Biology Major Field Test Study Set – Evolution

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

a chain of ancestors and their descendants

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

convergent evolution
the independent origin of similar traits in separate lineages

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

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

any change to the genomic sequence of an organism

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

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

taxon (plural, taxa)
a group of organisms that a taxonomist judges to be a taxonomic unit, such as a species or order

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

the study of prehistoric life

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

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

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

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)

sexual selection
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

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

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

an organism and all of its descendants

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

evolutionary reversal
the reversion of a derived character state to its ancestral state

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

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

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

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

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

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

chromosomes that do not differ between sexes

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

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)

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

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

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

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

all of the hereditary information of an organism

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

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

mobile genetic elements
types of DNA that can move around in the genome; common examples include transposons (“jumping genes”) and plasmids

vertical gene transfer
the process of receiving genetic material from an ancestor

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

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

cis-acting elements
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

trans-acting elements
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

somatic mutations
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

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

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

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

genetic recombination
the exchange of genetic material between paired chromosomes during meiosis

the genetic makeup of an individual

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

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

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

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

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

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

genetic locus (plural, loci)
the specific location of a gene or piece of DNA sequence on a chromosome

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

genetic bottlenecks
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

Founder effect
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

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

relative fitness (of a genotype)
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)

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

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

negative selection
selection that decreases the frequency of alleles within a population

positive selection
selection that increases the frequency of alleles within a population

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

additive allele
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

negative frequency-dependent selection
rare genotypes have higher fitness than common genotypes; this process can maintain genetic variation within populations

balancing selection
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

inbreeding coefficient (F)
the probability that the two alleles at any locus in an individual will be identical by descent

inbreeding depression
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

narrow sense heritability
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

selection differential (S)
a measure of the strength of phenotypic selection

quantitative trait loci (QTLs)
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

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

artificial selection
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

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

extended phenotypes
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.

selective sweep
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

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

maximum parsimony
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

distance-matrix methods
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

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

replacement (non-synonymous) substitutions
mutations that alter the amino acid sequence of a protein; these can affect the phenotype and are therefore more subject to selection

synonymous substitutions
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

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

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

regulatory networks
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

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

homologous genes that arise by gene duplication

gene recruitment
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

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)

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

deep homology
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

the formation of new individual organisms (offspring)

individuals that produce both female and male gametes

twofold cost of sex
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

Muller’s ratchet
the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner

genetic load
the burden imposed by the accumulation of deleterious mutations

Red Queen effect
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

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

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

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

operational sex ratio (OSR)
the ratio of male to female individuals who are available for reproducing at any given time

sexual dimorphism
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)

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

a mating system in which one male pairs with one female

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

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

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

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

life history
the investment an organism makes in growth and reproduction

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

phylogenetic species concept
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

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

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

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

isolating barrier
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

the evolutionary process by which new species arise

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

occurs when populations are in the same geographic area

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

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

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

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

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

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

ring species
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

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

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

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

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

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

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

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

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

the movement of populations from one geographic region to another

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

punctuated equilibria
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

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

background extinction
the normal rate of extinction for a taxon or biota

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

reciprocal evolutionary change between interacting species, driven by natural selection

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

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

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

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

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

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

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

game theory
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

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

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

inclusive fitness
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

kin selection
selection arising from the indirect fitness benefits of helping relatives

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

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

evolutionary medicine
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