Download Plant Diversity

Definition of Plants
Plant Diversity
Chapters 29 & 30
Plant Evolution
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Multicellular
Eukaryotic
Photosynthetic
Autotrophic
Cell walls made of cellulose
Chlorophylls a and b
4 Main Groups of Land Plants
• Bryophytes – non vascular plants
– Mosses, liverworts, hornworts
• Pteridophytes - seedless vascular plants
– Lycophytes, ferns, horsetails, whisk ferns
• Gymnosperms – naked seed plants
– Ginko, cycads, gnete, conifers
• Angiosperms – flowering plants
Charophyceans
Land Plant Evolution
• Ancestral green algae
• Aquatic plants: Charophyceans
• Land plants:
• Closest relative of land
plants
• Algal group
• Similarities with land
plants
– Rosette cellulosesynthesizing complexes
– Development of vascular tissue
– Development of seeds
– Development of flowering plants
• Located in plasma membranes
– Peroxisomes
– Flagellated sperm (some
land plants)
Evidence of common ancestor
with charophycean algae
Adaptations of Land Plants
• Apical meristems
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Homologous chloroplast
Homologous cellulose walls
Homologous peroxisomes
Homologous sperm
Molecular systematics
– Chloroplast DNA
– Ribosomal RNA
– Roots and shoots – growth
• Multicellular, dependent embryos
– “embryophytes”
– Transfer of nutrients from parent
• Alternation of generations
– Sporophyte (diploid) and gametophyte (haploid)
• Gametangia – gametes are produced within multicellular
organ
– Female – archegonia
– Male - Antheridia
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Walled spores – resist drying out
Cuticle – waxy covering, water conservation
Stomata – pores, water conservation
Vascular tissue – transport water and minerals
Apical meristems of plant shoots and roots
Embryos of land plants
Alternation of generations
Gametangia: Gametes produced within multicellular gametangia
Archegonium - female
egg
Antheridium - male
sperm
Vascular Tissue: Xylem and Phloem
Development of Alternation of Generations
Xylem
(water)
• Delay in meiosis until one or more mitotic divisions of the
zygote occurred
• Result: multicellular, diploid sporophyte
• Increases number of spores produced per zygote
Phloem
(food)
Bryophytes
• 3 phyla
– Hepatophyta: liverworts
– Anthocerophyta: hornworts
– Bryophyta: mosses
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Non-vascular
Earliest land plants
Gametophyte (haploid) is dominant form
Anchored by rhizoids
No true roots or leaves
Bryophytes
Life cycle of a moss
Vascular Plants
Moss life cycle
gametophyte
gametangia
sporophyte
sporophyte
spores
Protonemata
(pre-gametophyte)
Seedless Vascular Plants
• Vascular plants have
– Xylem – transports water
– Phloem – transports food
– Dominant sporophyte generation
• 2 phyla
– Lycophyta – lycophytes
– Pterophyta – ferns, whisk ferns, horsetails
• First vascular plants were seedless
• Most have true roots and leaves
• 3 Groups
– Seedless plants
– Gymnosperms
– Angiosperms
• Still require water for fertilization
Hypothesis for the development of leaves
Life cycle of a fern
• Probably evolved from a flap of stem
tissue
– Stem had vascular tissue
– Microphylls
• Macrophylls – larger leaves with branched
veins
Fern sporophyll, a leaf specialized for spore production & sori
Fern gametophyte
Archegonia of fern
Evolution of Seed Plants
Flagellated sperm
from antheridium
fertilize eggs in
archegonium
zygote
• Reduction of gametophyte
continued
• Seeds – important means of
dispersal
• Pollen – eliminated water
requirement for fertilization
– Pollination
• Two clades
– Gymnosperms
– Angiosperms
Gametophyte/ Sporophyte Relationships
• Seed plants: further reduced gametophyte
• Female gametophyte and embryo protected by parental
sporophyte
Seed Development
• Fertilization initiates the transformation
from ovule to seed
What is a seed?
Seed Dispersal
• Sporophyte embryo
• Food supply
• Protective coat
• Seeds have
adaptations for
dispersal
• May remain dormant for years
• May be carried by wind, water or animals
• Wind
• Water
• Animal
Gymnosperms
• 4 phyla
– Ginko
– Cycads
– Gnetophytes
– Conifers
• Naked seed – no fruit (ovary)
• Seeds develop on surface of sporophylls
• Evolved before angiosperms
Phylum Coniferophyta: Frasier Fir
Characteristics of Conifers
Life cycle of a pine
• Cone: reproductive structure
– Cluster of sporophylls
• Female cones: produce ovules - “pine cones”
• Male cones: produce pollen
• Seed develops from fertilized ovule – scale of cone
• Dominate in areas with short growing season
– High latitude or altitude
• Most are evergreens
• Some have needle-shaped leaves
– Adapted for dry conditions
– Thick cuticle
Pine embryo
Angiosperms: Flowering Plants
Major Clades:
Embryo
(new sporophyte)
Phylum Anthophyta:
Angiosperms
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Vascular seed plants
Reproductive structures: flowers, fruits
Most diverse group of plants today
2 groups
Monocots
Dicots
# Petals
# Cotyledons
Vascular bundles
Xylem cells in Angiosperms
• Trachids
– Support
– Water transport
• Fiber **
– Support
• Vessel element **
– More efficient
** Evolutionary adaptations
of angiosperms
Root
Flower Structure: Reproductive Adaptation of Angiosperms
Life cycle of an angiosperm
Fruit and Seed Dispersal
Flower-pollinator relationships