PLANTS

Explain the evolution of seedless vascular plants.
Assess the validity of basing plant phylogeny on available molecular and morphological data.

Electrical Energy Conversion: The conversion of chemical energy stored in coal into electrical energy through a typical steam-cycle power plant.
- Includes components like:
- Boiler (furnace)
- Steam turbine
- Generator
- Transmission lines
- Carboniferous Period: Highlighted by swamp forests abundant in club mosses and ferns.

Hierarchical Classification:
- Non-vascular Plants: Bryophytes
- Example Groups:
  - Liverworts
  - Mosses
  - Hornworts
- Vascular Plants (Tracheophytes):
- Free-sporing Vascular Plants: Isoetes
- Pteridophytes: Includes Lycophytes, Ferns, Horsetails
- Seed Plants (Spermatophytes): Angiosperms, Gymnosperms
  - Groups: Cycads, Ginkgo, Conifers, Gnetophytes, Basal angiosperms, Chloranthales, Magnoliids, Monocots, Ceratophyllum, Eudicots

Characteristics of Vascular Plants:
- Dominant branched sporophyte.
- Lignification: wood or woody tissue.
- Presence of vascular tissues and endodermis leading to a more complex sporophyte structure.

Haplodiplontic Alteration of Generations: Both sporophyte and gametophyte are multicellular.
- Haplontic: n is limited to zygote.
- Diplontic: n is limited to gametes.
Vascular plants display a nutrition-independent, photosynthetic, dominant, and persistent sporophyte stage, while the gametophyte stage is transient (dies off).

Stem Structure: Evolved to have a branching sporophyte axis due to the presence of an apical meristem.
- Parts of a Winter Twig:
- Node
- Internode
- Terminal buds
- Lateral buds
Types of Branching:
- Dichotomous Branching:
- Most primitive form; branches divide equally with limited specialization.
- Example genera: Rhynia, Aglaophyton
- Pseudomonopodial Branching:
- More advanced; one branch dominates the main axis.
- Monopodial Branching:
- Most advanced form; differentiation into stems, leaves, and reproductive structures is evident.
- Enations lead to the evolution of true leaves (microphylls, megaphylls).
Aglaophyton major: Transitional fossil exemplifying these branching structures.

Lignin: An organic polymer found in cell walls composed of phenolic compounds.
- Functions:
- Strengthens cell walls
- Provides mechanical support
- Enables plants to grow taller
- Waterproofs xylem vessels and tracheids.
Sclerenchyma: Ground tissue with heavily lignified secondary walls.
- Types:
- Fibers: Long, slender cells aiding in tensile strength.
- Sclereids: Shorter, irregular cells contributing to toughness and protection.

Xylem: Composed of tracheary elements arranged adjacently for water and ion conduction.
- Tracheids: Long, narrow cells allowing water movement through pits.
- Vessel Elements: Wider cells with perforations for increased growth and larger plant size.
Phloem: Composed of sieve elements arranged end to end for nutrient transport.
- Sieve Cells: Elongated cells associated with albuminous cells.
- Sieve Tube Members: Shorter, with large clustered pores for efficient translocation.

Endodermis: Specialized cylindrical layer of cells in roots, serving as a selective barrier.
- Regulates movement of water, minerals, and nutrients into the vascular system.
Casparian Strip: Band-like structure of suberin blocking apoplastic flow, ensuring selective absorption and preventing backflow of nutrients.

Photosynthetic Organ: Site of primary production derived from the primary growth meristem (SAM).
- Microphylls: Small leaves with single vascular strand, evolved from enations of stem tissue.
- Megaphylls: Larger leaves with branched vascular systems, evolved through telome theory, where flattening and fusion of branching systems created an expansive photosynthetic surface.

Bryophytes dominated for the first 100 million years; the earliest vascular plant ancestors appeared approximately 425 million years ago, characterized by the presence of sporophylls.
- Homosporous: One type of sporangium producing bisexual gametophyte.
- Heterosporous: Two types of spores lead to male (microspores) and female (megaspores) gametophytes.

Prominent groups: Phylum Lycopodiophyta and Monilophyta.
- Lycopsids: Club mosses with true roots and a dominant sporophyte stage.
- Monilophytes: Ferns with megaphylls, bearing sori that hold sporangia which are crucial for reproduction.

Characteristics:
- True, Y-shaped branching roots and microphylls.
- Club Moss: Features strobili which are clusters of sporophylls arranged at tips, operational in reproduction.
- Spike Moss: Heterosporous; characterized by small, creeping erect stems.
- Quillworts: Aquatic plants with unique microphylls and survival adaptations for underwater growth.

Pteridophytes with features like:
- Rhizomes and fronds (megaphylls).
- Sori: Clusters of sporangia.
- Frond: Functioning as both a photosynthetic and reproductive organ, bearing sori on the underside.
Horsetails (Equisetum): Recognized for their photosynthetic and reproductive functions from the erect stem.
Whisk Fern (Psilotum): Notable for reduction in structure, with dichotomous branching resembling whiskers.

Illustrations of the life cycles of Equisetum and Psilotum, highlighting key reproductive processes from sporophyte to gametophyte transformations.

Comprehensive understanding of seedless vascular plants, from their evolution, structure, classification to their ecological functions, reinforcing their significance in plant phylogeny.

The phylogeny diagrams and classification frameworks used in the lesson derived from established botanical literature, primarily focusing on empirical data from molecular and morphological studies.
- Source: Simpson, 2010.