What is Food Chain and Food Web?
All living plants and animals must have energy to survive. Plants depend on soil, water, and the sun for energy. Animals depend on plants as well as other animals for energy.
In an ecosystem, plants and animals both depend on each other for survival. Scientists sometimes describe this addiction using food chains or food webs.
Food Chain
Food chains describe how different organisms eat each other, starting with plants and ending with animals. For example, you could write a lion’s food chain like this:
grass —> zebra —> lion
Grasshoppers eat grass, frogs eat grasshoppers, snakes eat frogs, and eagles eat snakes.
Links of the Chain
There are names to help describe each link in the food chain. The names mainly depend on what the organism eats and how it contributes energy to the ecosystem.
Producers – Plants are producers. This is because they generate energy for the ecosystem. They do this because they absorb energy from the sun through photosynthesis. They also need water and nutrients from the soil, but plants are the only source of new energy.
Consumers – Animals are consumers. This is because they don’t produce energy, they deplete it. Herbivores are called primary consumers or herbivores. Animals that eat other animals are called secondary consumers or carnivores. If a carnivore eats another carnivore, it is called a tertiary consumer. Some animals play both roles, eating both plants and animals. They are called omnivores.
Decomposers – Decomposers feed on decomposing matter (such as dead plants and animals). They help put nutrients back into the soil for plants to eat. Examples of decomposers are worms, bacteria, and fungi.
Lets go back to this example:
grass —> zebra —> lion
grass = producer
zebra = primary consumer
lion = secondary consumer
Energy is Lost
As we said above, all the energy generated in the food chain comes from producers or plants, which convert sunlight into energy through photosynthesis. The rest of the food chain consumes only energy. So as you move up the food chain, less and less energy is available. Therefore, there are less and less organisms as you move up the food chain.
In our example above, there is more grass than zebras and more zebras than lions. Zebras and lions consume energy by running, hunting and breathing.
Each Link is Important
The upper links of the food chain depend on the lower links. Although lions do not eat grass, without grass they will not survive long, because then zebras will have nothing to eat.
Food Web
In any ecosystem there are many food chains, and usually most plants and animals are part of more than one chain. When you put all the chains together, you get a food web.
Trophic Levels
Scientists sometimes describe each level of a food web with a trophic level. Here are the five title levels:
Level 1: Plants (producers)
Level 2: Animals that eat plants or herbivores (primary consumers)
Level 3: Animals that eat herbivores (secondary consumers, carnivores)
Level 4: Animals that eat carnivores (tertiary consumers, carnivores)
Level 5: Animals at the top of the food chain are called apex predators. Nothing eats these animals.