BIOLS222 Test 1: Algal Features, Diversity, Reproduction, and Land Plant Evolution

Comprehensive vocabulary flashcards covering algal classification, cellular morphologies, reproductive strategies, cyanobacterial ultrastructure, and evolutionary adaptations of early land plants.

LECA

The Last Eukaryotic Common Ancestor; the single founding ancestral population from which all living eukaryotes (from microscopic yeast to giant redwood trees and humans) descended.

Endosymbiotic Theory

The evolutionary model explaining the origin of mitochondria and chloroplasts: an ancestral prokaryote engulfed aerobic bacteria, which remained as symbionts that removed harmful $O_2$ and produced ATP instead of being digested.

Planktonic Algae

Algae that float freely on the water surface; subdivided into euplanktons (which are never attached) and tychoplanktons (which are initially attached and then become detached).

Benthic Algae

Bottom-dwelling algae attached to the floor of shallow pools, existing as epizoic, epilithic, epipelic, or epiphytic forms.

Neustonic Algae

Algae adapted to grow specifically at the air-water interface, such as Nautococcus.

Supralittoral Algae

Algae inhabiting zones above the water level on rocky shores, kept moist solely by splashes from high spring tide waves (e.g., Ulothrix).

Sublittoral (Infra Littoral) Algae

Algae that grow submerged below the water level, such as Oscillatoria and Anabaena.

Littoral Algae

Algae that inhabit the junction between land and sea, adapted to periodic tidal exposure (e.g., Laminaria sp.).

Aerophytes

Algae adapted for aerial life that obtain moisture from rain, dew, and humidity; includes epiphloeophytes growing on tree bark and epiphyllophytes growing on leaves.

Cryophytic Algae

Cold-adapted algae growing in permanent or semi-permanent snow in polar or alpine regions, frequently imparting color to the snow pack (e.g., green Chlamydomonas nivalis and red Haematococcus nivalis).

Epizoic Algae

Algae that grow directly upon the outer surfaces of aquatic animals, including turtle shells, snail shells, or fish gills.

Epiphytic Algae

Algae that grow attached to other aquatic plants without displaying strict host-specificity (e.g., Rivularia growing on Scirpus).

Parasitic Algae

Algal organisms living as parasites or semiparasites on other algae or higher plants that cause severe tissue damage, such as Cephaleuros on tea and coffee crops.

Thermophytic Algae

Thermal-tolerant algae (mostly cyanophycean members like Cyanidium) thriving in hot springs where water temperatures can exceed $85^\circ\text{C}$.

Rhizopodial Form

Unicellular motile algae that lack a rigid cell wall, possess a naked periplasmic cell envelope, and move in an amoeboid fashion via pseudopodia and rhizopodia (e.g., Chrysamoeba).

Coccoid Form

Non-motile unicellular algal cells enclosed by a rigid cell wall, where flagella are absent and motility is completely absent or restricted strictly to reproductive stages.

Coenobium

A colony with a predetermined, constant number of cells arranged in a specific morphology set during the juvenile stage, which does not increase by cell division during subsequent growth.

Palmelloid Colony

A colony consisting of variable numbers of non-motile cells embedded in an amorphous gelatinous or mucilaginous matrix, where cell number, size, and shape are not fixed.

Dendroid Colony

A colony in which cells are joined in a tree-like branching pattern produced by the localized secretion of mucilage at the base of each individual cell (e.g., Chrysodendron).

True Branching

Branching produced by repeated transverse divisions of lateral outgrowths originating from scattered vegetative cells along the main filament.

False Branching

A branching appearance resulting when an intercalary cell degenerates, causing the trichome to fragment and push one or both ends out through the parent sheath.

Siphonocladous Organization

A filamentous thallus organization restricted to certain green algae where unbranched or branched filaments are constructed of multinucleate (semicoenocytic) cellular compartments.

Siphonous Organization

A coenocytic algal body form where continuous nuclear division occurs without cytokinesis or septum formation, resulting in a giant multinucleate single-celled thallus.

Akinetes

Thick-walled, non-motile resting spores enriched with abundant nutrient reserves, formed by the modification of vegetative cells to survive drought and harsh environmental conditions.

Aplanospores

Thick-walled, non-motile asexual spores formed under adverse conditions by rounding off cytoplasmic contents and secreting a wall within a parent sporangium.

Hypnospores

Thick-walled aplanospores that enter extended quiescence to withstand severe winter stress or prolonged drought before germinating.

Autospores

Non-motile, thick-walled asexual spores produced inside a sporangium that replicate the exact structural morphology of the parent cell in miniature.

Bispores

Spore pairs developed specifically inside a specialized structure called a bisporangium, producing two spores per unit.

Carpospores

Diploid spores generated within a carposporangium from the zygote during the triphasic life cycle of red algae (Rhodophyta).

Heterocyst

A specialized, transparent, thick-walled, oxygen-free cyanobacterial cell differentiated from vegetative filaments that lacks polyhedral bodies, polyphosphate bodies, and cyanophycin granules, serving as the site of nitrogen fixation.

Trichome

An unbroken cellular chain of cyanobacterial cells excluding the surrounding mucilaginous sheath.

Hormogonium

A short fragment detached from a cyanobacterial trichome capable of gliding away and developing into a new filament.

Eutrophication

The enrichment of an aquatic ecosystem with excessive nutrients, which triggers massive proliferations or blooms of simple organisms like cyanobacteria.

Isogamy

A sexual fusion mode involving gametes that are morphologically identical in size and structure as well as physiologically compatible.

Anisogamy

Sexual reproduction involving gametes that differ in size, morphology, or physiological behavior (with the larger gamete typically designated as female).

Oogamy

A specialized form of anisogamy in which a large, sessile, food-packed non-motile egg or ovum is fertilized by a smaller, motile sperm cell (antherozoid).

Autogamy

A self-fertilization process found in diatoms where haploid gametes derived from the same parent cell fuse to form a diploid zygote lacking genetic variation.

Pit Connections

Proteinaceous cytoplasmic plugs that traverse the cross-walls to structurally link adjacent cells in red algae (Rhodophyta).

Haptonema

A peg-like, specialized filiform appendage characteristic of prymnesiophytes used for prey capture or attachment, distinct from flagella.

Statospore

A heavily silicified, internally formed resting cyst characteristic of the golden-brown algae (Chrysophyceae).

Auxospore

A specialized cell stage in diatoms (Bacillariophyceae) that re-establishes normal cell size after successive generations of vegetative cell size reduction.

Isomorphic Alternation of Generations

A life cycle in which the multicellular diploid sporophyte and multicellular haploid gametophyte phases are morphologically identical.

Heteromorphic Alternation of Generations

A life cycle in which the multicellular diploid sporophyte and haploid gametophyte generations are morphologically distinct and easily distinguishable.

Triphasic Life Cycle

The life cycle characteristic of Florideophycidae (Rhodophyta) consisting of three successive phases: two diploid stages (carposporophyte and tetrasporophyte) and one haploid stage (gametophyte).

Outcrossing

A mating system promoting cross-fertilization, preventing deleterious recessive mutations from being expressed through genetic complementation.

Genetic Complementation

The masking of deleterious recessive alleles by functional dominant alleles inherited through cross-fertilization, driving hybrid vigor (heterosis).

Inbreeding Depression

The phenotypic decline in vigor and fitness occurring when self-fertilization or inbreeding exposes previously masked deleterious recessive mutations.

Sporopollenin

A durable, decay-resistant biopolymer encasing land plant spores that protects them against desiccation and ultraviolet (UV) radiation damage.

Lignin

A rigid polymer embedded in the conducting cell walls of tracheophytes providing structural support against gravity in terrestrial environments.

Convergent Evolution

An evolutionary pattern where distantly related lineages develop analogous phenotypic structures under similar selection pressures in comparable environments.

Chlorophyll f

A red-shifted form of chlorophyll discovered in cyanobacteria from Shark Bay (Australia) that absorbs near-infrared light.

Modes of Syngamy in Algae

Three sexual reproduction modes based on gamete morphology: Isogamy (equal, motile gametes), Anisogamy (motile gametes differing in size), and Oogamy (large non-motile egg fertilized by a smaller motile sperm).

Cyanobacteria Ultrastructure

The cellular architecture of a cyanobacterium highlighting the outer slime sheath, cell wall, photosynthetic thylakoid lamellae with phycobilisomes, central nucleoplasm, and inclusions such as polyhedral bodies (carboxysomes), polyphosphate bodies, and cyanophycin granules.

Ulvophycean Morphological Organization

Evolutionary organizational forms in green algae: monokaryotic multicellular thalli with septa (Ulva), multinucleate siphonocladous organization (Cladophora), giant uninucleate cells (Acetabularia), and coenocytic multinucleate siphonous tubes lacking septa (Caulerpa).