Ch. 6: Best-Laid Body Plans!

Shubin starts out this chapter with basic information we already know. We are made up of cells, we have a certain structure for where our organs go on our bodies, etc. Once again this relates us to creatures like reptiles and fish, which have the same basic body structures. The part about embryos was where it started getting interesting for me. It's pretty amazing that humans' and other species' embryos start out incredibly similar yet end up completely different. I learned about embryos and the development process in Health class two years ago, but I wasn't aware that we at some point took the form of a tube (more specifically, a tube inside a tube). I didn't really get the "ectopic implantation" that Shubin mentioned, but the three tissue layers (ectoderm, endoderm, and mesoderm) were easy to understand. I preferred Von Baer's approach on embryos better than Haeckel's. It makes more sense to me to compare embryos with embryos. What better way to see the similarities and differences between different species than from the very beginning of their development? The chapter made sense to me up until Shubin started talking about DNA. I understand that the Hox genes line up in a head-to-tail order and that they can be found in several species with similar basic body structures. The rest kind of lost me. Shubin's comparison to the sea anemone was also confusing at first, but it sort of made sense by the end of the chapter. Basically, genes like the Noggin found in sea anemone function the same way as the corresponding genes in other species. The cliff-hanger at the end leaves me intruiged to know how Shubin plans to compare us to creatures without bodies. The concepts Shubin is trying to explain to us are confusing, but I still find it just as interesting.

~Bryanna Streeter :)