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evolution

answer

changes in gene/allele frequencies in a gene pool from one generation to the next

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lineage

answer

a chain of ancestors and their descendants

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natural selection

answer

is a mechanism that can lead to evolution, whereby differential survival or reproduction of individuals causes some genetic types to replace (outcompete) others

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convergent evolution

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the independent origin of similar traits in separate lineages

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homologies

answer

characteristics that are similar in two or more species because they are inherited from a common ancestor

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phylogeny

answer

a visual representation of the evolutionary history of populations, genes, or species

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mutation

answer

any change to the genomic sequence of an organism

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genetic drift

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evolution arising from random changes in the genetic composition of a population from one generation to the next

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phenotypes

answer

measurable aspects of organisms, such as morphology (structure), physiology, and behavior

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taxon (plural, taxa)

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a group of organisms that a taxonomist judges to be a taxonomic unit, such as a species or order

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taxonomy

answer

the science of describing, naming, and classifying species of living or fossil organisms

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paleontology

answer

the study of prehistoric life

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extinction

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the permanent loss of a population or species, arising with the death or failure to breed of the last individual

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uniformitarianism

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was the idea that the natural laws observable around us now are also responsible for events in the past

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analogies

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traits that are similar because they have converged on a shared form; they are not derived from a common ancestor

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adaptations

answer

inherited aspects of an individual that allow it to outcompete other members of a population that lack the trait (or that have a slightly different version of the trait)

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sexual selection

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arises when individuals of one sex (usually males) compete with each other over access to individuals of the other sex; it can lead to the evolution of traits like showy ornaments or weapons that improve an individual's chances of mating

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tips

answer

terminal ends of an evolutionary tree, representing species, molecules, or populations being compared

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node

answer

a point in a phylogeny where a lineage splits (a speciation event)

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clade

answer

an organism and all of its descendants

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cladistics

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phylogenetic methods that construct trees by grouping taxa into nested hierarchies (clades) according to their shared derived characters (synapomorphies)

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evolutionary reversal

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the reversion of a derived character state to its ancestral state

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exaptation

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a trait that originates performing one function, but is later co-opted for a new function

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amino acids

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the structural units that, among other functions, link together to form proteins

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nucleotides

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the structural units that link together to form DNA (and RNA)

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genes

answer

segments of DNA whose nucleotide sequences code for proteins, or RNA, or regulate the expression of other genes

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gene expression

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the process by which information from a gene is transformed into a product

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sex chromosomes

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chromosomes that pair during meiosis but differ in copy number between males and females

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autosomes

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chromosomes that do not differ between sexes

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ploidy

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the number of copies of unique chromosomes in a cell (n)

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transcription

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the process that takes place when RNA polymerase reads a coding sequence of DNA and produces a complementary strand of RNA, called messenger RNA (mRNA)

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translation

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the process that takes place when a strand of mRNA is decoded by a ribosome to produce a strand of amino acids

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hormone

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a molecular signal that flows from cells in one part of the body to cells in other parts of the body

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RNA splicing

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the process of modifying RNA after transcription but before translation, during which introns are removed and exons are joined together into a contiguous strand

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alternative splicing

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the process of combining diff erent subsets of exons together, yielding different mRNA transcripts from a single gene

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genome

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all of the hereditary information of an organism

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microRNA

answer

one group of RNAs that act as post-transcriptional regulators of gene expression

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pseudogenes

answer

DNA sequences that resemble functional genes but have lost their protein-coding ability or are no longer expressed

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mobile genetic elements

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types of DNA that can move around in the genome; common examples include transposons ("jumping genes") and plasmids

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vertical gene transfer

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the process of receiving genetic material from an ancestor

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horizontal gene transfer

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any process in which genetic material is transferred to another organism without descent

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plasmids

answer

molecules of DNA, found most often in bacteria, that can replicate independently of chromosomal DNA

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cis-acting elements

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stretches of DNA located near a gene—either immediately upstream (adjacent to the promoter region), downstream, or inside an intron—that influence the expression of that gene

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trans-acting elements

answer

sequences of DNA that are located away from the focal gene (e.g., on another chromosome); these stretches of DNA generally code for a protein, microRNA, or other diffusible molecule that then influences expression of the focal gene

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somatic mutations

answer

mutations that affect cells in the body ("soma") of an organism; these mutations affect all the daughter cells produced by the affected cell and can affect the phenotype of the individual

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germ-line mutations

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mutations that affect the gametes (eggs, sperm) of an individual and can be transmitted from parents to off spring

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alleles

answer

one of several alternative forms of the DNA sequence of the same locus

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meiosis

answer

a form of cell division that occurs only in eukaryotes, in which the number of chromosomes is cut in half

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genetic recombination

answer

the exchange of genetic material between paired chromosomes during meiosis

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genotype

answer

the genetic makeup of an individual

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genetic polymorphism

answer

the simultaneous occurrence of two or more discrete phenotypes within a population

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polyphenic trait

answer

a trait for which multiple, discrete phenotypes can arise from a single genotype depending on environmental circumstances

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dominant allele

answer

alleles that produce the same phenotype whether they are paired with and identical allele or a different allele (i.e., a heterozygotic state)

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recessive allele

answer

alleles that produce their characteristic phenotypes only when they are paired with an identical allele (i.e., in homozygous states)

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quantitative traits

answer

measurable phenotypes that vary among individuals over a given range to produce a continuous distribution of phenotypes

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phenotypic plasticity

answer

changes in the phenotype produced by a single genotype in different environments

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genetic locus (plural, loci)

answer

the specific location of a gene or piece of DNA sequence on a chromosome

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population genetics

answer

the study of the distribution of alleles within populations and the mechanisms that can cause allele frequencies to change over time

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genetic bottlenecks

answer

events in which the number of individuals in a population is reduced drastically; even if this dip in numbers is temporary, it can have lasting effects on the genetic variation of a population

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Founder effect

answer

a type of genetic drift describing the loss of allelic variation that accompanies founding of a new population from a very small number of individuals (a small sample of a much larger source population); this effect can cause the new population to differ considerably from the source population

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fitness

answer

the success of an organism at surviving and reproducing, and thus contributing off spring to future generations

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relative fitness (of a genotype)

answer

the success of the genotype at producing new individuals (its fitness) standardized by the success of other genotypes in the population (for example, divided by the average fitness of the population)

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average excess of fitness (of an allele)

answer

the difference between the average fitness of individuals bearing the allele and the average fitness of the population as a whole

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pleiotropy

answer

the condition when a mutation in a single gene affects the expression of many different phenotypic traits

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negative selection

answer

selection that decreases the frequency of alleles within a population

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positive selection

answer

selection that increases the frequency of alleles within a population

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epistasis

answer

occurs when the effects of an allele at one genetic locus are modified by alleles at one or more other loci

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additive allele

answer

an allele that yields twice the phenotypic effect when two copies are present at a given locus than when only a single copy is present

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negative frequency-dependent selection

answer

rare genotypes have higher fitness than common genotypes; this process can maintain genetic variation within populations

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balancing selection

answer

selection that favors more than one allele; it acts to maintain genetic diversity in a population by keeping alleles at frequencies higher than would be expected by chance or mutation alone

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inbreeding coefficient (F)

answer

the probability that the two alleles at any locus in an individual will be identical by descent

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inbreeding depression

answer

a reduction in the average fitness of inbred individuals relative to that of outbred individuals; it arises because rare, recessive alleles become expressed in a homozygous state where they can detrimentally affect the performance of individuals

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narrow sense heritability

answer

the proportion of the total phenotypic variance of a trait attributable to the additive effects of alleles (the additive genetic variance); this is the component of variance that causes offspring to resemble their parents, and it causes populations to evolve predictably in response to selection

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selection differential (S)

answer

a measure of the strength of phenotypic selection

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quantitative trait loci (QTLs)

answer

stretches of DNA that are correlated with variation in a phenotypic trait; these regions contain genes, or are linked to genes, that contribute to population differences in a phenotype

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reaction norm

answer

the pattern of phenotypic expression of a single genotype across a range of environments

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artificial selection

answer

similar to natural selection, except that it results from human activity; when breeders nonrandomly choose individuals with economically favorable traits to use as breeding stock, they impose strong artificial selection on those traits

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gene flow

answer

the transfer of alleles from one population to another; it occurs when organisms or their gametes move from one location to another

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extended phenotypes

answer

structures constructed by organisms that can influence their performance or success; although they are not part of the organism itself, their properties nevertheless reflect the genotype of each individual; animal examples include the nests constructed by birds and the galls of flies.

question

selective sweep

answer

strong selection can "sweep" a favorable allele to fixation within a population so fast that there is little opportunity for recombination; in the absence of recombination, large stretches of DNA flanking the favorable allele will also reach high frequency

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coalescence

answer

the process by which, looking back through time, the genealogy of any pair of homologous alleles merges in a common ancestor

question

maximum parsimony

answer

a statistical method for reconstructing phylogenies which identifies the tree topology that minimizes the total amount of change, or the number of steps, required to fit the data to the tree

question

distance-matrix methods

answer

methods that construct phylogenetic trees by clustering taxa based on the proximity (or distance) between their DNA or protein sequences; these methods place closely related sequences under the same interior node, and they estimate branch lengths from the observed distances between sequences

question

microsatellites

answer

noncoding stretches of DNA containing strings of short (1-6 base pairs), repeated segments

question

replacement (non-synonymous) substitutions

answer

mutations that alter the amino acid sequence of a protein; these can affect the phenotype and are therefore more subject to selection

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synonymous substitutions

answer

mutations that do not alter the amino acid sequence of a protein; because these mutations do not affect the protein an organism produces, they are less prone to selection and often free from selection completely

question

novel traits

answer

traits that arise de novo (i.e., not inherited from an ancestor) within a lineage and have no obvious counterparts (homologs) in related lineages

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complex adaptations

answer

suites of coexpressed traits that together experience selection for a common function

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regulatory networks

answer

systems of interacting genes, transcription factors, promoters, RNA, and other molecules; they function like biological circuits, responding to signals with outputs that control the activation of genes during development, the cell cycle, and the activation of metabolic pathways

question

promiscuous proteins

answer

proteins capable of carrying out more than one function, such as catalyzing reactions of different substrates

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paralogs

answer

homologous genes that arise by gene duplication

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gene recruitment

answer

the co-option of a particular gene or network for a totally different function as a result of a mutation; the reorganization of a preexisting regulatory network can be a major evolutionary event

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orthologs

answer

homologous genes separated by a speciation event (as opposed to paralogs, homologous genes produced by gene duplication that are both possessed by the same species)

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parallelism

answer

convergent evolution that results from mutations to the same genes in different lineages

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deep homology

answer

a condition that occurs when the growth and development of traits in different lineages results from underlying genetic mechanisms (e.g., regulatory networks) that are inherited from a common ancestor

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reproduction

answer

the formation of new individual organisms (offspring)

question

hermaphrodites

answer

individuals that produce both female and male gametes

question

twofold cost of sex

answer

asexual lineages multiply faster than sexual lineages because all progeny are capable of producing off spring. In sexual lineages, half of the off spring are males who cannot themselves produce offspring; this effectively halves the rate of replication of sexual species

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Muller's ratchet

answer

the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner

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genetic load

answer

the burden imposed by the accumulation of deleterious mutations

question

Red Queen effect

answer

for coevolving populations, to maintain relative fitness, each population must constantly adapt to the other; this term was borrowed from Lewis Carroll's Through the Looking-Glass by Leigh Van Valen to refer to biological arms races, such as those between parasites and their hosts

question

anisogamy

answer

sexual reproduction involving the fusion of two dissimilar gametes; individuals producing the larger gamete (eggs) are defined as female, and individuals producing the smaller gamete (sperm) as male

question

fecundity

answer

the reproductive capacity of an individual, such as the number and quality of eggs or sperm; as a measure of relative fitness, fecundity refers to the number of off spring produced by an organism

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certainty of paternity

answer

the probability that a male is the genetic sire of the offspring his mate produces

question

operational sex ratio (OSR)

answer

the ratio of male to female individuals who are available for reproducing at any given time

question

sexual dimorphism

answer

a difference in form between males and females of a species, including color, body size, and the presence or absence of structures used in courtship displays (elaborate tail plumes, ornaments, pigmented skin patches) or in contests (antlers, tusks, spurs, horns)

question

leks

answer

assemblages of rival males who cluster together to perform courtship displays in close proximity

question

monogamy

answer

a mating system in which one male pairs with one female

question

polygyny

answer

a mating system where males mate (or attempt to mate) with multiple females

question

polyandry

answer

a mating system where females mate (or attempt to mate) with multiple males

question

sperm competition

answer

a form of sexual selection that arises after mating, when males compete for fertilization of a female's eggs

question

sexual conflict

answer

the evolution of phenotypic characteristics that confer a fitness benefit to one sex but a fitness cost to the other

question

life history

answer

the investment an organism makes in growth and reproduction

question

senescence

answer

the deterioration in the biological functions of an organism as it ages

question

phylogenetic species concept

answer

species are the smallest possible groups whose members are descended from a common ancestor and who all possess defining or derived characteristics that distinguish them from other such groups

question

biological species concept

answer

species are groups of actually (or potentially) interbreeding natural populations that are reproductively isolated from other such groups

question

metapopulation

answer

a group of spatially separated populations of the same species that interact at some level (e.g., exchange alleles)

question

general lineage species concept

answer

species are metapopulations of organisms that exchange alleles frequently enough that they comprise the same gene pool, and therefore, the same evolutionary lineage

question

isolating barrier

answer

an aspect of the environment, genetics, behavior, physiology, or ecology of a species that reduces or impedes gene fl ow from individuals of other species

question

speciation

answer

the evolutionary process by which new species arise

question

allopatry

answer

occurs when populations are in separate, non-overlapping geographic areas (i.e., they are separated by geographic barriers to gene flow)

question

sympatry

answer

occurs when populations are in the same geographic area

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reproductive isolation

answer

occurs when reproductive barriers prevent or strongly limit reproduction between populations; the result is that few or no genes are exchanged between the populations

question

gametic incompatibility

answer

occurs when sperm or pollen from one species fails to penetrate and fertilize the egg of another species

question

prezygotic reproductive barriers

answer

aspects of the genetics, behavior, physiology, or ecology of a species that prevent sperm from one species from fertilizing eggs of another species

question

postzygotic reproductive barriers:

answer

aspects of the genetics, behavior, physiology, or ecology of a species that prevent fertilized zygotes from successfully developing and reproducing themselves

question

reinforcement

answer

the increase of reproductive isolation between populations through the selection against hybrid offspring

question

isolation by distance

answer

populations that live nearby are genetically more similar to each other than populations that live farther apart

question

ring species

answer

a connected series of populations (each of which can interbreed with its neighboring populations) that have diverged sufficiently across their ranges so that the populations at the ends of the series are too different to interbreed

question

ecological speciation

answer

the evolution of reproductive barriers between populations by adaptation to different environments or ecological niches

question

allopolyploidy

answer

polyploidy (more than two paired chromosomes) resulting from interspecific hybridization; (If polyploidy arises within a species, it's called autopolyploidy.)

question

cryptic species

answer

groups of organisms that are genetically distinct and do not interbreed, but are morphologically almost indistinguishable

question

macroevolution

answer

evolution occurring above the species level, including the origination, diversification, and extinction of species over long periods of evolutionary time

question

microevolution

answer

evolution occurring within populations, including adaptive and neutral changes in allele frequencies from one generation to the next

question

standing diversity

answer

the number of species (or other taxonomic unit) present in a particular area at a given time

question

turnover

answer

the disappearance (extinction) of some species and their replacement by others (origination) in studies of macroevolution

question

biogeography

answer

the study of the distribution of species across space (geography) and time

question

dispersal

answer

the movement of populations from one geographic region to another

question

vicariance

answer

the formation of geographic barriers to dispersal and gene flow, resulting in the separation of populations

question

punctuated equilibria

answer

a model of evolution that proposes that most species undergo relatively little change for most of their geologic history; these periods of stasis are punctuated by brief periods of rapid change, often associated with speciation events

question

adaptive radiations

answer

evolutionary lineages that have undergone exceptionally rapid diversification into a variety of lifestyles or ecological niches

question

background extinction

answer

the normal rate of extinction for a taxon or biota

question

mass extinction

answer

a statistically significant departure from background extinction rates that results in a substantial loss of taxonomic diversity

question

coevolution

answer

reciprocal evolutionary change between interacting species, driven by natural selection

question

reciprocal selection

answer

selection that occurs in two species, due to their interactions with one another

question

Müllerian mimicry

answer

occurs when several harmful or distasteful species resemble each other in appearance, facilitating the learned avoidance of predators

question

Batesian mimicry

answer

occurs when harmless species resemble harmful or distasteful species, deriving protection from predators in the process

question

endosymbionts

answer

mutualistic organisms that live within the body or cells of another organism

question

behavioral ecology

answer

the science that explores the relationship between behavior, ecology, and evolution to elucidate the adaptive signifi ance of animal actions

question

individual selection

answer

differential performance (fitness) of individuals causes some genotypes to outcompete and replace other genotypes

question

group selection

answer

differential performance (fitness) of groups of individuals causes some groups to outcompete and replace other groups

question

game theory

answer

a mathematical approach to studying behavior that solves for the optimal decision in strategic situations (games) where the payoff to a particular choice depends on the choices of others

question

dilution effect

answer

the safety in numbers that arises through swamping the foraging capacity of local predators

question

altruism

answer

occurs whenever a helping individual behaves in a way that benefits another individual at a cost to its own fitness

question

inclusive fitness

answer

an individual's total fitness, including its own reproduction as well as any increase in the reproduction of its relatives due specifically to its own actions

question

kin selection

answer

selection arising from the indirect fitness benefits of helping relatives

question

eusociality

answer

a type of social organization in which species have complete reproductive division of labor

question

haplodiploidy

answer

a mechanism of sex determination where the sex is determined by the number of copies of each chromosome that an individual receives; offspring formed from the fertilization of an egg by a sperm (i.e., diploids) are female, while those formed from unfertilized eggs (i.e., haploids) are male

question

evolutionary medicine

answer

the integrated study of evolution and medicine to improve scientific understanding of the reasons for disease and actions that can be taken to improve health

Biology Major Field Test Study Set – Evolution – Flashcards

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