Life Cycle of Mosses

Introduction to Mosses

• Vascular vs Non-Vascular Plants
  • Most familiar plants are vascular, having tissues that transport water and nutrients.
  • Mosses are non-vascular and are considered the most primitive plants.

Understanding the Moss Life Cycle

• Cycle Nature
  • The life cycle is a continuous process without a true beginning or end.
  • Arrows in diagrams indicate the direction of the cycle.

Starting Point: Fertilization

• Fertilization Basics
  • Involves the coming together of a sperm (haploid) and an egg (haploid) to form a zygote (diploid).
• Diagram Key
  • Brown/cream color represents diploid organisms.
  • Fertilization transitions from haploid to diploid.

Diploid and Haploid Transition

• Pathways
  • Diploid to haploid occurs through meiosis.
  • Haploid to diploid occurs via fertilization.

Archegonium and Zygote Development

• Archegonium
  • Female part of the moss life cycle holding the egg and post-fertilization zygote.
• Zygote to Embryo
  • Zygote develops into an embryo through mitosis.
• Embryonic Development
  • Embryo grows into the sporophyte generation.

Sporophyte Generation

• Sporophyte Characteristics
  • Grows out of the archegonium.
  • Diploid and produces spores.
• Sporangium
  • Contains cells that undergo meiosis to produce haploid spores.

Spores to Gametophytes

• Diversity of Spores
  • Haploid spores generated by meiosis, genetically varied.
• Spores' Pathways
  • Some become female gametophytes (Archegonia).
  • Others become male gametophytes (Antheridia).

Gametophyte Generation

• Photosynthetic Role
  • Green, photosynthetic part of the moss.
  • Dominant stage in moss life cycle.

Antheridia and Archegonia

• Male and Female Parts
  • Antheridia (male) produce sperm by mitosis.
  • Archegonia (female) house eggs and facilitate fertilization.

Importance of Water

• Water Dependency
  • Mosses require water for reproduction due to flagellated sperm.
  • Found in moist environments; sperm swim through water to reach the egg.

Summary of Moss Life Cycle

• Cycle Overview
  • Fertilization leads to a diploid zygote.
  • Zygote develops into an embryo and then into the sporophyte.
  • Sporophyte undergoes meiosis to produce haploid spores.
  • Spores differentiate into male (Antheridia) and female (Archegonia) gametophytes.
  • Sperm from male gametophytes fertilize eggs in female gametophytes, continuing the cycle.