Darwin’s Theory_ Natural Selection

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Natural Selection Noun

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[nach-uh-ruhl suh-lek-shuhn]

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Natural Selection

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The process where organisms with variations best suited to their local environment survive and produce more offspring.

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Example: This diagram shows how different finches evolved unique beak shapes (adaptations) that are specialized for eating specific types of food, illustrating natural selection.

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Artificial Selection Noun

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[ahr-tuh-fish-uhl suh-lek-shuhn]

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Artificial Selection

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A process where humans, not the environment, select which individuals reproduce to pass on desired traits.

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Example: This diagram shows how humans selected the wild plant teosinte for its best traits over many generations to create the larger, more useful modern corn.

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Struggle for Existence Noun

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[struhg-uhl for eg-zis-tuhns]

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Struggle for Existence

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The competition among members of a population for finite environmental resources when more offspring are produced than can survive.

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Example: Multiple hands reaching for one piece of bread illustrates competition for limited resources, a key part of the struggle for existence.

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Adaptation Noun

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[ad-ap-tey-shuhn]

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Adaptation

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Any heritable characteristic that increases an organism's ability to survive and reproduce in its specific environment.

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Example: A chameleon changes its skin color to match the leaves on a branch, an adaptation called camouflage that helps it hide from predators.

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Fitness Noun

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[fit-nis]

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Fitness

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A measure of how well an organism can survive and successfully reproduce in its particular environment.

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Example: This diagram shows that the grey mice have higher fitness because their color helps them hide from the fox, so more of them survive to reproduce.

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Survival of the Fittest Noun

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[ser-vahy-vuhl uhv thuh fit-ist]

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Survival of the Fittest

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The differential reproductive success where individuals with high fitness survive and pass adaptations to the next generation.

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Example: This comic shows how 'fitness' means having traits that help an organism survive, like getting food or hiding from predators, to pass on those traits.

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Heritable Variation Noun

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[her-i-tuh-buhl vair-ee-ey-shuhn]

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Heritable Variation

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Natural, inheritable differences among individuals within a population that are passed from parents to their offspring.

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Example: This image shows different breeds of cattle, each with distinct, inheritable traits like horn size and coat color, demonstrating variation within a single species.

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Descent with Modification Noun

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[dih-sent with mod-uh-fi-key-shuhn]

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Descent with Modification

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The principle that living species are descended, with accumulated changes over time, from common ancestral species.

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Example: An ancestor finch passes its traits to descendants, but natural selection causes modifications, like different beak shapes, to help them survive on different foods.

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Common Descent Noun

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[kom-uhn dih-sent]

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Common Descent

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The principle that all species, both living and extinct, are united by being descended from ancient common ancestors.

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Example: This image shows different species of Darwin's finches, which all evolved from one common ancestor, demonstrating the principle of common descent through their varied beak shapes.

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Speciation Noun

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[spee-see-ey-shuhn]

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Speciation

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The evolutionary process by which new and distinct biological species arise, often from a single ancestral species.

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Example: This diagram shows how one ancestral species splits into new, distinct species over time, with each branching point representing a speciation event.