Neil Shubin Your Inner Fish Study Guide

Your Inner Fish essay

In Neil Shubin’s Your Inner Fish, he takes his readers on a journey throughout time, teaching how marine animals inevitably ended up on land. Shubin starts his book by describing how himself and other paleontologists found a missing piece, that showed how animals transitioned from water to land. With this discovery it allowed paleontologists like Shubin, to see transitions that could possibly link certain species of fish to humans. A major change between fish and humans is the use of limbs and its ability to use its limbs to take itself out of the water and away from the dangers within. Limbs are a vital part of everyday life for humans. The arm of a human is comprised of one large bone (the humerus) connected to two

DNA are inside genes, and genes are within cells. In each cell, there are different genes that have certain functions depending on where the are located in the body (Page 45). Within the cells, there are genetic switches that turn on and off the use of certain genes (Page 46). These genetic switches could have played a very important role in the genes that caused the development of the fish fin. With little changes over a long period of time, these genetic switches could have been the cause of the development of the human hand (Page 47). These changes could have been a result of the zone of polarizing activity (ZPA) (Page

It does this by using a molecule to tell all the cells where to go and what to do. Within the cell there is a gene called Sonic hedgehog that causes the ZPA to change its plan and this causes a deformation. Fly geneticists were the ones to discover this by using fruit flies. These geneticists turned genes on and off during the development of the flies. Once the flies were fully developed they noticed that one of the flies had a part of its body that looked different than the rest (Page 52). This is because the Sonic hedgehog has the ability copy the tissue that ZPA makes. Sonic hedgehog has great success with doing this because, in hands, digits, and arms of all animals have the mostly same DNA (Page 53). Geneticists have done countless experiments on many animals testing this. The most noticeable of these experiments was done with skates. With knowledge from previous experiments, the geneticists knew that Sonic hedgehog had roughly the same effects on the fin of a shark as a human hand. They used a skate embryo and injected it with Vitamin A (which makes the Sonic hedgehog gene to come out) and waited to see what happened. Sure enough, the skate had an exact replica of another fin (Page 57). This showed that Sonic hedgehog can be present but it doesn’t have to do anything. They were looking for the rods in the fins to get closer to each other showing a change that the Sonic hedgehog caused but there was