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Module 16 in the Syllabus

Evolution Images
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Question Drill for Evolution
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Conceptual Vocabulary
EvolutionEvolution is the change in the inherited traits of a population from generation to generation.
SelectionUnder selection, individuals with advantageous or adaptive traits tend to be more successful than their peers reproductively.
SpeciationSpeciation is the evolutionary process by which new biological species arise.
SpeciesA species is one of the basic units of biological classification, often defined as a group of organisms capable of interbreeding and producing fertile offspring.
Natural selectionNatural selection is the process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms, and unfavorable traits less common.
Charles DarwinCharles Robert Darwin (1809 - 1882) was an English naturalist who proposed and provided scientific evidence that all species of life have evolved over time from one or a few common ancestors through the process of natural selection.
Gene poolA gene pool is the complete set of unique alleles in a species or population.
MicroevolutionMicroevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level.
Divergent evolutionDivergent evolution occurs when two or more biological characteristics have a common evolutionary origin but have diverged over evolutionary time.
Convergent evolutionConvergent evolution is the process whereby organisms not closely related, not monophyletic, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Parallel evolutionParallel evolution is the independent evolution of similar traits, starting from a similar ancestral condition due to similar environments or other evolutionary pressures.
CladisticsCladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity.
CladeA clade is a taxonomic group of organisms comprising a single common ancestor and all the descendants of that ancestor.
Adaptive radiationAdaptive radiation describes the rapid speciation of a single or a few species to fill many ecological niches.
Reproductive isolationReproductive isolation is a category of mechanisms that prevent two or more populations from exchanging genes.
ExtinctionExtinction is the cessation of existence of a species or group of taxa, reducing biodiversity.
Founder effectThe founder effect is defined as the effect of establishing a new population by a small number of individuals, carrying only a small fraction of the original population's genetic variation.
Molecular evolutionMolecular evolution is the process of evolution at the scale of DNA, RNA, and proteins.
Stabilizing selectionStabilizing selection, also referred to as purifying selection, is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value.
Disruptive selectionDisruptive selection is a descriptive term used to describe changes in population genetics that simultaneously favor individuals at both extremes of the distribution.
Directional selectionDirectional selection occurs when natural selection favors a single allele and therefore allele frequency continuously shifts in one direction.
Negative selectionNegative selection is the selective removal of alleles that are deleterious.
Balancing selectionBalancing selection refers to forms of natural selection which work to maintain genetic polymorphisms within a population.
Peripatric speciationPeripatric speciation is a form of speciation in which new species are formed in isolated peripheral populations.
Allopatric speciationAllopatric speciation, also known as geographic speciation, is the phenomenon where large biological populations are physically isolated by an extrinsic barrier and evolve intrinsic reproductive isolation.
Parapatric speciationParapatric speciation is a form of speciation that occurs due to variations in mating frequency of a population within a continuous geographical area.
Sympatric speciationSympatric Speciation is the genetic divergence of multiple populations inhabiting the same geographic region from a single parent species, such that those populations become different species.
MimicryMimicry, also known as mimetism, describes a situation where one organism, the mimic, has evolved to share common outward characteristics with another organism, the model, through the selective action of a signal-receiver or dupe.
Common descentA group of organisms is said to have common descent if they have a common ancestor.
Jean-Baptiste LamarckJean-Baptiste Lamarck (1744 - 1829) was a French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws.
HomoHomo is the genus that includes modern humans and their close relatives.
Population geneticsPopulation genetics is the study of allele frequency distribution and change under the influence of the four evolutionary forces: natural selection, genetic drift, mutation and gene flow.
Hardy-Weinberg principleThe Hardy-Weinberg principle states that the occurrence of a genotype, perhaps one associated with a disease, stays constant unless matings are non-random or inappropriate, or mutations accumulate.
Allele frequencyAllele frequency is a measure of the relative proportion of an allele on a genetic locus.
Genotype frequencyThe genotype frequency is the proportion of genotypes in a population.
Genetic driftGenetic drift is the statistical effect that results from the influence that chance has on the survival of alleles, which may cause an allele, and the biological traits that it confers, to become more common or rare over successive generations.
Phylogenetic treeA phylogenetic tree, also called an evolutionary tree, is a tree showing the evolutionary relationships among various biological species or other entities that are believed to have a common ancestor.
Habitat fragmentationHabitat fragmentation describes the emergence of discontinuities in an organism's preferred environment.
Population bottleneckA population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more.
Heterozygote advantageHeterozygote advantage describes the case in which the heterozygote genotype has a higher relative fitness than either the homozygote dominant or homozygote recessive genotype.
HeteropatryHeteropatry refines the concept of sympatry in recognizing that although two variants of a population may coexist in the same geographical area, these variants may be behaviorally separated, exploiting niches that are interwoven within a patchwork landscape.
MonophyleticA group is monophyletic if it consists of an inferred common ancestor and all its descendants.
PolyphyleticA taxon is polyphyletic if the trait its members have in common evolved separately.
ParaphyleticA group of organisms is said to be paraphyletic if the group contains its most recent common ancestor, but does not contain all the descendants of that ancestor.
Gene flowGene flow, also known as gene migration, is the transfer of alleles of genes from one population to another.
Punctuated equilibriumPunctuated equilibrium is a theory in evolutionary biology which posits that evolution amongst sexually reproducing species takes place in rapid bursts separated by long periods in which little change occurs.
Hopeful MonsterHopeful Monster is the colloquial term used in evolutionary biology to describe an event of instantaneous-speciation, saltation, or systemic mutation, which contributes positively to the production of new evolutionary groups.
PaleoanthropologyCombining the disciplines of paleontology and physical anthropology, paleoanthropology is the study of ancient humans as found in fossil evidence such as petrifacted bones and footprints.
Genetic erosionGenetic erosion is a process whereby an already limited gene pool of an endangered species diminishes even more when individuals from the population die off without getting a chance to breed with others in their endangered low population.
ChronospeciesA chronospecies is a species which changes over time on an evolutionary scale such that the originating species and the species it becomes could not be classified as the same species had they existed at the same point in time.
Evolutionary relayEvolutionary relay describes how independent species acquire similar characteristics as a result of their evolution in similar ecosystems, but not at the same time.
ExaptationExaptation describes a process of evolution by which a trait may evolve to serve one function but subsequently evolve to serve another function.
Selective sweepA selective sweep is the reduction or elimination of variation among the nucleotides in neighbouring DNA of a mutation as the result of recent and strong natural selection.
Genetic hitchhikingGenetic hitchhiking is the process by which an evolutionarily neutral or even deleterious allele may spread through the gene pool by virtue of being linked to a beneficial mutation.
Assortative matingAssortative mating takes place when sexually reproducing organisms tend to mate with individuals that are like themselves in some respect, which is called positive, or dissimilar, which is called negative.
Advanced terms that may appear in context in MCAT passages
Evolutionary capacitanceEvolutionary capacitance is a theory stating that living systems have the ability to accumulate genetic variation that has no phenotypic effect until the system is disturbed, at which point the variation has a phenotypic effect and is subject to natural selection.
Phyletic gradualismPhyletic gradualism is a macroevolutionary hypothesis rooted in uniformitarianism stating that species continue to adapt to new challenges over the course of their history, gradually becoming new species.
Coalescent theoryCoalescent theory is a retrospective model of population genetics that traces all alleles of a gene in a sample from a population to a single ancestral copy shared by all members of the population.
Ecological geneticsEcological genetics is the study of genetics in the context of the interactions among organisms and between the organisms and their environment.
Mutational meltdownMutational meltdown refers to the process by which a small population accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which may lead to further accumulation of deleterious mutations due to inbreeding depression.
PanmixiaA panmictic population is one where all individuals are potential partners, and mating occurs regardless of any physical, genetic, or social preference.
SynapomorphyA synapomorphy is a derived character state shared by two or more terminal groups and inherited from their most recent common ancestor.
AdaptationismAdaptationism is a set of methods in the evolutionary sciences for distinguishing the products of adaptation from traits that arise through other processes.
Intragenomic conflictWithin the framework of the selfish gene theory, intragenomic conflict arises when genes inside a genome are not transmitted by the same rules, or when a gene causes its own transmission to the detriment of the rest of the genome.
PreadaptationPreadaptation describes a situation where an organism uses a preexisting anatomical structure inherited from an ancestor for a potentially unrelated purpose.
SpandrelSpandrel is a term used in describing a phenotypic characteristic that is considered to have developed during evolution as a side-effect of a true adaptation.
KoinophiliaKoinophilia is a term used in biology, meaning that when sexual creatures seek a mate, they prefer that mate not to have any unusual, peculiar or deviant features.
Modern evolutionary synthesisThe modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists.
Maximum parsimonyMaximum parsimony is a non-parametric statistical method commonly used in computational phylogenetics for estimating phylogenies under which the preferred phylogenetic tree is the tree that requires the least number of evolutionary changes.
Least squares inference in phylogenyLeast squares inference in phylogeny generates a phylogenetic tree based on an observed matrix of pairwise genetic distances and optionally a weight matrix.
Frozen plasticityFrozen plasticity is a hypothesis in evolutionary biology based on punctuated equilibria and augmenting it with a mechanism for species stability based on evolutionarily stable strategies on the gene and allele level.

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