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| The modern theory of evolution, synthesizing the ideas of Darwin and Mendel among others into a more complete theory of evolution. |
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| The sum of all the alleles of all the individuals of a population. |
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| A set of five conditions under which evolution cannot occur. These conditions are: random mating, large population, no net mutations, no gene flow and no natural selection. |
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| p + q = 1, so p^2 + 2pq + q^2 = 1, where p^2 and q^2 are the frequencies of homozygous recessive alleles and 2pq is the frequency of the heterozygous allele. |
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| Genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes from another population. |
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| Change in the genetic makeup of a population from generation to generation due to random DNA mutation. |
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| The study of how populations change genetically over time. |
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| A localized group of individuals that are capable of interbreeding and producing fertile offspring. |
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| Hardy Weinberg Equilibrium |
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| The state of a population that meets all the criteria of the Hardy Weinberg Theorem. |
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| A change in the nucleotide sequence of DNA, especially from one generation to the next. |
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| The duplication of chromosome segments, often producing detrimental effects but also an agent of genetic variation and hence evolution. |
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| A fluctuation of allele frequencies from one generation to the next due to random chance in the passing of genes. |
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| A phenomenon caused by a sudden change in the environment of a population which drastically reduces the population size and can change the genetic makeup of that population. |
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| A phenomenon in which a few individuals from a population found a new population, which may not be reflective of the genetic makeup of the original population and can eventually cause the creation of new species. |
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| A population is said to display this if two or more distinct characteristics are represented in high enough frequencies to be readily noticeable. |
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| The average percent of loci in a genome that are heterozygous. For example, a fruit fly is heterozygous on about 14% of its loci. |
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| Differences between the gene pools of separated populations or population subgroups. |
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| A graded change in a trait along a geographic axis, such as the shortening of plants as altitude increases. |
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| The contribution an individual makes to the gene pool of the next generation, relative to the contributions of others. |
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| A more mathematical expression of fitness; the contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus. |
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| A shift of the frequency curve of a population's genetic makeup to the left or right. This is often caused by a change in a population's environment or migration of a population to a new environment in which an extreme of a continuous genetic trait is disfavored. |
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| A favoring of both extremes of a gene curve, making individuals with intermediate phenotypes disfavored. An example is that of birds with distinctly different beak sizes - one specialized for one food source and one for another. The birds with intermediate beak lengths are specialized for neither, and their frequency drops. |
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| Selection in a population against the extremes of a certain trait, favoring intermediate traits. For example, most human babies weigh 3-4 kg; those who don't suffer higher rates of mortality. |
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| The maintaining of two or more phenotypic forms in a population, producing a state known as "balanced polymorphism". |
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| Selection for a locus with two or more alleles, such as heterozygous sickle cell carriers, who are protected against severe malaria symptoms and are also incapable of having sickle cell anemia. |
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| Frequency-dependent Selection |
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| The decline of one morph in a population due to a frequency that is too high. |
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| Genetic variation that has little or no impact upon reproductive success, and is thus unaffected by natural selection. |
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| Genes that have become inactivated by mutations. |
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| Natural selection for mating success. |
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| Marked differences between the sexes in secondary sexual characteristics. |
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| Selection within the same sex - direct competition among individuals of one sex for mates of the opposite sex. |
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| Choosiness of individuals of one sex in selecting their mates of the opposite sex. |
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| The favoring of individuals that possess certain heritable traits which leave more offspring than other individuals. |
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| The accumulation of inherited characteristics that enhance an organisms ability to survive and reproduce in specific environments. |
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| A change over time in the genetic composition of a population. |
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| The branch of biology concerned with naming and classifying organisms. |
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| Remains or traces of organisms from the past, most often found in sedimentary rock. |
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| The study of fossils, developed by French scientist Georges Cuvier. |
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| The speculation that boundaries between strata of time represent catastrophic events which eliminated large numbers of organisms and even species. |
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| The idea that profound change can take place through the cumulative effect of slow but continuous processes. |
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| The concept that the same geological processes are operating today as did in the past, and at the same rate. |
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| Descent with Modification |
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| Darwin's idea that all organisms are related through descent from an ancestor that lived in the remote past. |
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| The modification of other species by humans by breeding individuals with desired traits to produce desired offspring. |
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| Similarity resulting from common ancestry. |
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| Variations upon an ancestral structure that exist within different species. |
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| Bodily structures of marginal, if any, importance to an organism - remnants of structures that were important to ancestors. |
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| The geographic distribution of species across the Earth. |
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| Species that are found nowhere else in the world. |
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| The origin of new species. |
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| Evolutionary changes above the species level - for example the appearance of feathers in the evolution of birds into dinosaurs. |
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| Evolutionary changes above the species level - for example the appearance of feathers in the evolution of birds into dinosaurs. |
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| A population or group of populations whose members have the potential to interbreed in nature to produce viable, fertile offspring. |
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| The existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids. |
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| Barriers which impede mating between species or hinder the fertilization of ova when two different species try to mate. |
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| Barriers which prevent a hybrid zygote from developing into a viable, fertile adult. |
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| The Morphological Species Concept |
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| A concept which characterizes a species by its body shape, size and other structural features. |
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| The Paleontological Species Concept |
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| A concept which focuses on morphologically discrete species known only from the fossil record. |
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| The interruption of gene flow caused by the division of a population into geographically separated subpopulations. |
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| The separation of populations existing in the same locale caused by reproductive barriers between those populations. |
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| A condition caused by accidents in cell division that results in extra sets of chromosomes. |
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| An individual that has more than two chromosome sets, all derived from a single species. |
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| A common form of polyploidy caused by the interbreeding of two species to form a hybrid. If the hybrid is able to propagate itself asexually, then subsequent generations may become fertile, thereby entering this state. |
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| The evolution of many diversely adapted species from a common ancestor upon that ancestor's introduction to new environmental opportunities. |
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| The sudden appearance of new species in a geologic stratum, proceeded by the disappearance of the ancestor species. |
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| An evolutionary change in the rate or timing of developmental events. |
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| The retention of ancestrally juvenile traits in a sexually mature organism. |
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| Genes which determine the placement and spatial organization of body parts. |
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| Bodily structures which are similar in function but are not derived from a common ancestor - i.e. they arose independent of each other. |
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