The energy you need to live comes from the food you eat. This energy passes between living things along a food chain.
Level 1: All food chains begin with the energy from the sun.
The energy given off in the light of the sun provides the necessary ingredient for plants to make their own energy.
Level 2: The living part of food chains start with plants - the primary producers.
Plants take energy from the sun, nutrients from the soil, and they produce the energy to grow. Along the food chain, a series of organisms eat one another and the nutrients and energy flow into each level of the food chain.
Level 3: Herbivores (or plant-eaters) eat the primary producers.
This second level is also called the primary consumers, because they must consume (or eat) another organism to get their energy.
Level 4: The next level is called the secondary consumers,
which are usually the meat-eaters.
Level 5: The final level is usually the tertiary consumers -
the meat-eating carnivores like bears, lions, and sharks. These are the apex predators, the organisms on the very top of the food chain. Food chains can only support 3-6 levels in the food chain because each level loses energy. Each organism stores some energy and loses some energy through heat. Only about 10% of the energy is available to be passed on to the next level. This means the tertiary consumers get far less energy from their food than the primary consumers.
Remember, a consumer eats something for its energy, a producer makes its own energy.
The two images above show the same thing, just arranged in a different way. The top image shows a food chain arranged in a pyramid. You can see that at the bottom of the food chain is the sun, or "light energy", which is giving energy to the next level up- the primary producers, or plants. The plants use the energy from the sun to make their own energy. One more level up shows the grasshopper who eats the grass. This third level of the pyramid is smaller for a reason - there have to be more plants than grasshoppers since energy is lost in the transfer. The next level shows the toad who eats the grasshopper, and there are also less toads than grasshoppers. Moving up a level, the snakes eat the toads, and then the hawk eats the snake.
On the left side of the top image is the "decomposers." This is another part of the food chain - the decomposers are the organisms that break down dead organic material (or dead things that were once alive, like animals and plants). Decomposers eat dead plants and animals and return the nutrients to the environment and keep the ecosystem healthy. Sometimes decomposers are fungi or bacteria, but they can also be animals like earthworms, vultures, or crabs.
The bottom image shows the same sequence but it a more simple form. The sun feeds the grass, which feeds the grasshopper, which then feeds the toad, and so on.
Every level in the food chain relies on all the other levels.
Lets look at the image below:
In this image, the phytoplankton (on the top left) are the first level of the food chain in the ocean, after the sun. Phytoplankton are microscopic algae - the plants of the ocean.
If the small fish were to disappear, say from overfishing, the mackerel would not have food. Once the mackerel disappears from lack of food, the tuna will also run out of prey. Therefore, a reduction of small fish will impact sharks, even though sharks don't directly eat them. Similarly, if small fish disappear, there will be more zooplankton (the "shrimp-like creatures") because they are not being eaten by the small fish. Therefore, each level of the food chain effects the others, and keeps all the others in balance.
Food chains are a simple way to illustrate who eats whom. However, many animals have a varied diet. Omnivores are animals that eat both plants and animals, which means they depend on at least two different levels of the food chain. Most plants and animals are also eaten by more than one consumer. This more complex relationship is referred to as a food web. This is briefly illustrated in the video below.
While the energy needed to live is passed along the levels of the food chain, so do chemicals and other environmental pollutants. As pollutants move up the food chain, they increase. For example - plastic breaks down into tiny fragments over time. These microplastics are small enough that the plankton, that are at the bottom of the food chain in the ocean, will eat them. Small fish eat many plankton, which means they have much more microplastics in their bodies. Larger fish eat many small fish, meaning they have even higher amounts of microplastics. This is called biomagnification. This can poison the animals on the higher levels of the food chain - including humans. Next time you eat fish, consider how important it is to keep your environment clean!
Photo credit: Catalina Island Marine Institute
Print out the document below. Cut out each image (plant, coyote, beetle, sun, and lizard) and arrange them on a blank piece of paper. They should show the correct flow of energy along the food chain. Once you have the images in the right order, glue them down. Label each organism with "primary producer", "primary consumer", "secondary consumer", and "tertiary consumer." On the back of the paper, write a paragraph describing how energy flows through your food chain. Also describe what will happen to the hawk if all the grasshoppers die
Carnivore: Animal that eats meat
Herbivore: Animal that eats plants
Omnivore: Animal that eats plants and animals
Primary producer: Plants that produce their own energy from the sun. The bottom of the food chain.
Primary consumer: Herbivorous animals. The second level of the food chain.
Secondary consumer: Animals that eat primary consumers. Can either be carnivores or omnivores.
Tertiary consumers: Animals that eat secondary consumers. Usually carnivores but can also be omnivores.
Autotrophs: Another name for plants/ primary producers. An organism that creates its own energy.
Heterotrophs: Any organism that cannot make its own food, and must eat another organism to get its energy.
Biomagnification: The concentration of toxins in the bodies of organisms in increasing amounts at higher levels of the food chain.