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a FEATURE of an organism CREATED by the process of natural selection.

continuous variation

ex: height in humans, birthweight

discontinuous variation

phenotypic variation in which there are a discrete number of phenotypes with no intermediate types. Ex: pea color in Mendel's experiment

stabilizing selection

selection pressuresd that favor average phenotypes. Stabilizing sleection reduces the amount of variation in the population but doesn't alter the mean value of the trait.

directional selection

where a single phenotype is favored, causing the allele frequency to continuously shift in one direction

disruptive selection

driving force behind sympatric speciation extreme values for a trait are favored over intermediate values. E.g.: large nose rather than medium sized nose


refers to cells that have pairs of homologous chromosomes, where one chromosome of each pair is inherited from each parent. All primates are diploid


a diploid organism whose chromosomes have two copies of the SAME allele. Opposite of heterozygous


the genetic makeup of a trait


the shown trait

parapatric speciation

two-step process in speciation where selection causes the differentiation of geographically separate, isolated populations of a species and the populations become reproductively isolated as well


carries genes and appears during cell division

homologous traits

structural similarities derived from two species with independent ancestors. Eg. a bat's wing and a human's hands

natural selection

the process that produces adaptation


the process of division of normal body cells through which new diploid cells are created


the process of cell division in which haploid gametes (eggs and sperm) are creatred


the form and structure of an organism


many genes?


genes that influence multiple traits


evolution of populations within a species


evolution of new species, families, and higher taxes


a spontaneous change in the chemical structure of DNA

sympatric speciation

a hypothesis that speciation can result from selective pressures favoring different phenotypes within a population without geographic isolation as a factor

character displacement

the result of competition between two species that causes the members of different species to become morphologically or behaviorally more different from each other


one of two or more alternative forms of a gene

reproductive isolation

a relationship between two populations in which there is no gene flow between them

balanced polymorphism

a steady state in which two or more alleles coexist in a population.

founder effect

occurs when a new colony is started by a few peope from the original population. Not much diversity, usually mutations.

bottleneck effect

occurs when a population endures a natural disaster and alleles are greatly reduced in diversity


opposite of punctuated equilibrium

punctuated equilibrium

where there are specific, extreme changes in evolution. Like a square like tree

allopatric speciation

speciation that occurs when two or more populations of a single species are geographically isolated from each other and then diverge to form two or more new species


the evolutionary relationships among a group of species. diagrammed as a family tree

adaptive radiation

the process in which a single lineage diversifies into a number of species

genes are carried on


what's a nucleotide composed of?

a phosphate-sugar base

What are the differences between DNA and RNA

DNA is double stranded while RNA is single stranded, DNA has only a nucleus but RNA can have a nucleus or a cytoplasm, the main ingredient in DNA is Thymine while in RNA it's Uracil.

genetic drift

the change in frequency of a gene do to randomness

gene flow

the transfer of alleles of genes from one population to another


where two somewhat related species eventually form a new species


a gradual transformation of one species to another

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