Dear Presley and Brianna,

So far, we’ve investigated how recyclables like plastic, aluminum, and paper can end up in the trash. If our clothes get damaged, or we simply outgrow them, we might toss them in the trash, too. Or send them to a thrift shop. Either way, they often end up buried in a landfill.

Dear Presley,

If you’re anything like me, maybe one of your weekly chores is helping take out the trash or making sure all your tuna cans get into the right recycle bin. The truth is, I wasn’t entirely sure where the garbage goes either, so I decided to ask my friend Karl Englund.

Dear Asma and Friends:

Lots of bees have pointy behinds, but not all of them. The ones that do have a pointy behind, or a stinger, can use it to help defend their homes, food, and fellow bees. That’s what I found out from my friend Megan Asche, a graduate student at Washington State University who studies honey bees and takes super close-up photos of insects.

Dear Max,

Clap your hands. Stomp your feet. Blink your eyes. Every time you move, the brain and body send messages to each other. Under your skin, your nerves stretch out like a network of wires across the body. They help carry these messages from one part of the body to another.

Dear Jamie,

Everyone is different. Maybe you are adventurous, shy, outgoing, funny, or kind. Before you were even born, your unique personality was beginning to take shape.

Dear Sam,

If you’ve ever been near a herd of mooing cows, it might have sounded like all their moos were the same. But just as each person’s voice is a little different, so is each cow’s moo.

[caption id="attachment_2942" align="alignleft" width="592"] Dr. Universe examines a gray hair.[/caption]

Dear Darae,

Hair comes in lots of different colors. There’s black, medium brown, auburn, light brown, strawberry blonde, and copper, to name just a few. But in the end, almost everyone will have hair that’s gray or white.

Dear Marcelina,

Lots of warm-blooded animals get sick, including cats. I’ve had a fever before, but I wasn’t entirely sure why we warm up when we get sick. I decided to ask my friend and professor Phil Mixter at Washington State University.

Dear Mrs. Rubert and Students,

Fish swim in big schools. Baby ducks waddle in a straight line. Ants and bees divide up labor. The world is full of animals that live in groups and they do it for a few different reasons.

Dear Ellie,

Sleep is one of the most important functions of our body. It helps us feel rested and gives us energy. Getting a good night’s sleep is important for our health. But when we don’t get enough sleep, or haven’t slept in a long time, we feel tired.

Dear Hasandi and Harrison,

If you’ve ever been near a cat or dog when they tooted, the smell might have sent you running right out of the room. A lot of animals pass gas. But believe it or not, some animals do not.

Dear Andrea,

You're right. If we took a trip into the mountains, we would find that it felt a lot colder. It all has to do with our atmosphere. We may not always think about it, but we are basically living in a giant ocean of air.

Dear Nisi,

Just like humans, us cats lose hair. Have you ever brushed your hair and found that some ends up on the brush? Sometimes human hair falls out. It is the body’s way of shedding, or getting rid of dead skin and hair.

Dear Coleman,

People have wondered if Mars has life for a long time. About a hundred years ago, an astronomer named Percival Lowell looked through a telescope and thought he saw canals—a possible sign of water and life as we know it—on Mars.

Dear Karri,

Because cats and dogs are different species, they aren’t usually friends in nature. Dogs in the wild see cats as prey, and cats see dogs as a threat.

Dear Brayton,

Snakes slither to move around because they have no legs. They rely on their muscles and scales.

The scales on a snake are made from a material called keratin. That’s the same material that makes up human fingernails. They help the snake move on different surfaces.

Dear Charleigh,

Whenever there’s heavy rains or winds, butterflies seem to disappear. This is because butterflies hide when it rains. That’s what I found out from my friend David G. James who is an associate professor at Washington State University. He studies insects, including butterflies, in the Pacific Northwest.

Dear Brianna,

A parasite is an organism that steals resources from another organism in order to survive. Our planet is home to all kinds of parasites and organisms that host them.

Dear Brody and Friends:

While a stove or oven produces heat, a fridge can’t actually produce something called “cold.” So, how does a refrigerator manage to keep all your food cool?

Dear Ana,

When the northern lights come out, beautiful, colorful patterns stretch across the night sky. But they begin with a star that is millions of miles away: our sun.

Dear Brody,

By the time you finish reading this sentence, about twenty babies will have been born into our world. Sometimes they’re twins.