Genetic Drift and Gene Flow

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Evolution Noun

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[ev-uh-loo-shun]

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Evolution

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The process of change in the inherited traits of a population over successive generations, also described as descent with modification.

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Example: This diagram shows a 'tree of life,' where different animal groups branch off from common ancestors, illustrating the long-term pattern of evolution.

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Variation Noun

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[vair-ee-ey-shun]

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Variation

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The difference in the physical traits of an individual from those of other individuals in the same population or group.

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Example: This image shows many different breeds of dogs, illustrating the concept of variation—the wide range of physical differences that can exist within a single species.

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Heritability Noun

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[her-i-tuh-bil-i-tee]

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Heritability

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The ability of a trait to be passed down from one generation to the next through an organism's genes.

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Example: This graph shows that student height is related to their parents' average height, demonstrating that height is a heritable trait passed through genes.

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Gene Pool Noun

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[jeen pool]

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Gene Pool

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The total collection of all genes and their different alleles that exist within a specific population at a given time.

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Example: This image shows a population of frogs with different colors and then represents all their genes (alleles) as a collection of colored dots, defining the gene pool.

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Allele Frequency Noun

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[uh-leel free-kwen-see]

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Allele Frequency

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

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Example: This image shows a population of pea plants with different gene pairs (alleles). Counting the dominant 'W' and recessive 'w' alleles lets you calculate their frequency.

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Mutation Noun

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[myoo-tey-shun]

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Mutation

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A permanent alteration in the DNA sequence of a gene, which is the ultimate source of new genetic variation.

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Example: UV radiation from the sun can cause a mutation by changing the structure of DNA, such as by incorrectly bonding two thymine bases together.

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Natural Selection Noun

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

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Natural Selection

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The process where organisms better adapted to their environment tend to survive and produce more offspring than less adapted individuals.

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Example: This image shows that giraffes with the advantageous trait of a long neck can reach food and survive, while those with shorter necks cannot.

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Genetic Drift Noun

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[juh-net-ik drift]

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Genetic Drift

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A mechanism of evolution characterized by random fluctuations in allele frequencies, which has a significant effect in small populations.

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Example: A random event, like pouring beads from a bottle, can cause a 'bottleneck,' leaving a surviving population with a different mix of traits by chance.

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Gene Flow Noun

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[jeen floh]

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Gene Flow

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The transfer of genetic material from one population to another through the movement of individuals or their reproductive cells (gametes).

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Example: This diagram shows gene flow where one bacterium transfers genetic material (a plasmid) to another bacterium, changing its genetic makeup.

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Single-gene trait Noun

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[sing-guhl jeen treyt]

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Single-gene trait

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A phenotypic characteristic that is controlled by the action of only one gene, often showing distinct, non-continuous variations.

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Example: This diagram shows how a trait is controlled by one gene. An individual can have two identical alleles (homozygous AA or aa) or two different alleles (heterozygous Aa).