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change in the genetic makeup of a population over time


branch of biology that names and classifies the diverse forms of life

binomial nomenclature

every organism has a two word name


earth was molded by slow gradual change, not by sudden violent events

stabilizing selection

eliminates the extremes and favors the intermediates

diverse/disruptive selection

invreases the extremes at the expense of the intermediates

sexual selection

variation in secondary sexual characteristics used in competing for and attracting mates

artificial selection

humas breed individuals with desired traits

balanced polymorphism

population divides into two distinct types

homologous structures

structures in different species that are similar because of a common ancestor

analogous structures

structures that have the same function because of adaptations to similar environments, not common ancestors

vestigial structures

remnants of structues that served important functions in the organism's ancestors

comparative embryology

reveals additional anatomical homologies not visible in adult organisms

molecular homology

genes that are shared among organisms inherited from a common ancestor


comparison of the geographical distribution of similar animals


changes in one gene pool in a population


development of an entirely new species


a group of individuals belonging to one species and living in the same geographic area

gene pool

all the alleles for all the genes in a population

balanced polymorphism

presences of two or more phenotypically different forms of a trait in a single population of a species


provides new alleles in a gene pool

sexual reproduction

provides variatino due to shuffling of alleles during meiosis and fertilization


mating of organisms that aren't closely related


2N condition maintains and shelters a hidden pool of alleles that may not be suitable for present conditions but that could be advantageous if conditions change

heterozygous superiority

the hybrid state is selected for because it has a greater survival rate and reproductive success

frequency dependant selection

works to decrease the frequency of the more common phenotypes and increase the frequency of the less common phenotypes

evolutionary neutral traits

no selective value and scientists don't know why they have stayed in the human population


graded variation in the phenotype of an organism

genetic drift

change in the gene pool due to chance

bottleneck effect

natural disasters reduce the size of a population resulting in a loss of genetic variation

founder effect

a small population breaks away from a larger one to colonize a new area

gene flow

movement of alleles into or out of a population

non-random mating

individuals choose their mate for a specific reason

natural selection

individuals better adapted to an environment survive and have more offspring to pass their genes to

p (in hardy-weinberg)

dominatnt allele

q (in hardy-weinberg)

recessive allele


the evolutionary history of a species or group of species

divergent evolution

populations become isolated and evolve into a new species

convergent evolution

unrelated species occupy the sme environment and show similar adaptations

parallel evolution

two related species that have made similar evolutinoary adaptations after their divergence from a common ancestor


reciprocal evolutinoary adaptations of two interacting species

adaptive radiation

emergence of numerous species from a common ancestor


branch of biology that focuses on classifying organisms and determining their evolutionary relationships


a taxonomic unit at any given level of classification


type of systematics in which a common descent is the primary criteria used to classify


a diagram depicting patterns of shared characteristics of species


group of species that includes an ancestral species and all its descendants

phylogenic tree

a branching diagram that represents a hypothesis about the evolutinoary history of a group of organisms


population whose members have the potential to interbreed in nature and produce fertile offspring


development of a new species

allopatric speciation

separation caused by geographic isolation

sympatric speciation

separation occurs in the same geographic area


a condition where a cell has more than two complete sets of chromosomes

habitat isolation

two organisms live in the same habitat but rarely come in contact with each other

behavioral isolation

organism's behaviors do not attract one another

temporal isolation

isolated by time

reproductive isolation

unable to mate because they are anatomically incompatible

prezygotic barriers

prevent mating

postzygotic barriers

prevent fertile offspring once mating has occured


organisms descend from a common ancestor gradually in a linear or branching fashion

punctuated equilibrium

a species goes through little or no morphological change followed by brief periods of sudden change

adaptive radiation

emergence of numerous species from a common ancestor

allopatric model

a new species arises in a different place and expands its range competing with or replacing the ancestral species after it has become extinct

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