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Why Do I Breathe Air?

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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.     

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Why Do I Get Cavities?
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iStock/Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

Your mouth is a busy place. There are hundreds of different kinds of bacteria living on your teeth, tongue and gums. Bacteria, as you may know, are tiny little critters that can only be seen with a microscope. We need some of them to help keep us healthy. Others are more of a pain—especially when they cause cavities (CAA-vih-teez), or little holes in our teeth. If you get a cavity, a dentist will have to treat it. You may get a filling.

During the day, you put all kinds of food into your mouth. When you eat, the bacteria that live in there eat, too. Some bacteria make acid out of the sugar in food. So when you eat sweet stuff—candy, cookies, and sugary drinks—you are helping bacteria to make more acid. The acid eats through the enamel, or the hard coating on your teeth. Over time, this can cause cavities and infections. Ouch! Luckily your spit, or saliva (suh-LIE-vuh), has minerals in it, like calcium and phosphate, that fight back by making your tooth enamel stronger and cutting down on acid. The fluoride in toothpaste helps do this, too. If you have a cavity, a dentist can fill the hole to keep bacteria from getting in and causing a bad infection. Unfortunately, there’s another reason for cavities that you don’t control: genes (jeenz).

Genes are little codes inside our cells that get passed down from our parents. They are instructions to our bodies that affect how we look, act, and grow. Genes may play a big part in whether we get cavities. Some people end up with cavities because of their genes, even if they take really good care of their teeth. Other people hardly get any. We can’t change our genes, but we can control other things. Brushing your teeth, visiting the dentist, and avoiding sweets can all help you keep cavities away.

Want to find out more about what lives inside your mouth? Watch the cartoon below from the National Institutes of Health.

 

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Why Do Lizards Lose Their Tails and Regrow New Ones?
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WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

Many species of lizard lose their tails when they are being chased. When a predator (PREH-duh-tor)—an animal that wants to eat them, like a bird or cat—grabs for the tail, it falls off, and the lizard can run away. How does it happen? Scientists looking at geckos (a type of lizard) under a microscope have found out that some parts of the tail are weaker than other parts.

It’s no accident. The sections of a lizard’s tail will hold together until the lizard is in danger. Scientists think that’s when special cells inside the tail make chemicals that attack the weak points. Then—surprise!—the tail breaks off. It will also keep wiggling for a while to distract the predator while the lizard speeds off. Pretty awesome! That’s not the end of the story, either. Most lizard species can also grow a new tail. 

Lizard tails have a lot of jobs to do. Lizards move their tails around to “talk” to each other. It’s a kind of secret lizard language. The tail also helps lizards keep their balance when they’re scrambling up a tree or jumping from rock to rock. So even though losing the tail is a useful trick, growing it back is pretty important, too. Sometimes lizards can get carried away, though: one busy lizard from Argentina grew six new tails at once!

Watch a gecko regrow its tail in this video

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