Plant Diversity: Summary Notes

Plant Diversity

Plant Categories

• Non-vascular plants (Bryophytes): Lack specialized tissues for water and nutrient transport.

• Vascular plants (Tracheophytes): Have vascular tissue with lignin for water and nutrient transport.

  • Further divided into spore-producing and seed-producing plants.

Bryophytes (Mosses, Liverworts, and Hornworts)

• Non-vascular, small plants that obtain water by osmosis.

• Restricted to moist environments due to water needs for reproduction.

• Thalli: Stem and leaf-like structures lacking vascular tissue.

• Rhizoids: Root-like structures.

• Life cycle dominated by the haploid gametophyte.

• Antheridia: Male gametophytes produce sperm.

• Archegonia: Female gametophytes produce eggs.

• Sperm fertilizes the egg internally, forming a diploid zygote.

• Zygote develops into a diploid sporophyte, dependent on the gametophyte.

• Sporangium: Sporophyte develops a capsule, producing spores by meiosis.

• Protonema: Spores germinate into tangled green filaments.

Pteridophytes (Ferns)

• Vascular tissue and waxy cuticle allow for larger size and drier environments.

• Require water for reproduction.

• Diploid sporophyte is more prominent than the gametophyte.

• Rhizomes: Underground stems.

• Fronds: Leaves.

• Sori: Clusters of sporangia on the underside of fronds.

• Gametophyte grows rhizoids and a heart-shaped prothallium.

• Antheridia and archegonia on the prothallium produce sperm and egg cells.

• Zygote develops into a new sporophyte after fertilization.

Vascular Seed Plants

• Adaptable to drier environments, replacing mosses and ferns.

• Reproduce without water via cones or flowers.

• Pollination: Transfer of sperm.

• Embryos protected in seeds.

• Male gametophyte contained in pollen grain.

• Zygote encased in seed coats, forming a seed.

• Embryo survives in the seed until germination conditions are right.

Gymnosperms

• Include Cycadophyta, Ginkgophyta, Gnetophyta, and Pinophyta.

• Adaptations for land:

  • Alternation of generations

  • Seeds resistant to drying

  • Seeds contain fully formed plant embryo

  • Food storage

  • Airborne pollen

  • Waxy cuticle

  • Vascular tissue

• Cone-bearing plants with exposed seeds - "naked seed".

• Conifers (Pinophyta): Pines, spruce, and fir trees with needle-like leaves; important for lumber.

Angiosperms

• Flowering plants, most diverse and numerous.

• Flowers facilitate pollination via insects or birds.

• Ovaries enclose eggs, developing into seeds within a fruit.

Monocots & Dicots

• Monocots: One cotyledon, parallel leaf veins, flower parts in multiples of three, scattered vascular bundles, no pith region.

• Dicots: Two cotyledons, net-like leaf veins, flower parts in multiples of four or five, vascular bundles in a ring arrangement.