Learning Unit 3: How Plants Colonized Land

Vocabulary terms covering the evolutionary adaptations, life cycles, and classification of land plants and seedless vascular plants.

Charophyceans

Green algae most closely related to land plants, sharing traits like rosette-shaped cellulose-synthesizing complexes and flagellated sperm.

Peroxisome Enzymes

Enzymes that minimize carbohydrate loss during photorespiration, a trait shared by charophytes and land plants.

Cuticle

A terrestrial adaptation in land plants used to prevent desiccation.

Sporopollenin

A durable organic material that protects spores from harsh environments; found in the walls of plant spores.

Apical Meristems

Specific regions at the tips of shoots and roots where plant growth occurs.

Alternation of Generations

A life cycle characterized by a multicellular haploid (gametophyte) stage and a multicellular diploid (sporophyte) stage.

Placental transfer cells

Specialized cells that facilitate the transfer of nutrients from the maternal plant to the multicellular, dependent embryo.

Sporangia

Multicellular organs in the sporophyte where spores are produced.

Gametangia

Multicellular organs where gametes are produced; in plants, these are distinct from the unicellular gametangia of algae.

Bryophytes

A group of non-vascular plants including mosses, liverworts, and hornworts where the gametophyte is the dominant stage.

Protonema

A one-cell-thick filament that forms from spore germination in mosses.

Gametophore

The upright structure produced from meristems in the protonema that produces gametes in mosses.

Rhizoids

Structures that anchor gametophytes; they are single elongated cells in liverworts and hornworts, or filaments of cells in mosses.

Phylum Lycophyta

A phylum of seedless vascular plants including club mosses, which originated in the Devonian period and once included trees up to $35\,m$ tall.

Microphylls

True roots, stems, and leaves characteristic of Lycophyta sporophytes.

Strobilus

An organized group of sporophylls (specialized leaves) that bear sporangia.

Phylum Pterophyta

A phylum of seedless vascular plants that includes true ferns, whisk ferns (psilophytes), and horsetails (sphenophytes).

Psilophytes

Whisk ferns characterized by dichotomous branching stems and a lack of true roots and leaves.

Sphenophytes

Horsetails, characterized by hollow stems with jointed nodes and a rough texture, belonging to the genus Equisetum.

Peat

Accumulated organic material formed from dead plants that did not fully decay in stagnant water during the Carboniferous period.