Plant Evolution and Classification

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Plant Evolution and Classification
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Adapting to Land

• More exposure to sunlight
• Increased CO2 levels
• Greater supply of inorganic nutrients
• Susceptible to drying out
• cuticle (waxy coating to prevent water loss)
  with stomata (for gas exchange)

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Reproduction

• Developed structure to protect reproductive cells
  from drying out
• Spore - haploid reproductive cell surrounded by
  a hard outer wall
• Seed - embryo surrounded by a protective coat

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Absorbing and Transporting Nutrients

• Some plants have vascular tissue to transport
  food (phloem) and water (xylem), and help support
  the plant

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Classifying Plants

• 12 phyla (formerly divisions), include more than
  270,000 species.
• Three phyla of nonvascular plants
• Have neither true vascular tissue not true
  roots, stems, or leaves.

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Classifying Plants Cont.

• Nine phyla of vascular plants (have vascular
  tissue and true roots, stems, and leaves)
• Vascular plants can be divided into two groups
• Seedless plants - ferns and fern-like plants
• Seed plants - plants that produce seeds

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Classifying Plants Cont.

• Seed plants can be divided into two groups
• Gymnosperms - produce seeds not enclosed in
  fruits (pine trees)
• Angiosperms - produce seeds enclosed in fruits

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Alternating Life Cycles

• All plants have life cycles consisting of two
  phases, which are named for the type of
  reproductive cells they produce
• Alternation of generations
• Sporophyte (2n) - produces spores
• Gametophyte (1n) - produces gametes

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Alternating Life Cycles Cont.

• In the nonvascular plant life cycle, the
  gametophyte is the dominant phase.

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Alternating Life Cycles Cont.

• In the vascular plant life cycle, the sporophyte
  is the dominant plant.

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