This week we return to the Paleozoic and examine developing marine communities, followed by a discussion of the causes of the Permian Mass Extinctions — the greatest disaster in the History of Life. Paleogeographic maps of Pangaea at the end of the Permian can be found on the Paleomap website (note that it was not “99% of all life” which went extinct). Wikipedia has a good Permian Extinctions article, although the topic is controversial enough that some parts of it may be biased by partisan editors of one cause or another.
Probably on Friday our vertebrate cousins will appear in our narrative. The best place on the Web for simple and thorough descriptions of the chordates and their history is at the University of California Museum of Paleontology. Check out their pages on the urochordates (tunicates), cephalochordates, and chordates in general. The Berkeley tetrapod (four-legged) webpage is especially useful for us. This page on limb evolution from an anti-creationist website is very useful, even if the illustrations are a bit clunky. I like this website lovingly devoted to the ancient coelacanth fish Latimeria. It has many illustrations and an extensive history of what we know about this remarkable evolutionary survivor. The Tree of Life page on terrestrial vertebrates will show you current ideas about the relationships of fish and early amphibians. It is a rich source of further links. You might like the short Japanese 3-D animation of Eusthenopteron (an ancient bony fish near the origin of the amphibians) embedded in this link.
Test results! Here is the Fall 2017 student HOL test #1 answers pdf. The grade range was 42%-100%, with 11 students earning 90-100, 11 earning 80-89, 7 earning 70-79, 4 earning 60-69, and 6 with scores below 60. About 28% of the class has A grades on the test, and about 25% has D and F grades. Over half of the class earned A or B. The class test average was 78%. This is good, overall, but if you earned below 80% you need to reform your study habits. You can make an appointment to talk to me by signing up on my weekly schedule posted on my office door (Scovel 120).
A pycnodontid fish tooth, Menuha Formation (Upper Cretaceous), southern Israel. Collected by Andrew Retzler. (Click to enlarge.)
Geology in the News –
You may have heard that mammoths are about to be cloned. Fake news!
Great music video on evo-devo. Starts with hox genes. “This is how we go from single cells to people.” The channel A Capella Science is highly recommended!
Cnidarians in the news! Sleeping jellyfish, even though they have no brains. It is also a great example of how science is really done.