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| evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing |
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| loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population |
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| proportion of all copies of a gene that is made up of a particular gene variant (allele) |
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| increased strength of different characteristics in hybrids; the possibility to obtain a genetically superior individual by combining the virtues of its parents. |
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| process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations |
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| organisms whose ranges are entirely separate, so that they do not occur in any one place togethe |
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| organisms whose ranges overlap or are even identical, so that they occur together at least in some places |
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| evolutionary process by which new biological species arise |
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| acquisition of the same biological trait in unrelated lineages |
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| accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species adapting to different environments, leading to natural selection defining the success of specific mutations |
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| changes in population genetics that simultaneously favor individuals at both extremes of the distribution |
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| type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value |
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| natural selection favors a single phenotype and therefore allele frequency continuously shifts in one direction |
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| reproductive isolation that occurs before the formation of a zygote can take place |
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| reproductive isolation that occurs after members of two different species have mated and produced a hybrid offspring. Such hybrids are usually unable to reproduce |
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| two species that live in different habitats within the same area may encounter each other, if at all, even though they are not geographically isolated. (Water and terrestrial habitats of the Genus Thamnophis) |
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| lack of interbreeding or little genetic mixing between organisms of the same species |
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| Copulation is often impossible between different animal species because of the incompatible shape and size of the genitalia |
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| scale of analysis of evolution in separated gene pools. |
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| change in the relative frequency with which a gene variant (allele) occurs in a population due to random sampling and chance: the alleles in offspring are a random sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces |
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| transfer of alleles of genes from one population to another |
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| complete set of unique alleles in a species or population |
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| allele within a gene pool is not changing in frequency (i.e. evolving) |
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| intentional breeding for certain traits, or combination of traits |
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| the change of a biological object triggered by the change of a related object |
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| mutually advantageous development of characteristics in two or more species of organisms |
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| rapid evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single, rapidly diversifying lineage |
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| study of the similarity and differences in the anatomy of different groups of animals. It helps to reveal how animals are related to each other and how they have changed through evolution |
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| development of a similar trait in different not closely related species (that is in species of a different clade), but descending from the same ancestor |
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| speciation hypothesis rooted in uniformitarianism. The hypothesis states that species continue to adapt to new environmental and biological selection pressures over the course of their history, gradually becoming new species |
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| perform the same or similar function by a similar mechanism but evolved separately |
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| characteristics of organisms that is due to their shared ancestry |
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| adaptation of pest species targeted by a pesticide resulting in decreased susceptibility to that chemical |
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| occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as "change below the species level" |
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| study of prehistoric life, including organisms' evolution and interactions with each other and their environments (their paleoecology) |
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| theory proposed by Charles Darwin that states that certain evolutionary traits can be explained by intraspecific competition |
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| systematic difference in form between individuals of different sex in the same species |
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| occurs in cells and organisms when there are more than two paired (homologous) sets of chromosomes |
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| theory in evolutionary biology which proposes that most sexually reproducing species will experience little evolutionary change for most of their geological history (in an extended state called stasis) |
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