"My Inner Fish" Relate and Review

In class we watched the two episodes "Your Inner Fish" and "Your Inner Reptile", through which the main themes are that humans, who are closely related to reptiles, have a shared ancestry with fish. In its early stages of development, a human and fish embryo look very similar because of their shared Hox genes, which suggest common ancestry. In other words, the Hox genes that were found in fish embryos are also present in human embryos, leading on theories of ancestry. Other evidence for common ancestry includes similar body structures like bony skeletons, backbones, skulls, and shared basic brain anatomy. Another important key aspect of the relationship between fish and humans is the Sonic Hedgehog gene, which sends out an organizing signal that tells cells to do different things. This gene helps create the array of digits on the hand in many mammals. As we moved from fish to reptiles, we explored our evolutionary relationship to these other organisms. An example of humans' relation to reptiles is their hearing anatomy. Mammals have a wide range of hearing because they have 3 bones in their middle ear while reptiles only have 1 bone in their middle ear. Scientists think that two jaw bones evolved and got smaller and moved upwards towards the ear as reptiles led to mammals over time. 

The reptile ear has only one bone where as the mammal's ear has three distinct parts.