Skip to main content Skip to navigation

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

Why do weeds grow sooo fast?

Dr. Universe: Why do weeds grow sooo fast?

– Leah, 9, British Columbia

Dear Leah,

If you’re like me, you’ve picked up a little dandelion fluff ball and blown the seeds around. Weeds like these make a lot of seeds. They get picked up by the wind and planted far and wide. And as you observe, they grow pretty fast, too. » More …

How does water in the ocean move?

Dear Dr. Universe:

HOW DOES WATER IN THE OCEAN MOVE? I THINK IT’S BECAUSE OF THE WIND.

–Case, 5, Yakima

Dear Case,

You know, most cats like to stay a comfortable distance from water.

But when I got your science question about our big ocean, I was ready to jump right in.

Ocean water moves in all kinds of ways. Waves curl and crash on the shore. Big conveyer belts of water, currents, flow for thousands of miles around our planet. The tides go out and come back in.

And yes, the wind plays a big part in all of it. That’s what I found out when I went to visit my friend Jeff Vervoort, a geologist and professor of oceanography at Washington State University.

If you stand on the shore, you can often hear and feel the ocean breeze. On windy days, waves start stirring. The smallest waves, called capillaries, start growing as the wind blows across their surfaces.

The stronger the wind blows, the bigger the waves can get. They can reach great heights—some as tall as six-story buildings. When the wave reaches shallower waters, it will start to curl, then break.

If you’re anything like me, you might be wondering where the wind comes from, too. Vervoort explained that our planet is rotating around on its tilted axis. The sun heats the Earth unevenly as it turns. These conditions actually affect the air and wind patterns on the planet surface. All of this moving air pushes the water in the ocean around.

Vervoort pulled down an Earth-shaped beach ball from the shelf in his office. He explained that winds blow in different directions. If Earth wasn’t rotating on a tilted axis, winds would blow very differently.

But, because of the Earth’s spin, wind belts in the northern hemisphere bend to the right. It also makes the winds in the southern hemisphere go to the left. Ocean currents bend in the same way, caused by the Coriolis effect.

The moving water can sometimes also act like a food delivery system. Some currents deliver important sources of nutrients and oxygen down to animals that live in the deep ocean.

Other currents bring up nutrients for animals that live near the surface. These nutrients allow tiny organisms—plankton—to live and grow to great numbers. These very tiny plankton get eaten by bigger animals like krill. Krill are an important food source for even bigger animals such as whales.

Meanwhile, back up on the surface tides go in and out. While wind impacts the tides a little bit, they mostly happen because gravity from the moon, and a little less from the sun’s gravity, pull water on Earth.

For the most part when it comes to water moving in the ocean, your hypothesis is correct, Case. It’s wind that mostly keeps our ocean surface in motion.

Sincerely,
Dr. Universe

 

Find this article printed in Washington State Magazine!