Evolution and Diversity of Protists, Fungi, and Land Plants

Comprehensive vocabulary flashcards covering the evolutionary origins, structural anatomy, reproductive life cycles, and taxonomic diversity of Protists (Chapter 21), Fungi (Chapter 22), and Land Plants (Chapter 23).

Endosymbiotic Hypothesis

The evolutionary model proposing that eukaryotic organelles evolved from prokaryotic organisms engulfed by ancestral cells, specifically that aerobic bacteria became mitochondria and photosynthetic cyanobacteria became chloroplasts.

Mixotroph

An organism capable of combining autotrophic and heterotrophic modes of nutrition, utilizing photosynthesis in the presence of light and phagocytosis or nutrient absorption when light is absent.

Cyst (Protistan)

A dormant, resistant outer covering formed by parasitic or free-living protists to survive hostile environmental conditions and facilitate transfer between hosts.

Excavata

A eukaryotic supergroup defined by atypical or absent mitochondria, distinctive flagella, and specialized deep feeding grooves (excavated grooves), encompassing diplomonads, parabasalids, and euglenozoans.

Giardia lamblia

A flagellated diplomonad with two nuclei and two sets of flagella that survives anaerobically in animal hosts, produces cysts spread via contaminated water, and causes severe diarrhea in humans.

Trichomonas vaginalis

A sexually transmitted parabasalid protozoan possessing a distinctive fibrous connection between its Golgi apparatus and flagella that causes symptomatic vaginal infections in human females.

Pellicle

A flexible layer of protein bands beneath the plasma membrane in euglenoids that allows the cell to change shape while swimming without having a rigid cell wall.

Kinetoplast

A large, dense mass of mitochondrial DNA characteristic of kinetoplastid flagellates such as trypanosomes.

Trypanosoma brucei

A parasitic kinetoplastid transmitted by the bite of the tsetse fly that causes African sleeping sickness by compromising oxygen transport to the host brain.

Alveolates

A major Chromalveolata lineage defined by flattened vesicles called alveoli beneath the plasma membrane, including dinoflagellates, apicomplexans, and ciliates.

Zooxanthellae

Mutualistic endosymbiotic dinoflagellates that dwell inside coral tissues, providing organic photosynthates to the coral in exchange for protective habitat and inorganic nutrients.

Red Tide

A toxic bloom of marine dinoflagellates (such as Alexandrium catanella) that discolors water and synthesizes neurotoxins that cause extensive fish mortality and human paralytic poisoning.

Apicoplast

A specialized, non-photosynthetic plastid organelle found in apicomplexan parasites that is essential for invading host animal cells.

Trichocyst

An extrusible, barbed organelle located in the pellicle of ciliates used for defense, mechanical anchoring, and prey capture.

Diatom

A single-celled stramenopile characterized by a rigid, two-part protective cell wall composed of hydrated silica, forming siliceous sediment deposits known as diatomaceous earth.

Laminarin

A complex storage polysaccharide utilized by brown algae (phaeophytes) to store carbohydrate reserves.

Oomycetes

Water molds; a group of fungus-like diploid stramenopile protists with cellulosic cell walls and flagellated zoospores that decompose organic matter or act as agricultural pathogens.

Test (Rhizarian)

The external skeleton or shell surrounding rhizarian protists, constructed from calcium carbonate ($\text{CaCO}_3$) in foraminiferans and silica ($\text{SiO}_2$) in radiolarians.

Volvox

A colonial green chlorophyte forming a hollow spherical ball made up of thousands of coordinated, flagellated vegetative cells enclosing interior reproductive daughter colonies.

Spirogyra

An unbranched filamentous freshwater charophyte possessing spirally coiled chloroplasts that undergoes sexual reproduction by forming conjugation tubes.

Pseudoplasmodium

A transient, slug-like mobile aggregate of individual cellular slime mold amoebae that forms in response to stress chemical signals to migrate toward spore development sites.

Choanoflagellates

Single-celled or colonial aquatic opisthokont filter feeders that possess a single flagellum surrounded by a collar of microvilli, closely resembling the choanocyte cells of sponges.

Saprotroph

A heterotrophic organism that feeds by releasing extracellular enzymes to digest complex organic matter in its surroundings before absorbing the simpler decomposed nutrient molecules.

Mycelium

The vegetative feeding body of a fungus, consisting of an extensive subterranean or inter-tissue network of filamentous threads called hyphae.

Septate Hyphae

Fungal hyphae that are subdivided into distinct cellular sections by perforated transverse partitions known as septa, which allow the flow of organelles and cytoplasm.

Dikaryotic Stage

A phase in fungal sexual life cycles where a hypha carries two distinct, compatible haploid nuclei per cell ($n + n$) following plasmogamy, prior to karyogamy.

Microsporidia

Obligate, spore-forming, single-celled intracellular parasites of animals that are considered a highly specialized sister group of kingdom Fungi.

Zoospore (Fungi)

A flagellated, motile asexual spore found in ancestral aquatic fungal lineages such as blastocladiomycetes and chytrids that swims toward a substrate before germinating.

Neocallimastigiomycota

A phylum of obligately anaerobic, mitochondrion-lacking fungi residing symbiotically in the digestive tracts of herbivorous ruminants to break down cellulose and lignin.

Batrachochytrium dendrobatidis

A pathogenic parasitic chytrid fungus that colonizes amphibian skin, disrupting cutaneous respiration, hydration, and osmoregulation, leading to worldwide amphibian population declines.

Zygospore

A thick-walled, melanized resting spore formed by the sexual conjugation of gametangia from opposite mating types ($+\text{ and }-\text{ hyphae}$) in Zygomycota.

Arbuscular Mycorrhizal (AM) Fungi

Glomeromycete soil fungi that form mutualistic symbioses with plant root cortical cells, forming highly branched invaginations called arbuscules to transfer soil phosphate and minerals.

Ascus

A microscopic, finger-shaped reproductive sac produced by Ascomycota in which karyogamy and meiosis take place to yield eight haploid ascospores.

Conidia

Asexual, non-motile fungal spores produced directly at the tips of specialized aerial reproductive hyphae called conidiophores in ascomycete molds.

Basidium

A club-shaped terminal cell found on the gills or pores of a basidiocarp fruiting body that bears four external haploid basidiospores following meiosis.

Amanita phalloides

A notorious poisonous basidiomycete commonly called the death cap mushroom, which produces fatal amatoxins that cause liver and kidney failure.

Claviceps purpurea

An ascomycete grain pathogen that infects rye spikes, forming hardened black sclerotia known as ergot that synthesize toxic alkaloids causing ergotism in consumers.

White-Nose Syndrome

A catastrophic fungal infection in North American hibernating bats caused by the psychrophilic ascomycete Pseudogymnoascus destructans, which induces winter arousal and starvation.

Lichen

A composite symbiotic organism consisting of a mycobiont (typically an ascomycete and/or basidiomycete) and a photobiont (a green alga or cyanobacterium), displaying crustose, foliose, or fruticose morphology.

Cuticle (Plant)

A waxy, hydrophobic external secretion composed of cutin that coats the epidermal cell walls of aerial plant organs to prevent water loss via evaporation.

Stomata

Microscopic pores bordered by pairs of guard cells situated in the epidermis of plant leaves and stems that regulate photosynthetic gas exchange and transpiration.

Alternation of Generations

The terrestrial plant life cycle in which a multicellular haploid generation ($\text{gametophyte, } n$) alternates with a multicellular diploid generation ($\text{sporophyte, } 2n$).

Gametophyte

The multicellular haploid ($n$) phase of the plant life cycle that produces haploid gametes (eggs and sperm) by mitotic division within gametangia.

Sporophyte

The multicellular diploid ($2n$) phase of the plant life cycle that produces haploid spores through meiotic division within sporangia.

Bryophytes

Nonvascular land plants (liverworts, hornworts, and mosses) that lack specialized conducting tissues, rely on surface water for motile flagellated sperm, and maintain a dominant gametophyte generation.

Gemmae

Small haploid cellular disks produced inside cups on the dorsal thallus of liverworts (e.g., Marchantia) that detach during rainfall to establish new clonal plants asexually.

Xylem

The specialized vascular tissue in plants responsible for transporting water and dissolved inorganic minerals upward from roots, reinforced with rigid lignin polymers.

Phloem

The living vascular conducting tissue that transports photosynthetically manufactured sucrose and organic nutrients bidirectionally throughout vascular plants.

Cooksonia

An extinct, primitive Silurian-Devonian vascular plant consisting of leafless, dichotomously branched stems capped with terminal sporangia that produced windblown spores.

Microphyll

A small leaf possessed by lycophytes that is served by a single unbranched vascular strand originating from the stem.

Megaphyll

A broad leaf containing an extensively branched network of vascular strands that evolved from the webbed flattening of branch systems, characteristic of pteridophytes and seed plants.

Equisetum

The sole surviving genus of horsetails, distinguished by jointed, silica-impregnated photosynthetic aerial stems, whorled microphyll leaves, and terminal spore-bearing strobili.

Psilotum

A genus of whisk ferns characterized by leafless, dichotomously branched photosynthetic green stems anchored by subterranean rhizomes and bearing three-lobed yellow sporangia.

Sorus

A discrete, macroscopic cluster of spore-filled sporangia located on the abaxial (underside) surface of mature fertile fern fronds.

Pollen Grain

The protective, microspore-derived immature male gametophyte of seed plants, surrounded by a durable sporopollenin coat that enables wind or vector transport without external water.

Ovule

A female reproductive structure in seed plants consisting of a megasporangium enclosed by protective integuments that develops into a viable seed following fertilization.

Gymnosperms

Vascular plants (conifers, cycads, ginkgoes, and gnetophytes) whose seeds develop exposed on the surfaces of cone scales or stalks ('naked seeds') rather than enclosed in a carpel.

Monoecious

Having both staminate (pollen-producing male) and ovulate (seed-producing female) reproductive structures situated on the same individual plant.

Dioecious

Having male and female reproductive organs located on separate individual plants, exemplified by Ginkgo biloba and cycads.

Welwitschia

A desert gnetophyte native to southwest Africa that possesses an underground woody stem and two wide, strap-like leaves that grow continuously from a basal meristem, fraying over centuries.

Cotyledon

An embryonic leaf present within the seed of an angiosperm that participates in the absorption, storage, or transport of nutrients from the endosperm to the growing embryo.

Monocotyledon (Monocot)

An angiosperm lineage characterized by one cotyledon, parallel venation, floral organs in multiples of three, scattered stem vascular bundles, and a fibrous root system.

Eudicotyledon (Eudicot)

An angiosperm lineage characterized by two cotyledons, net venation, floral organs in multiples of four or five, stem vascular bundles organized in a ring, and a central taproot system.

Stamen

The male reproductive pollen-producing unit of a flower, composed of an elongated filament supporting a terminal four-lobed anther containing microsporangia.

Carpel

The ovule-bearing female organ of a flower, consisting of a receptive terminal stigma, an elongate style, and a basal ovary that encloses one or more ovules.

Double Fertilization

The angiosperm fertilization mechanism where one sperm nucleus fertilizes the egg to yield a diploid ($2n$) zygote, while a second sperm fuses with two polar nuclei to yield a triploid ($3n$) nutritive endosperm.