Homologous, Analogous, and Vestigial Structures

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Morphology Noun

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[mor-fol-uh-jee]

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Morphology

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The scientific study of the form and structure of living organisms and their specific structural features.

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Example: This image shows the morphology (physical form) of finch beaks, comparing two parent species to their hybrid offspring to illustrate how traits are inherited.

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Homologous Structures Noun

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[ho-mol-uh-gus struk-cherz]

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Homologous Structures

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Structures shared by related species that have been inherited from a common ancestor but may have different functions.

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Example: This image shows that the forelimbs of a human, cheetah, whale, and bat share a similar bone structure, demonstrating they evolved from a common ancestor.

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Analogous Structures Noun

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[uh-nal-uh-gus struk-cherz]

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Analogous Structures

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Features in different species that have similar functions but evolved separately and do not share a common ancestral structure.

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Example: A bird's wing and an insect's wing are analogous structures because both are used for flight, but they have very different internal structures.

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Vestigial Structures Noun

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[ves-tij-ee-ul struk-cherz]

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Vestigial Structures

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Anatomical features or behaviors that no longer seem to have a purpose but were important for an ancestral species.

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Example: This diagram shows a whale's skeleton, highlighting the small, unused pelvic bone—a vestigial structure left over from its land-dwelling ancestors that had legs.

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Embryology Noun

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[em-bree-ol-uh-jee]

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Embryology

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The branch of biology that studies the prenatal development of gametes, fertilization, and development of embryos and fetuses.

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Example: This image shows that mouse and human embryos look very similar, sharing homologous structures like pharyngeal arches and a tail, which is evidence for a common ancestor.

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Homology Noun

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[ho-mol-uh-jee]

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Homology

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The existence of shared ancestry between a pair of structures or genes in different taxa, indicating a common origin.

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Example: This image shows that the forelimbs of a human, whale, turtle, frog, and bird share a similar underlying bone structure, even though they are used for different functions.

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Analogy Noun

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[uh-nal-uh-jee]

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Analogy

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A functional similarity between anatomical parts that is based on usage rather than common evolutionary origin.

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Example: A bird's wing and an insect's wing are analogous structures; they both are used for flight but evolved independently from different original structures.

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Divergent Evolution Noun

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[di-vur-juhnt ev-uh-loo-shuhn]

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Divergent Evolution

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The process where groups from the same common ancestor evolve and accumulate differences, resulting in the formation of new species.

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Example: This diagram shows how the forelimb bones of different mammals, inherited from a common ancestor, have evolved into different shapes for different functions.

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Convergent Evolution Noun

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[kuhn-vur-juhnt ev-uh-loo-shuhn]

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Convergent Evolution

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The process where distantly related organisms independently evolve similar traits to adapt to similar necessities or environments.

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Example: This diagram uses arrows to show how different, unrelated ancestors can evolve similar traits or structures when adapting to similar environments or pressures.

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Parallel Evolution Noun

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[par-uh-lel ev-uh-loo-shuhn]

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Parallel Evolution

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The independent evolution of similar traits, starting from a similar ancestral condition, in species of the same lineage.

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Example: This image shows a marsupial mole and a golden mole, two unrelated species that independently evolved similar body shapes and features for burrowing underground.