Sexual Life cycles Plant structure and Phylogeny The Angiosperms.
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Transcript of Sexual Life cycles Plant structure and Phylogeny The Angiosperms.
![Page 1: Sexual Life cycles Plant structure and Phylogeny The Angiosperms.](https://reader035.fdocuments.in/reader035/viewer/2022081506/56649e385503460f94b28428/html5/thumbnails/1.jpg)
Sexual Life cyclesPlant structure and Phylogeny
The Angiosperms
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Outline
• Brief review• 9. ALTERNATION OF GENERATIONS• 8. PLANT EVOLUTION• 7. ANGIOSPERM LIFE HIST.
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Define sex cell.
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All life is organized into 3 domains
• 2 Domains of prokaryotes, 1 of all eukaryotes
• Bacteria & Archaea- prokaryotic
• Eukaryota- Includes all 4 eukaryotic kingdoms: protista, animalia, plantae, fungi
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Most of the many
Eukaryotic species
reproduce sexually
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Despite an inherent twofold cost, higher species reproduce sexually
• Sexually reproducing species must have 2 offspring to “break even”
• 2 offspring from an asexually reproducing species doubles the population
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Animal species alternate between diploid (mitotic) and haploid (meiotic)
In animals, only the diploid stage is multicellular
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Sexual life cycle of Animalsgametic or diplontic- meiosis forms gametes, no
spores- mainly like a sporophyte (2n)- produce gametes (1n) via
meiosis- fertilization results in zygote
(2n)- sporophyte grows via mitosis
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Schematic gametic life cycle
Sporophyte
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Many fungi work the opposite wayzygotic or haplontic- zygote undergoes meiosis- mainly like a gametophyte
(1n)- produce gametes (1n) via
mitosis- fertiliz. results in zygote
(2n)- produce spores (1n) via
meiosis- gametophyte grows via
mitosis
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Most plants have two multicellular life cycle stages- gametophyte and sporophyte
plants - sporic or diplohaplontic- alternate sporo- &
gametophyte- meiosis forms spores- sporophytes (2n) dominate- produce spores (1n) via
meiosis- gametophyte (1n) develops
inside cone/flower via mitosis- prod. gametes (1n) via mitosis- fertiliz. results in zygote (2n)- sporophyte grows via mitosis
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8. PLANT EVOLUTION
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Plant phylogeny
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The Phylum Bryophyta includes liverworts and mosses
Simplest terrestrial plants- avascular
evolve multicell. & terrestrial
- adapt to gravity, so small/low
- no roots, rhizoids only anchor
- sperm needs H2O to fertilize ova
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In mosses, the sporophyte and gametophyte are similar in size
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Ferns are vascular plants
ferns (Phylum Pterophyta) evolve vasculature
(vessels),allows fronds to grow large- true roots absorb H2O,
minerals- no seeds, sperm still
needs H2O
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The gametophyte is smaller in the fern life cycle
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The gametophyte nurtures the young sporophyte
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Conifers are the prototypical gymnosperm
gymnosperms (Phy. Coniferophyta)
- evergreen needles reduce evap.
• ova in larger female cones• sperm in pollen grains from
male cones, dispersed by wind
• no fruit, naked seeds protect + provide nutrients to embryo
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Gymnosperms include cycads & ginkoes
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Gymnosperms have no flowers
or fruits• Mostly wind-
pollinated• The most massive
indiviual living things- Giant sequoia
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The tallest and most massive- here in CA
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Male & Female Gametophytes are greatly reduced in gymnosperms
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Angiosperms are flowering plantsangiosperms (Phylum Anthophyta)- deciduous leaves drop off in
winter, surv. low temp/H2O• flowers attract animal pollinators
with color-smell-nectar,• more efficient for fertilization• endosperm in seeds stores
nutrients, esp. in grains/nuts• fruit attracts animals to disperse
& fertilize seeds, reduces comp.
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Basic (monoecious) Flower structure
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The male angiosperm gametophyte is even smaller
inside anthers- meiosis prod. microspore
(1n)- becomes the pollen grain= male gametophyte (1n)- with 2 sperm cells + tube
cell
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The female gametophyte houses the seed
• inside carpels- meiosis prod.
megaspore (1n)becomes the ovary= female gametophyte
(1n)• = ovum + central cell
(n+n)
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Pollination
• pollination - pollen grain to stigma
- tube cell grows pollen tube to reach ovary
• double fertilization • - 1st sperm cell (1n) +
ovum (1n)• = zygote (2n
sporophyte)
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The seed is a capsule containing a plant embryo
• - 2nd sperm cell + central cell (n+n) = endosperm (3n, food in seed)
• seed - seed coat around
endosperm- zygote grows into embryo via mitosis- ovary around seed
becomes fruit
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The plant embryo is already formed
• embryo - epicotyl becomes shoot• - hypocotyl becomes root• - cotyledons becomes
leaves
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Plant phylogeny
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6. MONOCOTS VS. DICOTS• angiosperms - flowering plants• - divided into 2 major groups• monocots - corn, grasses• - 1 cotyledon (embryonic leaf)• - narrow leaves with parallel veins• - flower parts in 3’s, fibrous roots• - vascular bundles scattered,• primary growth only• dicots - most other angiosperms• - 2 cotyledons absorb endosperm• - broad leaves with network veins• - flower parts in 4 or 5’s, taproot• - vasc. bundles arranged in ring, • secondary growth possible
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Monocots vs. Dicots