Summer Career Connections Session 6, Day 2, Conservation Paleobiology
Day 2 of SAVY kicked off with a bang, as students entered the room in exasperation of the terms they did not understand from last night’s reading. We went through the article and used context clues (including hints from elsewhere in the sentence and Latin roots and prefixes) to define complex terms including temporal (relating to time), biogeochemical cycles (a natural cycle involving the movement of an element via organisms or natural sources – e.g., carbon and water cycles), extirpate (local extinction), and clade (a group of organisms that share a last common ancestor). I’d say this was good practice for future standardized tests, and in any case we used these terms to have students co-teach one another about their prior night’s reading.
Next, we addressed a simple question: What, exactly, is a species? We discussed a few of the historical ways that scientists described species and concluded that there are problems with all of these definitions. For example, species DO change over space and time (adaptation…), they CAN interbreed (mules, anyone?), and they sometimes perform different roles in different ecosystems. Did you know that there are an estimated 1.5 million named animal species, and about 10,000 new ones are named every year??? By some estimates, there are likely over 10 million animal species on the planet.
Following this, we talked about how scientists classify organisms (Linnean Classification, a.k.a. King Phillip Came Over For Great Spaghetti) and how we organize all of this diversity. Students learned how to construct a phylogenetic tree (another of our unknown terms – simply a hypothesis of evolutionary relationships among organisms) using a group of vertebrates that they should be familiar with (e.g., bird, lizards, alligators, whales, hippos, and zebras). Students worked in groups to come up with a grouping for all of these animals, during which time we discussed how a variety of evidence informs paleontologists about these relationships, including DNA, fossils, and proteins, among other things.
After lunch, students practiced making phylogenetic trees for coins. They learned how scientists can have different opinions that must be reconciled (maximum likelihood estimation) and how the most likely scenario is the one that involves the fewest number of evolutionary changes (parsimony). The goal here was to show how morphological data can be used to define the relationships among species, and to learn that our definitions among species continually evolve with new information (including genetic data!)
Finally, we began to look at tools that paleoecologists use to reconstruct past environments. To begin with, plants! Students learned about how fossil pollen and phytoliths (microscopic spherules of quartz embedded in grass blades) can be used to reconstruct ecosystems, determine what crops were grown by ancient peoples, and even how extinction events occurred (For example, sediments recovered from the geologic layer that includes the remnants of the asteroid that killed the dinosaur shows pollen that is actually CHARRED! How cool is that?!)
Students ended the day by conducting a Leaf Margin Analysis. This is a paleoecological tool that takes advantage of the fact that leaves with smooth margins (e.g., oaks and magnolias) tend to occur in warmer latitudes, while leaves with toothed margins(e.g., birch and aspen) tend to occur in cooler latitudes. The relationship can be summarized by the following equation:
where MAT = mean annual temperature in °C
To see how reliable this method is at a place like Vanderbilt, students collected a sample of ~230 leaves and calculated the percentage of smooth vs. toothed leaves. We ended up calculating a mean annual temperature of 61.3°F – only 1.5°Fhigher than Nashville’s actual mean annual temperature of 59.8°F. Close, but not exactly on target. Why not? Turns out that our sample was overwhelmingly comprised of oak leaves. Oaks, which tend to be found more abundantly in warmer climates like Georgia and Florida, were planted here about 150 years ago prior to and just at the founding of Vanderbilt University by Bishop McTyeire. It would be interesting to compare this sample with a sample from the trees behind your house. I encourage you to get your child to do this and see if a larger, more natural sample might yield an even closer estimate!
Happy learning, and we’ll look forward to tackling vertebrate and invertebrate fossils tomorrow!
Warmly,
Dr. Smith