Plant Evolution and Diversity: From Green Algae to Seed Plants Exam 2

Flashcards covering key botanical terms, terrestrial adaptations, vascular developments, and seed evolution across Archaeplastida, Bryophytes, Tracheophytes, and Spermatophyta.

Archaeplastida

A eukaryotic supergroup that includes red algae, green algae (chlorophytes and charophytes), and land plants.

Charophytes

The green algal clade identified as the sister taxon to land plants.

Chlorophytes

One of the two paraphyletic clades of green algae within Archaeplastida, alongside charophytes.

Cellulose

A structural polymer composed of glucose units connected by $\beta\text{-1,4-glucopyranosides}$ that forms cell walls in green algae and land plants.

Embryophytes

The clade comprising land plants, characterized by multicellular dependent embryos retained within maternal tissues.

Apical Meristems

Localized regions of cell division at the tips of roots and shoots that continuously divide by mitosis to elongate the plant body.

Cuticle

A waxy layer covering the epidermis of land plants that functions in waterproofing to prevent desiccation.

Sporopollenin

A highly resistant polymer found in plant spore walls and pollen walls that protects against environmental desiccation.

Gametangia

Multicellular structures in land plants that enclose and protect gametes from desiccation.

Archegonia

The female gametangia in plants that produce and enclose a single non-motile egg ($n$).

Antheridia

The male gametangia in plants that produce and release flagellated sperm ($n$).

Alternation of Generations

A reproductive life cycle in plants alternating between a multicellular haploid gametophyte ($n$) and a multicellular diploid sporophyte ($2n$).

Placental Transfer Cells

Specialized maternal and embryonic cells featuring wall ingrowths that facilitate the transfer of nutrients from gametophyte to dependent sporophyte.

Bryophytes

Nonvascular land plants (liverworts, mosses, and hornworts) characterized by a dominant gametophyte, lack of vascular tissue, and motile sperm requiring water for fertilization.

Sphagnum

A genus of moss (peat moss) that forms extensive deposits of partially decayed organic material, serving as a fuel source, soil conditioner, and major carbon sink covering $3\%$ of Earth's land surface.

Tracheophytes

Vascular plants characterized by dominant sporophytes, organ systems (roots and shoots), and lignified vascular tissue (xylem and phloem).

Cooksonia

An early genus of extinct seedless tracheophytes from approximately $433\text{ to }393\text{ million years ago}$ possessing terminal sporangia and dichotomous branching, but lacking true roots and leaves.

Xylem

Vascular tissue responsible for conducting water and minerals upward, containing tube-shaped cells called tracheids strengthened by lignin.

Phloem

Vascular tissue arranged into tubes that distribute sugars, amino acids, and other photosynthetic products throughout the plant.

Lignin

A strong, hydrophobic polymer embedded in xylem cell walls that provides structural support enabling tall plant growth.

Microphylls

Small leaves supported by a single unbranched strand of vascular tissue, unique to lycophytes.

Megaphylls

Leaves with a highly branched vascular system that capture more light and enhance photosynthetic capacity.

Sporophylls

Modified leaves that bear sporangia for spore production.

Sori

Clusters of sporangia located on the undersides of fern sporophylls.

Strobili

Cone-like structures formed by clusters of sporophylls in lycophytes and gymnosperms.

Homosporous

Plant species producing a single type of spore that develops into a bisexual gametophyte with both antheridia and archegonia.

Heterosporous

Plant species producing two distinct types of spores: megaspores that form female gametophytes and microspores that form male gametophytes.

Lycophytes

A phylum of seedless vascular plants comprising club mosses, spike mosses, and quillworts, characterized by microphyll leaves.

Lepidodendron

An extinct genus of tree-sized lycopods that dominated Carboniferous coal swamps.

Equisetum

The single surviving genus of horsetails (Sphenophyta), featuring jointed stems ringed by whorled microphylls, silica cell wall deposits, and terminal strobili.

Psilotum

A genus of whisk ferns reminiscent of early tracheophytes, lacking true roots and leaves, bearing simple sporangia on dichotomously branching stems.

Spermatophyta

The clade of seed plants (gymnosperms and angiosperms) defined by synapomorphies including seeds, highly reduced dependent gametophytes, heterospory, pollen, and ovules.

Seed

A structure consisting of a plant embryo and nutrient food reserves enclosed within a protective seed coat.

Ovule

A structure composed of a megasporangium ($2n$), megaspore ($n$), and protective integument layers ($2n$) that develops into a seed following fertilization.

Pollen Grain

A structure derived from a microspore containing a male gametophyte protected within a sporopollenin-coated pollen wall.

Pollination

The physical transfer of pollen to the plant structure containing the ovules, eliminating the need for environmental water during fertilization.

Elkinsia polymorpha

An early fossil seed plant species dating to approximately $375\text{ million years ago}$.