Plant Diversity

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Plant Diversity
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Vascular vs. Nonvascular

• Vascular tissue in plants is the xylem (moves
  water) and phloem (moves sugars)
• Specialized transport system
• Vascular plants can be much bigger than
  nonvascular plants
• Advantageous (competition for light)

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Division of plants

• Nonvascular Bryophytes (24,000 sp.)
• Vascular Seedless Plants (14,715)
• Vascular Seed Plants
• Gymnosperms (771)
• Angiosperms (275,000)

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Evolution of plants (1)

• Unlike protists and fungi, excellent fossil
  record
• Larger and hard parts to fossilize
• Earliest fossils are of vascular plants
• Nonvascular plants evolved from vascular plants
  (simplification)

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Evolution of plants (2)

• Seedless plants predominant in Devonian period
  (360 mya)
• Produced coal, oil, and gas deposits
• Seed plants appear in late Devonian period
• Climate change was accompanied by diversification
  of Angiosperms, seed plants that evolved flowers
  and fruits
• Angiosperms are most successful group

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Evolution of Plants
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Alternation of Generations in Plants
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Nonvascular plants (Bryophytes)

• All lack vascular tissue
• Must absorb water directly, thus small
• Also need water for their gametes to swim in
• Predominant part of the life-cycle is haploid
• Peat moss harvested and used in many ways

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Mosses, Liverworts, Hornworts

• Alternation of Generations
• Haploid phase predominant in moss
• Diploid phase lives on body of haploid (not
  photosynthetic)

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Vascular Plants (Tracheophytes)

• Have vascular tissue xylem and phloem
• Much larger than nonvascular plants
• Unlike nonvascular plants, the diploid part of
  the life-cycle is the predominant phase
• Either seedless (have spores) or seeds

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Seedless Plants

• Pterophytes (Ferns)
• Psilotophytes (Whiskferns)
• Lycophytes (Lycopods)
• Equisetophytes (Horsetails)

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Fern Life-Cycle
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Seed Plants

• Seeds can persist in harsh environments
• Have protective seed coat
• Divided into two groups
• Gymnosperms and Angiosperms
• Gymnosperms do not have flowers or fruits,
  Angiosperms do

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Structure of a Seed
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Gymnosperms-Seed Plants, No flowers or fruits

• Conifers-Pines, Junipers, Cypress, Firs, Spruce,
  Hemlock, Cedar, Redwood
• Cycads-Tropical(Florida Coontie), resemble palms,
  poisonous seeds
• Gingkos-Extinct in wild, from China, planted in
  cities
• Gnetae-Rare tropical, link between Gymnosperms
  and Angiosperms

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Gymnosperm Life-Cycle
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Angiosperms-Seed Plants, Flowers and Fruits

• Flower is a specialized structure that presents
  the gametes
• Fruit is a specialized tissue that surrounds the
  seed, used for dispersal
• Double Fertilization unique to Angiosperms
• 1 sperm fuses with egg to form zygote
• 1 sperm fuses with 2 nuclei to form endosperm
  (food reserve)

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Parts of a Flower
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Flower parts (1)

• Arranged in concentric whorls
• Outer to inner (sepals, petals, stamens, carpels)
• Sepals and petals function in protection and
  attraction (color, scent, nectar)
• Stamens are male sex organs
• Carpels are female sex organs

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Flower parts (2)

• Stamens contain a
• filament (stalk)
• anther (site of pollen production)
• Carpels contain
• Stigma (pollen lands)
• Style (pollen grows through)
• Ovary (contains ovule that pollen fuses with)

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Angiosperm Life-Cycle
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Angiosperm Diversity

• Monocots-Flower parts in multiples of 3s,
  parallel leaf venation
• Dicots-Flower parts in multiples of 4s and 5s,
  pinnate leaf venation