Evolutionary Biology Exams

adaptation

a process of genetic change in a population. A result of natural selection, the average state of a character becomes improved with reference to a specific function, or whereby a population is thought to have become better suited to some feature of its environment.

an adaptation

a feature that has become prevalent in a population because of a selective advantage conveyed by that feature in the improvement in some function.

adaptation

a process of genetic change in a population. A result of natural selection, the average state of a character becomes improved with reference to a specific function, or whereby a population is thought to have become better suited to some feature of its environment.

an adaptation

a feature that has become prevalent in a population because of a selective advantage conveyed by that feature in the improvement in some function.

divergence

The evolution of increasing difference between lineages in one or more characters.

evolution

The origin of organisms possessing different states multiple characteristics and changes in the proportions of those organisms over time.

Organic evolution/biological evolution

a change over time in proportions of organisms differing genetically in one or more traits. changes transpire by the origin and subsequent alteration of the frequencies of genotypes from generation to generation within populations. By alteration of the proportions of genetically differentiated populations within a species, or by changes in the numbers of species with different characteristics, thereby altering the frequency of one or more traits within a higher taxon.

evolutionary synthesis

The reconciliation of Darwin's theory with the findings of modern genetics, which gave rise to a theory that emphasized the coaction of random mutation, selection, genetic drift, and gene flow; also called the modern synthesis.

frequency

in evolutionary biology means proportion

genetic drift

Random changes in the frequencies of two or more alleles or genotypes within a population.

genotype

The set of genes possessed by an individual organism; often, its genetic composition at a specific locus or set of loci singled out for discussion.

higher taxon

A taxon above the species level, such as a named genus or phylum.

hypothesis

An informed conjecture or proposition of what might be true.

inheritance of acquired characteristics

The formerly widespread belief that modifications of an individual during its lifetime, due to its behavior or its environment, could be transmitted to its descendants.

Lamarckism

The long disproven theory that evolution is caused by inheritance of character changes acquired during the life of an individual due to its behavior or to environmental influences, also known as soft inheritance.

macroevolution

A vague term, usually meaning the evolution of substantial phenotypic changes, usually great enough to place the changed lineage and its descendants in a distinct genus or higher taxon. Cf. microevolution.

microevolution

A vague term, usually referring to slight, short-term evolutionary changes within species. Cf. macroevolution.

natural selection

The differential survival and/or reproduction of classes of entities that differ in one or more characteristics. To constitute natural selection, the difference in survival and/or reproduction cannot be due to chance, and it must have the potential consequence of altering the proportions of the different entities. Thus natural selection is also definable as a deterministic difference in the contribution of different classes of entities to subsequent generations. Usually, the differences are inherited. The entities may be alleles, genotypes or subsets of genotypes, populations, or, in the broadest sense, species. See also genic selection, individual selection, kin selection, group selection.

neo-Darwinism

Originally, the theory of natural selection of inherited variations, that denied that acquired characteristics might be inherited; often used more broadly to mean the modern theory that natural selection, acting on randomly generated particulate genetic variation, is the major, but not the sole, cause of evolution.

neutral theory of molecular evolution

The hypothesis (first proposed by Kimura) that most alleles that are polymorphic within populations and that become fixed do not significantly alter fitness and evolve by genetic drift.

phenotype

The morphological, physiological, biochemical, behavioral, and other properties of an organism manifested throughout its life; or any subset of such properties, especially those affected by a particular allele or other portion of the genotype.

Phylogeny

The history of descent of a group of taxa such as species from their common ancestors, including the order of branching and sometimes the absolute times of divergence.

population

A group of conspecific organisms that occupy a more or less well-defined geographic region and exhibit reproductive continuity from generation to generation.

scientific theory

A coherent body of statements, based on reasoning, facts, and evidence, that explains some aspect of nature by recourse to natural laws or processes.

speciation

Evolution of reproductive isolation within an ancestral species, resulting in 2 or more descendant species.

uniformitarianism

The proposition that natural processes that operated in the past are the same as in the present. (The term has usually implied gradual rather than catastrophic change.)

adaptive radiation

Evolutionary divergence of members of a single phylogenetic lineage into a variety of different adaptive forms; usually the taxa differ in the use of resources or habitats and have diverged over a relatively short interval of geological time.

anagenesis

Evolutionary change of a feature within a lineage over a given period of time.

character

A feature, or trait. Cf. character state.

character state

One of the variant conditions of a character (e.g., yellow versus brown as the state of the character "color of snail shell").

clade

The set of all species descended from a particular ancestral species or lineage.

cladogenesis

Branching or bifurcation of lineages during phylogeny.

common ancestor

A lineage (often designated as a taxon) from which two or more descendant lineages evolved.

conservative characters

Features that evolve slowly and are retained with little or no change for long periods of evolutionary time.

convergent evolution (convergence)

Evolution of similar features independently in different evolutionary lineages, usually from different antecedent features or by different developmental pathways.

evolutionary reversal

The evolution of a character from a derived state back toward a condition that resembles an earlier state.

gene duplication

The process whereby new genes arise as copies of preexisting gene sequences. The result can be a gene family.

gene family

Two or more loci with similar nucleotide sequences that have been derived from a common ancestral sequence

gene tree

A diagram representing the history by which gene copies have been derived from ancestral gene copies in previous generations.

haplotype

An individual DNA sequence that differs from homologous sequences at one or more base pair sites, usually reserved for mtDNA sequences.

lineage

A series of ancestral and descendant populations through time; usually refers to a single evolving species, but may include several species descended from a common ancestor.

homoplasy

Possession by two or more species of a similar or identical character state that has not been derived by both species from their common ancestor; embraces convergence, parallel evolution, and evolutionary reversal.

molecular clock

The concept of a steady rate of change in DNA sequences over time, providing a basis for dating the time of divergence of lineages if the rate of change can be estimated.

monophyletic

Refers to a taxon, or a branch of a phylogenetic tree or gene tree, that includes all the species (or genes) that descended from a common ancestor. Cf. paraphyletic, polyphyletic.

mosaic evolution

Evolution of different characters within a lineage or clade at different rates, hence more or less independently of one another.

orthologous

Refers to corresponding (homologous) members of a gene family in two or more species.

outgroup

A taxon that diverged from a group of other taxa (the ingroup) before they diverged from one another.

parallel evolution (parallelism)

The evolution of similar or identical features independently in related lineages, thought usually to be based on similar modifications of the same developmental pathways.

paralogous

Refers to the evolutionary relationship between two different members of a gene family, within a species or in a comparison of different species. Cf. orthologous.

paraphyletic

Refers to a taxon, phylogenetic tree, or gene tree whose members are all derived from a single ancestor, but which does not include all the descendants of that ancestor. Cf. monophyletic.

parsimony

Economy in the use of means to an end (Webster's New Collegiate Dictionary); the principle of accounting for observations by that hypothesis requiring the fewest or simplest assumptions that lack evidence; in systematics, the principle of invoking the minimal number of evolutionary changes to infer phylogenetic relationships.

phylogenetic tree

A diagram representing the evolutionary relationships among named groups of organisms, i.e., their history of descent from common ancestors.

phylogeny

The history of descent of a group of taxa such as species from their common ancestors, including the order of branching and sometimes the absolute times of divergence.

polyphyletic

Refers to a taxon, phylogenetic tree, or gene tree composed of members derived by evolution from ancestors in more than one ancestral taxon; hence, composed of members that do not share a unique common ancestor. Cf.monophyletic.

taxon (plural: taxa)

The named taxonomic unit (e.g., Homo sapiens, Hominidae, or Mammalia) to which individuals, or sets of species, are assigned. Higher taxa are those above the species level. Cf. category.

altruism

Behavior by an individual that increases the fitness of another individual while decreasing the fitness of the actor, allows an individual to increase the success of its genes by helping relatives that share those genes.

character displacement

As originally used, a pattern of geographic variation in which a character differs more greatly between sympatric than between allopatric populations of two species; now often used for the evolutionary process of accentuation of differences between sympatric populations of two species as a result of the reproductive or ecological interactions between them.

comparative method

A procedure for inferring the adaptive function of a character by correlating its states in various taxa with one or more variables, such as ecological factors hypothesized to affect its evolution.

exaptation

The evolution of a function of a gene, tissue, or structure other than the one it was originally adapted for, (ex: penguins swimming with structures adapted for the marine environment, originally evolved as wings); can also refer to the adaptive use of a previously nonadaptive trait

fittness

The success of an entity in leaving descendants to the next generation. Most often refers to the average contribution of an allele, genotype, or phenotype; can also refer to the contribution of a specific entity (e.g., an individual). See also relative fitness.

genic selection

A form of selection in which the single gene is the unit of selection, such that the outcome is determined by fitness values assigned to different alleles. See individual selection, kin selection, natural selection.

group selection

The differential rate of origination or extinction of whole populations (or species, if the term is used broadly) on the basis of differences among them in one or more characteristics. May also refer to differences among populations in their contribution of genes to the combined gene pool. See also interdemic selection, species selection.

Hamilton's rule

describes mathematically weather or not a gene for altruistic behavior will spread in a population

hypothetico-deductive method

A scientific method in which a hypothesis is tested by deducing expected data or observations from it, if it were true, and comparing the deduced predictions with real data.

individual selection

A form of natural selection consisting of nonrandom differences in fitness among different phenotypes (or genotypes) within a population. See also genic selection, natural selection.

interdemic selection

A form of natural selection consisting of nonrandom differences in fitness among different phenotypes (or genotypes) within a population. See also genic selection, natural selection.

kin selection

A form of selection whereby alleles differ in their rate of propagation by influencing the impact of their bearers on the reproductive success of individuals (kin) who carry the same alleles by common descent.

levels of selection

The several kinds of reproducing biological entities (e.g., genes, organisms, species) that can vary in fitness, resulting in potential selection among them.

meiotic drive

A form of segregation distortion that occurs during meiosis and causes an allele to have greater than 50% probability of being transmitted to a gamete

neutral alleles

Alleles that do not differ measurably in their effect on fitness.

optimality criterion

A statistical term used in phylogenetics, optimality criteria provide a measure of fit of the data to a given hypothesis. A model is designated as the "best" of the candidate models if it gives the best value of an objective function measuring the degree of satisfaction of the criterion used to evaluate the alternative hypotheses. The term has been used to identify criteria used to evaluate phylogenetic trees. For example, in order to determine the best topology between two phylogenetic trees using the maximum likelihood optimality criterion, one would calculate the maximum likelihood score of each tree and choose the one that had the better score. For parsimony, the tree which requires the least number of steps to explain the relationships is selected. However, different optimality criteria can select different trees. In such circumstances caution should be exercised when making strong conclusions.

preadaptation

Possession of the necessary properties to permit a shift to a new niche, habitat, or function. A structure is preadapted for a new function if it can assume that function without evolutionary modification.

reproductive success

The fitness of a genotype or other biological entity, often measured by the average per capita number of offspring that a newly formed zygote will have, or by similar measures.

segregation distortion

Any of several biological processes that alter the rules of Mendelian inheritance such that some alleles when heterozygous have a greater than 50% chance of transmission to the offspring. See meiotic drive.

sexual selection

Differential reproduction as a result of variation in the ability to obtain mates.

species selection

A form of group selection in which species with different characteristics increase (by speciation) or decrease (by extinction) in number at different rates because of a difference in their characteristics.

trade-off

The existence of both a fitness benefit and a fitness cost of a mutation or character state, relative to another.

Allele

One of several form of the same gene, presumably differing by mutation of the DNA sequence. Alleles are usually recognized by their phenotypic effects; DNA sequence variants, which may differ at several or many sites, are usually called haplotypes.

allele frequency

The proportion of gene copies in a population that are a given allele; i.e., the probability of finding this allele when a gene is taken randomly from the population; also called gene frequency.

Aposematism

warning coloration. Describes antipredator adaptation where a warning signal is associated with the unprofitability of a prey time to potential predators. Ex. strawberry poison dart frog

bp (base pair)

AGTC (adenine, guanine, thymine, cytosine)

Codon

A nucleotide triplet that encodes an amino acid or acts as a "stop" signal in translation.

Cultural inheritance

the storage and transmission of information by communication, imitation, teaching and learning. It is transmitted by the brain rather than by genes.

Deleterious Mutation

A mutation that reduces fitness.

Duplication

The production of another copy of a locus (or other sequence) that is inherited as an addition to the genome.

Epigenetic inheritance

Inherited changes in gene expression or phenotype that are not based on changes in DNA sequence.

Epistasis

An effect of the interaction between two or more gene loci on the phenotype or fitness whereby their joint effect differs from the sum of the loci taken separately equilibrium

Exon

That part of a gene that is translated into a polypeptide (protein). Cf. intron.

Fission

the action of dividing or splitting something into two or more parts.

Fusion

come together to form a single entity

Gene family

two or more loci with nucleotide sequences that have been derived from a common ancestral sequence.

Genetic code

written in linear form using ribonucleotide bases that compose mRNA, each "word" consists of 3 ribonucleotide letters or a triplet code, unambiguous - each triplet specifies only one amino acid

Gene mixing

results in different combinations of genes through segregation, recombination, asexual inheritance

Hardy- Weinberg equilibrium

Pertaining to the genotype frequencies expected at a locus under ideal equilibrium conditions in a randomly mating population.

Horizontal gene transfer (HGT)

Movement of genes or symbionts (such as parasites) between individual organisms other than by transmission from parents to their offspring (which is vertical transmission). Horizontal transmission of genes is also called lateral gene transfer

Intron

part of a gene that is not translated into a polypeptide. Cf. exon

Inversion

A 180° reversal of the orientation of a part of a chromosome, relative to some standard chromosome

Linkage disequilibrium

The association of two alleles at two or more loci more frequently (or less frequently) than predicted by their individual frequencies.

Maternal effect

nongenetic effect of a mother on the phenotype of her offspring, stemming from factors such as cytoplasmic inheritance, transmission of symbionts from mother to offspring, or nutritional conditions.

Mutation

the ultimate source of variation

nonsynonymous substitution

A base pair substitution in DNA that results in an amino acid substitution in the protein product; also called replacement substitution. Cf. synonymous substitution.

Phenotype

The morphological, physiological, biochemical, behavioral, and other properties of an organism manifested throughout its life; or any subset of such properties, especially those affected by a particular allele or other portion of the genotype