Comprehensive Biology Review: Evolutionary Processes, Genetics, Phylogenetics, and Osmoregulation

A vocabulary flashcard set covering key terminology across all five provided lectures: Homology & Phylogenetics, Sexual Selection, Co-Evolution, Agents of Evolutionary Change, and Water Balance & Excretion.

Homology

A similarity between two or more features across species that is due to inheritance from a shared common ancestor.

Sequence Alignment

The computational process of arranging DNA, RNA, or protein sequences to identify equivalent, homologous nucleotide or amino acid positions across species.

Cladogram

A phylogenetic tree that illustrates only topology (branching relationships between taxa), where branch lengths carry no quantitative meaning.

Phylogram

A phylogenetic tree in which branch lengths are explicitly proportional to the amount of evolutionary change, such as the number of nucleotide or amino acid substitutions.

Ultrametric Tree

A rooted phylogenetic tree in which all terminal branch tips align at the same point, with branch lengths proportional to elapsed time.

Outgroup

A taxon included in phylogenetic analysis known or assumed to have diverged prior to all other taxa under study, used to establish a root and determine evolutionary direction.

Molecular Clock Hypothesis

The hypothesis that nucleotide or amino acid substitutions accumulate within a given gene or protein lineage at an approximately constant rate over time.

Monophyletic Group

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

Population Genetic Structure

Systematic differences in allele frequencies between sub-populations or geographic groups of a larger species resulting from isolation and restricted gene flow.

Private Variant

A genetic variant or mutation detected exclusively within one specific population and absent in others.

Sexual Selection

A specialized mode of natural selection acting on traits that enhance an individual's mating and fertilization success rather than pure survival.

Intersexual Selection

A mechanism of sexual selection involving mate choice, where individuals of one sex (typically females) preferentially mate with individuals of the opposite sex bearing specific phenotypic traits.

Intra-Sexual Selection

A mechanism of sexual selection involving direct competition between individuals of the same sex (typically males) for access to mates.

Ornament

A physical or behavioral trait favoured by intersexual selection that attracts mates and signals biological quality to the opposite sex.

Armament

A physiological or morphological feature favoured by intra-sexual selection that is utilized in physical combat or threat displays against sexual rivals.

Honest Signal

A costly morphological or behavioral trait that reliably reflects an individual's true genetic or physiological quality because low-quality individuals cannot afford its production or maintenance.

Sexual Dimorphism

A systematic difference in form, size, or appearance between males and females of the same species resulting from sexual selection.

Cryptic Female Choice

A post-copulatory mechanism by which a female biases fertilization in favour of preferred males, such as by physically ejecting or selectively storing sperm.

Sperm Competition

Direct competition between sperm from two or more males to fertilize a female's eggs when she mates multiply within a single reproductive cycle.

Sexual Conflict

An evolutionary tension arising when the reproductive interests of males and females diverge, driving co-evolutionary arms races of adaptations and counter-adaptations between the sexes.

Mate Guarding

A behavioral adaptation, such as prolonged physical attachment after copulation, in which an individual prevents rival suitors from mating with their partner.

Polyandry

A mating system in which a single female mates with multiple males during a single breeding event or season.

Co-Evolution

A process in which two or more interacting species reciprocally exert selective pressures on one another, driving back-and-forth evolutionary adaptation over time.

Red Queen Hypothesis

The proposition that species must continuously adapt and evolve merely to maintain their current fitness level because interacting competitors, predators, parasites, and hosts are also constantly evolving.

Antagonistic Interaction

An interspecific relationship where one species benefits at the expense of another, driving evolutionary arms races.

Mutualistic Interaction

An interspecific relationship in which both participating species derive a net evolutionary or physiological benefit.

Brood Parasitism

An antagonistic strategy where a bird species lays its eggs in the nest of another species, shifting all parental care costs onto the host parents.

Virulence

The degree of damage or mortality caused by a pathogen to its host, which typically trades off against the pathogen's rate of transmission.

Altruism

A behavior that increases another individual's fitness while incurring a direct fitness cost to the individual performing the action.

Kin Selection

A form of selection that favors behaviors increasing the reproductive success of genetic relatives, thereby promoting the transmission of shared alleles to the next generation.

Haplodiploidy

A sex-determination system seen in Hymenoptera where females develop from fertilised diploid eggs and males develop from unfertilised haploid eggs, causing full sisters to share an average of $75\%$ of their genome.

Eusociality

An advanced social structure characterized by cooperative brood care, overlapping generations within a colony, and division of labor into reproductive and non-reproductive castes.

Assortative Mating

A non-random mating pattern where individuals with similar phenotypes or genotypes mate with each other more frequently than expected by chance, increasing homozygosity.

Disassortative Mating

A non-random mating pattern where individuals with dissimilar phenotypes or genotypes preferentially mate with one another, maintaining high heterozygosity.

Gene Flow

The transfer of alleles between distinct populations through migration, hybridisation, or gamete dispersal, calculated as $\Delta p = m \times (p_{\text{migrant}} - p_{\text{resident}})$.

Genetic Drift

Random fluctuations in allele frequencies within a population from generation to generation due to sampling chance.

Independent Assortment

The random separation and distribution of homologous chromosome pairs into gametes during meiosis, shuffling maternal and paternal chromosome combinations.

Recombination (Crossing-Over)

The physical exchange of genetic segments between non-sister chromatids of homologous chromosomes during meiosis, creating novel combinations of alleles on the same chromosome.

Co-Dominance

An inheritance pattern in which both alleles in a heterozygote are simultaneously and fully expressed in the phenotype without blending.

Two-Fold Cost of Sex

The demographic disadvantage of sexual reproduction relative to asexual reproduction, arising because sexual lineages invest half their reproductive effort into males that do not directly bear offspring.

Agents of Evolutionary Change

The combined evolutionary mechanisms—including natural selection, mutation, genetic drift, non-random mating, gene flow, and recombination—that alter genetic structure across generations.

Osmosis

The net passive movement of water molecules across a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Tonicity

The relative solute concentration of an external solution compared to a cell's cytoplasm, determining the net direction of osmotic water flow.

Osmoconformer

An organism whose internal body fluid osmolarity dynamically matches the osmolarity of its external surrounding environment in a $1:1$ ratio.

Osmoregulator

An organism that maintains a constant internal body fluid osmolarity despite fluctuating external environmental conditions.

Excretion

The physiological elimination of metabolic wastes, excess ions, and unwanted substances from body fluids.

Secretion

The active release of synthesized substances (such as enzymes or hormones) that perform specific functional roles after release.

Ammonotelic

Organisms (such as aquatic invertebrates and bony fish) that excrete nitrogenous waste primarily as highly toxic, highly soluble ammonia requiring substantial water loss.

Ureotelic

Organisms (such as mammals, adult amphibians, sharks, and rays) that convert nitrogenous waste into urea, which features moderate toxicity and moderate water expenditure.

Uricotelic

Organisms (such as birds, insects, and non-avian reptiles) that excrete nitrogenous waste as low-toxicity, low-solubility uric acid paste, minimizing water loss at high metabolic cost.

Guanotelic

Organisms (such as spiders and scorpions) that excrete nitrogenous waste as guanine crystals, requiring virtually no water loss at the highest energy production cost.

Protonephridia

An invertebrate excretory system found in flatworms consisting of dead-end tubular networks with flame cells whose beating cilia drive fluid filtration.

Metanephridia

An annelid excretory organ where coelomic fluid enters a ciliated funnel called a nephrostome for selective tubule reabsorption before exiting via a nephridiopore.

Malpighian Tubules

Outpocketings of the insect gut that actively pump ions and uric acid into the lumen, drawing water osmotically before selective rectal reabsorption.

Loop of Henle

A U-shaped segment of the vertebrate nephron that establishes a steep medullary osmotic concentration gradient, enabling birds and mammals to produce urine hyperosmotic to blood.

Thick Ascending Limb

The nephron segment in the loop of Henle that actively transports $\text{Na}^+$ and $\text{Cl}^-$ out into the medullary interstitium while remaining completely impermeable to water.

Countercurrent Multiplier

The active loop-of-Henle mechanism where active solute pumping in the ascending limb multiplies osmotic concentration in the renal medulla to concentrate urine.

Aquaporins

Specialized transmembrane water channel proteins abundant in collecting ducts that regulate water reabsorption; reduced expression leads to increased dilute urine excretion.

Estivation

A state of dormant metabolic dormancy undergone by animals during extreme hot and dry periods to conserve water and energy.

Guttation

The exudation of liquid water droplets containing solutes from uninjured leaf margins driven by positive root pressure under high soil moisture or nitrogen conditions.