General Biology: Evolution, Microbes, Eukaryotes, Fungi, and Marine Algae

Vocabulary practice flashcards covering evolutionary mechanisms, microbial diversity, metabolic pathways, early life, eukaryogenesis, fungal biology, and marine plant lineages.

Biogeography

The scientific study of the geographic distributions and spatial patterns of organisms and ecological communities across Earth.

Abiotic factor

A non-living physical or chemical component of an environment, such as temperature, water, light, or salinity, that influences living organisms and ecosystems.

Biotic factor

Any living component, organism, or biological interaction within an ecosystem that affects another organism.

Biological fitness

The quantitative measure of an individual's ability to survive and reproduce in a specific environment, passing its genes to the next generation.

Natural selection

The evolutionary process by which heritable traits that improve an organism's survival or reproduction become more frequent in a population over successive generations.

Evolution

A change in the frequency of alleles or genetic variants within a population over generations.

Directional selection

A mode of natural selection that favors individuals at one extreme of a phenotypic range, resulting in a consistent shift in population trait values toward that extreme.

Disruptive selection

A mode of natural selection that simultaneously favors individuals at both phenotypic extremes over individuals with intermediate traits, promoting population diversification.

Stabilizing selection

A mode of natural selection that favors intermediate phenotypes and selects against extreme variants, thereby reducing phenotypic variance in the population.

Genetic drift

Random fluctuations in allele frequencies from generation to generation due to chance events, which exert a substantially greater evolutionary impact in smaller populations.

Sexual selection

A specific form of selection in which individuals with certain inherited traits are more likely than others to obtain mates and achieve reproductive success.

Allele

One of two or more alternative versions or molecular variants of a gene situated at a specific chromosomal locus.

Genotype

The complete genetic constitution or specific combination of alleles possessed by an individual organism.

Fixation

The condition wherein an allele reaches a frequency of $100\%$ ($1.0$) within a population, entirely replacing all alternative alleles for that gene.

Speciation

The evolutionary process through which ancestral populations diverge and become distinct, reproductively isolated species.

Ecological niche

The specific set of biotic and abiotic conditions, resources, and functional roles an organism occupies and utilizes within an ecosystem.

Sister taxa

Lineages, clades, or species that represent each other's closest evolutionary relatives by sharing an immediate common ancestor not shared by any other group.

Phylogenetic outgroup

A reference organism, species, or taxon outside the monophyletic group being analyzed that serves as an ancestral comparison point.

Internal node (phylogeny)

A branching divergence point on a phylogenetic tree representing the hypothetical most recent common ancestor of descendant clades.

Polyploidy

The genomic condition of possessing more than two complete sets of homologous chromosomes, which can drive instantaneous, sympatric speciation.

Phenotypic plasticity

The capacity of a single genotype to produce different morphological, physiological, or behavioral phenotypes when exposed to differing environmental conditions.

Microbe (microorganism)

A microscopic or single-celled organism—including bacteria, archaea, microscopic eukaryotes, and viruses—too small to be resolved by the naked human eye.

Spontaneous generation

The historically disproven theory postulating that fully formed living organisms arise spontaneously and directly from non-living matter.

Symbiosis

An ecological relationship wherein two or more organisms belonging to distinct species live together in intimate, long-term physical association.

Microbiome

The entire collective community of microorganisms—and their combined genomes—residing in or on a host organism or distinct environmental site.

Transcription

The enzymatic synthesis of a single-stranded messenger RNA ($\text{mRNA}$) molecule directed by a complementary DNA template strand.

Translation

The ribosome-mediated synthesis of a protein consisting of a specific linear sequence of amino acids specified by the sequence of codons in an $\text{mRNA}$ strand.

Codon

A specific sequence of three contiguous nucleotides in an $\text{mRNA}$ transcript that codes for a specific amino acid or translation stop signal.

Horizontal gene transfer (HGT)

The direct lateral movement of genetic material between distinct individual organisms rather than the vertical transmission from parent to offspring.

Plasmid

A small, typically circular extrachromosomal DNA molecule found in bacteria that replicates autonomously from the bacterial chromosome.

Autotroph

An organism capable of synthesizing its own complex organic matter utilizing inorganic carbon sources like carbon dioxide ($\text{CO}_2$).

Heterotroph

An organism that requires preformed organic carbon compounds from its environment to fuel growth, maintenance, and synthesis of cellular materials.

Phototroph

An organism that absorbs and converts electromagnetic light radiation into usable metabolic chemical energy.

Chemotroph

An organism that derives its primary metabolic energy from the oxidation of chemical compounds, which can be either organic or inorganic.

Redox reaction

A paired chemical reaction involving simultaneous electron transfer, wherein oxidation (loss of electrons) is strictly coupled to reduction (gain of electrons).

Proton motive force (pmf)

An electrochemical potential difference and proton concentration gradient generated across a biological membrane used to synthesize ATP via ATP synthase.

LUCA (Last Universal Common Ancestor)

The most recent hypothetical cellular ancestor from which all modern cellular life lineages present on Earth descend.

Ribozyme

An RNA molecule capable of folding into a catalytic tertiary structure and driving specific biochemical enzymatic reactions.

Stromatolite

A layered, organosedimentary rock structure produced through the binding, trapping, and mineral precipitation of sediments by active photosynthetic microbial mats.

Microbial mat

A vertically organized, multi-layered benthic sheet composed of cooperative and competing microorganism communities bound together by extracellular polymeric substances (EPS).

Molecular biomarker

A chemically stable organic molecule, hydrocarbon, or lipid skeleton preserved in sedimentary strata that provides diagnostic evidence of historical biological origins.

Anoxygenic photosynthesis

A primitive form of light-driven energy capture utilizing electron donors other than water—such as $\text{H}_2\text{S}$, $\text{H}_2$, or ferrous iron—without generating molecular oxygen ($\text{O}_2$).

Oxygenic photosynthesis

A metabolic process characteristic of cyanobacteria, algae, and plants that splits water ($\text{H}_2\text{O}$) as a source of electrons, generating molecular oxygen ($\text{O}_2$) as a byproduct.

Great Oxidation Event (GOE)

The geological interval occurring approximately $2.4\text{ to }2.1\,\text{Ga}$ when biologically produced oxygen accumulated significantly within Earth's atmosphere.

Endosymbiosis

An intimate, permanent symbiotic relationship where one organism resides directly within the body or cells of another host organism.

Eukaryogenesis

The evolutionary transitional sequence involving cellular and endosymbiotic mergers that produced the first complex eukaryotic cells from prokaryotic ancestors.

Archaea

A primary biological domain of unicellular prokaryotes distinguished by branched isoprenoid ether-linked membrane lipids and eukaryote-like transcriptional machinery.

Asgard archaea

A monophyletic deep-branching archaeal group recognized as the closest living prokaryotic relatives of eukaryotes due to their encoding of eukaryotic signature proteins.

Metagenomics

The direct high-throughput extraction and sequencing of collective genomic DNA from environmental samples without the requirement of laboratory culturing.

Bacteriophage

A specialized virus composed of nucleic acid packaged within a protein coat that targets, infects, and replicates exclusively within bacterial or archaeal hosts.

Hypha

A microscopic, tubular filamentous branching thread that serves as the basic vegetative structural unit of most multicellular fungi.

Mycelium

A dense, interconnected vegetative network of branching fungal hyphae adapted for subterranean nutrient absorption and environmental colonization.

Septa

Cross-walls that compartmentalize fungal hyphae into cell-like units, typically containing pores through which organelles and cytoplasm can pass.

Chitin

A rigid, structural polysaccharide containing nitrogen that serves as the primary reinforcing macromolecule in fungal cell walls.

Saprophyte

An organism that secretes hydrolytic digestive enzymes externally onto dead organic matter to absorb the liberated soluble nutrients.

Plasmogamy

The initial sexual stage in fungi wherein the cytoplasmic membranes of two compatible haploid mycelia fuse without the immediate fusion of their nuclei.

Karyogamy

The sexual stage in fungi wherein two haploid nuclei within a dikaryotic cell unite to form a single diploid ($2n$) zygotic nucleus.

Dikaryotic stage

A unique phase of the fungal sexual life cycle ($n + n$) where each cellular compartment retains two unfused, genetically distinct haploid nuclei.

Conidia

Asexually formed, non-motile fungal spores produced directly at the tips or sides of specialized aerial hyphae called conidiophores.

Mycorrhizae

Mutualistic subterranean associations established between soil fungal mycelia and plant root systems that enhance reciprocal mineral, water, and carbohydrate exchange.

Alternation of generations

A reproductive life cycle seen in plants and certain algae where a multicellular diploid sporophyte ($2n$) alternates with a multicellular haploid gametophyte ($n$).

Sporophyte

The multicellular diploid ($2n$) developmental phase of a plant or algal life cycle that undergoes meiosis to produce haploid spores.

Gametophyte

The multicellular haploid ($n$) developmental phase of a plant or algal life cycle that generates haploid gametes through mitosis.

Secondary endosymbiosis

The evolutionary event in which a non-photosynthetic eukaryote engulfs and permanently retains a photosynthetic eukaryote, yielding plastids enclosed by three or four membranes.

Thallus

A macroscopic, undifferentiated vegetative algal or plant body that lacks complex vascular systems and true roots, stems, or leaves.

Trophic cascade

A top-down ecological process whereby changes in the abundance of apex predators propagate across multiple intermediate and lower trophic levels, reshaping community structure.

Keystone species

A species that exerts a disproportionate control over the structural diversity and functional stability of an ecosystem relative to its total biomass or abundance.