Phylogenetics, Protists, and Plant Diversity

Vocabulary practice flashcards covering biological classification, phylogenetics, protistan diversity, and the evolutionary history of nonvascular, seedless vascular, gymnosperm, and angiosperm plants.

Systematics

The scientific discipline focused on classifying, naming, and determining the evolutionary relationships of organisms, encompassing taxonomy and phylogenetics.

Latin Binomial

A two-word scientific name for a species consisting of the genus name (capitalized) followed by the specific epithet (lowercase), both italicized.

Branch Point (Node)

A point on a phylogenetic tree representing the divergence of two evolutionary lineages from a common ancestor (a speciation event).

Sister Taxa

Groups of organisms that share an immediate common ancestor not shared by any other group, representing each other's closest relatives.

Basal Taxon

A lineage that diverges early in the evolutionary history of a group, originating from a branch point near the common ancestor of the group.

Synapomorphy

A shared, derived homologous character that evolved in an immediate common ancestor and is unique to a particular clade.

Maximum Parsimony

A principle of phylogenetic inference stating that the most likely tree is the simplest hypothesis requiring the fewest evolutionary steps or character changes.

Monophyletic Group (Clade)

A taxonomic grouping consisting of an ancestral species and all of its evolutionary descendants.

Paraphyletic Group

A taxonomic grouping consisting of an ancestral species and some, but not all, of its descendants.

Polyphyletic Group

A taxonomic grouping consisting of distantly related organisms without including their most recent common ancestor, typically grouped by convergent traits.

Homoplasy

A character state shared by a set of species that is not present in their common ancestor, arising instead through convergent evolution or evolutionary reversal.

Mitosome

A reduced, modified mitochondrion lacking electron transport chains and DNA, found in anaerobic diplomonad protists such as Giardia intestinalis.

Hydrogenosome

A modified, anaerobic organelle derived from mitochondria that generates ATP without oxygen and releases molecular hydrogen, found in parabasalids such as Trichomonas vaginalis.

Crystalline Rod

A spiral or crystalline rod running parallel to the ring of microtubules inside the flagella of euglenozoans.

Kinetoplast

A dense, organized mass of mitochondrial DNA housed within the single large mitochondrion characteristic of kinetoplastid protists.

Pellicle

A flexible, reinforcing layer composed of interlocking protein strips located beneath the plasma membrane in euglenids.

Frustule

The rigid, box-and-lid cell wall of diatoms composed of hydrated silicon dioxide (silica).

Thallus Structures of Brown Algae

Plantlike anatomical regions of a multicellular brown alga consisting of a rootlike holdfast (anchorage), a stem-like stipe (support), and leaflike photosynthetic blades.

Alveoli

Flattened, membrane-bound sacs situated directly beneath the plasma membrane in alveolate protists.

Zooxanthellae

Mutualistic, photosynthetic dinoflagellates inhabiting reef-building coral tissues that provide the host coral with photosynthetic sugars in exchange for nutrients like nitrogen.

Apical Complex

A specialized cluster of organelles located at the anterior apex of apicomplexan protists used to penetrate and enter host cells and tissues.

Phycoerythrin

A red accessory pigment found in red algae that absorbs blue and green wavelengths of light, masking chlorophyll and enabling photosynthesis in deep water up to $200\,m$.

Plasmodium (Mycetozoan)

A multinucleate, brightly colored feeding mass formed by plasmodial slime molds that is undivided by plasma membranes and creeps across substrates engulfing food particles.

Sporopollenin

A durable, highly resistant polymer that coats plant spores and charophyte zygotes, protecting them against environmental desiccation.

Cuticle

A protective, waxy covering on the epidermis of land plants that prevents excess water loss and desiccation.

Stomata

Specialized microscopic pores in the plant epidermis that facilitate gas exchange of $CO_2$ and $O_2$ while regulating water loss.

Alternation of Generations

A life cycle characteristic of plants featuring two alternating multicellular stages: a haploid gametophyte ($n$) and a diploid sporophyte ($2n$).

Gametophyte

The multicellular haploid ($n$) generation in plants that produces haploid gametes (egg and sperm) via mitosis.

Sporophyte

The multicellular diploid ($2n$) generation in plants that produces haploid spores via meiosis within sporangia.

Antheridium

The multicellular male gametangium of nonvascular and seedless vascular plants that produces and releases sperm.

Archegonium

The multicellular, flask-shaped female gametangium of plants that produces and houses a single non-motile egg where fertilization occurs.

Placental Transfer Cells

Specialized cells equipped with extensive plasma membrane and wall ingrowths that mediate nutrient transfer from the parent gametophyte to the developing embryo in embryophytes.

Apical Meristem

Localized regions of rapid cell division at the tips of roots and shoots that allow plants to grow continuously in length.

Bryophytes

Nonvascular land plants (liverworts, mosses, and hornworts) lacking specialized vascular tissues, characterized by flagellated sperm and a persistent, dominant gametophyte stage.

Protonema

A branched, filamentous, photosynthetic mass produced by germinating moss spores that develops into gametophores.

Elaters

Coiled, hygroscopic cells found in liverwort sporangia that twist and untwist with changes in humidity to facilitate spore ejection.

Pyrenoid

A specialized micro-compartment inside the single large chloroplast of hornwort cells that aids in carbon fixation and starch storage.

Peristome

A specialized ring of interlocking, tooth-like structures around the mouth of a moss capsule that regulates the gradual discharge of spores.

Tracheids

Elongated, tube-shaped xylem cells with walls strengthened by lignin that conduct water and mineral nutrients while providing structural support.

Microphylls

Small, typically spine-shaped leaves supported by a single unbranched vein, found exclusively in the lycophyte lineage.

Megaphylls

Leaves supported by a highly branched vascular network, found in monilophytes and all seed plants.

Sporophyll

A modified leaf that bears sporangia specialized for spore production.

Sori

Clusters of sporangia located on the undersides of reproductive fern leaves (fronds).

Strobili

Cone-like aggregations of sporophylls that bear sporangia in lycophytes and gymnosperms.

Dichopodial Roots

Roots that bifurcate into two equal branches at growing tips through dichotomous branching, unique to Lycophyta.

Monopodial Roots

Roots in which branch roots emerge laterally along the sides of the primary root axis, characteristic of monilophytes and seed plants.

Heterospory

The condition of producing two morphologically and functionally distinct types of spores: megaspores (female) and microspores (male).

Gymnosperm Seed

A reproductive dispersal unit consisting of a diploid ($2n$) embryo, haploid ($n$) nutritive tissue derived from the female gametophyte, and a protective diploid seed coat.

Ovule

A seed plant structure consisting of a megasporangium, megaspore, and one or more protective integument layers that develops into a seed following fertilization.

Pollen Grain

A structure that develops from a microspore, containing the reduced male gametophyte protected by a sporopollenin-rich wall.

Integument

A layer of sporophyte tissue that encloses and protects the megasporangium within an ovule; gymnosperms possess one, whereas angiosperms typically possess two.

Gymnosperms

Vascular seed plants whose seeds are 'naked' and exposed on sporophylls (often arranged in cones) rather than enclosed inside fruit ovaries.

Cycadophyta

A gymnosperm phylum characterized by large seed-producing cones, palm-like compound leaves, flagellated swimming sperm, and predominant insect pollination.

Ginkgophyta

A gymnosperm phylum represented by a single extant species (Ginkgo biloba) native to China, possessing fan-shaped deciduous leaves and flagellated sperm.

Coniferophyta

The largest gymnosperm phylum (~$600$ species), typically evergreen with needle- or scale-like leaves, non-flagellated sperm, and resin containing turpentine and rosin.

Flower Anatomy

A specialized angiosperm reproductive shoot composed of four whorls of modified leaves: sterile sepals and petals, pollen-producing stamens (microsporophylls), and ovule-bearing carpels (megasporophylls).

Angiospermae

Flowering plants characterized by seeds enclosed within fruits, double fertilization, ovules with two integuments, and a female gametophyte reduced to an embryo sac.

Sepals (Calyx)

The outermost sterile floral organs that enclose and protect the flower bud prior to opening, preventing mechanical injury and desiccation.

Petals (Corolla)

Sterile floral organs interior to the sepals that are typically brightly colored to attract animal pollinators.

Radial Symmetry (Actinomorphic)

A floral morphology that can be divided into two equal mirror-image halves along multiple vertical planes passing through the center.

Bilateral Symmetry (Zygomorphic)

A floral morphology that can be divided into two equal mirror-image halves along only a single vertical plane.