Chapter 5. The Cambrian Explosion
These pages are arranged in some sort of system, believe it or not.
List of images for use in lectures (mainly from the book)
Substantial comments or mini-essays, often with links of their own. They are laid out in the order I deal with them in the Chapter.
Pages that consist almost entirely of Web links on a particular topic.
Small comments and asides ("footnotes", if you like), including useless information, again arranged in order. I have listed them under page number as well as topic.
Chapter 5: images for lectures
Mostly Web links
The Beginning of the Cambrian: Small Shelly Fossils
Larger Cambrian Animals
Trilobite page from Sam Gon III. Looks great!
The Cambrian Explosion
A new 2013 study assesses rates of morphological and rates of genetic change in Cambrian times versus later times. Obviously information is incomplete for both. By using arthropods as a test case, however, information is as complete as one can get because arthropods were so important in Cambrian seas, and were morphologically diverse, and because there are living representatives of many Cambrian groups to provide genetic data. The data show that rates or morphological AND genetic change in the Cambrian were about 5 times as fast as they were in later times. And that result is statistically very strong. That means that the Cambrian evolution really was an "explosion". It doesn't explain the explosion, but it shows that it was real.
The paper is Lee, M. S. Y. et al. 2013. Rates of phenotypic and genomic evolution during the Cambrian Explosion. Current Biology 23: 1-7. It is available as a .pdf file, with nice clear diagrams. Here is a press release
References for Chapter 5
Page last updated September 13, 2013
All links last checked, September 7, 2012
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