lecture 13

Evolution of Plants onto Land

• Modern plants evolved from green algae (Chlorophyta).

• Key groups:

  • Ulvophyceae, Chlorophyceae, Charophyceae, etc.

  • Streptophyta includes land plants and green algae.

Key Characteristics of Land Plants

• Land plants exhibit multicellularity, vascular structures (xylem and phloem), and a cuticle to prevent water loss.

• Photosynthesis is facilitated by chloroplasts derived from cyanobacteria through endosymbiosis.

• Chlorophyll a and b are involved in photosynthesis; lignin contributes to structural support.

Life Cycle and Reproduction

• Alternation of generations is a fundamental aspect (sporophyte and gametophyte phases).

• Seed plants evolved mechanisms of reproduction that do not require water for gamete transport.

• Many plants exhibit vegetative reproduction, allowing genetic diversity.

Genetic and Evolutionary Insights

• Polyploidy is common, leading to the rapid formation of new plant species.

• Evolution of plants is marked by the transition from aquatic environments to land, driven by nutrient exchange with symbiotic fungi.

Historic Timeline

• Earliest evidence of land plants dates back to around 540 million years ago.

• Key evolutionary milestones include the emergence of wood, seeds, and vascular systems, impacting plant growth and diversity.

• The fossil record aligns with the evolutionary history of plants and their development over 350 million years.