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Kingdom: Plantae (Phylogeny, Evolution, Alternation of Generations)

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Presentation on theme: "Kingdom: Plantae (Phylogeny, Evolution, Alternation of Generations)"— Presentation transcript:

1 Kingdom: Plantae (Phylogeny, Evolution, Alternation of Generations)
earliest plants evolved from algal ancestors 0.5 BYA converted bare rock into soil to be able to support successive generations eukaryotic, multicellular, autotrophic cell walls contain cellulose, mostly terrestrial develop from embryos protected by parental tissues

2 All plants exhibit an alternation between gametophyte (haploid) and sporophyte (diploid) generations  more primitive plants (i.e. mosses and ferns) are dominated by the gametophyte generation, while seed-producing vascular plants (i.e. gymnosperms and angiosperms) are dominated by the sporophyte generation

3 4 main groups, arising from evolutionary advances
(green alga)  multicellularity  mosses  vascular tissue  ferns  seeds  conifers  flowers  flowering plants an intro to cladistics flowers seeds vascular tissue multicellularity

4 Life Cycle 4.2 – Non-Seed Plants: Bryophytes (mosses)
distinguished from algae by female sex organs (archegonia) in which an egg is surrounded by a layer of tissue Sphagnum (peat moss) gives rise to the great peat bogs of the northern hemisphere acts as a giant sponge in watersheds, added to soil to improve water-holding capacity (undergoing commercial overharvest), used in Ireland as fuel, used in surgical dressings and diapers Polytrichum (star moss) is common in Canadian woodlands, used for stuffing pillows and mattresses (recommended by Linnaeus as it harbors neither fleas nor disease) Life Cycle haploid spore germinates, develops into male, female, or bisexual gametophyte  biflagellate sperm swim from antheridia of male gametophyte to an egg in the archegonium of the female gametophyte  zygote develops into a sporophyte in situ (on the gemetophyte), which undergoes meiosis, gives rise to haploid spores

5 Typical Life Cycle Vascular Plants (vascular tissues)
xylem and phloem transport materials, allow for greater height  2 groups Spore-Producing Vascular Plants (Ferns) ferns are small descendents of plants that dominated forests several hundreds of millions of years ago, now restricted to marshes and riparian zones (flanking streams), fossilized into coal deposits  ferns are widely distributed ( species) Typical Life Cycle haplod spore germinate, develop into leave-like, often bisexual gametophyte thallus with rhizoids (underground stems)  archegonia produce single egg, antheridia produce many sperm  zygote  embryo  sporophyte (stipe and root radicle) develops into fronds containing vascular tissue meiosis produces haploid spores within sporangia protected by sori on the underside of fronds  released, germinate to produce gametophyte

6 Life Cycle 4.3 - Seed-Producing Vascular Plants
highly specialized organs (leaves, stems, roots) allow for adaptation to diverse habitats (including arid ones) as seeds are resistant to dessication airborne pollen transfers sperm to egg to produce a seed (an embryo with its lunch) dominated by sporophyte generation Gymnosperms (cone-producing: ginkgos, cycads, conifers) cycads dominated 225 MYA, now only in the tropics Gingko biloba is the only remaining gingko conifers are the most common gymnosperms, characterized by leaves modified to needles Life Cycle male and female cones produce pollen (sperm) and ovules (eggs)  airborn pollen undergo meiosis in female cones to produce many sperm  zygote develops into seeds on female cone scales  seeds dispersed, germinate under suitable conditions (soil, moisture, temperature) to produce new sporophyte (i.e. tree)

7 Angiosperms (flower producing seed plants: 250 000 diverse species)
pollination often requires a vector, seeds develop within fruit, dispersed in a variety of ways (wind, water, on and in animals) Life Cycle flower contains both male and female parts, protected by sepals and petals pollen is produced within an anther (antheridium) on an aerial filament (anther + filament = stamen) egg develops within an ovary at the base of the carpel (archegonium) connected to a pollen-receptive area (stigma) by the style, which will house the pollen tube (carpel = stigma + style + ovary + ovule) pollen lands on stigma  tube cell within pollen grain creates pollen tube in style for sperm to travel in pollen lands on stigma  tube cell within pollen grain creates pollen tube in style for sperm to travel in generative nucleus divides into 2 sperm nuclei  one fertilizes the ovule to produce a zygote which develops into a seed, other fuses with 2 polar nuclei of the ovule to form the endosperm (= lunch)  ovary develops into fruit  sepals and petals die seed germinates  root and stem radicals  sporophyte with flowers

8 fruit can be fleshy or dry (i. e. nuts), simple (from single ovary, i
fruit can be fleshy or dry (i.e. nuts), simple (from single ovary, i.e. tomatoes, plums, pears) or aggregate (from many ovaries in a single flower, i.e. raspberries) different pollination methods have created intricate co-evolution between flowering plants and vectors

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