How the Sun Provides Energy within the Ecosystem

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll be looking at how the Sun provides energy for all life on Earth. Here you can learn about what powers the Sun and how that energy gets from outer space to Earth to help us feed the whole planet!

How Do We Get Energy?

Every moment you're alive, you're using energy. Even though you might just be sitting here reading right now, you're still using energy. Your lungs are breathing, your heart is beating, and your brain is thinking. All of these things use energy! So, how does your body get that energy? If you're thinking about food or drinks, you're on the right track.

Humans get our energy by eating food. Our food is made of molecules that store chemical energy, a type of energy that is stored in the bonds of chemicals. When we eat food, our body breaks down those molecules and coverts the chemical energy in our food to another type of chemical energy our body can use, called ATP.

Food is converted to a usable form of chemical energy by the body.
food to chemical energy

But, you might still be wondering where the energy in our food comes from. Even the energy in pre-packaged snacks like crackers ultimately comes from other living things, in this case plants. Plants are the source of energy for all living things on Earth, including humans. But, to understand how plants make this energy we need to look at the ultimate source of energy on Earth, the Sun.

Reactions of the Sun

When you think of the Sun, you might be thinking of a nice day at the beach, or a sunny day at the park. The Sun might look small up in the sky, but its actually incredibly large and produces tremendous amounts of energy. So, what kinds of energy do you think the Sun produces?

What we see on Earth is light energy, a type of energy that comes from electromagnetic radiation, or light waves. But, the bulk of the Sun's energy is in the form of nuclear energy that comes from nuclear reactions inside the Sun. Let's take a look at how this happens.

The Sun isn't actually solid like Earth, but rather a ball of high energy gases and plasma. The Sun is extremely hot. The outer layer is at least 500,000 Kelvin. That's nearly 900,000 degrees Fahrenheit, about 10,000 times hotter than some of our hottest days in the summer.

When molecules heat up, they gain energy and move faster. So, due to the temperature of the Sun, its particles move very quickly and aren't locked in place like we know to be true of Earth.

The second reason the Sun can produce so much energy is that it is very large. It's over 100 times greater in diameter than Earth, and over 300,000 times more massive! All this mass leads to intense gravity, which actually pulls the gases on the outside of the Sun inward towards the core. When the gas particles get to the core, they are under so much pressure that they smash together during nuclear fusion. This type of reaction produces lots of energy that leaves the Sun and travels to Earth as light.

The massive size of the Sun creates the gravity and pressure needed for nuclear fusion.


Let's go back to humans now and how we get our energy. Like we said, humans get energy from food. But, our food comes from other plants and animals, which ultimately get their energy from the Sun. The Sun's light provides the energy for all the ecosystems on Earth. The process starts with photosynthetic producers, or organisms that make their own energy from the Sun.

Photosynthetic Producers

Producers are organisms that make their own food. They are always at the base of the ecosystem and provide energy for every other living thing, including humans. Some producers use chemicals in the environment to make energy, but the ones we're concerned about are photosynthetic producers, which use light energy from the Sun to make their own food. Most photosynthetic producers are green plants.

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