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Evidence of evolution: embryology

Review your understanding of embryological evidence of evolution in this free article aligned to NGSS standards.

Key points

  • Embryos are unborn or unhatched organisms early in the course of development.
  • Embryos grow and develop in a series of stages. During this growth, an embryo’s physical features change. Some features get more specialized. Other features disappear.
  • Embryos of different species can have similarities that are not visible when the organisms are fully formed. Many of these similarities are homologous features. These features provide evidence that the species are related through evolution.
  • For example, all
    embryos have homologous structures called pharyngeal arches, or gill arches. In fish, these arches develop into parts of the gills. In mammals, these arches develop into parts of the ears and jaw.
  • In general, embryos of related species have more features in common at earlier stages of development than they do at later stages.
A diagram shows six stages of mouse embryonic development. An arrow below the six embryos points to the right and is labeled time. The diagram shows that as a mouse embryo develops, it looks more and more like a fully-formed mouse.
A diagram showing six stages of mouse embryonic development. As the embryo grows, it develops more of the specialized structures that are present in a fully-formed mouse. Image created with Biorender.com.

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