Transcript PLANT DIVERSITY I - Falmouth Schools

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.
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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.
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
embryo.
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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.
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• Female gametangium (gamete
producing organ) – archegonium produces single egg cell in vaseshaped organ.
• Male gametangia – antheridia produce many sperm cells released
to environment.
• Sperm fuses with egg in
archegonium.
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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 - nutrientconducting cells arranged into
tubes distribute sugars, amino
acids, other organic products.
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• 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.
http://www.naturalproductsmarketplace.com/articles/i461a12.jpg
Origin of land plants
• Chloroplasts of land plants most
similar to plastids of green algae.
• In both - cellulose comprises 2026% of cell wall.
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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.
• 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.
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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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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 highlybranched.
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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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Fig. 29.23
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• 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.
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• 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, nongreen leaves.
• Dispersed by wind.