Evolutionarily speaking all of us are tetrapods and contain a fish inside! Take the retention of embryonic gill arches for example, still observed in quite a few people. Preaurucular pit is the scientific term for this ancestral structure. Its presence in Humans reflects the “evo-devo” aspect of our shared biological heritage with all vertebrates living on earth.
Here, animated by Edwin Mutuma Murungi, the annotated animation of zebrafish embryo development produced by Norwegian University of Life Sciences – NMBU Learning Center is quite informative for understanding the big picture of “Evo-Devo” concept. Evo-Devo compares the developmental processes of organisms to infer the evolutionary ancestral relationships.
Embryo development has been a curious subject in biology. Since 1920s the salamander embryo development have been studied with great detail and success.
The genetics of many critical genes such as the HOX genes or the limb development through sonic hedgehog gene have been unraveled through these kinds of embryonic studies showing how fins became limbs and hands and fingers.
Tissue regeneration is a fascinating biological subject. Many invertebrate organisms such as crabs, starfishes, sponges and planarian flatworms can regenerate body parts. Some vertebrates such as the jawless fish lampreys and salamanders especially the axolotl demostrate a fascinating ability to regenerate lost body parts. Curiously, although both are amphibians salamanders can regenerate but frogs cannot. Comparison of such contrasting groups is particularly useful in understanding organ and tissue regeneration. Fishes are ancestral to all land vertebrates. Due to its extraordinarily transparent embryos the Zebra fish (Danio rerio) is a model organism providing a foundation to the vertebrate development.
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