Plant Kingdom: General Characteristics and Classification

General Characteristics of the Plant Kingdom

  • Photosynthetic (chlorophyll).
  • Cell walls (cellulose).
  • Multicellular organization.
  • Alternation of generations.
  • Sessile lifestyle.
  • Autotrophic nutrition.

Major Groups

  • Thallophyta (Algae): Most primitive, simple body (thallus), aquatic, no vascular tissue.
  • Bryophyta (Amphibians of Plant Kingdom): First true land plants, no vascular tissue, gametophyte dominant, require water for reproduction.
  • Pteridophyta (Ferns): First plants with true vascular tissue, sporophyte dominant, reproduce by spores.
  • Progymnosperms: Extinct, transitional group, secondary growth, reproduced by spores.
  • Gymnosperms (Naked Seed Plants): Seeds not enclosed in fruits, well-developed vascular system, wind pollination.
  • Angiosperms (Flowering Plants): Seeds enclosed in fruits, flowers as reproductive organs, double fertilization, most diverse.

Detailed Comparison Table (Part 1)

Characteristic Thallophyta Bryophyta Pteridophyta
Common Name Algae Amphibians Ferns
Body Organization Thallus Simple plant body Complex with organs
Vascular Tissue Absent Absent Present
Roots Absent (holdfast) Rhizoids True roots
Stems Absent Simple True stems
Leaves Absent Simple True leaves

Detailed Comparison Table (Part 2)

Characteristic Thallophyta Bryophyta Pteridophyta
Dominant Generation Gametophyte Gametophyte Sporophyte
Reproduction Spores/gametes Spores Spores
Fertilization External water Water needed Water needed
Seeds Absent Absent Absent
Flowers Absent Absent Absent
Fruits Absent Absent Absent
Habitat Mostly aquatic Moist terrestrial Moist terrestrial

Detailed Comparison Table (Part 3)

Characteristic Progymnosperms Gymnosperms Angiosperms
Common Name Seed ferns Naked seed plants Flowering plants
Body Organization Tree-like Complex plant body Complex plant body
Vascular Tissue Present Present Present (most advanced)
Roots True roots True roots True roots
Stems Woody stems Woody/herbaceous Woody/herbaceous
Leaves Compound leaves Needle/scale leaves Diverse leaf types
Dominant Generation Sporophyte Sporophyte Sporophyte
Reproduction Spores Seeds (naked) Seeds (in fruits)
Fertilization Wind/water Wind pollination Various mechanisms
Seeds Absent Present (naked) Present (enclosed)
Flowers Absent Absent (cones) Present
Fruits Absent Absent Present
Habitat Terrestrial Terrestrial All habitats

Evolutionary Progression

  1. Thallophyta → Bryophyta: Aquatic to terrestrial transition.
  2. Bryophyta → Pteridophyta: Development of vascular tissue and true organs.
  3. Pteridophyta → Gymnosperms: Evolution of seeds, reduced water dependence.
  4. Gymnosperms → Angiosperms: Flowers, enclosed seeds, diverse reproduction.

Special Terminology

  • Tracheophytes: All vascular plants (Pteridophyta, Gymnosperms, Angiosperms).
  • Amphibians of plant kingdom: Bryophytes (live on land, need water for reproduction).
  • Cryptogams: Plants reproducing by spores (Thallophyta, Bryophyta, Pteridophyta).
  • Phanerogams: Plants with visible reproductive organs (Gymnosperms, Angiosperms).
  • Spermatophytes: Seed plants (Gymnosperms, Angiosperms).