Grade by Grade
D. Structures and Mechanisms · Strong and Stable Structures

What Is a Structure? Natural and Built

D2.1 A1.1 A1.5About 35 minutes
Learning goals
  • I can explain that a structure is a supporting framework that holds a load.
  • I can describe a structure by its size, its shape and its function (its job).
  • I can find structures in the natural environment and in the built environment.
  • I can sort structures as natural or built and explain my sorting.

Words to know

structure
Something with a supporting framework that holds a load. It has a definite size, shape and function. A bridge, a chair and a bird's nest are structures.
load
The weight or force that a structure holds up or carries. Cars are a load on a bridge.
framework
The parts that hold a structure up and give it its shape, like the poles of a tent or the bones of your body. Also called a frame.
function
The job something does. The function of a chair is to hold up a person who is sitting.
natural structure
A structure found in nature, made by plants, animals or the Earth itself. A tree, a spider's web and a beaver lodge are natural structures.
built structure
A structure made by people. Houses, bridges, fences and playgrounds are built structures.

Look around you!

You are sitting on a chair. The chair is holding you up. Above you, a roof holds up snow in the winter. Outside, a maple tree holds up branches, leaves and maybe a bird's nest. The nest holds up eggs.

All of these things hold something up. Scientists and engineers call them structures. In this unit you will learn what makes a structure strong and stable, so it does not break or fall over.

A robin's nest with four blue eggs sits in the fork of a maple tree branch.
A nest is a natural structure. The branch holds up the nest, and the nest holds up its load: the eggs. AI-generated image

Remember from Grade 1

In Grade 1 you learned that a structure holds up a load, and that many objects have a frame inside, like the poles in a tent or the skeleton in your body. You also found out that a wide bottom helps a structure stay steady. In Grade 3 we look much more closely: why are some structures strong, and how can we make them stronger and steadier?

What is a structure?

A structure is something with a supporting framework that holds a load.

  • The framework (or frame) is the part that holds everything up and gives the structure its shape.
  • The load is what the structure holds up or carries. A bookshelf's load is the books. A bridge's load is the cars, trucks and people that cross it.

Every structure also has a definite size, shape and function:

  • Size: how big or small it is. A doghouse is small. An apartment building is very big.
  • Shape: what it looks like: tall, wide, round, flat, pointed.
  • Function: its job. A bridge's job is to carry things across a river or a road.
load (books)frame(top and legs)
A table is a structure. Its frame (the top and the legs) holds up a load of books.

Natural and built structures

Some structures are found in nature. They are made by plants, by animals, or by the Earth itself. We say they are in the natural environment.

Other structures are made by people. We say they are in the built environment.

Natural structures (made by nature)Built structures (made by people)
a tree (the trunk and branches hold up leaves)a house
a bird's nesta bridge
a spider's weba playground climber
a beaver lodge and a beaver dama hockey net
a honeycomb made by beesa tent
your skeletona snow fort
a turtle's shella bus shelter
Some natural and built structures

Describing a structure like a scientist

When scientists describe a structure, they tell its size, shape, function and load. They also say whether it is natural or built. That gives a clear picture to someone who cannot see it.

Worked example

Let's describe a structure together

Describe a bird's nest like a scientist.

  1. Natural or built? A bird makes it, so it is a natural structure.
  2. Size: Most nests are small. Many fit in your two hands.
  3. Shape: It is shaped like a bowl, round with a hollow in the middle.
  4. Function: Its job is to hold the eggs and the baby birds safely.
  5. Load: The eggs, the babies and the parent bird sitting on them.
  6. Framework: Twigs and grass woven together hold the nest up and give it its bowl shape.

A bird's nest is a small, bowl-shaped, natural structure. Its function is to hold the eggs and baby birds. Its framework is woven twigs and grass.

LOADthe eggs (and the baby birds)FRAMEWORKtwigs and grass woven togetherSHAPEa bowl with a hollow middleNATURALbuilt by a birdbranch
A bird's nest described like a scientist: its load, its framework, its shape, and whether it is natural or built.
Worked example

Let's sort some structures

Sort these into natural or built: a spider's web, a fence, an ant hill, a snow fort, a tree, a bridge.

  1. Ask: Who made it? Nature (plants, animals, the Earth) or people?
  2. A spider made the web: natural. Ants made the ant hill: natural. A tree grew by itself: natural.
  3. People made the fence, the snow fort and the bridge: built.
  4. Even though a snow fort is made of snow (a natural material), people built it, so it is a built structure.

Natural: spider's web, ant hill, tree. Built: fence, snow fort, bridge.

Is it a structure?

Ask yourself: Does it have a frame that holds a load? A bridge does. A shelf does. A loose pile of sand does not have a framework, so it is not really a structure. A ball is an object, but it is not built to hold up a load.

Just for fun

If you are sitting on a chair right now, guess what? You are its load! Engineers would even call you a live load, because you get up and walk away.

Hands-on activity

Structure hunt

You need: paper, a pencil, and a grown-up to go for a walk with you.

  1. Fold your paper in half. Write Natural on one side and Built on the other.
  2. Walk through your home, then outside around your street, yard or park.
  3. Find at least 5 natural and 5 built structures. Draw or write each one on the right side.
  4. Pick your favourite one. Under it, write its size, shape, function and load.
  5. Tell a grown-up about it like a scientist: "This is a ___. It is natural/built. Its job is to ___. Its load is ___."

What to look for: natural structures like trees, nests, webs and ant hills; built structures like fences, swings, benches, mailboxes, lamp posts and bridges. Safety: stay with your grown-up near roads, and look at nests and webs without touching them.

Your turn

1

What is a structure?

2

What is the load on a bookshelf?

3

Is a beaver lodge natural or built?

4

Is a playground slide natural or built?

5

What is the function of a bridge?

6

Name two natural structures and two built structures you could find near your home.

7

What part of your body is a natural framework?

More practice: warm-up

1

Is a spider's web natural or built?

2

Is a tent natural or built?

3

What do we call the job of a structure?

4

What is the load on a chair?

5

Is a tree a structure?

More practice: on your own

1

Describe a hockey net by its size, shape and function.

2

A snow fort is made of snow, which comes from nature. Why do we call it a built structure?

3

What is the framework of a tent? What is its load?

4

A honeycomb is made by bees. What is its function?

5

Is a pile of loose leaves a structure? Explain.

Challenge

1

A tree and a lamp post are both tall structures. Give one way they are the same and one way they are different.

2

Your friend says, "A turtle's shell is not a structure because nobody built it." Is your friend right? Explain.

3

Think of a structure that has more than one function. Name it and its functions.

Check your understanding

Quiz

1.

A structure is something that...

2.

Which is a natural structure?

3.

Which is a built structure?

4.

The function of a structure is...

5.

What is the load on a bridge?

6.

Kids build a snow fort. It is...

For parents and teachers

Big idea: A structure has a supporting framework that holds a load, and it has a definite size, shape and function. Structures can be natural (trees, nests, webs, beaver lodges) or built (bridges, houses, fences) (D2.1). The structure hunt is a small research task (A1.1), and describing a structure by size, shape, function and load is scientific communication (A1.5).

How to help: On walks or drives, play "Natural or built?" Point to something and ask, "Who made it? What is its load? What is its job?" Encourage full sentences: "The lamp post is a built structure. Its job is to hold up a light."

Common difficulties:

  • Deciding by material instead of maker. A snow fort or a log cabin is made from natural materials, but people built it, so it is a built structure.
  • Calling every object a structure. A ball or a spoon is an object, not a structure; it is not built to hold up a load. Ask, "What does it hold up?"
  • Mixing up shape and function. Shape is what it looks like; function is what it does.

Safety: look at nests, webs and wasp nests without touching them, and stay with your child near roads.