Biology: Speciation, Phylogenetics, Prokaryotes, and Protists

Comprehensive vocabulary flashcards covering evolutionary mechanisms, speciation concepts, phylogenetics, archaeal and bacterial diversity, and protistan classifications from the lecture notes.

Biological Definition of Species

A group of organisms that maintains a distinct set of attributes in nature.

Macroevolution

Evolutionary changes that create new groups of species.

Microevolution

Evolutionary changes to a population's gene pool.

Species Concept

A framework where members of a single species are identified by having a unique combination of characteristics.

Morphospecies Concept

A subjective species concept championed by Carolus Linnaeus stating that if two individuals are morphologically different, they belong to different species.

Biological Species Concept

Championed by Theodosius Dobzhansky (1937) and Ernst Mayr; defines a species as one or more populations of organisms whose members interbreed to produce viable offspring and are isolated by reproductive barriers.

Evolutionary Species Concept

Proposed by George Gaylord Simpson (1961); defines a species as derived from a single lineage that is distinct from other lineages and maintains its own evolutionary tendencies and historical fate.

Ecological Species Concept

A concept defining species by the distinct ecological niche that they occupy.

Competitive Exclusion Principle

The principle stating that no two species can occupy the exact same niche without dividing resources; competing individuals are likely to belong to the same species.

Prezygotic Isolation

Reproductive isolating mechanisms that prevent fertilization from occurring between organisms.

Temporal Isolation

A prezygotic barrier where reproduction between populations occurs at different times.

Habitat Isolation

A prezygotic barrier where geographic or physical barriers prevent populations from meeting to mate.

Mechanical Isolation

A prezygotic barrier where anatomical differences prevent successful mating because genitalia do not match.

Gametic Isolation

A prezygotic barrier where mating occurs but gametes fail to fuse to form a zygote.

Behavioral Isolation

A prezygotic barrier where specific behaviors, signals, or courtship rituals are required to attract mates.

Postzygotic Isolating Mechanisms

Reproductive barriers that prevent gene exchange after fertilization has occurred.

Hybrid Sterility

A postzygotic isolating mechanism where interspecies hybrids develop normally but are sterile (e.g., a male donkey and female horse producing a sterile mule).

Hybrid Breakdown

A postzygotic isolating mechanism where first-generation hybrids are viable and fertile, but recombination in the $F_2$ generation results in genetic combinations that reduce fitness, viability, or cause sterility.

Anagenesis

A pattern of speciation in which an entire single species transforms into another species in a linear evolutionary path ($A \rightarrow B$).

Cladogenesis

A branching pattern of speciation where an ancestral lineage divides into multiple ramifications to produce new species.

Allopatric Speciation

Speciation that occurs when populations become geographically isolated and experience differing evolutionary selective pressures.

Adaptive Radiation

A burst of speciation occurring when a single ancestral species rapidly diversifies into a large number of descendant species adapted to different ecological niches.

Hybrid Zones

Geographic regions where the distributions of two related species overlap, reproductive barriers fail, and interbreeding produces hybrid offspring.

Sympatric Speciation

Speciation that takes place in populations living within the same geographic area without physical isolation.

Autopolyploidy

A type of polyploidy where an organism acquires multiple chromosome sets derived from a single species, such as spontaneous tetraploidy ($4\text{n}$).

Allopolyploidy

A condition in which an organism carries multiple sets of chromosomes originating from two or more different ancestral species.

Gradualism

A model of evolution proposing that species diverge continuously and steadily over very long periods of time.

Punctuated Equilibrium

A model of evolution where species experience long periods of evolutionary stasis interrupted by sudden, rapid bursts of speciation.

Allometric Growth

A developmental pattern where different parts of an organism grow at different rates, potentially driving evolutionary changes in morphology.

Systematics

The study of biological diversity and evolutionary relationships aimed at reconstructing phylogeny.

Monophyletic Taxon

A phylogenetic grouping consisting of a common ancestor and all of its descendants.

Paraphyletic Taxon

A phylogenetic group that includes a common ancestor but excludes some of its descendants.

Polyphyletic Taxon

A group consisting of taxa that do not share a direct immediate common ancestor with one another.

Principle of Parsimony

A rule in phylogenetic reconstruction stating that the preferred evolutionary tree is the one requiring the fewest evolutionary changes or steps.

Synapomorphy

A shared derived character that is found in two or more taxa and first evolved in their most recent common ancestor.

Shared Primitive Character

An ancestral trait found in two or more taxa that originated in a distant ancestor rather than a recent common ancestor (e.g., a backbone).

Character Matrix and Cladogram Reconstruction

A phylogenetic method classifying primitive vs. derived characters (such as backbone vs. fur, milk production, and 3 ear bones) to establish branching lineages among taxa.

Horizontal Gene Transfer

The movement of genetic material between distinct evolutionary lineages, such as bacteria giving rise to mitochondria and chloroplasts via endosymbiosis.

Methanogens

A group of anaerobic archaea that produce methane gas.

Halophiles

Extremophilic archaea that thrive in high salt concentrations and often possess high concentrations of rhodopsin.

Acidophiles

Extremophiles adapted to living in highly acidic environments, such as acid mine drainage.

Cyanobacteria

Photosynthetic, blue-green bacteria that contain chlorophyll pigments, can form symbiotic lichens with fungi, and use heterocysts for nitrogen fixation ($N \rightleftharpoons N$).

Quorum Sensing

A cell-to-cell communication process in which individual bacteria secrete small signaling molecules that coordinate collective behaviors when population threshold is reached.

Biofilm

A structured community of bacterial cells enclosed in a self-produced polymeric mucilage matrix, such as dental plaque adhering to teeth.

Gram-Positive Bacteria

Bacteria with a thick peptidoglycan cell wall containing teichoic acids and lipoteichoic acids, lacking an outer membrane and retaining crystal violet stain.

Gram-Negative Bacteria

Bacteria that lose crystal violet stain, possessing a thin peptidoglycan layer surrounded by an outer membrane rich in lipopolysaccharides.

Akinete

A large, thick-walled survival cell packed with nutrients produced by cyanobacteria to withstand cold or unfavorable environmental conditions.

Endospore

A tough, dormant, and highly viable structure formed inside bacterial cells that encloses DNA to ensure survival through adverse conditions.

Bacterial Conjugation

A process of genetic exchange where an $F^+$ donor bacterium transfers DNA directly to an $F^-$ recipient cell through a sex pilus.

Photoautotrophs

Organisms that utilize sunlight as an energy source to synthesize organic compounds from carbon dioxide.

Chemoautotrophs

Organisms that extract energy from the chemical oxidation of inorganic molecules to fix carbon dioxide into carbohydrates.

Photoheterotrophs

Organisms that harvest energy from sunlight but must obtain organic compounds from their environment as a carbon source.

Chemoheterotrophs

Organisms that rely entirely on organic molecules to supply both their energy and carbon needs.

Aerotolerant Anaerobes

Organisms that do not use oxygen for metabolic respiration but are not poisoned by its presence.

Obligate Anaerobes

Organisms that are poisoned by oxygen and cannot survive in its presence.

Supergroup Excavata

A major eukaryotic protist group characterized by an excavated feeding groove running along the axis of the cell.

Euglenozoa

A protistan group within Excavata characterized by a flexible pellicle composed of protein strips underlying the plasma membrane.

Kinetoplastids

A specialized group of excavate protists with distinct mitochondrial DNA aggregates, including Trypanosoma, the causative agent of sleeping sickness.