Why Do I Breathe Air?

chloe effron
chloe effron

Kids ask a lot of questions. mental_floss has answers. This week we launched WHY?, our new series for kids and parents. We'll tackle all types of questions children have about how the world works by providing science-based, kid-friendly content. Our answers are written with early readers (ages 4 to 7) in mind, but we think they're interesting—and educational—for everyone.

Have a question? Send it to why@mentalfloss.com.

Air surrounds the surface of the Earth. Air is a mix of gases: 78 percent nitrogen, 21 percent oxygen, 1 percent argon, a little bit of carbon dioxide, and tiny amounts of 13 other gases. Plus, air contains water vapor, a mix of hydrogen and oxygen. Air is the part of the atmosphere closest to the Earth. Like a big blanket surrounding Earth, the atmosphere keeps us from getting too hot from the sun or too cold from space—and allows us to breathe. 

Land animals can’t exist without the oxygen in the air. More than 2.3 billion years ago the atmosphere was mostly nitrogen. But then the number of tiny microbes called cyanobacteria (SIGH-an-oh-back-TEER-e-uh) grew. Cyanobacteria use sunlight to change carbon dioxide into a kind of food—a process called photosynthesis. The waste product of photosynthesis is oxygen. So much oxygen was created that it began to fill up the atmosphere. After time, more animals evolved that were aerobic (air-OH-bick), meaning they need oxygen to survive—like us. 

Because plants photosynthesize! Remember, oxygen is a waste product of photosynthesis, and an important part of air. Without oxygen, we can’t breathe. Thanks for making oxygen, plants! But we do something for plants too. We breathe out carbon dioxide, which plants convert into simple food. So plants and animals work together to keep all creatures alive. How cool is that? 

For fun further reading about photosynthesis, visit this gardening guide for kids from the BBC.     

Alcohol-Producing Gut Bacteria May Harm Livers—Even if You Don't Drink

itakdalee/iStock via Getty Images
itakdalee/iStock via Getty Images

Teetotalers might think their liver is safe from the damaging effects of alcohol consumption, but new research is hinting that even non-drinkers and light drinkers might have cause for concern. It turns out a type of gut bacteria is capable of producing alcohol—and enough of it to potentially cause some pretty serious health consequences, including liver disease.

A study led by Jing Yuan at the Capital Institute of Pediatrics in Beijing, China and published in the journal Cell Metabolism offers details. After evaluating a patient with auto-brewery syndrome (ABS), a rare condition brought on by consumption and fermentation of sugary foods that leaves a person with high blood alcohol levels, researchers made an intriguing discovery. Rather than finding fermenting yeast that may have led to the condition, the patient’s stool contained Klebsiella pneumonia, a common gut bacteria capable of producing alcohol. In this subject, K. pneumonia was producing significantly more alcohol than in healthy patients.

The patient also had nonalcoholic fatty liver disease (NAFLD), characterized by fatty deposits in the liver. While many cases of NAFLD are relatively benign, too much fat can become toxic. Examining 43 other subjects with NAFLD, scientists found that that K. pneumonia was both present and potent, pumping out more alcohol than normal in 60 percent of participants with NAFLD. In the control group, a surplus was found in only 6.25 percent.

To further observe a correlation, scientists fed the bacteria to healthy, germ-free mice, who began to see an increase in fat in their livers after only one month. While not conclusive proof that the bacteria prompts NAFLD, it will likely trigger additional research in humans.

It’s not yet known how K. pneumonia acts in concert with the bacterial profile of the gut or what might make someone carrying stronger strains of the bacteria. Luckily, K. pneumonia can be treated with antibiotics. That’s good news for people who might never touch a drink and still find themselves with a damaged liver.

[h/t Live Science]

5 Hilarious Discoveries from the 2019 Ig Nobel Prize Winners

andriano_cz/iStock via Getty Images
andriano_cz/iStock via Getty Images

Each September, the Ig Nobel Prizes (a play on the word ignoble) are given out to scientists who have wowed the world with their eccentric, imaginative achievements. Though the experiments are usually scientifically sound and the results are sometimes truly illuminating, that doesn’t make them any less hilarious. From postal workers’ scrotal temperatures to cube-shaped poop, here are our top five takeaways from this year’s award-winning studies.

1. Left and right scrota often differ in temperature, whether you’re naked or not.

Roger Mieusset and Bourras Bengoudifa were awarded the anatomy prize for testing the scrotum temperatures in clothed and naked men in various positions. They found that in some postal workers, bus drivers, and other clothed civilians, the left scrotum is warmer than the right, while in some naked civilians, the opposite is true. They suggest that this discrepancy may contribute to asymmetry in the shape and size of male external genitalia.

2. 5-year-old children produce about half a liter of saliva per day.

Shigeru Watanabe and his team nabbed the chemistry prize for tracking the eating and sleeping habits of 15 boys and 15 girls to discover that, regardless of gender, they each produce about 500 milliliters of spit per day. Children have lower salivary flow rates than adults, and they also sleep longer (we produce virtually no saliva when we sleep), so it seems like they may generate much less saliva than adults. However, since children also spend more time eating than adults (when the most saliva is produced), the average daily levels are about even—at least, according to one of Watanabe’s previous studies on adult saliva.

3. Scratching an ankle itch feels even better than scratching other itches.

Ghada A. bin Saif, A.D.P. Papoiu, and their colleagues used cowhage (a plant known to make people itchy) to induce itches on the forearms, ankles, and backs of 18 participants, whom they then asked to rate both the intensity of the itch and the pleasure derived from scratching it. Subjects felt ankle and back itches more intensely than those on their forearms, and they also rated ankle and back scratches higher on the pleasure scale. While pleasure levels dropped off for back and forearm itches as they were scratched, the same wasn’t true for ankle itches—participants still rated pleasurability higher even while the itchy feeling subsided. Perhaps because there’s no peace quite like that of scratching a good itch, the scientists won the Ig Nobel peace prize for their work.

4. Elastic intestines help wombats create their famous cubed poop.

In the final 8 percent of a wombat’s intestine, feces transform from a liquid-like state into a series of small, solid cubes. Patricia Yang, David Hu, and their team inflated the intestines of two dead wombats with long balloons to discover that this formation is caused by the elastic quality of the intestinal wall, which stretches at certain angles to form cubes. For solving the mystery, Yang and Hu took home the physics award for the second time—they also won in 2015 for testing the theory that all mammals can empty their bladders in about 21 seconds.

5. Romanian money grows bacteria better than other money.

Habip Gedik and father-and-son pair Timothy and Andreas Voss earned the economics prize by growing drug-resistant bacteria on the euro, U.S. dollar, Canadian dollar, Croatian luna, Romanian leu, Moroccan dirham, and Indian rupee. The Romanian leu was the only one to yield all three types of bacteria tested—Staphylococcus aureus, Escherichia coli, and Vancomycin-resistant Enterococci. The Croatian luna produced none, and the other banknotes each produced one. The results suggest that the Romanian leu was most susceptible to bacteria growth because it was the only banknote in the experiment made from polymers rather than textile-based fibers.

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