Agenda

Birds and Juvenile Dinosaurs

EXTRA LEARNING: Great job again on the presentations today, especially the Reptiles group who got the audience so engaged that they kept asking questions! Also great job to Scott for presenting the multiple views about the relationship between birds and dinosaurs. Scientists are indeed still debating about this particular relationship. Some think that birds evolved directly from one lineage of dinosaurs. Others think that birds and dinosaurs shared a common ancestor. Here is another more recent hypothesis published in Scientific American (based on a paper in the science journal Nature) proposing that birds were originally juvenile dinosaurs: "Did Retained Juvenile Traits Help Birds Outlive Dinosaurs?" The debate goes on as scientists discover new fossils and new lines of evidence. 

Coelacanth

EXTRA LEARNING: Since today's presentations were about fishes and amphibians, I thought I'd share the following documentaries about coelacanths, a "living fossil" that provides a link between fishes and tetrapods. This is the video clip I showed in class: "Finding the Coelocanth" from National Geographic Wild. Here is a longer documentary about the history of scientists' search for these creatures: "Coelacanth: The Fish that Time Forgot." One of my students asked about how these creatures lived and reproduced. What scientists know is that the coelacanth is ovoviviparous (recall what that means) because they have found dead specimen that carried live young within their bodies. The young had yolk sacs attached. These fish are thought to have one of the longest gestation periods among vertebrates--from one to three years! Some neat features that illustrate how ancient these creatures are can be seen in their lobed fins (with arm-like bones!), their hollow notochords, and the peculiar way in which they swim. These fish do not have a backbone at all, but rather a more primitive feature: a hollow notochord. Additionally, their swimming pattern is similar to how tetrapods walk; more accurately speaking, tetrapods evolved their walking pattern from ancient ancestors similar to the coelacanth. The next time you're walking about, notice how your arms and legs move: left leg and right arm move together and right leg and left arm move together. Creatures like the coelacanth were the first to develop that pattern of motion.

Other interesting things related to fishes and amphibians: mudskippers, flying fish, flying rays, axolotl, new species of caecilians, fish vs. fishes.

Prehistoric Insects and Birds

EXTRA LEARNING: Since one of today's presentations was about arthropods, I thought I'd share this recent article published in National Geographic (originally based on a paper in the Proceedings of the National Academy of Sciences). Previously, scientists had linked insect size to fluctuations in oxygen levels in the atmosphere of prehistoric Earth. Recall how insects respire. Higher oxygen levels would thus allow them to evolve larger bodies. Recent studies by researchers at UC Santa Cruz, however, propose a different story. According to them, insect size decreased due to predation from birds which were showing up on the evolutionary scene. Small insects were more maneuverable than large insects, thus conferring small insects an advantage. These researchers note that after the appearance of birds, even during periods of higher oxygen levels, insect size remained small. Interesting. Read more about it if you like: "Giant Bugs Eaten Out of Existence by First Birds?"

Also interesting: carnivorous caterpillars on Hawaii. Similar video clip.

Animal Presentations this Week

This week is devoted almost entirely to your Animal Kingdom Presentations! Remember to carefully observe your classmates' presentations both for the Animal Kingdom Test on the last day of school as well as for ideas on how to improve your own presentations. Also check the "Lecture" tabs for the PowerPoint slides from these presentations. On Thursday and Friday, we will have block schedule (of ~2 hours per period) to accommodate senior finals. Sixth period will meet on Thursday and seventh period will meet on Friday.

For your notebook for this unit, you have two-ish options: (1) recopy notes as you've been doing for the other units or (2) write down two pages (or two sides of one page, depending on how you see it) of thinking. This thinking can be in the form of a summary of the presentations, an organized comparison of the different animal phyla, or responses to the review questions after each section on animals in your textbook. When I check your notebook, I will be looking for two pages of work per presentation. I suggest you make the presentation topics stand out. For example, if your notes are on mollusks, then highlight "mollusks" or write "mollusks" in huge letters, followed by two pages of work on this group of animals. Then repeat for each presentation. Colored drawings/diagrams earn extra credit, as do highlighting and underlining.

Finally, I've created a Kingdom Animalia Study Guide for your test on June 14th. You may use this study guide on the test, so I suggest you take good notes. The notes must be handwritten (not typed), and yes, you may write the responses on a separate sheet of paper. The study guide is not an assignment, so I will not be collecting it. It is mostly to guide you on what to study for the test.

EXTRA LEARNING: For those who are interested in how to form the plural of "octopus," here is an explanation from one of the editors of the Merriam-Webster Dictionary: octopuses vs. octopi.