Science Grade2 - Way to Grow

Way to Grow

Living Things

Is there a new baby in your family? Maybe one of your friends has a baby brother or sister. A baby grows and changes a lot. You can look at your baby pictures to see how you have grown. Now you are taller. You can do most things for yourself. You can even help take care of a baby sister or brother. 

Humans are part of the family of living things. All living things grow and reproduce. Dogs have puppies. The puppies grow and become grownup dogs. Oak trees have acorns. Acorns grow into oak trees. Living things need air, food, and water to survive and grow.

Air

A baby begins to breathe air as soon as it is born. It often cries then, too. Crying helps the baby’s body take in air. But the first breath a baby takes is only the beginning. How would you like to try to count how many times a person breathes in a lifetime?

Humans cannot stay alive for very long without air. The body uses oxygen in air to help make energy from food. Air enters the nose or mouth.

Blood carries oxygen to different parts of the body. When you run or work hard, you breathe faster to get more oxygen.

Food

Think about all of the different things you do in a day. You wake up, get dressed, and go to school. You walk to your classroom, play sports, and talk to friends. Your body needs energy to do all these things. It even needs energy to do things like growing and sleeping. You get energy from food, just as all living things do.

The body breaks down food into nutrients. Your body gets the energy it needs from nutrients. The body also uses nutrients to repair itself. Blood carries the nutrients to all parts of the body.

There are many kinds of nutrients. People need to eat many different foods to get all of the nutrients they need. For example, breakfast might be cereal with milk and fruit. Or, it might be eggs with bacon and toast. 

Humans eat many foods from plants and animals. Some animals eat only a few kinds of food. Cattle eat mostly grass. Sometimes it does not rain for a long time, and the grass dries up. Then the ranchers have trouble feeding the cattle. Humans can choose from many foods. This has helped people survive. 

At first, babies can drink only milk. In a few months, they can eat soft foods. As they grow, they learn to enjoy different kinds of foods, the way that you do.

Water

Living things must have water to survive. People can live without food for weeks. But without water, we can survive only about one week. It might surprise you to know that most of the human body is made of water. For example, human blood is mostly water. Blood could not carry air and nutrients through the body without enough water. Muscles are mostly water, too. Even bones have water in them.

Water is important because it helps the body work. Water is needed to change food into energy. The body needs water to repair itself. Water also helps the body stay cool. Think of the last time you ran or worked hard. Little drops of water came through your skin. As air moved against the drops, your skin felt cooler.

Some water is lost as your body uses it, for example, when the drops on your skin dry. It is important to put water back into the body. Humans need to drink several glasses of water each day. Some foods can also give water to the body. Fruits and vegetables are good sources of water. Watermelon is almost all water. Lettuce, carrots, and cucumbers all contain large amounts of water.

Growth

The body of a grown-up human can reproduce, or have a baby. When babies are born, an exciting process begins. They take in air, food, and water so that their bodies can grow. At first, babies sleep most of the time. They begin to make sounds. Slowly they learn to hold things in their hands. Before long, they can sit up. After babies can crawl, they try to walk. Babies who are 18 months old can usually walk by themselves. 

Growth continues for many years. You are still going through the process that began when you were born. Think of how much you’ve changed since you were a baby!

Think and Write

1. What happens to your breathing when you run hard?

2. What does your body need energy for?

3. Narrative Writing Write a paragraph about how you grew between the end of first grade and now. Do you wear a different size of clothing or shoes? What new things have you learned?

Hands-On Activity

Time Line Make a time line of your life. Include things you learned to do and foods you learned to eat.

School-Home Connection

Growth Measurements Have a family member measure your height. Do this once a month. Make a table or a graph that shows how much you grow during this school year.