydrophillic HCO 3r hydrophobic CO 2 – require specialized mechanisms to bring 2O in for photosynthesis • Survive even higher concentrations of oxygen than in the upper layers of the ocean or ponds Bryophytes • Non-vascular plants • Can be though of as algae that colonized land • Flagellated sperm • Chlorophylls a andb • Starch as storage • Cellulose-rich cell walls • No lignin – Compare these characters to algae! A few general characteristics • No or very primitive vascular tissue – Hydroids and leptoids... – Water + nutrients absorbed through the plant body – No true leaves or roots • No Roots; but rhizoids – Not real conducting tissue – Anchor the plant – Where have we seen rhizoids previously? Generalized, simplified life cycle • Asexual reproduction by gametophyte fragmentation • Gametophyte is the dominant generation – Gametophyte nutritionally independent – Sporophyte (usually) non-photosynthetic, parasitic (?) on the gametophyte • In algae, sporophyte and gametophyte both free-living and often isomorphic • Hornworts exception Introduction • Plants and green algae share the following: – Chlorophylls a and b, carotenoids – Starch as food reserve – Cellulose in cell walls – Phragmoplast and cell plate during cell division • Shared features suggest common ancestor. • Land plants first appeared 400 million years ago. • Ancestor progressed from aquatic to land habitat even earlier. Introduction • By the time plants became establishedon land, they had several features to prevent them from drying: – Plant surfaces developed fatty cuticle to retard water loss. – Gametangia (gamete-producing structures) and sporangia (spore-producing structures) became multicellular and surrounded by jacket of sterile cells. • From the Bryophytes into higher plants, all species have a clear alternation of Generations life cycle – Zygotes developed into multicellular embryos within parental tissues that originally surrounded egg. Introduction to the Bryophytes • Exhibit alternation of generations – In mosses, leafy plant is major part of gametophyte generation. • Gametophyte produces gametes. – Sporophyte generation grows from gametophyte. • Sporophyte produces spores. • Three distinct bryophyte phyla – None appear closely related to other living plants. • Bryophyte lines may have arisen independently from ancestral green algae. – Bryophytes lines are almost certainly evolving now! Evolution never stops! Consider the mechanisms! Phylum Hepaticophyta – Liverworts – Marchantia • Upper surface is divided into diamond-shaped segments that mark the limits of chambers below. – Each segmenthas small bordered pore openinginto chamber. – Short, erect rows of cells with chloroplastssit on floor o. chambers – Why do these chambersexist? How does this specieto live on land? Which algae have dispensable somatic cellsMarchantia? Phylum Hepaticophyta – Liverworts • Thalloid liverworts – Marchantia - Asexual reproduction: • By means of gemmae (singular: gemma) – Gemmae - Tiny, le-shaped pieces of tissue that become detached from thallus – Produced in gemmae cups scattered over upper surface of thallus Phylum Hepaticophyta – Liverworts • Thalloid liverworts – Marchantia - Sexual reproduction: • Gametangia formed on gametophores. – Male gametophore = antheridiophore » Antheridia that contain sperm found on upper surface. » Sperms have numerous flagella. Phylum Hepaticophyta – Liverworts – Marchantia - Sexual reproduction: • Gametangia formed on gametophores. – Female gametophore =archegoniophore » Archegonia with eggs in rows and hang down beneath spokes of archegoniophore. Phylum Hepaticophyta – Liverworts – Marchantia - Sexual reproduction: • Embryo dependent on gametophyte for sustenance. – Foot of sporophyte anchors to archegoniophore. – Seta - Short stalk – Capsule - Meiosis produces haploid spores inside. » Other cells inside capsule do not undergo meiosis and develop into elaters with spiral thickenings. « Elater = plant cell sensitive to humidity disperses spores o Immature sporophyte protected by calyptra = caplike tissue that grows out from gametophyte. o Capsule splits at maturity to release spores. Green = 2n Brown = 1n Phylum Bryophyta – Mosses • Structure, form and classes: – Leaves of moss gametophytes have blades nearly always one-cell thick, except at midrib, and never lobed or divided. • Cells usually contain numerous chloroplasts. • Peat moss leaves have large transparent cells without chloroplasts that absorb water; and small, green, photosynthetic cells sandwiched between. • Axis stemlike, without xylem or phloem. – Often with central strand of hydroids Phylum Bryophyta – Mosses • Asexualreproduction – not all mosses – Some mosses do not undergo true “alternation of Generations” • Sexual reproduction: – Gametangia at apices of leafy shoots. • Archegonium cylindricalwith eggin swollenbase,and narrow canal.aining – Multicellular filaments = paraphyses scattered among archegonia. Phylum Bryophyta – Mosses • Sexual reproduction: – Antheridia on short stalks, surrounded by walls one cell thick. • Sperm cells, each with pair of flagella, formed inside. • Sperm forced out top of antheridium. • Paraphyses scattered among antheridia. Green = 2n Brown = 1n Themes shared between Liverworts and Algae Ulthorix – asexual fragmentation/dispersal Volvox Flagellated gametes, Somatic 1n cells protect sexual/2n cells Oedogonium – protected fertilization Ulva - holdfasts Which of the following most accurately reflects Bryophytathemes shared with some Algae? A. They have common ancestry B. They represent parallel evolution C. They represent convergent evolution D. They were clearly designed to be similar Which of the following most accurately reflects Bryophytathemes shared with some Algae? A. They have common ancestry B. They represent parallel evolution C. They represent convergent evolution D. Both A and C Is is very likely that the common ancestor between algae and bryophytes shared some of these characters. Which have common ancestry and which are convergent evolution? Ferns and The skinny on Gymnosperms: Dipping into the biggest plant evolutionary advancement since the plastid BidlackChapter 22 Supplehttp://www.seedbiology.de/evolution.asp evolution) http://www.ucmp.berkeley.edu/seedplants/progymnosperms.html http://www.devoniantimes.org/who/pages/archaeopteris.html Phylum Lycophyta: Lycopodium Reproduction Homosporous in red Phylum Lycophyta: Selaginellareproduction: Heterosporous in red 3) Phylum Equisetophyta - horsetails • Equisetumonly living genus • No true leaves (microphyll); stem is the photosynthetic organ • Sporangia on terminal strobili. Form either on the vegetative or separate, non-green, fertile shoots Microphyll -leaves with unbranched veins Megaphyll -true leaves with branching veins Equisetum palustre 3) Phylum Equisetophyta • Equisetum reproduction: – Asexual by fragmentation of rhizomes – Sexual reproduction: • Strobili at tips of stems with sporangia connected to sporangiophores. • Spores green with 4 ribbon- like elaters attached. – Aid in spore dispersal • Gametophytes lobed, green, cushionlike, up to 8 mm in diameter. Spores with Phylum Equisetophyta • Stem anatomy: – Hollow central cavity from break down of pith – Two cylinders of smaller canals outside pith. – Carinal canals conduct water with xylem and phloem to outside. – Vallecular canals outside carinal canals contain air. v Silica deposits on walls of stem epidermal cells. 3) Phylum Equisetophyta: Equisetum reproduction: 4) Phylum Polypodiophyta – The • Structure and form: Ferns – Vary in size from tiny floating forms less than 1 cm to giant tropical tree ferns up to 25 m tall • Fern leaves are megaphylls - Referred to as fronds. – Typically divided into smaller segments • Require external water for reproduction 4) Phylum Polypodiophyta- ferns • Fern leaves usually fertile; but form no strobili. • Instead, on lower leaf surfaces have clusters of sporangia called sori (read more about the ingenious catapulting of spores; p. 402 and Fig. 21.20) Aspleniumsori on the underside of Phylum Polypodiophyta– The Ferns Objectives • Know the geological events surrounding the evolution of ferns and seeds in plants • Know what was so important about the evolution of gymnosperms • Know what a progymnosperm is and where you would find them – Hint, not in the forest! • Know examples of gymnospersmsand where you would find them and why – Hint, not all are in the forest! Archaeplastidia , this is your life! Why Gymnosperms are so important… The Chloroplast Seeds = = Unlimited cheetos! Storing cheetos for later! Seeds • The origin of seeds ranks up there with the colonization of land by plants and animals as a major evolutionary event. • The seed habit frees a plant to live in drier environments as the gametophyte no longer requires a moist environment to survive. • Seeds can also increase dispersal and be a “resting stage ” and delay growth until the best time . • Gymnosperms have – Reduced male and female gametophyte size (compare to ferns and/or bryophytes) – Better adaptation to terrestrial habitat; water not necessary for fertilization (compare to ferns and allies) – Seeds with their own food supply - nucellus (endosperm in Angiosperms) – An embryo (young diploid sporophyte) that is able to grow and develop prior to dispersal of seed The Four Major Steps in the Origin of Seeds • Heterospory • Retention of the female gametophyte on the sporophyte • Development of the seed coat or testa • Adaptations to deliver the male gametophyte to a receptive female gametophyte (pollination) Dinosaurs Permian-Triassic Extinction Olson’s Extinction Fern Allies Ferns and Seed Plants Devonian Adaptive radiation of life First vertebrates No herbivores yet Pangeaseparating into two supercontinents Devonian, generally wet and warm, no glaciers Carboniferous Lignocellulosic plants that became coal (contrast with crude oil that is algal/cyanobacterial in origin!) Amphibians and herbivores Started hot and humid By the late carboniferous the rainforest collapse lead to reptile evolution and increased herbivory Climate went to cold and dry Permian Dry Highly varied climate Rapidly cycled Plants needed to adapt – seeds were the answer! Cladogram of seed plants • By now, all clades have roots, true leaves (megaphyllous), and seeds • Gnetophytesshare the most recent ancestor with the angiosperms – Attempt of double fertilization (similar to that in Angiosperms?) – Gnetophytes also the only Gymnosperms with vessel elements, not just tracheids in their xylem. Loss of flagellum in sperm Vessel elements and double fertilization General features of the Gymnosperms • Heterosporous- all seed plants. Most seedless plants were homosporous (Selaginella is an exeption) – Hetero = different (googleit for some fun!) – Homo = same – Male and female sporangia, male and female spores, microspores and megaspores • Although a single plant individual may bear male and female sporangia, they are rarely in the same cones Fossil record of the evolution of seeds: Lygenopteris a seed fern Seed ferns were the first seed plants. They were trees with fern-like foliage and secondary wood. Glossopteris abov common hemisphere. in the southern Where do the first seed plants come from? • The first seed plants were trees with almost modern gymnosperm -like wood and fern - like leaves. • The closest thing to these early seed producers were Archaeopterisand its relatives. These were heterosporus trees. • Archaeopteris had modern secondary wood and was the first real tree. • Archaeopteris is a progymnosperm Archaeopteris: a progymnosperm and the first real tree in the forests of the Devonian Foliage showing webbed leaflets and fertile branches intermixed on the same axis. It was heterosporus. Woody stem is C allixylon. The wood is like early Gymnosperms. Archaeopteris It reproduced like a fern, but it grew like a modern woody plant. Some were homosporus and some were heterosporus and the latter were probably the ones that gave rise to the seed ferns. Fossil trunks a meter across have been found and some fossil logs are 30 meters long! Now that is a TREE! http://www.ucmp.berkeley.edu/seedplants/pr ogymnosperms.html A fun read : http://www.800oakwilt.com/mostancient.html The progymnosperm Archaeopterishad several modern developmental characters like the plants of the present. • Lateral buds and branches. • Bi-directional (bifacial) cambium (a feature found in all seed plants) that makes a ring of growing tissue that produces wood both in toward the center and out away from the center . • It was a true, long lived, perennial plant and dominated the forests world wide for 15 Million years. Generalized features of the Gymnosperm life cycle • Megasporocyte is retained within the megasporangium, enclosed in an integument • Megasporangium is called nucellus, encloses the megasporocyte and the egg(s) • Together, megasporangium and integuments form the ovule Meproducing the female gametophyteduces spores ovule = megasporangium+ integuments Micropyle= opening at one end Generalized features of the life cycle • Male/female (micro -and megagametophyte) gametophytes in separate male/female cones (strobili) • Micro-/megaspore mother cell (2n) goes through meiosis resulting in 4 micro- /megaspores (1n) • The 4 microspores develop into the microgametophytes Male and female strobili oPinuswith their respective (micro/megagametophytes) Generalized features of the life cycle • Cell walls form later around each nucleus: resulting megagametophyteis multicellular • After this, 2 or more archegonia develop in the micropylarend of the ovule • Each archegoniumcontains an egg, which may be fertilized + develop into an embryo Pinus archgonium in the megasporangium Generalized features of the life cycle • Microgametophyte sticks to the pollination droplet and is sucked into contact with the nucellus; directly to ovule, not to stigma (Angiosperms) • Pollen tube digests the nucellus tissue to reach the egg • Single sperm fertilizes each egg; diploid zygote • Zygote develops into a seed with seed coat (former integuments), embryo with apical meristems, cotyledons, and hypocotyl Generalized features of the life cycle • However, in the megasporangium , three of these nuclei are aborted; only one develops into the megagametophyte – Where have we seen this before? • This remaining functional megaspore undergoes mitotic divisions, which are not immediately followed by cytokinesis - free-nuclear gametophyte, i.e., multinucleate megagametophytethat is not divided into cells by cell walls. Life Cycle of a Pine All phyla of gymnosperms have similar life cycles and produce seeds that have exposed ovules. The sperm of all gymnosperms except the Pinophyta are flagellated and some require water to complete fertilization. It takes almost 2 years to produce a mature pine seed. Other gymnosperms are faster . Making a pine seed is a slow process. • Meiosis occurs in the male and female cones in late winter • Pollination occurs in May and the development of the female gametophyte is slow….9 months!! • Fertilization occurs in February and in pines and some other conifers that seed will be mature the for another year. Up to a year! Five months Nine months! Phyla of extant Gymnosperms • Four extant Phyla – 1) Phylum Cycadophyta • Mainly tropical cycads – 2) Phylum Ginkgophyta • Maidenhair tree - Ginkgo biloba – 3) Phylum Pinophyta • conifers – 4) Phylum Gnetophyta • Gnetophytes 1) Phylum Cycadophyta • Mainly tropical; two species in the US - Zamia spp. in Florida • flagella • Palm -like leaves • Stems subterranean and tuberous • Like Ginkgo - flagellated • Species ofZamia sperm 2) Ginkgo biloba - a Gymnosperm with a flagellated sperm • Ginko is one of the two basal, extant gymnosperms with flagellated sperm • Only one species, Ginkgo biloba. Even this is rare (absent?) in nature. Cycads and Ginkgos - only seed plants with flagellated sperm • biloba= two lobed leaf, also leaves without the notch • Deciduous (like larch), dioecious Ginkgo flagellated sperm Bilobed leaves Ginkgo biloba • Flagellated sperm; flagella not necessary for fertilization, nor does the sperm tube deliver the nuclei to the egg -the egg engulfs the sperm cell • Mature seed’s integument (seed coat) 3- layered – Fleshy outer laye stinks – Stony middle layer – Inner, thin layer • Why don’t the trees on campus on campus stink? 3) Phylum Pinophyta • Northern hemisphere genera include pines, firs, larches, spruces among other things • Sequoiadendron - big trees • Larix sp. -larch • Piceaspp -spruce• Pinusspp -pines 3) Phylum Pinophyta • The most successful Phylum of Gymnosperms? – Drought resistant • Small leav-minimize heating + evapotranspiration • Thick cuticles • Sunken stomata Sunken stomata • Veins in the center of the leaves Thick cuticle and central veins of Pinus Tiny leaves 4) Phylum • Double fertilization Gnetophyta • Three very odd genera – 1) Ephedra – 2) Gnetum – 3) Welwitschia • Welwitschia unique because of • Ephedra double fertilization: one sperm cell fertilizes the egg, another fuses with another • Gnetum megagametophyte cell which disintegrates • Welwitschia 4) Phylum Gnetophyta • Welwitschia – Central, concave woody stem – Basal meristem; leaves grow continuously from the base – Shares most recent ancestor with flowering plants • Double fertilization, though incomplete • Aborted ovule in the pollen cone, suggesting monoecious, potentially bisporangiate ancestor - many Angiosperms have male and female structures in same plants • Vessels- not tracheids -in xylem Welwitchia and its cones A possible phylogeny of seed plants Human Uses of Gymnosperms 1. LUMBER is the primary use of Gymnosperms. Eastern white pine stems were used as masts for sailing vessels and for crates, furniture, flooring, paneling and matchsticks. Western white pine and Douglas firs are the source of most lumber. 2. Resin from pines consists of turpentine and rosin. Turpentine is used as a solvent, and rosin is used by musicians and by baseball players. 3. White spruce is the chief source of newsprint. 4. Coastal redwoods are prized for their wood, which is resistant to fungi and insects. 5. Ginkgo seeds are edible, and Ginkgo plant extracts are used to improve blood circulation. Ephedra (Mormon tea, ma huang, or joint fir) produces Ephedrine a powerful stimulant. 6. Eastern white cedar ’s wood was used for canoes. Yew wood is used for making bows, and an extract (taxol) is used for the treatment of human ovarian cancer Gymnosperms Bidlack Chapter 22 Phyla of extant Gymnosperms • Four extant Phyla – 1) Phylum Cycadophyta • Mainly tropical cycads – 2) Phylum Ginkgophyta • Maidenhair tree - Ginkgo biloba – 3) Phylum Pinophyta • conifers – 4) Phylum Gnetophyta • Gnetophytes 1) Phylum Cycadophyta • Mainly tropical; two species in the US - Zamia spp. in Florida • Loss of • Palm-like leaves flagella • Stems subterranean and tuberous • Like Ginkgo - flagellated • Species ofZamia sperm 2) Ginkgo biloba - a Gymnosperm with a flagellated sperm • Ginko is one of the two basal, extant gymnosperms with flagellated sperm • Only one species, Ginkgo biloba. Even this is rare (absent?) in nature. Cycads and Ginkgos - only seed plants with flagellated sperm • biloba= two lobed leaf, also leaves without the notch • Deciduous (like larch), dioecious Ginkgo flagellated sperm Bilobed leaves Ginkgo biloba • Flagellated sperm; flagella not necessary for fertilization, nor does the sperm tube deliver the nuclei to the egg -the egg engulfs the sperm cell • Mature seed’s integument (seed coat) 3- layered – Fleshy outer layer stinks – Stony middle layer – Inner, thin layer • Why don’t the trees on campus on campus stink? 3) Phylum Pinophyta • Northern hemisphere genera include pines, firs, larches, spruces among other things • Sequoiadendron - big trees • Larix sp. -larch • Piceaspp -spruce • Pinusspp -pines 3) Phylum Pinophyta • The most successful Phylum of Gymnosperms? – Drought resistant • Small leav- minimize heating + evapotranspiration • Thick cuticles • Sunken stomata Sunken stomata • Veins in the center of the leaves Thick cuticle and central veins of Pinus Tiny leaves • Double fertilization 4) Phylum Gnetophyta • Three very odd genera – 1) Ephedra – 2) Gnetum – 3) Welwitschia • Welwitschia unique because of • Ephedra double fertilization: one sperm cell fertilizes the egg, another fuses with another • Gnetum megagametophyte cell which disintegrates • Welwitschia 4) Phylum Gnetophyta • Welwitschia – Central, concave woody stem – Basal meristem; leaves grow continuously from the base – Shares most recent ancestor with flowering plants • Double fertilization, though incomplete • Aborted ovule in the pollen cone, suggesting monoecious, potentially bisporangiate ancestor - many Angiosperms have male and female structures in same plants • Vessels - not tracheids - in xylem Welwitchia and its cones Evolution of flowers: Angiosperms 1 Bidlack Chapter 23 Objectives • Why angiosperms are so successful? • What is the angiosperm life cycle? – What happens to the female meiotic products? – What happens to the male meiotic products? – What is double fertilization? – Why does double fertilization contribute to the success of angiosperms Anza Borrego Desert Park – Most of the time Anza Borrego Desert Park after a rainy winter – 1-2 weeks only Angiosperms • Angiosperms = flowering plants • Seeds enclosed in carpel that resembles a leaf that has folded over and fused at the margins. – Pistil composed of a single carpel, or two or more united carpels. v Seed develops from ovule within carpel. v Ovary becomes a fruit. Bleeding hearts • Angiosperms in Phylum Magnoliophyta. • Has been divided into two large classes: – Magnoliopsida - Dicots • DNA and cladistic evidence suggest that two groups of dicots should be recognized, possibly more • Two cotyledons – Liliopsida – Monocots • Single cotyledon • Flower is modified stem bearing modified leaves. – Most primitive flower: • Long receptacle • Many spirally arranged flower parts that are separate and not differentiated into sepals and petals Phylum Magnoliophyta – The Flowering Plants • Heterosporous • Sporophytes dominant. • Female gametophytes wholly enclosed within sporophyte tissue and reduced to only a few cells. • At maturity, male gametophytesconsist of a germinated pollen grain with three nuclei. Structure of the flower Function of the components: Stamen: microspore producing organ •Anthers: fused, microspore-containing chambers •Filament: supports anthers Pistil: megaspor-producing organ •Stigma: area capturing the pollen •Style: elevates stigma to enhance pollination •Ovary: swollen base of the pistil, contains ovules •Ovule: More later Structure of the flower Function of the components: Petals (corolla): odor + color to attract the pollinators, shape to make sure that the pollen sticks Sepals (calyx): protect the inner flower parts prior to opening Receptacle: tip of the flower stalk upon which the other parts are attached Peduncle: the main axis of an inflorescence on which individual flowers arise - stem Function of the flower • Stamens deliver pollen • Stigma receives the pollen; holds on to it until the fertilization has taken place • Development of gametophytes - Female: – Diploid megasporocyte differentiates in ovule. • Undergoes meiosis and produces four haploid megaspores. Three degenerate. – Remaining cell enlarges and nucleus divides to produce 8 nuclei (without walls). – Outer two layers of ovule differentiate into integuments that later become seed coat. • Micropyle at one end of ovule • Development of gametophytes- Female: – 8 nuclei form two groups, 4 near each end of cell. – One nucleus from each group migrates to cell middle and form central cell. • Cell walls form around remaining six nuclei. – Egg and two synergids closest to micropyle – Three antipodals at opposite end - No apparent function • Female gametophyte (megagametophyte, embryo sac) = large sac containing 8 nuclei and 7 cells • Development of gametophytes- Male: – Formation of male gametophytes takes place in anthers. – Four patches, corresponding to pollen sacs, of microsporocyte cells differentiate in anther. • Each microsporocyte undergoes meiosis to produce quartet of haploid microspores. • Development of gametophytes - Male: – Microspores undergo three important changes: • Divide once by mitosis to form a small generative cell inside the larger tube cell Nucleus of tube cell = vegetative nucleus • Members of each quartet of microspores separate. – Wall becomes two-layered. o Outer layer = exine « Finely sculptured « Contains chemicals that may react with chemicals in stigma • Generative nucleus will later divide to produce two sperm. • Pollination: – Pollination - Transfer of pollen grains from anther to stigma • Self-pollination - Pollen grains germinate on stigma of same flower. – Fertilization - Union of sperm and egg – Pollination by insects, wind, water, animals or gravity. • Fertilization and developmentof the seed: – After pollination, further development of male gametophyte may not take place unless pollen grain is: • From a different plant of the same species. • From a variety different from that of the receiving flower. – Pollen tube grows between cells of stigma and style until it reaches ovule micropyle. – Vegetative nucleus stays at tips of pollen tube, while generative cell lags behind and divides into two sperm. – Pollen tube enters female gametophyte, destroying synergid in the process, and discharges sperms. • Fertilization and developmentof the seed: • Mature male gametophyte = germinated pollen grain with its vegetative nucleus and two sperms within tube cell • Male pollen is not mature until is produces a pollen tube • Fertilization and development of the seed: – Double fertilization: • One sperm unites with egg, forming zygote, then embryo. • Other sperm unites with central cell nuclei, producing triploid endosperm nucleus that develops into endosperm tissue. Endosperm tissue = nutritive tissue for embryo Endosperm becomes extensive part of seed in some monocots, such as corn and other grasses. » Wheat, rice and corn - Major source of nutrition for humans due to nutritional quality of endosperm Endosperm absorbed into cotyledons in most dicots. • Ovule becomes seed, ovary matures into fruit, integuments harden into seed coat. Pollination • Several different ways – Wind – Water – Insects – Mammals – Birds The importance of insect pollination • Less pollen needs to be dispersed compared to wind pollination - lesser energy consumption . • Several ways to specifically attract a particular type of animal (shapes, colors, odors). Pollination • Insects, mammals, and birds are usually attracted to the flower by flashy colors and/or tempting odor • The pollinators are either after nectar or pollen for food. • Do the insects eat pollen? • Gentiana sp. • Crocus vernus
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