Transcript Plant Diversity

Plant Diversity
Chapters 29 & 30
Biology – Campbell • Reece
Background
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Charophytes are the green algae most closely
related to land plants
4 main groups of land plants :
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Bryophytes – mosses
Pteridophytes – ferns
Gymnosperms – conifers
Angiosperms – flowering plants
Classification of Plants
Evolutionary Adaptations
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Vascular tissue – transports water & nutrients
throughout the plant
Apical meristems – regions of cell division at
the tips of shoots and roots
Multicellular, dependent embryos – the
developing embryos are retained within
tissues of the female parent
Evolutionary Adaptations cont.
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Alternation of
generations:
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Gametophyte – haploid
generation during
which gametes are
formed
Sporophyte – diploid
generation during
which spores are
formed
Evolutionary Adaptations cont.
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Spores produced in sporangia
Multicellular gametangia where gametes are
produced (archegonia – female; antheridia –
male)
Cuticle – waxy layer to prevent water loss
Stomata – pores used for gas exchange
Bryophytes
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Nonvascular plants – do not contain xylem
and phloem
3 phyla:
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Hepatophyta (liverworts)
Anthocerophyta (hornworts)
Bryophyta (mosses)
Most grow close to the ground, anchored by
rhizoids
Bryophytes
Bryophytes
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Gametophyte is the dominant generation
Sporophytes disperse enormous numbers of
spores
The sperm are flagellated and must swim
through a film of water to reach the eggs
Found in moist alpine, boreal, temperate,
tropical forests, and wetlands
Pteridophytes
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Seedless vascular plants
Two phyla:
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Lycophyta (club mosses)
Pterophyta (ferns, whisk ferns, & horsetails)
Have true roots with lignified vascular tissue
Microphylls – small leaves with a single
unbranched vein
Sporophyte is the dominant life cycle
Formed “coal forests” during the Carboniferous
period
Pteridophytes
Homosporous vs. Heterosporous
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Homosporous
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Heterosporous
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Sporophyte → single type of spore → bisexual
gametophyte → eggs and sperm
Sporophyte → megaspore → female gametophyte → eggs
Sporophyte → microspore → male gametophyte → sperm
Sperm are still flagellated and must swim in water to
reach the eggs
Life Cycle of a Fern
Seed plants
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Vascular plants that produce seeds
Includes the gymnosperms & angiosperms
Three important reproductive adaptations:
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Continued reduction of the gametophyte
(microscopic)
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All seed plants are heterosporous
Development of seeds for dispersing offspring
Pollen eliminated the liquid-water requirement
for fertilization
Gymnosperms
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“naked seeds”
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Seeds develop on the surface of specialized
leaves called sporophylls
Most familiar are the conifers – the conebearing plants such as pines
Dominant plant life in the Mesozoic era
There are four phyla of gymnosperms
The 3 Small Gymnosperm Phyla
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Ginkgophyta
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Cycadophyta
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Includes only Ginkgo biloba
Includes the cycads, which resemble palms
Gnetophyta
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Consists of 3 genera that are very different in
appearance
The 3 Small Gymnosperm Phyla
Phylum Coniferophyta
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The largest of the gymnosperm phyla
The cone is the reproductive structure
Examples: pines, firs, spruces, junipers, cedars,
and redwoods
Most are evergreens
Where we get much of our lumber and paper
pulp
Among the largest & oldest organisms on Earth
Phylum Coniferophyta
Life Cycle of a Pine
Angiosperms
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Flowering plants
Vascular seed plants that produce flowers and
fruits (as reproductive structures)
All are in a single phylum, Anthophyta
Are the most diverse and geographically
widespread of all plants
Marks the transition from the Mesozoic era to
the Cenozoic era
Flower
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Four types of modified leaves:
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Sepals – enclose the flower before it opens
Petals – brightly colored to attract pollinators
Stamens – male reproductive organs
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Anther – where pollen is produced
Filament – stalk
Carpels (pistils) – female reproductive organs
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Stigma – sticky, receives the pollen
Style – stalk that leads to the ovary
Ovary – where the ovules are located
Flower
Fruits
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A mature ovary
Protect dormant seeds and aid in their
dispersal
Life Cycle of an Angiosperm
Life Cycle of an Angiosperm
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Double fertilization – one sperm unites with
the egg forming the zygote; the other sperm
fuses with 2 nuclei in the ovule to form the
endosperm (food supply)