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What leeches and ligers can teach you about evolution

This is the first story in a four-part, weekly series on taxonomy and speciation. It’s meant to help you as you participate in Armchair Taxonomist — a challenge from the Encyclopedia of Life to bring scientific descriptions of animals, plants, and other living things out from behind paywalls and onto the Internet.

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Getting to know "Mitochondrial Eve"

By studying the way it has mutated and changed over time, scientists can trace human mitochondrial DNA — the DNA that is passed from mother to daughter — back to a single woman. Basically, everybody alive is descended from her. But that's not the same thing as saying that Mitochondrial Eve was once the only woman alive. In a very nice piece — with helpful illustrations — the Christian (but evolution-accepting) scientists at BioLogos explain what Mitochondrial Eve really means and why she can't be used as an argument for creationism. Whether or not you've ever found yourself arguing this point with a family member or friend, the piece is really useful for deepening your understanding of a pop-science concept that's often thrown around without a clear explanation behind it. Maggie

Iron Egghead: Explain biology using eight everyday items

Scientific American has an awesome contest going on right now. They're challenging you to make a video explaining some part, process, or system in the human body using eight objects: Yourself, a writing surface, a writing implement, rubber bands, paper clips, string, cups , and balls. You have to use all eight items. You can't use anything else.

You can read the full instructions and rules online. And check out the sample video, made by Scientific American interns Isha Soni and Mollie Bloudoff-Indelicato.

Bonus: The first 100 qualified entries all get a free digital subscription to Sci Am.

Via Bora Zivkovik

Why do trees fall over in a storm?

The more accurate version of this question would really be something like, "Why do some trees fall over in a storm while others stay standing?" The answer is more complex than a simple distinction between old, rotted, and weak vs. young, healthy, and strong. Instead, writes Mary Knudson at Scientific American blogs, trees fall because of their size, their species, and even the history of the human communities around them.

“Trees most at risk are those whose environment has recently changed (say in the last 5 – 10 years),” Smith says. When trees that were living in the midst of a forest lose the protection of a rim of trees and become stand-alones in new housing lots or become the edge trees of the forest, they are made more vulnerable to strong weather elements such as wind.

They also lose the physical protection of surrounding trees that had kept them from bending very far and breaking. Land clearing may wound a tree’s trunk or roots, “providing an opportunity for infection by wood decay fungi. Decay usually proceeds slowly, but can be significant 5-10 years after basal or root injury.” What humans do to the ground around trees — compacting soil, changing gradation and drainage “can kill roots and increase infection,” Smith warns.

Read the full piece at Scientific American Blogs

Image: West Philly Storm - Trees Down, a Creative Commons Attribution (2.0) image from kwbridge's photostream

Two very good dogs teach you chemistry

Paige the border collie can load the washing machine, pick up trash, and make toaster waffles (although you probably don't want to eat them afterwards).

And, with the help of her colleague Dexter — and their owner/trainer, who is also a chemist — Paige can even teach chemistry.

Here, Paige and Dexter serve as models for a discussion about chemical bonds — the forces that attract one atom to another and form the basis of all the chemicals that make up our world.

Via Matthew Hartings

F&*#ing Internet, how does it work?

For the next 60 years or so—basically, until everyone roughly my age has died off—former Alaskan senator Ted Stevens will be widely remembered (and mocked) for once describing the Internet as "a series of tubes".

But here's the thing. It's easy to make fun of Ted Stevens. It's harder (much harder) to explain quickly and at a relatively simple level—for lay people with no tech background—what actually happens when they call up a web page.

That's why Greg Boustead and the nice folks at the World Science Festival put together this short video, explaining the basics of the Internet, specifically the basics of packet switching. The video should help the average person understand the Internet just a little better and it has been run by several experts for accuracy, Boustead says.

I have to admit that when I had to screen it for "father of the Internet" Vint Cerf, who invented this process, I was more than a little nervous, certain he would pick it apart. When he replied with "This is so good - can I please use it to explain the concept of packets at public lectures," needless to say, I was over the moon.

So, the Internet. It's not a big truck. It's not a series of tubes. It's more like a bus full of tourists.

Video Link

What cancer statistics actually mean

Genius science writer Ed Yong used to work for a cancer charity, so he's seen how the cancer research sausages get made. In a new post at Not Exactly Rocket Science, Ed takes you on a brief tour of the factory, explaining why even good data doesn't necessarily mean what you think it means.

The post is based around a new study that says 16.1% of all cancers worldwide are caused by infections. This statistic is talking about stuff like HPV—viruses and other infections that can prompt mutations in the cells they infect. Sometimes, those mutations propagate and become a tumor.

That statistic tells us that infections play a role in more cancers than most laypeople probably think, Ed says. It gives us an idea of the scale of the problem. But you have to be careful not to read too much into that 16.1%.

The latest paper tells us that 16.1% of cancers are attributable to infections. In 2006, a similar analysis concluded that 17.8% of cancers are attributable to infections. And in 1997, yet another study put the figure at 15.6%. If you didn’t know how the numbers were derived, you might think: Aha! A trend! The number of infection-related cancers was on the rise but then it went down again.

That’s wrong. All these studies relied on slightly different methods and different sets of data. The fact that the numbers vary tells us nothing about whether the problem of infection-related cancers has got ‘better’ or ‘worse’. (In this case, the estimates are actually pretty close, which is reassuring. I have seen ones that vary more wildly. Try looking for the number of cancers caused by alcohol or poor diets, if you want some examples).

And that's only one of the complications involved in understanding cancer statistics. You really should read Ed's entire post. After you do, a lot of apparent inconsistencies in cancer data will make a lot more sense to you. For instance: What about the cancers caused by radiation exposure?

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