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| 43225403 | evolution | descent with modification; the idea that living species are descendants of ancestral species that were different form present-day ones | |
| 43225404 | fossils | preserved remains of once-living organisms | |
| 43225405 | strata | layers of sediment that have formed over millions of years | |
| 43225406 | paleontology | the study of fossils | |
| 43225407 | catastrophism | The principle events in the past occured suddenly and were caused by different mechanisms than those operating today | |
| 43225408 | uniformitarianism | the principle stating that mechanisms of change are constant over time | |
| 43225409 | adaptations | modification of an organism or its parts that makes it more fit for existence under the conditions of its environment | |
| 43225410 | natural selection | the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations. | |
| 43225411 | artificial selection | selective breeding of domesticated plants and animals to produce offspring with desired genetic traits | |
| 43225412 | fossil record | shows that past organisms differed from present-day organisms and that many species have become extinct | |
| 43225413 | homology | similarity in characteristics resulting from a shared ancestry | |
| 43225414 | homologous structures | Structures in different species that are similar because of common ancestry. | |
| 43225415 | vestigial structures | remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species. | |
| 43225416 | evolutionary tree | a branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms | |
| 43225417 | convergent evolution | the evolution of similar features in independent evolutionary lineages | |
| 43225418 | analogous | having characteristics that are similar because of convergent evolution | |
| 43225419 | biogeography | the study of the past and present distribution of species | |
| 43225420 | continental drift | the slow movement of the continental plates across Earth's surfce | |
| 43225421 | pangaea | The supercontinent formed near the end of the Paleozoic era when plate movements brought all the landmasses of Earth together. | |
| 43225422 | endemic | referring to a species that is confined to a specific, relatively small geographic area | |
| 43225423 | microevolution | a change in a population's gene pool over successive generations; evolutionary changes in species over comparably brief periods of time | |
| 43225424 | average heterozygosity | the percent, on average, of a population's loci that are heterozygous in members of the population | |
| 43225425 | geographic variation | differences between the gene pools of separate populations or population subgroups | |
| 43225426 | cline | a graded change in a trait along a geographic axis | |
| 43225427 | mutation | a change in the nucleotide-base sequence of a gene or DNA molecule | |
| 43225428 | population | A group of individuals of the same species that interbreed, producing fertile offspring | |
| 43225429 | gene pool | all of the alleles for all the loci in all the individuals that make up a population | |
| 43225430 | hardy-weinberg principle | the principle that frequencies of alleles and genotypes in a population remain the constant from generation to generation, provided that Medelian segregation and recombination of alleles are at work | |
| 43225431 | hardy-weinberg equilibrium | the condition describing a non-evolving population | |
| 43225432 | genetic drift | a process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next, effects are most pronounced in small populations | |
| 43225433 | founder effect | when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool isn't reflective of the source population | |
| 43225434 | bottleneck effect | Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population. | |
| 43225435 | relative fitness | The contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus. | |
| 43225436 | directional selection | Natural selection that favors individuals at one end of the phenotypic range. | |
| 43225437 | disruptive selection | both forms at extreme endfavors are favored, intermediate forms eliminated | |
| 43225438 | stabilizing selection | Natural selection that favors intermediate variants by acting against extreme phenotypes | |
| 43225439 | sexual selection | Selection based on variation in secondary sex characteristics, leading to the enhancement of sexual dimorphism. | |
| 43225440 | sexual dimorphism | marked differences between the secondary sex characteristics of males and females | |
| 43225441 | intrasexual selection | A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex. | |
| 43225442 | intersexual selection | Individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex, also called mate choice. | |
| 43225443 | balancing selection | Natural selection that maintains two or more phenotypic forms in a population (balanced polymorphism) | |
| 43225444 | heterozygous advantage | greater reproductive success of heterozygous individuals compared to homozygotes, tends to presever variation in gene pools | |
| 43225445 | frequency-dependent selection | a decline in the reproductive success of individuals that have a phenotype that has become too common in a population | |
| 43225446 | neutral variation | genetic variation that does not appear to provide a selective advantage or disadvantage | |
| 43225447 | speciation | process by which new species are formed | |
| 43225448 | macroevolution | evolutionary change above the species level, including the origin of a new group of organisms or a shift in the broad pattern of evolutionary change over a long period of time | |
| 43225449 | biological species concept | definition of a species as a population or group of populations whose members can breed with one another in nature and produce fertile offspring | |
| 43225450 | species | a group of organisms so similar to one another that they can interbreed and produce viable, fertile offspring but do not produce viable, fertile offspring with members of other such groups | |
| 43225451 | reproductive isolation | the existence of biological factors (barriers) that impepde members of two species from producing viable, fertile hybrids | |
| 43225452 | hybrids | offspring that results from the mating of individuals from two different species or two true-breeding varieties of the same species | |
| 43225453 | prezygotic barriers | A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted | |
| 43225454 | postzygotic barriers | a reproductive barrier that prevent hybrid zygotes produced by two different species from developing into viable, fertile adults | |
| 43225455 | morphological species concept | A definition of species in terms of measurable anatomical criteria. | |
| 43225456 | ecological species concept | A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment. | |
| 43225457 | phylogenetic species concept | A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life. | |
| 43225458 | allopatric speciation | formation of new species in populations that are geographically isolated from one another | |
| 43225459 | sympatric speciation | formation of a new species within the same geographic area | |
| 43225460 | polyploidy | A chromosomal alteration in which the organism possesses more than two complete chromosome sets. | |
| 43225461 | autopolyploid | An individual that has more than two chromosome sets, all derived from a single species. | |
| 43225462 | allopolyploid | a fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chormosomes | |
| 43225463 | hybrid zone | a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry | |
| 43225464 | reinforcement | a process in which natural selection strengthens prezygotic barriers to reproduction, thus reducing the chances of hybrid information, likely to occur only if hybrid offspring are less fit that members of the parent species | |
| 43225465 | punctuated equilibria | in the fossil record, long periods of apparent stasis, in which a species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change | |
| 43225466 | protobionts | collection of abiotically produced molecules surrounded by a membrane or membrane-like structure | |
| 43225467 | ribozymes | An enzymatic RNA molecule that catalyzes reactions during RNA splicing. | |
| 43225468 | radiometric dating | method used to determine the age of rocks and fossils using the rate of decay of radioactive isotopes | |
| 43225469 | half-life | the amount of time it takes of a sample of a radioactive isotope to decay | |
| 43225470 | stromatolites | Rock made of banded domes of sediment in which are found the most ancient forms of life: prokaryotes dating back as far as 3.5 billion years. | |
| 43225471 | geologic record | The division of Earth's history into time periods, grouped into three eras: Archaean, Proterozoic, Phanerozoic, and further subdivided into eras and epochs. | |
| 43225472 | endosymbiosis | Process through which early prokaryotic cells are thought to have engulfed other, smaller cells and eventually incorporated them as organelles; these cells evolved into modern-day eukaryotes. | |
| 43225473 | serial endosymbiosis | A model of the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells. | |
| 43225474 | cambrian explosion | A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 545-525 million years ago | |
| 43225475 | mass extinction | period of time when global environmental changes lead to the elimination of a large number of species throughout Earth | |
| 43225476 | adaptive radiation | the development of many different forms from an originally homogeneous group of organisms as they fill different ecological niches | |
| 43225477 | heterochrony | evolutionary change in the timing or rate of an organism's development | |
| 43225478 | paedomorphosis | The retention in an adult organism of the juvenile features of its evolutionary ancestors. | |
| 43225479 | homeotic genes | Any of the genes that control the overall body plan of animals by controlling the developmental fate of groups of cells. | |
| 43225480 | phylogeny | The evolutionary history of a species or group of related species | |
| 43225481 | systematics | study of the diversity of organisms to classify them and determine their evolutionary relationships | |
| 43225482 | taxonomy | discipline of classifying organisms and assigning each organism a universally accepted name | |
| 43225483 | binomial | The two-part latinized name of a species, consisting of genus and specific epithet. | |
| 43225484 | genus | a taxonomic category above the species level, example: panthera | |
| 43225485 | family | In classification, the taxonomic category above genus, example: felidae | |
| 43225486 | orders | In classification, the taxonomic category above family, example: carnivora | |
| 43225487 | classes | In classification, the taxonomic category above order, example: mammalia | |
| 43225488 | phyla | A taxonomic category. are divided into classes, example: chordata | |
| 43225489 | kingdoms | a taxonomic category the second broadest after domain, example: animalia | |
| 43225490 | domains | a taxonomic category above the kingdom level; examples: Archaea, Bacteria, and Eukarya | |
| 43225491 | taxon | The named taxonomic unit at any given level of classification | |
| 43225492 | phylogenetic tree | a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms | |
| 43225493 | phylocode | Only names groups that include a common ancestor and all of its decendants. | |
| 43225494 | branch points | The representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor | |
| 43225495 | sister taxa | Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives | |
| 43225496 | rooted | describing a phylogenetic tree that contains a branch point representing the last common ancestor of all taxa in the tree | |
| 43225497 | polytomy | in a phylogenetic tree, a branch point from which more than two descendant taxa emerge. A polytomy indicates that the exoutionary relationships among the descendant taxa are not yet clear. | |
| 43225498 | analogy | similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with that same trait | |
| 43225499 | homoplasies | Analogous structures that evolved independently | |
| 43225500 | molecular systematics | the comparison of nucleic acids or other molecules in different species to interfere relatedness | |
| 43225501 | cladistics | an approach to systematics in which organisms are placed into groups called clades based primarily on common decent | |
| 43225502 | clades | a group of species that includes an ancestral species and all its descendants | |
| 43225503 | monophyletic | pertaining to a group of taxa that consists of a common ancestor and all its descendants | |
| 43225504 | paraphyletic | pertaining to a group of taxa that consists of a common ancestor and some but not all of its descendants | |
| 43225505 | polyphyletic | pertaining to a group of taxa derived from two or more different ancestors | |
| 43225506 | shared ancestral character | a character, shared by members of a particular clade, that originated in an ancestor that is not a member of that clade | |
| 43225507 | shared derived character | an evolutionary novelty that is unique to a particular clade | |
| 43225508 | outgroup | a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied | |
| 43225509 | ingroup | a species or group of species whose evolutionary relationships we seek to determine | |
| 43225510 | maximum parsimony | a principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts | |
| 43225511 | maximum likelihood | as applied to systematics, a principle that states that when considering multiple phylogenetic hypotheses, one should take into account the hypothesis that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time | |
| 43225512 | phylogenetic bracketing | an approach in which features shared by two groups of organisms are predicted (by parsimony) to be present in their common ancestor and all of its descendants | |
| 43225513 | orthologous genes | homologous genes that are found in different species because of speciation | |
| 43225514 | paralogous genes | homologous genes that are found in the same genome as a result of gene duplication | |
| 43225515 | molecular clock | a method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes appear to evolve at constant rates | |
| 43225516 | neutral theory | the hypothesis that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection | |
| 43225517 | horizontal gene transfer | the transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms |
