Food Chains & Ecosystems
Producers, consumers, decomposers — energy flows through life
A food chain shows how energy flows from one organism to another through eating. Producers (plants) capture energy from sunlight through photosynthesis. Primary consumers (herbivores) eat plants. Secondary consumers (carnivores) eat herbivores. Decomposers (bacteria, fungi) break down dead organisms and return nutrients to the soil. At each step, about 90% of energy is lost as heat — only 10% passes to the next level. This is why there are always far more plants than rabbits, and more rabbits than foxes. Removing any link from the chain disrupts the whole ecosystem.
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Sign in →What is Food Chains & Ecosystems?
A food chain shows the order of who eats whom in nature. It starts with plants. Plants use sunlight to make their own food. That is why we call them producers — they produce food. Animals that eat plants are called herbivores, or primary consumers. Rabbits, deer, and caterpillars are examples. Animals that eat the plant-eaters are called carnivores, or secondary consumers. Foxes, hawks, and wolves are examples. Then there are decomposers — tiny living things like bacteria and fungi that break down dead plants and animals. Decomposers are nature's recyclers. They send nutrients back into the soil so plants can grow again. In this simulation you can change the number of plants, how many plant-eaters there are, and how many meat-eaters there are. You can also change how much sunlight the plants get. Watch what happens when you take out one part of the chain — the whole ecosystem feels the change!
Parameters explained
- Plant Population
- Plant Population changes how many producers are in the ecosystem. Producers are plants. They make food using sunlight, and many animals depend on them. When you move this slider up, there is more plant food for plant-eaters. When you move it down, food becomes harder to find. Watch what happens to the animals after the plants change. Do they have enough to eat? Try the Balanced Ecosystem preset first, then try Drought Season to see what can happen when there are fewer plants.
- Predator Population
- Predator Population changes how many hunters are in the ecosystem. Predators are animals that eat other animals. When this slider is low, plant-eaters may have fewer animals chasing them, so their group can grow. When this slider is high, predators may catch more plant-eaters. That can leave more plants behind, but too many predators can also run out of food. Move only this slider and watch the chain. Then try Predator Surge to compare your own setting with a preset.
Common misconceptions
MisconceptionPlants are not really part of the food chain because nothing eats them back.
CorrectPlants are the most important part of the food chain! They are called producers because they capture energy from the sun and turn it into food. Every animal in the chain depends on plants, directly or indirectly. Without plants, the whole food chain collapses.
MisconceptionDecomposers are gross and not useful.
CorrectDecomposers like bacteria and fungi do a very important job. They break down dead animals and plants and return nutrients to the soil. Without them, dead things would pile up everywhere and plants could not get the nutrients they need to grow. Decomposers keep the cycle going.
MisconceptionIf one animal disappears from a food chain, it does not really matter.
CorrectEvery part of a food chain is connected. If foxes disappear, rabbits have no predator and their numbers explode. Too many rabbits eat too many plants, and then plants disappear. Then rabbits run out of food and crash too. Removing one animal causes big changes all the way through the chain.
MisconceptionThere are usually more wolves than rabbits in an ecosystem.
CorrectIt is usually the opposite. In this simple land food-chain model, there are usually many more plants than plant-eaters, and many more plant-eaters than meat-eaters. This is because a lot of energy is lost at each step — only about 10% passes to the next level, so each level needs many individuals from the level below to support it. To feed one fox, you need many rabbits. To feed those rabbits, you need many plants.
How teachers use this lab
- Start with the Balanced Ecosystem preset. Have students record the Plant Population and Predator Population values, then describe how energy moves from producers to consumers in support of NGSS 5-LS2-1.
- Use the Predator Surge preset as a prediction task. Ask students to explain how a sudden increase in predators may affect plant-eaters and producers, then compare their predictions with observations.
- Use the Drought Season preset to model reduced producer availability. Connect student observations to how changes in one part of an ecosystem can affect many organisms.
- Have students change only the Plant Population slider while keeping Predator Population constant. Ask them to identify which changes are direct effects and which are indirect effects.
- Run a quick CER activity: students choose one preset, cite slider values and visible changes as evidence, and make a claim about whether the ecosystem is balanced or stressed.
Frequently asked questions
What is the difference between a producer and a consumer?
A producer makes its own food using sunlight. Plants, algae, and some bacteria are producers. A consumer cannot make its own food, so it must eat other living things to get energy. Rabbits consume plants, foxes consume rabbits. Decomposers are a special kind of consumer that eat dead material and recycle nutrients back into the soil.
Why are there usually more plants than animals in an ecosystem?
At each step in the food chain, most of the energy is used up or lost as body heat. Only a small amount passes to the next level. It takes many plants to feed a rabbit, and many rabbits to feed a fox. So the lower you are in the food chain, the more individuals there must be to support the levels above.
Which NGSS standards does this experiment address?
This simulation supports 5-LS2-1 (develop a model to describe the movement of matter among plants, animals, decomposers, and the environment). The ecosystem animation shows energy and matter flowing from sun to plants to herbivores to carnivores, with decomposers returning nutrients to soil.
What would happen if all the decomposers disappeared?
Dead plants and animals would pile up everywhere and never break down. The nutrients locked inside those dead things would never return to the soil. Plants would run out of nutrients and stop growing well. Without plants, herbivores would go hungry, and then carnivores too. The whole ecosystem would break down. Decomposers may be invisible, but they are essential.
Can one animal belong to more than one level in a food chain?
Yes! Many animals eat both plants and other animals. Bears eat berries, fish, and sometimes small mammals. Humans eat plants and animals too. An animal that eats many different things is called an omnivore. Real ecosystems are actually more like food webs — many food chains tangled together — rather than one simple straight chain.