Hi, I’m Lindsey, and I’m going to take you through the lesson “Earth: The Apple of Our Eye.” This lesson uses a sliced-up apple as a model to show how much agricultural land is currently being used on Earth. By the end of this lesson, students will be able to state the percentages of different types of land on Earth.
Older students will be able to discuss environmental threats to farmland, and conduct research on the relationship between population growth and human-caused threats to agricultural land.
Younger students will be able to identify two ways people can protect agricultural land, and also make pie charts using their knowledge of fractions.
There are different versions of this lesson for elementary, middle, and high school students. The first part of the lesson, the apple-cutting, is the same for all versions, but the second part varies a little. In all versions, the discussion questions are tailored to meet the grade-specific audience.
This lesson is cross-curricular, and works well for social studies and science classes of all grade levels, as well as elementary math.
To conduct the demonstration, you’ll need an apple, a sharp knife, and a cutting board. If you’d rather use a non-food option, a ball of modeling clay with some floss works just as well.
Part One: The Size of Agricultural Land
Let’s check out Part One!
This apple represents our planet.
The first cut divides the apple into four equal pieces. Three of these pieces is three-fourths of the Earth. What can you find on roughly three-quarters of the Earth?
If you answered water, you’re correct. These pieces represent all of the water on the planet, not just the oceans.
One fourth of the apple remains. This represents all of the Earth’s land.
We’re looking for agricultural land, and we know that we don’t use all of the land on Earth for agriculture. So I’m going to make another cut, and divide this quarter into three equal pieces. Each piece is one twelfth of the planet.
This piece (1/12) represents all of the inhospitable land on Earth. If somewhere is inhospitable, it means that people can’t live or grow food there. Some types of land that are inhospitable are deserts, mountain tops, polar regions, or salt flats.
The remaining two pieces are 2/12, or one sixth, of the Earth. This represents all of the land that is habitable, or capable of growing food and supporting human life. But, we don’t use all of this land for agriculture.
This piece (1/12) represents all of the land that is habitable but not used for agriculture. This includes forests, national parks, nature reserves, public land, and developed areas like roads, cities, and houses. You’d think that all of the world’s cities and towns would make up a big part of this, but actually only one percent of this land is developed by people!
And that leaves us with one twelfth of the Earth’s surface for agriculture. This land produces all of the food for all of the people on Earth. But it’s not really this entire slice of apple that’s growing the food – in fact, it’s only the very surface, the topsoil, that we need for plants to grow. Let’s peel this piece to better represent that topsoil.
But now consider that not all crops grown in this soil are being used the same way. So I’m going to cut this 1/12 into 4 equal pieces. This one piece is 1/48 of the Earth’s surface. That’s all the land we use for all the plants that people eat. Grains, beans, fruits, and vegetables are all represented in this category.
That means 3/48 of the Earth’s surface (or ¾ of agricultural land) is for livestock. Some of this land is used to grow livestock feed like corn, soybeans, oats, and barley. And a large portion of this land is used for grazing – pastures where livestock eat grasses and other plants.
This tiny slice of topsoil is a lot smaller than the whole Earth, but it has an important job for all of the people that live here.
During the demonstration, elementary students can follow along by making divisions on the provided pie chart. It’s also helpful to do the demonstration next to a world map or a globe, to point out some of the geographic features that are discussed.
There are several grade-appropriate discussion questions in all three versions of the lesson, that will help students process what they saw in the demonstration, and also to get them to start thinking about some ways our soil can be preserved. Part Two
Part Two: Soil Health & Conservation
In the second part of the activity, students consider factors that affect soil health and what can be done to help. Every student will read “Do We Treat Our Soil like Dirt?”, an article from National Geographic, that introduces some of the threats to soil conservation. Different versions are linked in each lesson plan to correspond to each age group’s reading level.
The rest of the activity will be a little different depending on what age group you’re working with.
Elementary students can practice math skills with some provided word problems, and will take part in a whole class discussion that reinforces what they read about soil health. For example, one question asks students what they think it means to let soil ‘rest?’”
Middle and high school students are asked to complete a research project, with extra scaffolding provided for middle schoolers. After reading the National Geographic article, students form small groups and create presentations about one of the current threats to soil. A list of potential topics, like overgrazing or slash and burn farming, is included to help decide what to cover. Middle schoolers share their presentations directly, while high schoolers set up a booth, and serve as an expert on their topic, in an “Ask the Expert” soil fair.
This activity, Earth the Apple of Our Eye, touches on a lot of topics that students see in their everyday lives, and it can be especially impactful to pair with a trip to a local farm or community garden.
To download this lesson plan, and many others, visit www.PopulationEducation.org.