Energy from Food & the Sun
Use models to describe that energy in animals' food was once energy from the sun, transferred through plants or other organisms
What a learner can do afterwards
- Explain that plants capture energy from sunlight to make food (photosynthesis)
- Trace an energy pathway: sun → plant → animal → another animal
- Explain that animals use food energy for body repair, growth, movement, and warmth
1 · Read
You have learned that plants use air and water to grow. Green plants also use light energy to make food. Animals such as rabbits and people get food energy by eating plants or other animals. In the feeding paths here, that energy can be traced back to sunlight.
Photosynthesis uses light energy to make sugars from carbon dioxide and water. These sugars store energy the plant can use. Soil provides minerals, but these do not replace light as the energy source for photosynthesis. Plants, algae and some bacteria can photosynthesize.
Wheat stores food in its seeds. Cereal made from those seeds supplies food energy when you eat it. A farmer helps the wheat grow by caring for the crop. The wheat plant captures sunlight energy through photosynthesis; the farmer does not create the energy stored in its food.
Your body uses energy stored in food for growth, repair, movement and keeping warm. Running and healing a scrape both need energy. Food also supplies materials for building and repairing your body. Water and vitamins help your body work, but they do not supply food energy.
A green plant in complete darkness cannot photosynthesize. Water and soil cannot replace light. The plant may keep living for a while by using food it stored earlier. If it stays without light long enough, those stores run low and the plant weakens.
In these feeding paths, plants store sunlight energy in food. Animals obtain food energy by eating and use it for growth, repair, movement and warmth.
These five readings were independently written for this dataset. Supplied Khan Academy, OpenStax and OER Commons records informed fact checks and teaching approaches; their prose is not reproduced.
More to read
Two things a meal supplies
When a rabbit eats a leaf, it receives materials and stored energy. Materials help build its body. Energy powers body processes, including movement and repair. These are different jobs. Making new tissue needs materials as well as energy. The leaf grew on a plant that used light energy to make sugars. A rabbit gets food energy by eating; sitting in sunlight cannot replace its meals.
Water and carbon dioxide supply materials; light supplies energy
Water and carbon dioxide provide materials for making a plant's sugars. Light supplies energy for this process, called photosynthesis. Minerals help the plant grow, but they cannot replace light energy. Plants are not alone in capturing sunlight this way: algae and some bacteria do it too. Photosynthesis supports most food chains. Some organisms instead make food using chemical energy, so sunlight is not the starting point for every living thing.
How much energy reaches the next eater?
Picture a caterpillar eating a leaf, followed by a bird eating the caterpillar. Some energy stored in the plant's food reaches the caterpillar and then the bird. The caterpillar also uses energy to live and move. Some energy spreads into its surroundings as heat. The bird therefore does not receive all the energy the caterpillar took in. Less energy is available to eaters farther along a food chain.
Which way does a feeding arrow point?
A feeding arrow points toward the eater. Grass followed by an arrow toward a grasshopper means the grasshopper eats grass and receives food energy. Follow the arrows to trace transfers between organisms. Some diagrams also show sunlight followed by an arrow toward a plant. That arrow shows light energy reaching the plant. It does not mean the sun is a living thing being eaten.
Follow food energy through milk
A cow eats grass and other feed to obtain food energy and nutrients. The plants in that feed captured sunlight energy while making food. The cow uses nutrients from its food to produce milk. Milk contains nutrients that supply energy to a person who drinks it. This route passes through an animal between the plants and the person. Eating a plant food follows a route without that animal step.
2 · Watch
Take it off screen
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.