This lesson is on the desert energy pyramid. In this lesson we’ll cover what an energy pyramid is and how energy flows through an ecosystem, particularly the desert.
What is Energy?
As you’re driving through Death Valley on your way to vacation in Las Vegas, the sun beats down and the car is sweltering hot.
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The energy from the sun pours onto the earth.
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How do we harness that energy to sustain life? The answer is plants! There are even plants in the dry conditions of the desert that capture the energy of the sun to provide food for other animals. Today, we’re going to look at how that energy is collected and moved between different types of animals.
What is an Energy Pyramid?
To start, lets take a look at what an energy pyramid is and what’s in each level. An energy pyramid shows the transfer of energy from plants, which use the Sun to make food, to the other animals in the ecosystem. Plants are called producers because they make their own food.
After the producers come the primary consumers, or herbivores, which eat only producers. The secondary consumers eat the herbivores, and lastly the top predators eat both the primary and secondary consumers.
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Desert Ecosystem
A desert is an area that gets very little rain. Even though we think of deserts as extremely hot, deserts can be cold too, as the deciding factor is rainfall. For this lesson though, let’s focus on a traditional, hot and dry desert, like the Mojave Desert in California.
The producers in a desert are green plants, like grasses, cacti and small trees adapted to dry conditions, like the Joshua Tree.
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Primary consumers only eat producers, and in the desert these are small mammals such as rodents, like the kangaroo rat, as well as rabbits and deer.
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Secondary consumers eat primary consumers and these animals include lizards, scorpions, rattlesnakes and omnivorous birds, like the road runner.
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The top predators in the desert are bobcats, barn owls and coyotes, which eat both primary and secondary consumers.
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Energy Transfer
Now let’s look at how energy flows between the different levels in the desert. Producers, like cacti and trees, have the most direct access to energy from the Sun, so they can use almost all the energy they get. This allows for a large population of producers in an ecosystem.
Next comes the primary consumers. These guys get a lot less energy than what the plants originally got, because the plants use a lot of their energy just to grow, reproduce and keep living. The primary consumers actually only get 10% of the energy inside the plants when they eat them.
So, as you can imagine, if there is less energy, there are less primary consumers.Next, the secondary consumers get 10% of the energy in the primary consumers they eat, so there are even less. Finally, the top predators have the least energy available to them, since only 10% of the energy in the secondary consumers is available. This is called the ten percent rule, which states that each energy level only gets 10% of the energy available before it.After we do the math, let’s check out what percentage of the original energy is transferred to each level of consumer.
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As you can see, as we go up in the pyramid there is less energy, and thus less of that type of animal can be supported in the ecosystem. Let’s use an analogy of a company to help us understand this. Think of the owner of a big business. He gets all the profit, like the producers.
But, he has to use some of that profit to pay the bills, so he can only hand down 10% of his pay to the top managers. The same thing happens with our top managers, they need to take their own cut, then they can hand down their extra 10% to the workers in the factory. Each level gets less money, or energy, than the one before it.
Desert Energy Pyramids
Based on the 10% rule, each level gets less energy than the level before it. Since each level gets less energy, less animals can be supported. This is why plants are plentiful, but there may only be a handful of top predators, like barn owls, in an area.
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Lesson Summary
In summary, an energy pyramid shows the flow of energy from producers, to primary consumers, secondary consumers and top predators. The 10% rule says each level in the energy pyramid gets only 10% of the total energy in the level below it, which causes there to be less of each organism as we move up the energy pyramid. In the desert, the producers are grasses, cacti and small trees, which are the most prevalent. There are less primary consumers, which are small rodents, rabbits and deer. There are even less secondary consumers, like rattlesnakes, birds and lizards.
Finally, the top predators, such as the coyote, barn owl and bobcat, are extremely sparse.
