Plant Diversity I. Terrestrial environments - deserts, grasslands, forests. 4 groups of land plants:...
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Transcript of Plant Diversity I. Terrestrial environments - deserts, grasslands, forests. 4 groups of land plants:...
Plant Diversity I
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• Terrestrial environments - deserts, grasslands, forests.
• 4 groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms.
• Most common bryophytes - mosses.
• Pteridophytes - ferns.• Gymnosperms – pines, conifers.• Angiosperms - flowering plants.
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Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Bryophytes - offspring remain attached to parent plant.
• Non-vascular plants.• Vascular plants - vascular
tissues, cells join into tubes that transport water, nutrients throughout plant body.
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http://www.science.siu.edu/landplants/Bryophyta/images/Physcomitrium.JPEG
• Ferns - seedless plants. • Seed - plant embryo packaged
along with food supply within protective coat.
• Early seed plants gave rise to diversity of present-day gymnosperms, including conifers.
• Modern plants angiosperms.QuickTime™ and a decompressor
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http://www.rockhillridge.com/images/hayes/Ferns,%20Hayes%20Tract%206%2003-web.jpg
Fern
• Plant evolution: • 1Origin of bryophytes from algal
ancestors.• 2Origin, diversification of
vascular plants.• 3Origin of seeds.• 4Evolution of flowers.
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• Plants – multicellular, derive energy and nutrition through photosynthesis.
• Plant cell walls - cellulose.• Different from algae - apical
meristems, alternation of generations, sporangia that produce walled spores.
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http://www.botany.hawaii.edu/faculty/webb/BOT311/bot311-00/PlantCellWalls00/CellWallHemiLab.jpg
• Plants need to grow to maximize absorption.
• Done through apical meristems - undifferentiated cells that divide when needed.
• Located at tips of roots, shoots.
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• Multicellular plant embryos develop from zygotes - stay in tissues of female parent.
• Land plants - embryophytes. • Parent provides nutrients to
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• Alternation of generations - gametophyte produces haploid gametes that get fertilized; form a diploid zygote that will grow into mature sporophyte.
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• Sporophyte produces haploid single-celled spores - grow into gametophyte.
• Spore - reproductive cell that can develop into new organism.
• Size of sporophyte and gametophyte differ in plant species.
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• Bryophytes - gametophyte dominant generation.
• Pteridophytes, gymnosperms, and angiosperms - sporophyte dominant generation.
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http://www.sbs.auckland.ac.nz/info/schools/nzplants/images/moss/moss_major_parts1.jpg
• Spores - haploid reproductive cells -grow into gametophyte by mitosis.
• Covered by sporopollenin – resistant to outside stress.
• Sporangia found on sporophyte - produce spores. QuickTime™ and a
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• Female gametangium (gamete producing organ) – archegonium - produces single egg cell in vase-shaped organ.
• Male gametangia – antheridia - produce many sperm cells released to environment.
• Sperm fuses with egg in archegonium. QuickTime™ and a
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Female
Fusion of sperm and egg
• Land plants have cuticle – protects from drying out, microbes.
• Stomata, in epidermis of leaves allow exchange of carbon dioxide and oxygen between outside air and leaf interior.
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• Land plants - true roots, stems, leaves.
• Xylem carry water, minerals up from roots.
• Dead at maturity.• Phloem - living tissue - nutrient-
conducting cells arranged into tubes distribute sugars, amino acids, other organic products. QuickTime™ and a
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http://www.bbc.co.uk/schools/gcsebitesize/img/bixylemphloem.gif
• Plants also produce secondary compounds.
• Include alkaloids, terpenes, tannins, and phenolics such as flavonoids - bitter tastes, strong odors, or toxic effects.
• Some used for medicinal purposes.
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Origin of land plants
• Chloroplasts of land plants most similar to plastids of green algae.
• In both - cellulose comprises 20-26% of cell wall.
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http://www.rsbs.anu.edu.au/profiles/Brian_Gunning/Web%20PCB/Ch%2010%20Plastids/Topic%2005%20Chloroplasts-Charophyceae/10%2005%2010.jpg
Bryophytes
• 3 phyla - phylum Hepatophyta – liverworts, phylum Anthocerophyta – hornworts, phylum Bryophyta – mosses.
• Gametophytes dominant phase of life cycle.
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• Bryophytes anchored by tubular cells or filaments of cells - rhizoids.
• Lack conducting tissues to distribute water and organic compounds within gametophyte – very small.
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http://userwww.sfsu.edu/~biol240/labs/lab_10plantoverview/media/rhizoids.jpg
• “Leaves” of most mosses lack a cuticle and are only 1 cell thick – allow quick absorption from surroundings.
• Mature gametophores of bryophytes produce gametes in gametangia.
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• Archegonium - single egg.• Antheridia - many flagellated
sperm. • Sperm swim toward archegonia,
drawn by chemical attractants.• Zygotes and young sporophytes
retained and nourished by parent gametophyte.
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• Moss sporophytes consist of foot, elongated stalk (seta), and sporangium (capsule).
• Foot gathers nutrients and water from parent gametophyte via transfer cells.
• Stalk conducts materials to capsule.
• Capsule – disperse spores.
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• Common in wetlands, wind dispersal allows for inhabiting many different areas.
•Sphagnum, wetland moss, abundant and widespread – forms deposits of undecayed organic material – peat.
• Forms peat bogs. QuickTime™ and a decompressor
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• Vascular plants have food transport tissues (phloem) and water conducting tissues (xylem) with lignified cells.
• 1st vascular plants, pteridophytes, were seedless.
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http://www.florelaurentienne.com/flore/Groupes/Pteridophytes/images/Adiantum_pedatum_940528_21_800.jpg
Seedless Vascular Plants•Cooksonia, extinct plant over 400
million years old, earliest known vascular plant.
• Seedless vascular plants, pteridophytes consists of 2 modern phyla:
• Phylum Lycophyta – lycophytes.• Phylum Pterophyta -- ferns, whisk
ferns, and horsetails.
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Cooksonia
• Lycophytes have small leaves (microphylls) with single unbranched vein.
• Leaves of other vascular plants, megaphylls much larger and highly-branched.
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• Homosporous sporophyte produces a single type of spore.
• Heterosporous sporophyte produces 2 kinds of spores.
• Megaspores - females gametophytes.
• Microspores - male gametophytes.
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Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 29.23
• Modern lycophytes include tropical species that grow on trees as epiphytes, using the trees as substrates, not as hosts.
• Specialized leaves (sporophylls) bear sporangia clustered to form club-shaped cones.
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http://www.tcr.gov.nl.ca/nfmuseum/images/osmundaclaytoniana3barrdharbourhilljuly122002.jpg
• Phylum Pterophyta – ferns and relatives.
• 1Psilophytes - whisk ferns.• 2Sphenophytes – horsetails - often
found in marshy habitats and along streams and sandy roadways.
• Roots develop from horizontal rhizomes that extend along ground. QuickTime™ and a decompressorare needed to see this picture.
• 3Ferns - horizontal rhizomes.• Fern leaves (fronds) may be
divided into many leaflets. • Produce clusters of sporangia
(sori) on back of green leaves (sporophylls) or on special, non-green leaves.
• Dispersed by wind.
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