You Animal

When you look at the great variety of animals on Earth, the first thing that might strike you is how unbelievably different every species is from each other. There is plenty of diversity to go around...

Yet, if you look at the basic body structure of all animal bodies, as well as their genetic structure, something else emerges: animal bodies, including your own, are all variations on a single theme controlled by similar sets of genes, placed in roughly the same sequence (check out the evolution of whales, for instance). In other words, for just about every part of your body, there is a corresponding part in other animals, and this similarity increases as our evolutionary relatedness to these animals increases.

In fact, when these genetic sequences are drastically altered, you may get animals that grow legs on their heads and antennae out of their torsos, as you can see in this documentary.
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