The Greening of the Earth: Evolution of Plants (November 9)

Remember: No classes on Monday and Wednesday this week. I’m in Indianapolis with a large contingent of Wooster Earth Scientists at the annual meeting of the Geological Society of America. I’ll be giving this talk on Wednesday afternoon. Wish me luck.

We’ll start Friday with a review of your second test results, then begin our discussion of early plants.

Plants have been in this course for awhile as a leafy background to tetrapod evolution, but now it is time to take them seriously. The best place to start a general survey of our very distant green cousins is with the summary Tree of Life page on land plants (embryophytes). There are lots of links there. Berkeley’s fossil plants range chart may be especially useful, although we won’t be using most of the names given there. The most detailed plant website is the University of California on-line paleobotany lab. The diagrams and hierarchical systems of detail here are impressive. You may want to scan these pages for the beautiful line drawings alone. If you want professional detail of fossil plant systematics and distribution, click the homepage of the International Organisation of Palaeobotany.

Here’s a ginkgo webpage for everything you want to know about this beautiful tree common on our campus (although it is hardly the only “link between the lower and higher plants”). What is the tallest plant and where is it? A redwood in California measures an astonishing 379 feet.  Check out the oldest living plant — an impressive 13,000 years of life as a clone. It’s also in California. Finally, a short video clip of stomata in action.

The evolution of angiosperms (flowering plants) is a bit contentious these days. Most paleontologists agree that the first definite angiosperm fossil is Cretaceous, but genetic and molecular studies suggest they evolved sometime in the Jurassic. There are disputes over what the fossil record really shows.

Now that you’ve accumulated quite a bit of life’s history, you might appreciate this deep-time clock. I can’t guarantee that all the dates will be correct, but the order of events is good. The main thing you will gain from this page is an appreciation for the scale of geologic time.

Here is a copy of the Fall 2018 second test you took last week. We’ll go over it in class. The average score was 82%, with a high grade of 99%. The breakdown: 90s (10 students), 80s (10 students), 70s (6 students), 60s (2 students), below 60 (3 students).

Merycoidodon skull, left side (Oligocene of Nebraska).

Geology in the News –

The End-Permian Extinction happened much more rapidly than we previously thought. In fact, from this study, it was geologically instantaneous. Life was doing OK until quite suddenly a tipping point was reached to throw it into catastrophe. Implications, people, implications.

The ornithischian dinosaur Pachycephalosaurus may have eaten meat, according to a recent paper. It has been found with sharp front teeth typical of a theropod. I think this is a stretch, though, because some plant eaters have sharp teeth.

A Cretaceous bird in, you guessed it — China, has its lungs preserved as a carbon film. This is a critical piece of evidence for our theories of bird flight.

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