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Plant Diversity I: How Plants Colonized Land. Kingdom - Plantae. nonvascular. vascular. (xylem/phloem). (water) . ( food). Nonvascular. Division - Bryophyta. mosses. liverworts. vascular. Seedless. Seed. horsetails. club mosses. ferns. seed. gymnosperm. angiosperm. (Naked). - PowerPoint PPT Presentation
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Plant Diversity I: How Plants Colonized Land
Kingdom - Plantae
nonvascular vascular(xylem/phloem)
(food)(water)
Nonvascular
Division - Bryophyta
mossesliverworts
vascular
Seedless Seed
horsetailsclub mossesferns
seed
gymnosperm angiosperm(Naked) (Covered)
GinkgoGnetophytaCycadsConifers
Angiosperm
Anthophyta
DicotsMonocots
anth - male
arch - female
epi - upon
phyte - plant
Plant Characteristics:
1. Structure:
specialized – cells and tissuesphotosynthetic – (autotrophic)multicellular – (many celled)
2. Pigments:
carotenoidschlorophyll bchlorophyll a
3. Storage polysaccharide (carbohydrate) – amylose starch
Structural polysaccharide (carbohydrate) – is cellulose
Strengthening agents: pectin lignin
4. Sporic life cycle:
Alternation between diploid sporophyte and haploid gametophyte
5. Reproduction: embryo is multicellular (many-celled) housed in multicellular gametophyte tissue
•meiosis in diploid (2n) sporophyte yields single celled, haploid (n) spores
• then, cells in the gametophyte form gametes (sperms/eggs)
• sperm and egg meet - fertilize to form new diploid (2n) sporophyte (In animals there is no equivalent to gametophyte in plants)
Nonvascular plants – bryophytes
includes mosses, liverworts, and hornworts
• gametophyte is dominant
• sporophyte is reduced
• all other plants – sporophyte is dominant (plant)gametophyte is reduced
Spores: homospory - one form of spore
Small spores - microspores give rise to microgametophytes (male)
(in seed plants – the pollen)
heterospory - 2 distinct types of spores
megaspores – give rise to megagametophytes (female)
(in the ovule, located in the ovary of the flower)
• require water to reproduce (sperm swims)
Bryophytes - mosses, liverworts, and hornworts
• conducting/supporting tissue? no, therefore size is limited
• cannot tolerate pollutiontherefore they may be an indicator species
• anchorage – threadlike rhizoids
Rhizoids are not used for absorption of water
liverworts: name from the fact they were once used to treat liver disease
• wort - herb• leafy, gametophyte body - thallus
thallus
• pore-like stomata (exchange of gases)
• example of liverwort - Marchantia
Asexual: 2 ways
• fragmentation - parts grow into complete gametophyte
• gemmae - form cups
Sexual: 2 kinds of gametangia
1. egg-forming - archegonia produces stalked archegoniophores
2. sperm-forming - antheridia produces stalked antheridiophores
• may be monoecious (one house) or dioecious (two houses)
• sperm are splashed against archegonia
•upon fertilization – new diploid sporophyte produces sporangia meiosis (reduction division) produces haploid spores which develop into new gametophytes
Mosses: most numerous and most common of the bryophytes
• withstand drying conditions by “drying out”
• ground cover in tundra (arctic)
• importance - pioneer (colonizing) plants
• peat - Sphagnum for mulching(flavor in scotch whiskey)
Moss gametophyte - protonema (similar to filamentous green algae)
gametophyte
sporophyte – capsule (which is spore-filled)
•may produce 50 million spores
operculum (cap) falls away releasing haploid spores
sporophyte
Class Musci - mosses
gametophyte
sporophyte
capsule
Vascular Plants - tracheophytes (tube plants)
• contain vascular tissue: xylem (conducts water) and phloem (conducts food)
• horizontal stems - rhizomes
• water conducting elements (tube-like) - tracheids
Early: club mosses / horsetails (ground pine) (scouring rushes)
cone - strobilus at end of branches
Pterophyta - ferns
• leaves which emerge above ground from the rhizomes - fiddleheads
• spores produced in sporangiaclustered into sori (sorus)
• fern gametophyte - prothallus - heart-shaped (short lived)
• the embryo develops into sporophyte (plant)
• sperm escape from antheridia and swim to archegonia where fertilization occurs
Seed Plants:
• came about due to climate changes – geological changes(upheavals) - drying, cooling trends
• female gametophyte fully enclosed in sporophytic tissues for protection
Reproductive adaptations:
1. different spores – heterosporous
2. pollen - minute, resistant – carried from one plant to another by air and water currents or animals
• the pollen grain contains a generative cell which gives rise to 2 sperm cells and a tube cell which directs the growth of the pollen tube after pollination has occurred
• pollen tubes literally digest their way to the female gametophyte, no water is necessary
Seeds: consist of embryo region of stored food
hardened seed coat
gymnosperm means “naked seed”
Division - Ginkgophyta
•one species left - Ginkgo biloba
• thought to be extinct – therefore a “living fossil”
• common name – maidenhair tree
• living Ginkgo found on grounds of oriental temple(year 1946)
• now commonly cultivated as decorative plants
• trees have separate sexes - dioecious
• sheds leaves in autumn
• primitive trait – swimming sperm
Division – Cycadophyta - cycads (palm-like)
• common in time of dinosaurs• today live in tropics
• sperms produced in strobili (cone-like)
• swimming sperm
Division - Gnetophyta
• have water-conducting xylem vessels within stem(other gymnosperms have water-conducting tracheids)
•Welwitschia – description - twisted
Where do they grow? African desert
• examples: pine, firs, spruce, hemlock
Division - Coniferophyta
• male pollen conesfemale ovulate cones
• biome - taiga
• remain green - evergreen
• sperm enter through micropyle
• zygote gives rise to the embryomade up of root - hypocotyl2 apical meristems8 cotyledons (seed leaves)
3. major catastrophe - giant asteroid hit earth (Alvarez theory) blocked sun
Geological changes at the end of the Mesozoic:
1. mountain building
2. plate tectonics
• pollination more efficient and selective
co-evolution with insects
Division Anthophyta (flowering plants)
Class – Dicotyledonae (dicots)
• larger class
Class – Monocotyledonae (monocots)
Monocot
Veins - parallel
Cotyledon - one
Flowers – 3’s
Vascular bundles - scattered
Dicots
Veins – branching (net)
Cotyledon - two
Flowers – 4’s or 5’s
Vascular bundles – in a ring
carpels are above receptacle
Flower:
primitive – floral parts are numerous and unfused
symmetry - radialexample: buttercup
bilateral symmetry
advanced - fused parts
Plant body has four organs:
1. Root – anchors plant, absorbs water and minerals, stores food
2. Stem – conducts water and minerals to leaves, displays leaves to light, conducts food to roots, stores food
3. Leaf – photosynthesizes food
4. Flower - reproduction
• flowers are modified leaves
Flower Parts
Sepal – outer, green, leaf-like part which covered the bud
Calyx – ring of sepals
Corolla – ring of petals
Stamen – male structure of filament and anther which produce pollen
Pistil – female structure consisting of the following:
Stigma – sticky tip
Style – slender neck leading to the ovary
Ovary – base containing ovules