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Why do feet smell?

Why do feet smell?

-Jose, 10, Costa Mesa, Calif.

Dear Jose,

We live in a world filled with all kinds of smells. Take off a pair of tennis shoes after a long day and you might even get a whiff of something pretty stinky. You can blame it on your bacteria. Millions of these tiny things live on your feet. » More …

Why are there different blood types?

Dr. Universe: Why are there different blood types?

-Sarah, Tacoma, Wash.  

Dear Sarah,

At this very moment, several quarts of blood are circulating through your body at nearly 4 mph. But as you’ve pointed out, not everyone’s blood is the same.

Your question made me wonder exactly what we mean when we talk about blood types. I decided to ask my friend Amber Fyfe-Johnson, a researcher at Washington State University who studies cardiovascular diseases–diseases of the blood vessels– in kids.

Believe it or not, she said, there are more than 20 different blood groups. We’ll stick to the main one for now: ABO. There are 4 different types in this group: A, B, O, and AB.

You have trillions of blood cells. Each blood type refers to a specific marker on a red blood cell. It’s kind of like a little flag.

In the early 1900s, an Austrian doctor named Karl Landsteiner discovered three of the little flags. Today, we call these three flags A, B, and O.

These little markers make blood types compatible with each other. If a person with Type A blood is given Type B blood, his or her body sees the Type B surface flag as foreign and rejects it.

Meanwhile, Type O doesn’t have those surface markers. There is nothing on the surface of the red blood cell to reject. Type O blood can be transferred to pretty much anyone who needs it.

Fyfe-Johnson explained that the blood types we have today evolved a very long time ago. Type A is the most ancient blood type and has been found in hominids – or pre-humans. Scientists can use DNA from some blood cells found in fossils to help figure this out. Type O probably originated next, about 5 million years ago. Scientists are still trying to pinpoint when exactly each blood type evolved.

As is often the case, there are a few ways to think about the answer to your question.

One way to think about it is that our parents pass genetic information about our blood types down to us. It’s part of our DNA. Sometimes there’s a change, or mutation, in DNA.

“These different blood types evolved as a result of genetic mutations, but what caused certain blood types to be more successful is likely exposure to infectious diseases or other environmental pressures,” Fyfe-Johnson said.

The kinds of blood types that survive infections are often the ones that outlive the others.

For example, cells that are infected with a disease called malaria don’t stick to Type O or Type B red blood cells. Those with Type A blood who are infected with malaria are more likely to have clumps of cells form that can be harmful. Especially when they form in places like the brain or heart.

People with Type A blood are more likely to have serious complications or die as a result of malaria, whereas people with other blood types could survive. This happens with many kinds of diseases, she said.

“The short story is that blood types probably evolved as a way to fight infectious diseases or other environmental pressures,” she said. “Blood types that survived were more likely to be successful.”

In a way, it’s all about survival of the fittest blood.

Sincerely,
Dr. Universe

What do astronauts eat in space?

What do astronauts eat in space?

–Rhemi, 12, St. Louis, Mo.

Dear Rhemi,

Astronauts eat all kinds of different foods up in space. The food is often similar to what we have here on Earth. But in space, there’s very little gravity. There’s very limited refrigeration, too. On the International Space Station, the refrigerator is only about half the size of a microwave. That means scientists who prepare and package astronaut food have to do it in ways that take up very little room and don’t need to be kept cold. » More …

Why does meat brown on the grill?

Why does meat get brown on the grill?

– Christina, Seattle, Wash.

Dear Christina,

You know summer is just around the corner when the smell of barbecue is in the air. It’s a great question you ask and it leads us to the Meats Lab at Washington State University. That’s where I met up with my friend and animal scientist, Jan Busboom. » More …

Why does stuff decay?

Dr. Universe: I have a ginormous question for you. How come non-biodegradables take like a million, billion, zillion years to decay? -Madeline C., age 8

Dear Madeline,

You’re right. It can take a really long time for some things to decay.

If we buried an apple peel in the backyard it might only take a few weeks to break down into the soil. But if we buried a plastic water bottle, it would probably still be there hundreds of years from now.

There are a lot of living creatures in nature that help break down things. In fact, our trash cans are almost like an all-you-can-eat-buffet for tiny creatures called microbes. Well, an almost all-you-can-eat-buffet. There are some things that they can’t really feast on. It all depends on what’s in our trash bins.

For billions of years, microbes have been munching on plants and animals. They’ve also had some help from fellow decomposers, like worms, flies, and fungi.

The environment where they work can also speed up or slow down the process. The conditions of dirt, air, water, temperature, and sunlight can change the speed of decomposition.

These decomposers are pretty great at breaking down a lot of things we find in nature. But they aren’t as good at breaking down some other materials, such as plastic.

To find out why, I visited my friend Shuresh Ghimire, a scientist who studies biodegradables at Washington State University. He is also really curious about finding ways to decrease the amount of plastic waste in our world, particularly on farms.

Plastics were introduced in the 1930s, he explained. Now, that may seem like a long time ago to us. But for microbes that have been around for billions of years, that’s still a pretty new material.

Both an apple peel and a plastic bottle are made up of different kinds of atoms. Those atoms are bonded and held together in different ways. In an apple, the bonds between atoms are pretty weak. Microbes don’t have to use a lot of energy to break them into smaller parts.

But the plastic bottle has really strong bonds—especially where a carbon atom bonds with another carbon atom. It makes the material sturdy, but it also makes it pretty indestructible. Most microbes don’t recognize these bonds as something they can break down, at least not yet.

“There is a possibility that evolution of microbes over many years in the future may enable more of them to recognize bonds in plastics,” Ghimire said.

In fact, a group of scientists in Japan recently discovered a microbe that looks to be pretty good at eating plastic. They might be able to help us manage some of the plastic waste, but we can help, too.

A water bottle might last hundreds of years buried underground or in a land fill, but it could have a new purpose in our own lifetime if we remember to reuse or recycle it.

Sincerely,
Dr. Universe