YIF: Chapter 6

            This Chapter does a lot of explaining of evolution in terms of embryos yet again. But instead of the connection between humans and other animals being gill arches it is about the body plan of the embryo in the very early stages of development. Karl Ernst von Baer did experiments with the embryos of chickens and other animals and noticed some very strong similarities. And his ultimate conclusion was this: “Every animal organ originated in one of [the] three [germ] layers. Significantly, the three layers formed the same structures in every species.” This discovery is found in humans as well, the three layers being the ectoderm, mesoderm, and endoderm. This shows that von Baer’s conclusion of the evolution is relevant to human evolution because since most animals have it, then it is likely that we descended from the same ancestors. When the book was talking about the human embryo stages of development was my favorite part of the chapter. I loved how it talked about the early timeline of the fetus in the mother’s body and how childbirth is such a wonderful thing. It was also very fascinating to know and understand what the fetus looks like before it has any distinguishing features. I think the most interesting part of this section of the chapter would be when the author talked about the three germ layers, the mesoderm, endoderm, and ectoderm and how they will all develop into separate organs, like the mesoderm into the body cavity and other organs and the endoderm into the digestive tract and other organs. The Big Idea that has connections to this chapter of the book is the process of evolution drives the diversity and unity of life, because the author lectures about the genetics and embryonic similarities between species so that he can convey that they are unified and also diversified. This is one specific example that was used in this chapter but there are many more connections that can be found as well. An essential question that can be made from this chapter would be “What can similarities in genetics cause to be similar between two creatures?”