Tag Archives: Biology

Mundane Monday: Assembling the Bones

This week’s Mundane Monday theme is “bones.” For this theme, Dr. KO has a nice picture of an alligator snapping turtle skeleton, which you should definitely check out (also, raise your hand if you knew before this that there was a such thing as an “alligator snapping turtle.” My hand is not up). At first I was concerned I wouldn’t have anything for this week, and then I remembered. This is a great lead-in to the topic that’s been on my mind recently: Back to School!

I have not had much time for blogging lately because my teaching job has started up again. I teach middle-grade science with a non-profit organization called Science from Scientists. Regular school, including my kids’ high school and college, started already a while ago, but SciSci gives the teachers and students a week or two to get settled in before we start our visits. This year I have two completely new schools and two new co-Instructors to work with. I’m also going back to two schools I worked with last year and liked.

One of our most popular lessons at SciSci includes the dissection of an owl pellet. Most of my prior exposure to owls has been via children’s fiction, and I first learned about the pellets as an adult when I taught this lesson.

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Mr Rogers’ neighborhood had an owl in it!

Owls don’t poop. They eat their prey whole and digest it in the gizzard, a second stomach. They absorb nutrients like we do from the soft parts of the prey, and eventually regurgitate a pellet containing the indigestible bits (mainly fur and/or feathers and bones). This is a YouTube video of the process that we show our students. It was taken in Ontario in 2014:

Will you ever look at Hedwig quite the same way again?

harry_potter_and_hedwig

One of the many cool things about owl pellets is that you can dissect them and find out what the owl has eaten. If you buy the pellets from Carolina Biological Supply like we do, you usually find a mouse skeleton, maybe two, in the pellet. Occasionally you might find a bird. The prey animals can be identified by the skulls, and sometimes a large portion of the skeleton can be reconstructed.

AssemblingBones
Students dissecting an owl pellet and reconstructing a skeleton

These bones are quite small, but very interesting!

BirdSkeleton

 

Happy DNA Day!

Today, April 25, is National DNA Day. This is an obscure holiday, ranking somewhere above International Violin Day but probably below the recent pi day, or even the upcoming May the 4th be with you.

It celebrates something important, though. National DNA Day commemorates the successful completion of the Human Genome Project in 2003 and the discovery of DNA’s double helix by James Watson and Francis Crick in 1953.

DNA stands for DeoxyriboNucleic Acid. The “nucleic” part means it is found in the nucleus of all cells. There are many different ways to visualize DNA. These are some of the most common:

Francis Crick's DNA model, Rosalind Franklin's X-ray crystallography, a schematic double helix, a bacterial chromosome, some DNA isolated in the lab
Different views of DNA

The upper left shows Watson and Crick’s original wire model of the DNA double helix. On the lower left, the abstract X is one of Rosalind Franklin’s X-ray crystallograms that were used to help determine the structure. The upper right, looking like a beaded necklace, is a bacterial chromosome viewed under an electron microscope. And the lower right, with what looks like some cloudy snot in a tube, shows some DNA extracted from strawberries with common kitchen materials.

The center picture shows the DNA double helical model that has entered popular culture. A DNA molecule is composed of two complementary strands that wind around each other in a helical shape, a “twisted ladder.”  The rungs of the ladder, in primary colors, are the base pairs, which spell out the genetic code.

This song from “They Might be Giants” explains in 2 and a half catchy minutes how the DNA instructions are translated into making different cell types.

Every year the American Society for Human Genetics sponsors an essay contest for high school students and announces the winners on DNA day. This year’s question was about genetic testing.

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Do you think medical professionals should be required for all genetic testing, or should consumers have direct access to predictive genetic testing? 

Check out some of the winning essays here on their website. Congratulations to all who entered!

Science Stories for #WATWB

WATWIC-Bright-TuqBlkThe last Friday of the month is the day for my post for the We are the World Blogfest. This blogfest was born out of a desire to change the tone on social media to one of positivity, peace, and connection. Participants come from all around the world.

Continue reading Science Stories for #WATWB

Book Review: Bully for Brontosaurus by Stephen Jay Gould

Bully for Brontosaurus: Reflections in Natural HistoryBully for Brontosaurus: Reflections in Natural History by Stephen Jay Gould

My rating: 5 of 5 stars

I recently unearthed some book reviews that I wrote when I was in Neurosciences graduate school at Stanford in the early 1990s. There I was the editor of a student newsletter called the “Neuron Free Press,” and we published book reviews about Neuroscience topics. 

This newsletter was published while the internet was coming into its own, before blogs. The dead tree versions of these reviews that I found at the back of an old file cabinet may be the only copies still in existence.  The books are no longer new but I think each one has retained its relevance and stood the test of time.

The first book covered is Bully for Brontosaurus, reviewed back in Autumn 1991 when its author, the great evolutionary biologist Stephen Jay Gould, was still alive and writing. I think it’s especially appropriate for Darwin Day.

Continue reading Book Review: Bully for Brontosaurus by Stephen Jay Gould