Haeckel's statement that "ontogeny recapitulates phylogeny" differs from what we now call von Baer's law-the generalization that features common to a higher taxon often appear earlier in development than the specific characters of lower-level taxa. Compare and contrast these two ways of thinking about changes in development over the course of animal evolution. Even though we now know that Haeckel's dictum seldom holds, what can we learn about phylogeny from development?
Added by Kevin C.
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Haeckel's statement, "ontogeny recapitulates phylogeny," suggests that an organism's development (ontogeny) repeats or mirrors its evolutionary history (phylogeny). This idea implies that during an organism's development, it passes through stages that resemble the Show more…
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In the late 1800s, a biologist studying animal embryos coined the phrase "ontogeny recapitulates phylogeny," meaning that the physical development of an animal embryo (ontogeny) seemed to retrace the changing form of the species during its evolutionary history (phylogeny). Why would embryonic development retrace evolutionary steps?
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What is suggested by the similarity of early embryos of different species of vertebrates? evolution from a distant common ancestor no evolutionary relationship between the groups similar environments in the past recent common ancestry Some organisms that share a common ancestor have features that have different functions, but similar structures. These are known as vestigial structures. analogous structures. homologous structures. fossil structures. If an organism has a vestigial structure, that structure likely once had a function in a(n) close relative. early ancestor. unrelated organism. embryological stage.
Marlyn J.
Define what a phylogeny represents. Explain why only synapomorphies (shared derived traits) indicate a close evolutionary relationship. Define and identify synapomorphy (shared derived trait), symplesiomorphy (shared ancestral trait), and homoplasy in a cladogram. Define and identify monophyletic, paraphyletic, and polyphyletic groups in a phylogenetic tree. Apply the concepts of phylogenetics to infer the origin of a disease. Use the concept of parsimony to infer the evolution of traits.
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