Bryophytes and Pteridophytes Course Notes

Course Overview

• Title: Bryophytes and Pteridophytes (Biol 2032)
• Institution: Addis Ababa University College of Natural and Computational Sciences
• Prepared by: Hintsete W/dawit

Course Objectives

• Differentiate bryophytes from pteridophytes and other vascular plants
• Discuss major characteristics of representative groups of bryophytes and pteridophytes
• Explain adaptations of bryophytes and pteridophytes
• Appreciate diversities of bryophytes and pteridophytes
• Discuss morphological and anatomical diversity, phylogenetic relationships of nonvascular and vascular plants.

Introduction to Plants

• Definition: Multicellular, eukaryotic organisms in the kingdom Plantae, studied under Botany (from Greek 'Botane' meaning plant/herb)
• Characteristics:
  • Multicellular and mostly terrestrial
  • Autotrophic due to chlorophyll production in chloroplasts
  • Cell walls made of cellulose
  • Specialized organs for photosynthesis, reproduction, and nutrient uptake
  • Life cycle involves alternation of generations

Plant Life Cycle Phases

• Sporophyte Phase (2n):
  • Produces diploid spores (2n) via meiosis
  • Contains two copies of each chromosome
• Gametophyte Phase (1n):
  • Produces haploid gametes (1n)
  • Contains one copy of each chromosome

Taxonomy and Classification of Plants

• Taxonomy:

  • Science of classification based on similarities and differences
  • Organisms classified into hierarchical groups (domains to species)

• Plant Kingdom Divisions:

  • Brophyta: Non-vascular plants (Bryophytes)
  • Lack true roots, stems, leaves; includes:
    • Hepaticopsida (Liverworts)
    • Anthocerotopsida (Hornworts)
    • Bryopsida (Mosses)
  • Tracheophyta: Vascular plants with true roots, stems, leaves; includes:
  • Seedless (Pteridophytes): four phyla including true ferns
  • Seed plants (Gymnosperms and Angiosperms)

Bryophytes Overview

• Definition:
  • Greek origin ‘Bryo’ (moss) + ‘Phyto’ (plant); simplest land plants, primarily non-vascular
• Characteristics:
  • Lack lignin-coated vascular tissues
  • Dominant gametophyte generation
  • Require water for fertilization; reproduce via spores
  • Rhizoids for anchoring, but no true roots

Morphology and Structure

• Gametophyte:
  • Main photosynthetic body, contains male (antheridia) and female (archegonia) sex organs
• Sporophyte:
  • Dependent on gametophyte, produces spores within a capsule
  • Structure: foot (nutrition), seta (support), capsule (spore production)

Habitat of Bryophytes

• Prefer moist, damp, shaded environments
• Some species are adapted to survive in extreme conditions including deserts and tundras
• Grow on various substrates including soil, rocks, and trees

Reproductive Strategies

• Asexual Reproduction:
  • Through fragmentation and gemmae formation
• Sexual Reproduction:
  • Fertilization occurs in water; gametes produced via mitosis
  • Can be monoecious (both sex organs present in one individual) or dioecious (individuals have only male or female organs)

Phylums of Bryophytes

1. Phylum Hepaticophyta: Liverworts
2. Phylum Anthocerophyta: Hornworts
3. Phylum Bryophyta: Mosses

Characteristics of Pteridophytes

• Vascular, seedless plants
  • Examples: Whisk ferns (Psilophyta), Clubmosses (Lycopodiophyta), Horsetails (Sphenophyta), True ferns (Pterophyta)
• Primarily terrestrial forms, reproduction via spores

Evolutionary Trends

• Key adaptations for terrestrial life include:
  • Development of cuticles to prevent water loss
  • Role of stomata for gas exchange
  • Evolved vascular tissues for nutrient transport
• The transition from aquatic to terrestrial habitats involved significant structural and reproductive innovations.

Summary of Key Concepts

• Major Features:
  • Gametophyte dominance distinguishes bryophytes from vascular plants that exhibit sporophyte dominance.
  • Life cycle of bryophytes involves alternating generations; habitual reproduction relies on moisture availability.