Genes and Variation

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Species Noun

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[spee-sheez]

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Species

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A group of similar, interbreeding organisms that are reproductively isolated from other such groups.

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Example: This diagram shows two different-looking crows interbreeding to produce hybrid offspring, illustrating that the ability to reproduce is key to defining a species.

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Population Noun

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[pop-yuh-ley-shuhn]

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Population

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A group of individuals of the same species that live in the same area and interbreed to produce offspring.

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Example: This group of ladybugs represents a population. The differences in their spot patterns show the natural genetic variation that exists among individuals in a population.

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Gene Pool Noun

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[jeen pool]

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Gene Pool

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The complete set of all genes, including all different alleles, that are present within a given population.

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Example: This diagram shows a population of frogs with different colors, representing genetic variation. The oval represents the gene pool, containing all the different gene versions from every frog.

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Allele Noun

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[uh-leel]

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Allele

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One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

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Example: This image shows different versions of a gene, called alleles (represented by 'A' and 'a'), on a pair of chromosomes.

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Allele Frequency Noun

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[uh-leel free-kwuhn-see]

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Allele Frequency

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A measure of how common a specific allele is in a population, often expressed as a percentage or proportion.

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Example: This image shows a population of pea plants with different genotypes (WW, Ww, ww), allowing students to count the 'W' and 'w' alleles.

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Evolution Noun

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[ev-uh-loo-shuhn]

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Evolution

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Any change in the frequency of alleles within a population's gene pool from one generation to the next.

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Example: This diagram shows how different bird species evolved unique beak shapes (variation) to eat specific foods, a key example of evolution by natural selection.

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Genotype Noun

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[jee-noh-tahyp]

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Genotype

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The specific combination of alleles that an individual organism possesses for a particular genetic trait.

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Example: This image shows that a genotype is the combination of alleles (letters like B, b) on a pair of chromosomes, such as homozygous (BB, bb) or heterozygous (Bb).

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Phenotype Noun

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[fee-noh-tahyp]

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Phenotype

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The observable physical, physiological, and behavioral characteristics of an organism, resulting from its genotype and environment.

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Example: The variety of observable traits in dogs, such as fur color, size, and ear shape, are all examples of different phenotypes within a single species.

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Natural Selection Noun

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[nach-er-uhl si-lek-shuhn]

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Natural Selection

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The process where organisms with traits better suited to their environment tend to survive and reproduce more successfully.

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Example: This image shows different beak shapes among Darwin's finches, illustrating the genetic variation within a species that allows natural selection to favor advantageous traits.

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Evolutionary Fitness Noun

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[ev-uh-loo-shuh-ner-ee fit-nis]

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Evolutionary Fitness

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An individual's success in passing its genes on to the next generation, contributing to the population's gene pool.

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Example: An ancestor finch evolves into different species, each with a beak shape adapted for a specific food, showing how traits that improve survival and reproduction increase fitness.