Biodiversity Of Plants

• Non-vascular plants

  • Bryophytes
• During the life cycles of each of the four plant groups, two definitive generations exist
• Seedless plants

  • Pteridophytes
• Gametophyte generation

  Dominant generation represented by the adult moss plant
• Plants divided into groups according to

  • Presence or absence of vascular tissue (xylem and phloem)
  • True leaves, stems, and roots
  • Spores or seeds
  • Fruits
  • Dependency on water for reproduction
• Spores in mosses

  Form in the sporangium, dispersed by wind, germinate in damp soil to develop into a new plant representing the gametophyte generation
• Sporophyte generation in mosses

  Develops on the gametophyte, consists of a foot part anchored in the gametophyte, a seta bearing a sporangium, which produces and stores spores
• Classification of divisions in Kingdom Plantae
• Cone-bearing plants with naked seeds

  • Gymnosperms
• Mosses thought to have lived on land 400 million years ago
• Mosses grow in cool, moist, shady environments
• Rhizoids

  Anchor the moss plant in soil, absorb water and mineral salts
• Flowering plants with covered seeds

  • Angiosperms
• Vascular plants

  • Seed plants/Spermatophytes
• Moss plant body

  Known as a thallus, lacks true roots, stems, and leaves, has leaf-like structures, stem-like structures, and rhizoids
• Sexual reproduction in mosses

  Requires water for fertilisation to occur, zygote formation marks the beginning of the sporophyte generation
• Alteration of generations

  1. Two definitive generations: Gametophyte generation (sexual, produces gametes) and Sporophyte generation (asexual, produces spores)

  2. Generations alternate in giving rise to each other
• Kingdom Plantae divisions

  • Bryophytes: mosses, liverworts, hornworts
  • Pteridophytes: ferns
  • Gymnosperms: conifers, cycads, gnetales, ginkgo
  • Angiosperms: flowering plants
• Moss plants do not produce seeds and fruit
• The gametophyte generation is less prominent, has a shorter lifespan, and disappears after one cycle of gamete formation and fertilisation
• The adult fern plant represents the sporophyte generation
• Pteridophytes are a group of plants that are adapted to life on land
• Note that moss plants do not produce seeds and fruit
• Released sperm need water to move to the ovum in the female sex organ, making fertilisation dependent on water
• Ferns mostly occur in moist, shady environments
• Ferns

  • Have true roots, stems, and leaves (not a thallus)
  • In most ferns, the stem is a horizontal, underground rhizome
  • Adventitious roots anchor the plant in the soil and absorb water and mineral salts
  • Green compound leaves (fronds) with long leaf stalks develop from buds on the rhizome
  • Well-developed vascular tissue is present
  • The sporophyte is perennial and produces spores over many generations
  • Clusters of sporangia are found on the underside of the leaves
  • Spores are released from the sporangia and dispersed by the wind
  • When a spore germinates, it gives rise to a green, heart-shaped prothallus representing the gametophyte generation
  • Rhizoids on the ventral surface of the prothallus anchor it in the soil
  • Male and female sex organs are found on the ventral surface of the prothallus
  • Fertilisation is dependent on water
  • After fertilisation, a zygote is formed, giving rise to the new fern plant (sporophyte)
• Unlike the Bryophytes, the sporophyte generation is the dominant generation in ferns
• After fertilisation occurs, a zygote is formed, giving rise to the new fern plant (sporophyte)
• Ferns, like mosses, produce no seeds and no fruit
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• Plant groups

  • Gymnosperms
  • Angiosperms
• Groups of Gymnosperms

  • Conifers
  • Ginkgo
  • Cycads
  • Gnetales
• Fertilisation

  The process of fusion of male and female gametes to form a zygote
• Gametophyte Generation

  The generation in plants that produces gametes (sperm and ova)
• Pine trees are monoecious, carrying both male and female cones on the same plant
• Sporophyte Generation

  The dominant generation in plants, represented by the adult plant that produces spores
• Meiosis

  The process where cells divide to produce spores
• Gymnosperms are terrestrial plants that appeared on earth approximately 300 million years ago
• Pine trees are an example of conifers, which are the most abundant group of Gymnosperms
• Plant structures

  • Sporangia
  • Ferns
  • Sorus
  • Spores
  • True roots
  • Underground stem
  • Large compound leaves
  • Adult fern plant
  • Sperm
  • Male sex organs
  • Prothallus
  • Gametophyte
  • Xylem and phloem