Biology 2110: Evolution, Population Genetics, Speciation, and Mating Systems

Comprehensive vocabulary flashcards covering Mendelian genetics terms, Darwinian evolution, mechanisms of microevolution, Hardy-Weinberg equilibrium, modes of natural selection, speciation, and animal mating systems.

Genotype

An organism's complete genetic makeup.

Phenotype

The observable, expressed physical and physiological characteristics of an organism.

Gene

A segment of DNA that codes for a specific trait.

Allele

Different versions or alternative forms of a specific gene.

Dominant Allele

An allele that is expressed whenever it is present, typically designated by an uppercase letter.

Recessive Allele

An allele that is only expressed when both inherited alleles at the locus are recessive, typically designated by a lowercase letter.

Homozygous

Possessing two identical alleles for a given gene (either homozygous dominant or homozygous recessive).

Heterozygous

Possessing two different alleles for a given gene, typically one dominant and one recessive.

Scale of Nature

Aristotle's ladder ranking life from simple to complex, viewing species as fixed and unchanging.

Linnaean Classification

A hierarchical system that categorizes and groups organisms based on shared physical traits.

Struggle for Existence

The concept that populations grow faster than available resources, inevitably causing competition among organisms.

Uniformitarianism

The geological principle stating that Earth's geological processes occurring today also operated in the past, meaning change is gradual.

Population

A group of individuals of the same species that live in the same geographic area and can interbreed to produce viable offspring.

Descent with Modification

Darwin's definition of evolution stating that all species descend from a common ancestor, accumulating changes over time via mechanisms like natural selection.

Genetic Homology

Similarities in DNA, RNA, or gene sequences among species resulting from shared ancestry (e.g., chimpanzees and bonobos sharing $98.6\%$ of their DNA).

Structural Homology

Similarities in physical structures among different organisms inherited from a common ancestor (e.g., bone arrangements in human arms and bat wings).

Developmental Homology

Similarities in embryonic growth and developmental pathways across species (e.g., shared anatomical structures during chordate embryonic stages).

Transitional Fossils

Fossilized remains that exhibit traits common to both an ancestral group and its derived descendant group, enabling the reconstruction of how traits changed over time.

Vestigial Traits

Structures with little to no current biological function in an organism that are homologous to functional structures in other species (e.g., the human appendix or tailbone).

Homoplasies

Similar characteristics that arise when unrelated species converge independently on similar environmental strategies rather than inheriting them from a common ancestor.

Natural Selection

A non-random evolutionary process where individuals possessing inherited traits that best match their environment reproduce more successfully than other individuals.

Fitness

An individual's relative contribution to the gene pool of the next generation through successful reproduction.

Artificial Selection

Human-directed breeding of organisms to select for desirable traits and select against undesirable traits (e.g., breeding domestic dogs from wolves).

The Modern Synthesis

The paradigm connecting Darwinian evolution with Mendelian genetics, defining evolution as a change in allele frequencies between generations driven by mutation, recombination, and selection.

Gene Pool

The total genetic composition of a population at a specific time, consisting of all alleles at all gene loci across every individual.

Fixed Allele

An allele that is the only variant existing for a specific gene locus across all individuals in a population.

Allelic Frequency

The proportion or percentage of a specific allele relative to all alleles for that gene locus within a population.

Genetic Drift

Random, non-adaptive fluctuations in allele frequencies from generation to generation, occurring most prominently in small populations.

Gene Flow

The transfer of alleles between populations due to the migration of fertile individuals or their gametes, which reduces genetic differences between the populations.

Hardy-Weinberg Equilibrium

A mathematical model stating that allele and genotype frequencies in a population remain constant from generation to generation when five conditions are met: large population, random mating, no mutations, no gene flow, and no natural selection.

Directional Selection

A pattern of natural selection that favors individuals at one extreme of a phenotypic distribution, shifting the allele frequency curve in that direction.

Disruptive Selection

A pattern of natural selection that simultaneously favors individuals at both phenotypic extremes while selecting against the intermediate (mean) phenotype.

Stabilizing Selection

A pattern of natural selection that favors intermediate phenotypes and acts against both phenotypic extremes.

Biological Species Concept

The species concept identifying a species based on reproductive isolation, requiring that members interbreed and produce viable, fertile offspring under natural conditions.

Morphospecies Concept

The species concept that distinguishes and defines species based on distinct morphological and physical characteristics.

Phylogenetic Species Concept

The species concept identifying a species as the smallest diagnosable monophyletic group on a phylogenetic tree based on testable criteria.

Macroevolution

Evolutionary change at or above the species level, characterized by the appearance of new species over time.

Prezygotic Barriers

Reproductive isolating mechanisms that prevent mating or fertilization from occurring between different species, blocking the formation of a zygote.

Temporal Isolation

A prezygotic barrier in which species breed during different times of the day, seasons, or years, preventing mating.

Habitat Isolation

A prezygotic barrier where two species occupy different physical habitats within the same general geographic area and rarely or never encounter one another.

Behavioral Isolation

A prezygotic barrier where unique courtship rituals, vocalizations, or mating behaviors prevent different species from recognizing each other as mates.

Gametic Isolation

A prezygotic barrier where the gametes (sperm and egg) of different species are biochemically incompatible, preventing successful fertilization.

Mechanical Isolation

A prezygotic barrier where anatomical and morphological differences in reproductive organs physically prevent successful copulation.

Postzygotic Barriers

Reproductive isolating mechanisms that operate after fertilization, resulting in hybrid inviability or hybrid sterility.

Hybrid Sterility

A postzygotic barrier where hybrid offspring survive to adulthood but are sterile and cannot produce functional gametes (e.g., a mule).

Allopatric Speciation

The divergence of populations into distinct species caused by geographic separation and subsequent reproductive isolation.

Sympatric Speciation

The divergence of populations into distinct species while remaining in the same geographical area, without physical separation.

Polyploidy

A meiotic error resulting in an organism having extra sets of chromosomes, which can produce immediate reproductive isolation from parent populations.

Monogamy

A mating system characterized by an exclusive pair bond between one male and one female, often featuring increased parental care and minimal sexual dimorphism.

Polygyny

A mating system where one male mates with multiple females, typically occurring when males defend territories and display showy, ornamental secondary sexual traits.

Polyandry

A mating system where one female mates with multiple males, often found in environments with scarce resources where females select their mates.

Promiscuity

A mating system where multiple males mate with multiple females without the formation of strong or long-term pair bonds.