Lecture Notes: Seedless Plants and Seed Plants

Introduction

• Continuation on plants, focusing on seedless plants.
• Previous lecture introduced bryophytes and their phylogenetic tree.
• Bryophytes include three clades: liverworts, hornworts, and mosses.

Bryophytes

• Liverworts
  • Named due to thallus resemblance to a liver.
  • Unique feature: Gemmae Cups for asexual reproduction (detaches and grows into new gametophytes).
• Hornworts
  • Named for horn-like sporophytes.
  • Structure aids in spore release.
• Mosses
  • Tangle of photosynthetic filaments (gametophyte).
  • Sporophyte stalks aid in spore dispersal.

Evolutionary Innovations

• Transition from bryophytes to Tracheophytes (vascular plants).
• Vascular tissue (xylem and phloem) allows plants to grow larger.
• Vascular features: lignin, real roots/stems/leaves, increased support and photosynthesis.

Seedless Vascular Plants

• Still rely on water for reproduction (sperm swims to egg).
• Lycophytes (club mosses, quillworts, spike mosses).
• Pterophytes (whisk ferns, horsetails, true ferns).
  • Ferns have unique fiddlehead development and independent gametophytes.

Seed Plants

• Spermatophyta includes all seed plants.
• Dominance of sporophyte in life cycle (gametophyte microscopic).
• Key Innovations:
  • Pollen: Male gametophyte carried by wind, eliminating need for water in fertilization.
  • Seeds: Protect embryo, delay germination until conditions are favorable.

Gymnosperms

• Means "naked seeds" (no fruit or flowers).
• Seeds protected by sporophylls (e.g., pine cones).
• Types of Gymnosperms:
  • Conifers (monocious, mostly evergreen, some deciduous).
  • Cycads (dioecious, palm-like leaves, large cones).
  • Ginkgos (dioecious, deciduous, pollution-tolerant).
  • Gnetophytes (diverse features).

Summary

• Discussed bryophytes, tracheophytes, seedless vascular plants, and seed plants.
• Introduced gymnosperms and key characteristics.
• Next lecture will cover gymnosperm life cycles, focusing on conifers.