- 8½” x 11” square piece of white cardstock paper
- Colored pencils
- Transparent tape
- Books about the plants and animals of a desert
- Masking tape
- Push pins
- Corrugated cardboard
When you think of a desert, what do you see? We often think of deserts as hot, dry places, but we often refer to them as extreme environments because while many are hot, many are cold as well. Deserts receive very little rain, and cover about a third of the earth.
Different deserts have different species of animals and plants, but these animals and plants share certain characteristics. They all need to be comfortable in arid, or dry, climates. Some plants have thick or waxy skin, called a cuticle, that prevents water from moving out of its cells. The mesquite tree is one example of a desert plant. It lives in the southwest United States and Mexico. The tree has small, waxy leaves and a deep taproot that helps draw moisture up from the soil.
In a hot desert, animals either enjoy the heat, or they may choose to come out at night when the desert is much cooler. The pocket mouse lives near the mesquite trees and eats the tree’s seeds. This mouse doesn’t need to drink a lot of water because it gets its water from the seeds that it eats.
The sidewinder rattlesnake likes to eat the pocket mouse. This snake moves with a sideways motion and lifts much of its body off of the ground as it moves, reducing the amount of its body that has to touch the hot sand.
The red-tailed hawk eats sidewinder rattlesnakes. This hawk is adapted to living in many different environments. It can fly far away to find food and water, and can eat many different kinds of prey animals.
Can you think of another desert somewhere else in the world? Look up that desert and see what plants and animals live there.
In this activity, you’ll build a food chain, a food web, and a food pyramid. Let’s learn about what each term means, and how each model is different.
Creating a Food Chain
A food chain is a simple line-up of plants and animals. In a food chain, you begin with one plant. In the desert, this might be a plant that does well in dry areas, such as mesquite. A pocket mouse could come along and eat the seeds from the plant, and a snake such as a sidewinder might eat the mouse. What eats the snake? A hawk could fly over and snatch up a tasty meal.
- To create a food chain, place a foot-long piece of string on the cardboard. Pin it at either end. Create labels that say “mesquite,” “mouse,” “snake,” and “hawk” and add these labels to push pins.
- Place the plant pin at one end of the string, followed by the mouse, the snake, and the hawk.
- You’ve created a food chain – a simple line that shows how one small plant can feed a mouse, which feeds a snake, which then feeds a hawk.
Creating a Food Web
Life in the desert is more complicated than this, of course. You eat a lot of different foods during your day, and each of those foods comes from a different place. In other words, you have a polyphagous diet. The same thing is true of many organisms in the desert! Each herbivore, or plant-eater, eats a number of different plants, and the carnivores, or meat-eaters, eat a number of different kinds of animals. A pocket mouse sometimes eats seeds from grasses instead of nuts from a mesquite tree. An owl, instead of a hawk, could eat the mouse. Adding more complexity to your food chain turns it into a food web.
- Label two more push pins with the labels “grass” and “owl”. Place them into the cardboard as well.
- Connect the grass and the mouse, and the owl and the mouse.
- Connect the hawk directly with the mouse as well.
- Can you see a pattern forming? This pattern looks more like a web than a chain. Can you think of other animals that might eat mesquite or grass? Add them to push pins and continue building your web.
Creating a Food Pyramid
A food pyramid is different from a food chain or web. How is it different? Well, think about your mouse. How many seeds does it take to feed your mouse? Probably hundreds. How many mice does it take to feed your snake? One every day or two? How many snakes would a hawk eat in a week?
As you move up the food chain, each level can support fewer animals. Each level of the pyramid is called a trophic level, the position an organism occupies in a food chain. A single hawk (ultimate consumer) can eat many snakes (secondary consumer), and a single snake can eat many mice (primary consumer). Each mouse eats hundreds of mesquite seeds, which we call producers because plants produce food through photosynthesis (getting energy from the sun). This means that thousands and thousands of seeds end up indirectly feeding that hawk at the top of the food chain. A food pyramid shows the different numbers of organisms that are necessary at each level of the food chain. At the bottom of your desert food chain, you might draw many different seeds, but there will be only one hawk in the small triangle at the top.
- Have you decided what animals and plants you’d like to have in your desert food pyramid? Let’s build it! Print out this worksheet (preferably on cardstock paper) and let’s get started.
- First, cut out the template.
- Now, start folding. Fold the paper diagonally, unfold it, and fold it again in the opposite direction.
- From bottom to top, label the four parts of one triangle with the following names: producer, primary consumer, secondary consumer, ultimate consumer.
- From bottom to top, label the four parts of the second triangle with the names of the plants and animals you used in your food chain. You’ll begin with the plants at the bottom and put the name of the top predator at the top.
- Remember: The mesquite seeds are the producers, the mouse is the primary consumer, the snake is the secondary consumer, and the hawk is the ultimate consumer.
- On a third triangle, draw a picture of each plant or animal.
- To complete your desert food pyramid, tape the tab on your first triangle to the underside of your third triangle. You’ve made a food pyramid!